The Msimbazi Opportunity Transforming the Msimbazi Basin into a Beacon of Urban Resilience Volume B Detailed Plan for the Lower Basin Client: President’s Office – Regional Administration and Local Government Financier: Contractor: 29 January 2019, Dar es Salaam The Msimbazi Opportunity Transforming the Msimbazi Basin into a Beacon of Urban Resilience Volume B Detailed Plan for the Lower Basin Acknowledgements Responding to the call of Vice President of Tanzania, Honourable Samia Suluhu Hassan, to pragmatically address the recurrent flood risk in Dar es Salaam, the Msimbazi Opportunity Plan was developed through a participatory design process, known as a ‘Charrette’, that was undertaken from January to August 2018. It is the result of the invaluable time and dedication of more than 200 people, from 59 institutions and communities, across 30 working sessions. This unprecedented approach benefited from, and was championed by, Selemani S. Jafo (MP) Minister of State, President’s Office Regional Administration and Local Government and January Y. Makamba (MP) Minister of State, Vice President’s Office, Environment and Union Affairs. The collaboration and consensus building achieved through this process would not have been possible without the sustained efforts of the Dar es Salaam Metropolitan Development Project team within the President’s Office for Regional Administration and Local Government, led by Engineer Davis Shemengale. Through committing to the delivery of a unified solution to one of Dar es Salaam’s most pressing challenges, the Charrette brought together stakeholders from the Dar es Salaam Regional Administrative Secretariat, Dar es Salaam City Council, Ilala Municipal Council, Kinondoni Municipal Council, Ubungo Municipal Council, DART, DAWASA, DAWASCO, Ministry of Lands Housing and Human Settlements Development, Ministry of Water and Irrigation, Ministry of Works, National Environmental Management Council, Wami Ruvu Water Basin Authority, Prime Minister Office – Disaster Management Department, TANESCO, TANROADS, Vice President’s Office, Ardhi University, Korea Eximbank, Department for International Development, National Land Use Planning Commission, Private Sector Representatives, Tanzania Forest Service, National Housing Corporation, Tanzania Meteorological Agency, Non-Government Organizations, and critically Community Representatives from Hanasif, Idrisa, Mchikichini, Kigogo Kati, Kigogo Mkwajuni, Msimbazi Bondeni, Magomenu-Mapipia, Mikumi, and Suna subwards among others. A full list of participants can be found in Volume C. A flagship of the Tanzania Urban Resilience Program, the Charrette process was coordinated by Nyariri Nanai (Senior Engineer) of the President’s Office for Regional and Local Government, and Eric Dickson (Senior Urban Development & Disaster Risk Management Specialist) and Edward Anderson (Senior Disaster Risk Management & ICT Specialist) of the World Bank. The Charrette process was facilitated by a consortium of Max van der Sleen (Ecorys), Remco Rolvink (DASUDA), Bas van de Sande (CDR International), and Christina Geoffrey Mandara (WEMA Consult). Detailed review and comments were provided by a World Bank team comprised of Amy Faust (Urban Development & Resilience Consultant), MaryGrace Lugakingira (Urban Planning Consultant), Mussa Natty (Engineer Consultant), Nyambiri Kimacha (Disaster Risk Management Consultant), and Larissa Duma (Urban Ecology, Environment, and Sanitation Consultant). Special thanks are due to UK aid for their generous funding and support, without which the visionary outcomes of the Charrette process would not have been possible. Through the collective contributions of such a wide and diverse set of stakeholders, a unique opportunity lies ahead to transform the Msimbazi Basin into a beacon of urban resilience. This document offers a comprehensive and integrated Detailed Plan for the Lower Basin, hereinafter referred to as the DP. The context for the DP is part of the Msimbazi Opportunity Plan and based on the Strategy and Management Framework document; Volume A in this series. Both were developed and designed in a series of design workshops (“charrettes”) that took place from January to August 2018. The participants represented the key stakeholders in the current and future development of the wider Msimbazi Basin. This special process had everyhting to do Foreword with the great urge to solve the challenges which large parts of the Msimbazi experiences during flooding after heavy rains. Lives, livelihoods and assets are at risk. If nothing is done, urbanization pressures and climate change will increase the annual flood risks and associated damages. The Detailed Plan for the Lower Basin, is the design document to guide further technical designs, feasibility studies and implementation plans for the Msimbazi Lower Basin (4 km2) officially defined by the Msimbazi Special Planning Area (MSPA). The DP includes elements that will support the resilient development of Dar es Salaam as a megacity: Flood Protection, Environmental Rehabilitation, and Green City Park development are integrally treated and create a strong base for the immediate actions to be taken. Tuanze kazi. Selemani S. Jafo (MP) Minister of State President’s Office Regional Administration and Local Government Illustration of the dredging of the river, widening of the bridge and making the terraces Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity Table of contents 1 Acronyms 2 1. Introduction 5 1.1. Positioning the Detailed Plan in the MSMF 7 1.2. Charrette Design Process 9 Table of 1.3 1.4. Situation Analysis for the Lower Basin Report Contents 11 17 Contents 2. Concept 19 3.1. Design Principles 21 3.2. Integrate Functions 29 3. Detailed Plan 31 3.1. The Overall Plan 33 3.1.1. Land use map 33 3.1.2. Illustrative design 35 3.1.3. Overall impression 36 3.1.4. Bird’s eye view 38 3.2. River 41 3.2.1. Facet map of river and the flood plain 43 3.2.2. Sections of the river 45 3.2.3 The new Jangwani Bridge 47 3.3 Terraces 49 3.3.1 Facet map of the terraces 49 3.3.2 Visual section of the terraces 52 3.3.3 Robust design of terraces 55 3.3.4 Modelling results of river, bridge and terrace interventions 59 3.4. Detailed Areas 63 3.4.1. Variety of areas 63 3.4.2. Cross sections 65 3.4.3. The core of the City Park 71 3.4.4. Wetland and Mangroves 77 3.4.5. Urban development areas 81 4. Path Forward for the Lower Basin 101 4.1. Immediate Actions 102 4.1.1. Resettlement plan 103 4.1.2. Channel opening 104 4.1.3 Jangwani Bridge intervention 104 4.1.4 Implementation of terraces 105 4.2 Recources for Interventions 106 4.2.1. Time 106 4.2.2 Equipment to be deployed 107 4.2.3 Financial outline 108 4.2.4 Continuation of stakeholder and community participation and 109 engagement Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 1 AAT Architects Association of Tanzania ACCA Awareness, Comprehension, Commitment, Action ARU Ardhi University BORDA Bremen Overseas Research and Development Association NGO CC Climate Change CCI Centre for Community Initiatives, NGO in Dar es Salaam DART Dar es Salaam Rapid Transport Company DAWASA Dar es Salaam Water and Sewerage Authority DAWASCO Dar es Salaam Water and Sewerage Corporation DCC Dar es Salaam City Council DMDP Dar es Salaam Metropolitan Development Program (TURP) DFID Department for International Development, UK Government DP Detailed Plan for Msimbazi Lower Basin Area GIS Geographic Information System Mapping Technology HOT Humanitarian Open Street Map Team IMC Ilala Municipal Council Kata Ward level of the Local Government structure (divided into Sub-wards/Mitaa) KMC Kinondoni Municipal Council LRP Livelihood Restoration Program MADC Msimbazi Area Development Corporation MLHHSD Ministry of Land, Housing and Human Settlement Development. MNRT Ministry of Natural Resources and Tourism MOWI Ministry of Water and Irrigation MOF Ministry of Finance and Planning MOP Msimbazi Opportunity Plan MPA Msimbazi Planning Authority MSC Msimbazi Steering Committee MSMF Msimbazi Strategy and Management Framework MSPA Msimbazi Special Planning Area MWTC Ministry of Works, Transport and Communication 2 NBS National Bureau of Statistics, Ministry of Finance NEMC National Environmental Management Council NETF National Environmental Trust Fund NGOs Non-Government Organizations NLUP PAH National Land Use Planning Commission Project Affected Households Acronyms PAP Project Affected Persons/Properties PMO Prime Minister’s Office PO-RALG President’s Office – Regional Administration and Local Government RAP Resettlement Action Plan RAS Regional Administration Secretariat – Dar es Salaam RP Resettlement Plan RS Resettlement Strategy SC Strategy Component in the MSMF SDGs Sustainable Development Goals SEIA Strategic Environmental Impact Assessment Shina Area where the Wajumbe is the leader in the Mtaa SHW Stakeholder Workshop TAHMO Trans-African HydroMeteorological Observatory TAMISEMI PO-RALG TANROADS Tanzania National Roads Agency TARURA Tanzania Rural and Urban Roads Agency TFS Tanzania Forest Services THRGGC Tanzania Human Rights and Good Governance Commission TMA Tanzania Meteorological Agency TOR Terms of Reference TURP Tanzania Urban Resilience Program VPO Vice Presidents Office WRBWO Wami-Ruvu Basin Water Office Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 3 Volume B: Detailed Plan for the Lower Basin Introduction 1 The Msimbazi Opportunity Upper Basin Middle Basin Lower Middle Basin Lower Basin Kazimzumbwi and Pugu Forest Reserves (inside catchment) Kazimzumbwi and Pugu Forest Reserves (outside catchment) Park typology: Mangrove Forest Park typology: Central City Park North Park typology: Linear Riverbank Park Msimbazi Special Planning Area Urban (re)Development areas Figure 1: Overview map of the Msimbazi Basin Figure 2: Zoom in on the Lower Basin (area marked in red is Detailed Plan area) 6 1.1 The residents of Dar es Salaam are highly familiar with the flooding challenge in the Msimbazi valley; the impacts are easily remembered. Nearly every rainy season brings some degree of flooding. Major events have demonstrable impact - lives are lost, homes are destroyed, and negative health effects of the contaminated flood waters reverberate for months after flood waters subside. In response and within the context of the Dar es Salaam Metropolitan Development Program (DMDP), the Government of Tanzania through the President’s Office Positioning for Regional and Local Government (PO-RALG), in partnership with the World Bank and the UK Department for International Development’s (DFID), established the Tanzania Urban the Detailed Resilience Program (TURP)1 which supports “… flood mitigation efforts in the Msimbazi Basin Plan in the with the goal of taking an integrated approach to rehabilitation in the Msimbazi Basin. This will include flood control measures but also capitalize on the Ministry of Lands, Housing and Msimbazi Human Settlement Development’s (MLHHSD) plan to transform the river into a linear city park Strategy and that would provide much-needed public space in the city” 2. Management The Msimbazi Opportunity Plan (MOP) consists of the Msimbazi Strategy and Management Framework Framework (Volume A) and the Detailed Plan for the Lower Basin (Volume B). The broader basin framework re-envisions the Msimbazi through the implementation of four strategies: Mitigate, Protect, Transform and Govern. A series of ten complementary Strategy Components are presented in Volume A which provide the framework for a multi-annual program and action plan for realizing the Msimbazi Opportunity Plan in a phased implementation process. Some of these are related to the Lower Basin and the Detailed Plan. Volume B of the MOP is dedicated to this Detailed Plan, and elaborates on the Strategy Components from Volume A. The intention is that the Detailed Plan for the Lower Basin, which is spatially focused between Selander Bridge and the Kawawa Road Bridges, is realized over a five-year period from 2019- 2023. With this Plan the Vice President’s call from January 2018 for a task force which would coordinate various government initiatives and provide guidance for the future with respect to flood protection and environmental restoration of the Msimbazi Basin is answered, and ready for the first stage implementation. 1 TURP is a 5-year trust fund with resources from DFID’s International Climate Fund. The main objective of the TURP is to support national and local governments in Tanzania to strengthen the management of climate risk in cities. 2 Citation from the Terms of Reference prepared by the World Bank for the Msimbazi Charette Consultants contract. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 7 Figure 3: Charrette 3 and 4 working on comprehension of the solutions for the Lower Basin Figure 4:The three alternatives of the Lower Basin presented for group work. 8 1.2 The Detailed Plan presented in this document is the result of a participatory design process, which was tailor-made for this project. It is based on the “Charrette” methodology which comprises a series of interactive workshops in which participants are comprised of a comprehensive and diverse group of stakeholders working together to find a solution for a multi-faceted and complex problem. More background on the Charrette is offered in Chapter 1.2 of Volume A of the MOP. Charrette The Charrette stakeholder team not only focused on the definition of strategies for the entire Design basin, but also focused their attention on the design of the Lower Basin. The Charrette design Process process for the Lower Basin started with further analysis of the specific topics and challenges of the Lower Basin and built upon the insights gathered during the MSMF charrette sessions. The flood modelling, both the background explanation of the base case modelling showing the results of a flood event comparable to the event on 26 October 2017 and the interventions that are most effective, is the important foundation on which a Detailed Plan can be designed. More focus was also given to desired functions for the future City Park, and an inventory was made by design sessions in which stakeholders mapped spatial positions of selected functions. The information was arranged in three spatial approaches and formed a set of alternative models for the Lower Basin which comprised the Wetland Park, the Asset Islands and the River Front. These alternatives were then evaluated through the use of multi-criteria analysis and resulted in the concept for the Detailed Plan which is presented in this Volume B of the MOP. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 9 450 50 400 45 350 40 35 Dischargeinm3/sec 300 Rainfallinmm/h 30 72 hours 250 25 RIVERDISCHARGEͲSelanderBridge 200 20 RIVERDISCHARGEͲBetweenJangwaniand 150 KawawaRdBridge 15 100 10 RAINFALLͲArdhiuniversity 50 RAINFALLͲBRT 5 RAINFALLͲPugustationsecondaryschool 0 0 10/23/1712:00 10/24/170:00 10/24/1712:00 10/25/170:00 10/25/1712:00 10/26/170:00 10/26/1712:00 10/27/170:00 10/27/1712:00 Figure 5: Rainfall intensity and river discharge during the October 26 2017 flood event 700 600 500 Dischargeinm3/sec 400 300 200 100 RIVERDISCHARGEͲSelander(T10yr) RIVERDISCHARGEͲSelander(T100yr) 0 10/23/1712:00 10/24/170:00 10/24/1712:00 10/25/170:00 10/25/1712:00 10/26/170:00 10/26/1712:00 10/27/170:00 10/27/1712:00 Figure 6: River discharge comparison T10yr and T100yr event used as input for the flood simulation modelling Hazard x Exposure = Vulnerability This project utilises the concept of vulnerability as it relates to flooding and uses a multi-layered information approach. A conceptual vulnerability equation, which is generally used in environmental hazard assessments, forms the basis of the information model. Hazards are hazardous hydraulic conditions like inundation depths, inundation periods and increased flow velocities. Exposure can be understood to include people, flora, fauna, and various assets that may be exposed to flooding. The product of hazards and exposure reveals the vulnerability to flooding. 10 River Dynamics The flood hazard in the Msimbazi River Valley is triggered by intense rainfall. The concentrated bursts of rain, in combination with a large percentage of impermeable surfaces in the wider 1.3 catchment area, improper functioning drainage system in the urbanized areas, and the rising of the lower basin flood plain due to sediment deposits, results in flash floods and erosion of the unstable slopes and embankments. Flood Simulation Modelling To better understand the extreme flood dynamics, simulations were performed by means of Situation a dynamic numeric hydraulic model. This model simulates the sudden extreme changes in Analysis: hydrological conditions (rainfall bursts) over a relatively short period of time (order of hours to a couple of days), meeting the necessities to simulate the flash floods in the valley. The model Insights cascade has been setup based on a detailed Digital Terrain Model (DTM) and digitized streams of Flood and structures. The model was run with hourly rainfall from the Meteorological Observatory. Modelling Rainfall observations of the October 2017 event were used to simulate the flood and represented the base case. The October 2017 event is representative because the rainfall conditions were extreme and the impact caused by the flooding was large. 3 to 6 hourly observations were in the order of a 10-year event (T10yr), whereas the 24-hourly observations were in the order of a 100-year event (T100yr). The simulation was done for 72 hours, spanning October 24-27, 2017. The following can be observed from the modelling results: • The lowest section in the Detailed Plan area, the section between Selander Bridge and Jangwani Bridge, is inundated first and remains inundated for nearly the entire event. The area is inundated for over 30 hours, and has a maximum flood depth that exceeds 1 meter. • As peak flooding begins, the section between Jangwani Bridge and Kawawa Road Bridge is inundated as the discharge rates of the river exceed the hydraulic capacity of the Jangwani Bridge. The backwater effect causes inundation depths of between 1 meter to 2.5 meter at the Jangwani playing grounds and causes overflowing of the Jangwani Bridge. • The section between Jangwani Bridge and Kawawa Road Bridge, and particularly the Jangwani playing grounds remain inundated for a long period due to insufficient drainage capacity in the lowest area of this section. Like a filled bathtub the area remains inundated for over 30 hours with slowly reducing water depths after the peak. The measures that have been identified have been tested through simulations in a dynamic numeric Flood hydraulic model. This model was developed for the wider Msimbazi Basin to simulate flooding in the Detailed Plan area of the Lower Basin. A Wflow-sbm hydrological model and linked SOBEK 1D2D Simulation hydraulic flood model have been established and calibrated to better understand the causes of Modelling the floods and to properly identify, design and test interventions to reduce flood risk and/or protect people and assets from flooding. For further information about this model reference is made to the modelling report by Deltares3. 3 Deltares – Development of a hydrological and hydrodynamic model of the Msimbazi basin – July 9, 2018 Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 11 Maximum flood depths at 12 hours Maximum flood depths at 24 hours Maximum flood depths at 36 hours 2 1.8 1.6 Flooddepthin[m] 1.4 1.2 1 0.8 0.6 Maximum flood depths at 0.4 0.2 Mkunguni flood plain 0 Ͳ0.2 0 10 20 30 40 50 60 70 80 Timeinhours 2 1.8 1.6 1.4 Flooddepthin[m] 1.2 1 Maximum flood depths 0.8 0.6 downstream of Jangwani 0.4 0.2 Bridge 0 Ͳ0.2 0 10 20 30 40 50 60 70 80 Timeinhours 2 1.8 1.6 1.4 Flooddepthin[m] 1.2 1 0.8 0.6 Maximum flood depths 0.4 at the BRT bus depot 0.2 0 Ͳ0.2 0 10 20 30 40 50 60 70 80 Timeinhours 2.5 2 Flooddepthin[m] 1.5 1 Maximum flood depths at 0.5 Jangwani Playgrounds 0 0 10 20 30 40 50 60 70 80 Ͳ0.5 Timeinhours 2 1.5 Flooddepthin[m] 1 Maximum flood depths at 0.5 confluence Kibangu River 0 and Msimbazi River 0 10 20 30 40 50 60 70 80 Ͳ0.5 Timeinhours 00 Basecase 0.3m flood depth 0.9m flood flooddepth 1.8m flood depth 12 Flood simulation modelling: Existing situation 26 October 2017 Flood depth (m) N 0 250 500 1000 meters Maximum flood depths at 48 hours Maximum flood depths at 60 hours Maximum flood depths at 72 hours ! ! ! ! ! Flooddepth in [m] Flood depth (m) 0 0 - 0.3 ¸ 0.3 - 0.9 0 250 500 1,000 Meters 0.9 - 1.8 Figure 7: Overview of the flood simulation > 1.8 of the T10yr flood event of October 26 2017 in the existing situation © OpenStreetMap (and) contributors, CC-BY-SA Maximum flood depth map at 60 hours of the event Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 13 ! ! ! ! ! Sunna ! Idrisa ! ! ! ! ! ! ! ! ! ! ! ! !!! ! ! Dossi ! ! ! ! Makumbusho ! ! ! ! !! ! ! ! ! ! !! ! ! ! ! ! ! ! Idrissa ! !!! !!! !! !! ! ! !! ! !! !!! ! ! ! ! !! ! ! ! ! ! !! ! Fire ! ! ! ! ! Mtambani ! !! ! !! ! ! ! ! !!! ! ! ! !! ! ! ! !!! ! ! ! !! ! ! ! !! ! !! ! ! ! ! !! ! ! !! ! ! ! ! ! !! !!!! ! ! !! ! ! ! !!! ! ! ! Mwinyimkuu ! ! !! ! !!! !!!! ! ! ! ! Barafu ! ! ! ! ! !! ! ! ! ! ! ! ! !! ! ! ! !! ! ! Kigogo Kati !! !! !! ! ! !! !! !! !!! ! Mtambani ! ! ! ! !! !! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! !!! ! ! !!!! Ukombo ! ! !!!! ! ! ! !! ! ! ! !! ! !! ! !! !!!! !! ! !! ! ! !! ! ! ! ! ! ! ! ! ! !! !! ! ! ! !! ! !! ! ! !! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! !! ! ! !!! ! ! ! ! !! ! ! ! ! ! !! ! ! !! ! !! ! ! ! ! ! ! ! ! ! ! !!!!! !! !! ! !! !! ! !! ! !! !! ! !!!! ! !! ! ! !! ! !! ! ! ! ! !! ! !! !! !! !! ! !! ! ! ! ! !!! ! !! ! ! ! ! ! !! ! ! Mbuyuni !!! ! ! ! ! !!! !! ! ! ! ! ! ! !! ! ! !! ! ! ! ! ! !! ! !! ! !! !! !! ! ! !!!!! ! ! ! ! ! ! !!!! ! ! ! ! ! ! ! ! !!! ! ! !! ! ! !! ! ! ! !! ! ! !!!! ! !!! ! ! ! ! ! ! ! ! ! ! ! !!! !! ! ! ! ! !!! ! !!! ! !! ! ! ! ! ! ! ! !! ! ! !! ! !! ! ! ! ! !!! ! ! ! ! !! ! ! ! !! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! !! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! !! ! ! ! ! ! ! !!!! ! ! ! !! ! ! !! !! !! ! ! !! ! ! ! ! ! !!! ! ! ! !! ! ! ! ! ! ! ! !! ! ! ! ! !! !!! ! !! !! !! !! !!! ! !! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! !!! ! ! ! !! !! ! ! !!!! !! ! ! !! !!! ! !! ! !! ! !!! ! !! ! !! ! ! ! !! ! ! !! !! !! !! ! !! ! ! !! ! ! ! !!! ! ! ! !! !! ! ! ! !! !! ! ! ! ! !! ! ! ! ! ! ! !! ! !! ! !!!! !! ! ! ! !! ! ! ! ! !! ! !! ! ! !! ! !! ! Mtambani A !! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! !! ! ! ! ! !! ! !! ! ! ! ! ! ! ! !!!!! !! ! ! Msimbazi Bondeni ! !! !! ! !!! !! !! !!! ! ! ! ! !! ! ! ! !! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! !! !! ! ! ! !! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! !! ! ! !!! !! ! ! ! ! !!! ! ! ! ! !! ! !! ! !! !! ! ! ! !! ! ! ! ! ! !!! !! ! ! ! ! ! ! !! ! !! !!!! !! ! ! !!! ! !! ! ! ! !! ! ! ! ! ! ! ! !! !! ! ! ! ! ! ! !! !! ! !! ! !!! ! ! !! !! ! ! ! ! !! ! ! ! !! ! ! ! ! !!! !! !!! ! !!! ! !! !! !! ! ! ! ! !!! ! ! ! ! ! !! ! !!!! ! ! ! !! ! ! ! ! !! ! !! !! ! !! ! ! ! ! ! ! !!! ! !! ! !!!! ! ! ! ! !! !! ! ! ! ! ! ! !!! ! ! ! ! ! !! ! ! ! ! !! !! ! ! !!! !! ! ! ! ! ! ! !!! !! ! ! ! ! ! !! !!!! ! !!! ! !!!! !!!!!! ! ! ! !! ! ! ! ! !! !! !!! ! ! ! ! ! ! ! !! ! !! ! ! ! ! ! !! ! ! !! ! ! ! ! ! ! ! !!! ! !! !! !! ! !!! ! ! ! !! ! ! ! ! !! !! ! ! ! !! ! ! ! ! !!! !! !!! !!! !! ! !! ! ! ! !! ! ! ! ! ! ! ! ! ! !! ! !! ! ! ! !! !! ! ! !!! ! !! !! ! ! ! ! ! !! !! ! !! !! !! !! !!! ! !! ! ! ! ! !! !! !!! !! ! !! ! ! !! ! ! ! !!! ! ! ! ! ! ! ! ! ! ! !! ! ! !! ! !! ! ! ! ! !! ! !! ! !! ! !!!! ! !!! ! ! ! ! !! !!! ! ! !! ! !!! ! ! ! ! ! ! ! !!! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! !! ! ! ! !!!! ! ! ! !!! ! ! ! ! ! ! ! ! ! ! ! ! ! Kariakoo Kaskazini !! ! !! !!! ! !! !!!! ! ! ! ! !! !! ! ! !! ! ! !!! ! ! ! !! ! ! ! !! ! !! !! ! ! ! ! ! ! ! !! ! ! ! ! !!! ! ! ! ! !! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! !! ! !! ! !! ! !! ! ! ! ! ! ! ! ! !! ! !! ! ! ! !! ! ! !! !! ! ! ! ! !!! ! ! ! ! ! ! !! ! ! Kariakoo Mag ! ! ! ! Mission Quarter 0 200 400 800 m ! ! Ilala Kota Kisiwani North Shariff Shamba ! Figure 8: Community vulnerability and resilience map of subwards Suna, Ilala Kota, Mtambani A, Mbuyuni and Msimbazi Bondeni (Source: Ramani Huria project by Humantarian OpenStreetMap Team) Mkunguni B Bridges: Mwinjuma 1 Selander Bridge - Crossing Msimbazi River Sinz 1. 2 Mkwajuni Bridge - Crossing Sinza River a 3 Jangwani Bridge - Crossing Msimbazi River Ri 4 Old Kigogo Road Bridge - Crossing Msimbazi River ve r Sea View Mkunguni A 5 Madaba Road Bridge - Crossing Kibangu Tributary 6 Kawawa Road Bridge - Crossing Msimbazi River 2. Hananasif 7 Kawawa Road Bridge - Crossing Kibangu Tributary Kitonga Makuti 'A' Charambe Assets: A A Muhimbili Hospital r ive B BRT Bus Depot iR Sunna Idrisa C Jangwani Playing Grounds baz Dossi D Young African Grounds im Ms E Primary School F Gilman Rutihinda Primary School Idrissa 3. G Cement Depot and Mixing Industry H Fire H BRT Bus Stop Jangwani Mtambani Mwinyimkuu B fu Kibangu R C iver Mtambani Ukombozi 5. D Mbuyuni E F Mtambani A Msimbazi Bondeni 6. 4. G Kariakoo Kaskazini North Mission Quarter 0 300 600 1200 m Ilala Kota Figure 9: Map with main infrastructure and assets exposed to flooding in the Lower Basin 14 Flood Exposure in the Lower Basin Through the Charrette process, in combination with spatial analysis and numerical flood simulations, it became evident that the main vulnerabilities in the Lower Basin are: 1. Injuries and loss of lives, damage to houses and personal belongings, and interruptions in income earning activities (livelihood losses) as a result of flooding. The areas are characterized by unplanned and informal human settlements and small businesses that dwell in the flood plains and on the slopes of the river valleys; 2. Damage to infrastructure assets and interruptions in urban mobility because of flooding of bridges crossing the river valley and public infrastructure built in the flood plain [39]; 3. Damage to ecosystem-services and loss of biodiversity because sediments transported by the floods deposit in the mangrove forest and the natural wetlands of the Lower Basin. About 5% of the buildings in the Msimbazi Lower Basin are vulnerable in the sense that they have experienced riverine flooding at least once since 2011. The illustration (Figure 7) shows a maximum flood extent based on surveys conducted by Ramani Huria4 with the highest percentage of flooded households in the subwards of Suna, Ilala Kota, Mtambani A, Mbuyuni and Msimbazi Bondeni, ranging from 22% to 63%. In the Lower Basin, the Jangwani Bridge on Morogoro Road is the most vulnerable bridge to flooding. During extreme events the bridge and the road are often flooded, sometimes lasting for days after the peak. This interrupts transport and mobility as the main connections between Dar es Salaam’s City Centre and the city’s outskirts are cut. Other vulnerable assets are the Dar es Salaam Area Rapid Transit bus depot and Ali Hassan Mwinyi Road, which crosses the Msimbazi at Selander Bridge. Muhimbili National Hospital is located on higher ground, which on the edge of the river’s flood plain, but the property’s steep embankment has experienced severe erosion, which threatens some of the hospital’s facilities (Figure 8). 4 www.ramanihuria.org: Ramani Huria is a community- based mapping project in Dar es Salaam Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 15 16 1.4 This document sets out the Detailed Plan for the Lower Basin and presents the implementation steps that can be undertaken on the basis of the Msimbazi Charrette. The concepts for initiating the preparation of tendering engineering designs are subject of this Volume B. The Detailed Plan for the Lower Basin is structured as follows: 1. Introduction including Situation Analysis Report 2. 3. Concept The Detailed Plan contents 4. The Path Forward Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 17 Volume B: Detailed Plan for the Lower Basin Concept 2 The Msimbazi Opportunity Figure 10: The focus in the Lower Basin focus is on storm water conveyance. Figure 11: Principle of implementing conveyance interventions working from down to upstream 20 Enhance Conveyance: Start from the Ocean Extensive discussions in the Charrettes on how best to reduce flooding and protect against floods in the wider Msimbazi Basin, combined with expert judgement, produced two main principles which should shape interventions in the Detailed Plan area: 2.1 • Interventions in the Lower Basin should focus on storm water conveyance Design In the Lower Basin, interventions need to increase water conveyance during periods Principles of heavy rains (Figure 10). This contrasts with problems further upstream, where water retention may be an issue. • Interventions should be implemented sequentially from down to upstream By initiating interventions starting at the lowest point in the basin near the outlet to the Indian Ocean (Figure 11), interventions can be tackled structurally without leaving bottlenecks in the river profile that hamper the conveyance behind downstream. Scientifically Informed Flood Modelling The foundation of the Detailed Plan for the Lower Basin is based on flood hazard reduction interventions that have been identified and tested in a flood model. The flood modelling shows (Figure 12) that a cluster of three major interventions have the potential to significantly reduce the duration and inundation depths of the floods that are caused by peak rainfall in normal circumstances (T1yr – T10yr events): A. Dredging Msimbazi river from Selander Bridge to Jangwani Bridge to widen and deepen it B. Raising and widening the Jangwani Bridge C. Dredging to widen the river from Jangwani to the confluence with Kibangu River According to the models, many areas in the Lower Basin that now experience flooding will remain dry or have short and shallow inundation levels (0-30 cm) when these three interventions have been implemented. The model, however, also shows that in case of more severe rainfall as in 2011 (classified as a T100yr event; Figure 13), the proposed flood hazard reduction interventions are not sufficient to provide adequate safety levels. The outcome of the modelling exercise is that room for the river to overflow is required to ensure a safe situation during high water levels. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 21 Flood depths at 12 hours of the existing situation Flood depths at 24 hours of the existing situation Flood depths at 36 hours of the existing situation Flood depths at 12 hours with intervention A+B+C Flood depths at 24 hours with intervention A+B+C Flood depths at 36 hours with intervention A+B+C 2 1.8 1.6 This location remains dry. Main Flooddepthin[m] 1.4 1.2 contribution to the hazard reduction 1 0.8 is the widened and deepened 0.6 0.4 channel between Selander Bridge 0.2 0 and Jangwani Bridge. Ͳ0.2 0 10 20 30 40 50 60 70 80 Timeinhours Maximum flood depths at location Hananasif in the flood plain 2 1.8 1.6 This location remains dry. Main Flooddepthin[m] 1.4 1.2 1 contribution to the hazard reduction 0.8 0.6 is the widened and raised Jangwani 0.4 0.2 Bridge. 0 Ͳ0.2 0 10 20 30 40 50 60 70 80 Timeinhours Maximum flood depths at location upstream of Jangwani Bridge at Sunna 2 1.8 At this location a very low level 1.6 and short time of flood inundation Flooddepthin[m] 1.4 1.2 1 remains. Main contribution to the 0.8 0.6 hazard reduction is the widened 0.4 0.2 river channel between Jangwani 0 Ͳ0.2 0 10 20 30 40 50 60 70 80 Bridge and the confluence of the Timeinhours 00 Basecase 02 Intervention A PORALG 03 Intervention A+B PORALG04 Intervention A+B+C Kibangu and Msimbazi River. 00 Basecase 02 Intervention A 03 Intervention A+B 04 Intervention A+B+C 3 0.3m flood depth 0.9 m flood 0.3m flood depth depth 0.9m  flood depth mflood 1.81.8  depth m flood  depth Maximum flood depths at location downstream of Jangwani Bridge 22 Modelling results of T10yr in Exisiting Situation compared to Intervention A+B+C Flood depths at 48 hours of the existing situation Flood depths at 60 hours of the existing situation Flood depths at 72 hours of the existing situation Flood depth (m) N 0 250 500 1000 meters Flood depths at 48 hours with intervention A+B+C Flood depths at 60 hours with intervention A+B+C Flood depths at 72 hours with intervention A+B+C Intervention A, B and C - ! Rainfall return period T10 yr Intervention A, B and C significantly reduce the hazardous conditions in the detailed plan area. Morogoro Road and Jangwani Bridge do not ! overflow and some areas in the lower ! section of the Lower Basin remain dry throughout the event. However, the upper section inundates rapidly as the hydraulic capacity underneath Jangwani Bridge is still not sufficient. Also, the Jangwani Playing Grounds remains inundated for long periods after the peaks as the area is not well drained and works as a ‘bathtub’. depth (m) in Flooddepth Flood [m] 0 0 - 0.3 ¸ 0.3 - 0.9 0 250 500 1,000 Meters 0.9 - 1.8 > 1.8 Figure 12: Intervention A, B and C - Rainfall return period T10yr © OpenStreetMap (and) contributors, CC-BY-SA Maximum flood depth in 72 hours of the T10 event Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 23 Flood depths at 12 hours of T10yr event Flood depths at 24 hours of T10yr event Flood depths at 36 hours of T10yr event Flood depths at 12 hours of T100yr event Flood depths at 24 hours of T100yr event Flood depths at 36 hours of T100yr event 2 1.8 1.6 Compared to the T10yr conditions this 1.4 location gets inundated for a period of Flooddepthin[m] 1.2 1 about 5 hours during/right after the rain 0.8 0.6 peak with a maximum inundation depth 0.4 0.2 of about 70cm. 0 Ͳ0.2 0 10 20 30 40 50 60 70 80 Timeinhours PORALG Maximum flood depths downstream of Jangwani Bridge at Suna 2 1.8 Compared to the T10yr conditions this 1.6 1.4 location gets inundated for a period of Flooddepthin[m] 1.2 about 10 hours during/right after the 1 0.8 rain peak with a maximum inundation 0.6 0.4 depth of 1 meter. 0.2 0 Ͳ0.2 0 10 20 30 40 50 60 70 80 Timeinhours PORALG Maximum flood depths upstream of Jangwani Bridge 2 1.5 Confluence of Kibangu and Msimbazi Flooddepthin[m] 1 Rivers– Clearly visible that inundation 0.5 period is longer (starts earlier) and the 0 inundation peaks are higher. 0 10 20 30 40 50 60 70 80 Ͳ0.5 Timeinhours PORALG PORALG 3  depth 04 Intervention A+B+C(T10yr) InterventionA+B+C(T100yr) 0.3m flood depth 0.9m flood flooddepth 1.8m flood 04 Intervention A+B+C(T10yr) InterventionA+B+C(T100yr) 0.3m flood depth 0.9m flood flooddepth 3  depth 1.8m flood Maximum flood depths at confluence of Kibangu and Msimbazi Rivers 24 Modelling results with Interventions A+B+C in T10yr compared with T100yr Flood depths at 48 hours of T10yr event Flood depths at 60 hours of T10yr event Flood depths at 72 hours of T10yr event Flood depth (m) N 0 250 500 1000 meters Flood depths at 48 hours of T100yr event Flood depths at 60 hours of T100yr event Flood depths at 72 hours of T100yr event Intervention A, B and C - Rainfall return period T100yr As the rainfall in this modelled scenario is much higher, flooding conditions are worse. The mitigating effect of the interventions is still ! observable, but almost the entire ! floodplain in both the lower and the upper section of the Detailed Plan area is inundated. ! Flood depth (m) in Flooddepth [m] 0 0 - 0.3 ¸ 0.3 - 0.9 0 250 500 1,000 Meters 0.9 - 1.8 > 1.8 Figure 13: Intervention A, B and C - Rainfall return period T100yr © OpenStreetMap (and) contributors, CC-BY-SA Maximum flood depth in 72 hours of the T100yr event Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 25 Convey, Guide & Protect and Use + + Convey the water out of Guide the water out and Integrate suitable functions the Lower Basin protect the edges according river function Figure 14: Guiding principles for designing the Lower Basin 26 Room for the River and Wetlands Full protection of all people and assets at their current location is socially and economically unfeasible. In the Lower Basin ‘making room for the river and its wetlands’ should be embraced. When alternatives were discussed for the Detailed Plan layout, the Wetland Park (Figure 5) was selected as a base for further development of the plan as well as to provide flood safety. In order to enable safe urban development within the boundaries of the Special Planning Area, terraced reshaping of the floodplain is proposed as a complementary protection intervention. In this way the natural function of the floodplain is respected, large amounts of water can be conveyed downstream during a flood, and still people and urban functions have safe areas to occupy. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 27 a b c Figure 15: Concept of the terraces: At location where currently floods occure (a) cut and fill of dredged material from the river channel capital dredging and maintenance is used to build the terraces (b) with safe locations for new urban areas (c). The Resilient Integration Communities Principle Flood Waste Reduction Management Interventions “Focus on getting people out of harmsway.” “Technical measures Water to protect people and Mangrove assets.” & Forest & Sanitation Interventions in the basin in- Wetlands Land tegrate all aspects and make “Reshaping the basin flood the basin a pleasant place with Use room for the river, new safe plain to achieve a place for human activities.” Planning edges and additional uses of the space when the water level in the river is low Figure 16: Integration of a wide range of aspects Integration of land use for urban functions with the improvements of flood safety is needed to use potential opportunities of this valuable central location in the city. The Integration Principle of topics such as flood safety, housing, ecosystem-services, utilities for water, waste water and solid waste services offers the best range of possibilities to transform the area from a liability to an asset for Dar es Salaam as a resilient city. 28 Elevated terraces A long list of current and desired functions to be established in the Lower Basin was made during the Charrette process. To accommodate these urban functions, the excavated materials that are extracted when the river section is deepened and widened can also be used to make elevated areas along selected valley edges (Figure 15). While scientific testing is still required, 2.2 these terraces could be constructed using sediment materials up to 1 meter higher than Integrate floodplain level, while the second terrace level would be up to 2-3 meters higher than the floodplain level. The second terrace would seek to ensure flood safety considering T100yr Functions events. A safe margin needs to be taken into account because of increased rainfall intensities in the future as result of climate change. The two terraces will guide high water levels, protect areas from floods and offer safe space for community functions. Initial findings from associated studies on the Msimbazi River sediment characteristics5, indicate that the quality of the material that becomes available from the floodplains and river channels, consisting for larger parts of silt and sand, is sufficient to serve as fill material for stable terrace formation. Urban development potential at the edges The terraces create room for a mixed use city park that includes urban redevelopment at the highest flood safe levels. This new dry land offers sufficient scope for compensation and resettlement of the vulnerable communities who will have to relocate for flood protection reasons. Attempts in the past to relocate residents of the unplanned, informal and flood prone areas to the outskirts of Dar es Salaam had limited success given a lack of consideration to social context and opportunities for business, and considering livelihood in the central city context. In this regenerated space of the Lower Basin, a mix of (low cost) social housing, middle class categories and commercial activities is one of the business cases which can support the feasibility of the program and can offer some relief on the urgent need for housing for the increasing population of Dar es Salaam. 5 Aide Memoire by World Bank Technical Mission April 30 – May 4 2018 – Role of morphological (sediment deposition and erosion) processes in the Msimbazi River and the World Bank Technical Mission June 27 to July 5 2018 – Geomorphological Assessment for City of Dar es Salaam Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 29 Volume B: Detailed Plan for the Lower Basin Detailed Plan 3 The Msimbazi Opportunity 32 3.1.1 Land Use Map 3.1 The land use map of the Detailed Plan defines the principle structure given to the area. The concept of room for the river and wetlands can be seen by the areas of green that form the floodplain, wetland park, mangroves and recreation city park (Figure 17). At the edges are residential and mixed use The Overall areas, each with their own function, which will be further described in this chapter. Plan  N 0 50 100 150 200 250 500 meter Figure 17: Landuse map Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 33 34 3.1.2 Illustrative Design The illustrative plan provides a design that shows the future potential of the Msimbazi City Park. Recognizable elements such as housing blocks around the edges, footpaths crossing the park and the sports fields at the southern end, demonstrate the scale of the area and the size of the ‘green lung’ for the rapidly urbanizing and densifying city of Dar es Salaam.                      N 0 50 100 150 200 250 500 meter Figure 18: Illustrative design map Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 35 3.1.3 Overall Impression This overall impression highlights the main elements of the plan for the City Park. Starting from the left side the image shows the proposed new Selander Bridge at the ocean and the potential wastewater treatment plant just outside the project boundary. The mangrove forest has been extended further from the existing Selander Bridge and stretches past the new Hananasif Bridge. Approaching the confluence of Sinza River with the Msimbazi River, the wetlands stretch from edge to edge of the valley. Southeast from the raised and widened Jangwani Bridge, the core of the public park is situated with various leisure functions including sport fields, footpaths and an amphitheatre. New urban edges of the park are created at the safe level of the second terrace. The orange blocks in the impression visualize the new urban development that can take place within the boundaries of the Msimbazi Special Planning Area. Figure 19: Overall impression 36 N Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 37 3.1.4 Bird’s Eye View Figure 20: Bird’s eye view impression over the core of the City Park 38 N Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 39 40 3.2 3.2.1 Facet map of the River and Flood Plain In this plan the Msimbazi River is given room in the Lower Basin to respond to severe peaks of water that it transports from the upper catchment to the ocean. In order for this objective to be River realized, a set of interventions is required and sufficient space in the floodplain must be unobstructed to deal with the peak flows. In the Facet map (Figure 21) of river and floodplain, the location of the current central stream is identified. The light blue area shows a proposed new wider and deeper channel, created by a dredging intervention, and the light green shows the floodplain at the level of the valley floor that could be enhanced as wetland space. N 0 50 100 150 200 250 500 meter Figure 21.: Facet map of the river and flood plain Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 41 Figure 22: Current aerial view over the Msimbazi southward toward Jangwani Bridge and the bus depot (top) Figure 23: Aerial view with an illustration of the widening and deepening of the river channel 42 3.2.2 Sections of the River During the Charrette process different types of potential flood hazard reduction interventions and flood protection interventions were identified. To reduce vulnerability for people and assets two types of interventions are considered: • Flood hazard reduction: Reducing river hazards like water levels, inundation depth and inundation period by adjusting the river dynamics. • Flood protection: Making sure that people and assets are kept dry according to predetermined safety levels. Based on analysis of available information, site studies and results of the flood modelling simulation, a series of interventions have been conceptualized for the Lower Basin including: • Intervention A – Dredging the river channels between Selander Bridge and Jangwani Bridge • Intervention B – Widening and raising Jangwani Bridge • Intervention C – Dredging the river channel from Jangwani Bridge upstream Figure 24: Flood Intervention A: Figure 25: Flood Intervention B: Figure 26: Flood Intervention C: Dredging a wider and deeper channel between Widening and raising Jangwani Bridge Dredging a Wider Channel from Jangwani further Jangwani Bridge and Selander Bridge. upstream. These interventions align with the design principles of the Detailed Plan, namely to focus on storm water conveyance and implementing interventions from downstream towards upstream. As Interventions A and C both concern river channel interventions, they will be discussed together first because they are linked, consist of the same type of work, and preparation for implementation can also be undertaken in parallel. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 43 Figure 27: Sedimentation in the Lower Basin near Muhimbili National Figure 28: Sedimentation layer of more then 2 meters on top of Hospital original soil in the lower basin area Existing bathymetric and topographic level Intervention A: ID 1 - Dredging channel in Lower Basin 1V:6H 1V:6H High Tide MSL Depth according to thalweg design Low Tide Dredge level 25 m Figure 29: Flood Intervention A: Dredging a wider and deeper channel between Jangwani Bridge and Selander Bridge will reduce backwater effect in this area by increasing discharge rates into the ocean Intervention C: ID 5 - Dredging from Jangwani further upstream 1V:6H Existing bathymetric and 1V:6H 1V:6H 1m 20 m topographic level Depth according to thalweg design Dredge level 10 m ID 1 and ID 5 are not drawn in proportion, ID 4 is drawn in proportion (vertical/horizontal) Figure 30: Flood Intervention C: Dredging a wider channel from Jangwani Bridge further upstream will increase the hydraulic capacity from Morogoro Road further upstream 44 Intervention A The sediment deposition that has taken place between Selander Bridge and Jangwani Bridge strongly hampers the natural flow of the Msimbazi. This is particularly the case around the confluence of the Msimbazi and the Sinza Rivers, between Hananasif and Muhimbilli National Hospital (Figure 27). At these locations the river ‘squeezes’ through the narrow remaining channels, causing strong backwaters that extend upstream. Intervention A seeks to increase the hydraulic capacity of the existing river channel courses in order to reduce the existing flood hazard. In general, it is preferable to limit dredging to widening rather than deepening, as deepening channels can lower groundwater levels and have negative effects on water flows during the dry season. However, given that the sedimentation has occurred quite rapidly, accumulating several meters over a period of ten to twenty years, the plan proposes to restore the river to an earlier state of equilibrium by combining some deepening with widening the channel so that the river maintains a constant gradient longitudinally. At the lowest part of the river section, flow is affected by the tidal regime and the channel depth seems sufficient, but present channels will be considerably enlarged, so lateral shifts may be necessary to divert flows to the centre of the floodplain and away from the banks. For instance, this will be required at Muhimbili National Hospital, where the river channel flows adjacent to the property borders of the hospital. The design (Figure 29) is made so that a major portion of the peak flood discharge can be accommodated by the enlarged channels. However, the channel width is not only designed to cater for peak discharge; it is important to have sufficient flow velocities during baseflow conditions as well (in combination with intertidal currents), to minimize sediment deposition. There must be a balance between providing sufficient conveyance capacity during flood flows, and providing sufficient flow velocities during baseflow, to retain the flushing effect and transport capacity of sediments to the ocean. Intervention C Upstream of Jangwani Bridge the gradient of the river increases and there is no longer the intertidal influence that characterizes the estuary. In this section of the river a ‘floodplain’ profile will be applied (Figure 30) focusing on dredging a wider profile with only minor deepening in selected parts, thereby avoiding potential effects on groundwater levels and water availability issues during the dry season. This profile consists of two levels; the main channel level and a slightly higher floodplain level (in the order of 0.5 to 1 meter). Immediately downstream of Jangwani Bridge the profile will be used to gradually guide the flow towards the more deeply incised mono-channel after the confluence with the Sinza River. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 45 Existing bathymetric and topographic level Intervention A: ID 1 - Dredging channel in Lower Basin 1V:6H 1V:6H High Tide MSL Depth according to thalweg design Low Tide Dredge level 25 m Figure 31: Increasing hydraulic capacity at Jangwani Bridge Figure 32: Bridge over river and flood plain with enforced abutment Figure 33: A simply supported bridge type construction with enough height for an underpass on the lowest terraces Figure 34: A 300 meter long simply supported bridge type is needed to convey the water out without obstacles in a T100yr event Figure 35: References for the new Jangwani Bridge on Morogoro Road with longer span and widened opening, connectivity for all traffic modes, and park environment under the bridge 46 3.2.3 The new Jangwani Bridge Intervention B Interventions associated with the Jangwani Bridge will have multiple benefits. The basecase flood simulations reported in Chapter 2.1 concluded that the hydraulic flow under Jangwani Bridge is insufficient. During maximum flood peak, the problems are two-fold: i) flooding over the bridge interrupts traffic on the bridge approach and Morogoro Road, one of the most important traffic arteries in Dar es Salaam, and ii) flooding of surrounding areas also affects vulnerable assets like the DART bus depot. The bridge structure itself blocks water flow and results in strong backwater effects between Jangwani Bridge and Kawawa Road Bridge. Thus, in that section of the Lower Basin it seems to aggravate floods of higher frequency but shorter duration which do not pass over the bridge. To mitigate this bottleneck, it is suggested that the bridge underpass be widened (in longitudinal direction of the road) and the bridge deck be raised (Figure 31). This will increase the area of cross sectional flow below the bridge and improve the hydraulic capacity. This intervention is aligned with the envisioned terraces, which are explained in the next section. The proposed approach is to construct a multi-span, simply supported bridge, with spans between the piers of about 15-25 meter and a total span between both bridge abutments of 300 meter. The proposed bridge would be modular, allowing reconstruction of the bridge to be stepped or phased independently from the construction of the terraces. Adopting this approach can mitigate flood risk at an earlier stage of the overall development of the Lower Basin. Figure 36: The new Jangwani bridge integrated in the landscape Figure 37: Principle for a simply supported bridge type design of the Msimbazi City Park Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 47 48 3.3.1 Facet map of the Terraces Using a cut and fill principle The basic principle of the terraces is to use the material that 3.3 becomes available from capital dredging of the river channel, floodplain and maintenance dredging and excavation6 works Terraces (cut), for the formation of elevated terraces (fill) (Figure 38). The terraces will be constructed in phases, and filled terrace sections will be protected against erosion immediately at the end of each construction phase. The underlying principle is to create space for the river, while reclaiming parts of the floodplain for the development of the proposed City Park. Figure 38: Concept of the terraces: Cut and fill of dredged material from the river channel capital dredging and maintenance to build the terraces Second level Terrace First level Terrace Flood plain N 6 0 50 100 150 200 250 meter Excavation is digging in the ground and dredging is removing soil in wet conditions. Figure 39: Facet map of terraces Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 49 Floodplain First terrace level Second terrace level Second terrace level Wetland area, Park occasionally Safe level for park Urban development regularly inundated exposed to flooding with sports, leisure and social amenities Figure 40: Typical section of the terraces for Msimbazi Lower Basin Figure 41: Location of the two levels of terraces 50 3.3.2 Section of the terraces Three Levels in the Lower Basin The terrace concept consists of a composition of terrain plains (formations) of which the elevations increase in a stepped manner from the river course to the valley edges. For the Lower Basin three levels are envisioned; i) the floodplain, ii) first terrace, and iii) second terrace. The floodplain is the area that can directly inundate when the river discharge increases and the riverbanks overflow. The floodplain will be a seasonal wetland area, which could be made accessible by boardwalks. The first terrace will be approximately 1 meter higher than the floodplain level. This terrace will be used for sports, leisure, agriculture (mainly suitable for coconut and tree plantations) and community gardening activities and will occasionally be exposed to flooding (during extreme floods with a low return frequency), but will remain dry during more regular floods (less extreme flood events with a higher return frequently). The second terrace will be safe from flooding for at least T100yr flood events, and will be approximately 1 meter higher than the first terrace, but can be up to 2 meters higher at locations where it may be required after calculations during technical detailed design. This terrace will be suitable for real estate, and would include mixed use including social housing, community amenities, more formal sports fields, and commercial real estate. Approximately 57 hectares of new and safe terraced land can be created which will provide ample space for mixed urban functions. Preliminary estimates indicate potential to develop 14,500 housing units. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 51 Figure 42: Dredging the river channel wider and deeper Figure 43: Current flood plain level and first raised terrace level 1 Figure 44: Raised terrace level 2 52 Figure 45: New river landscape with terraces. Situation with a modest raised water level where water stays within the new widened edges of the river channel Figure 46: New river landscape with terraces. Situation with a T10yr rain event where water levels inundate the flood plain Figure 47: New river landscape with terraces. Situation with a T100yr rain event where water levels will inundate the first terraces, but the second terrace stays dry Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 53 Figure 48: Currently the banks retreat due to undercutting of the Figure 49: The hidden-protection solution is covered by a layer of earth slope by the migrating channel of the re-aligned bank with flow resistant vegetation Figure 50: The hidden protection material covers the bank which is Figure 51: Example of a green Figure 52: Vetiver grass, with exposed to erosion and protects the slope close to endangered assets surface slope at a wetland area deep roots, will form a stable environmental conditon. inner slope pre-treatment outer slope of slope root zone Figure 53: Where reinforcement of the embankment is needed Figure 54: Example of construction of a layered embankment with geotextile can be used concrete mattresses, soil and grass, to further enable vegetation growth 54 3.3.3 Robust Design of Terraces Terrace edge protection A hidden protection (Figure 49) can be installed that acts as a back-up to prevent total erosion of the bank and damage to the highest riverbank level (Figure 48). The protection is placed at some distance from the bank line and from the important asset(s) to be protected. The hidden protection can be created by digging a V-shape into the terrain above the potential erosion level and filling it with riprap or recycled crushed concrete and bricks from buildings that have been removed as part of the resettlement process. The protection is then covered by a layer of soil and vegetation, and will be invisible until outflanking erosion exposes it. When the zone in front of the hidden protection is ‘consumed’, the riprap or crushed material functions as a back-up resistance to stop further erosion and effectively prolongs protection of the bank slope (Figure 50). As an alternative, critical assets can also be protected with semi-technical solutions, such as open concrete or geosynthetic elements that allow for vegetation to be grown through the openings (for example open block mattresses and geogrids). Such protections, however, require specialist design and precise installation. Geotechnical design aspects of the terraces Available information indicates that the river depositions (sedimentation) in the Lower Basin are mainly dominated by non-cohesive sands with a particle size <0.5mm 7. In view of the large sedimentation rates observed it is expected these sandy soils will be a large portion of the upper soil layers in the valley. Information about the other soil strata was only available for a very limited coverage of the area, but revealed that the soil conditions are very heterogeneous, consisting of three groups: A. Alluvial deposits: sand, clay, gravels and pebbles B. Coastal plain deposits: white buff sands and gravels with intercalated clay layers C. Deeper layers: weathered limestone For detailed design of the terrace formations, more geotechnical investigations are required to determine among other aspects the soil bearing capacity8 and settlement9. In order to do so, two geotechnical information components shall be considered: 1. Conditions of the in situ soil/subsoil which will be the base for the built up terraces where urban development is planned. 2. Characteristics of the soil that will be removed from the river channels and flood plain and subsequently placed on the planned terrace locations. 7 Aide Memoire by World Bank Technical Mission April 30 – Geotechnical information on the first component can be obtained through ground investigation May 4 2018 – Role of morph- methods like cone penetration tests (CPTs), standard penetration tests (SPTs) and boreholes ological (sediment deposition and erosion) processes in including associated interpretation analysis. Information on the second component can be the Msimbazi River and the retrieved through collection and analysis of soil samples from the locations where the material World Bank Technical Mission will be dredged (borrow areas). Important parameters of soil analysis are soil particle size, June 27 to July 5 2018 – Geomorphological Assessment distribution and cohesiveness. for City of Dar es Salaam. 8 To support the loads applied to the ground. 9 Consolidation of the subsoil after placement of the terrace. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 55 Section Measure Cut Fill Delta Lower Section Channel 240,000 Floodplain 326,625 First terrace 212,361 Second terrace - First Meter 245,286 57245 m2 Second terrace - Second Meter 245,286 38340 m2 Lower Section Total 566,625 702,933 136,308 16766 m2 Upper Section Channel 40,000 6660 m2 Floodplain 201,738 First terrace 193,107 33 m2 Second terrace - First Meter 640,320 653216 m2 Second terrace - Second Meter 640,320 Upper Section Total 241,738 1,473,747 1,232,009 Grand Total 808,363 2,176,680 - 1,368,317 99695 m2 Table 1: Indicative soil balance 136487 m2 134 m2 67665 m2 34787 m2 19840 m2 6198 m2 5251 m2 403342 m2 614281 m2 187856 m2 Special Planning Area Boundary CHANNEL: Intervention A ¸ CHANNEL: Intervention C TERRACES 0 50 100 meter 0 250 500 1,000 Meters Floodplain First terrace Second terrace Figure 55: Indicative soil balance map Figure 56: River Maintenance Depot in the flood plain at the confluence of Kibangu and Msimbazi Rivers 56 In order to establish room for the river, and in order to construct the terraces, the dredging/ excavation and replacement of soil works will take place over nearly the entire floodplain area. To assure that the geotechnical aspects of the terrace design are adapted to the soil conditions, it is important that the ground investigations cover the most significant borrow areas. Soil balance The soil balance of material that will be removed from the borrow areas, which are the river channels and the flood plain, against material that is needed to construct the terraces is presented in Figure 55. During the initial capital excavation/dredging works, it will not be possible to construct all terraces from the borrowed material. To finish all terraces, either material needs to be imported or the construction of the terraces needs to be phased, whereby river maintenance dredging and excavation volumes will be used to complete the remaining terraces. In the Lower Section, the cut and fill volumes are better balanced than the upper section, but the total amount of fill needed in the upper section is two times higher than that in the lower section. Stockpile and River Maintenance Depots In order to be able to handle the dredged material before using it to construct the terraces, materials might need to be stockpiled. This starts at the capital dredging stage, but will continue during the maintenance dredging of the river channel. Therefore two locations in the Lower Basin are incorporated in the Detailed Plan to provide for strategic functional locations to deal with the practical differences in amounts of cut and fill material during the operations. One location is situated south of the confluence of the Msimbazi and Sinza River. Here the first terrace guides the main channel of the Sinza River north to avoid the flow during flood events block the conveyance of the Msimbazi River. The River Maintance Depot is situated on the first terrace and its’ dikes help to guide the water in the right direction in extreme events. (Figure 56). The second location is located just southwest of the confluence of Kibangu River and the Msimbazi River. Locations will be made by an enclosed dike in which the sand volumes can be stored temporarily while protected for at least the period of a rainy season. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 57 Modelled The flood model simulations present the interventions that contribute to the final Detailed Plan. The various identified interventions were tested in a sequential manner, adding interventions from Interventions downstream to upstream. Iterations were needed to better understand the effects of the applied interventions and to optimise them to achieve satisfactory results. In total 12 model runs were performed with different compositions of interventions and different hydrological conditions applied. Ultimately, based on the modelling results in combination with the participatory design process, the following interventions have been applied to the detailed plan: • Intervention A – Dredging the river channels between Selander Bridge and Jangwani Bridge • Intervention B – Widening and raising Jangwani Bridge • Intervention C – Dredging the river channel from Jangwani Bridge upstream • Terraces Other modelled interventions were: • Bridge interventions to Kawawa Road Bridge • Opening/cleaning of culverts underneath Morogoro Road at the Jangwani Playing Grounds • Conceptualised upstream interventions 58 3.3.4 Modelling results of river, bridge and terrace interventions The interventions have been tested in the hydraulic model with 1-in-10 year (T10yr) and 1-in- 100 year (T100yr) rainfall conditions. The modelling results of the following situations are presented: (1) Intervention A+B+C – Rainfall return period T10yr (2) Intervention A+B+C – Rainfall return period T100yr (3) Terraces – Rainfall return period T10yr (4) Terraces – Rainfall return period T100yr For the scenarios in which the terraces are incorporated, Interventions A, B and C are also incorporated. However, Intervention B (widening and raising Jangwani Bridge) has been modelled differently for run (1) and (2) than run (3) and (4). For flood simulation runs (1) and (2) the Jangwani Bridge was adjusted with 50 meters additional bridge span (resulting in 100 meters bridge span in total), and the bridge deck was raised by 2 meters. For flood simulation runs (3) and (4) the bridge span was set to 300 meters, in order to; i) increase hydraulic capacity underneath the bridge even further, and ii) to align the bridge design with the terrace design. The main conclusion with respect to the terraces is that most of the first level terraces only get flooded during T100yr events, and do not reach inundation depths exceeding 1 meter, which aligns with the planned park and recreational functions. The second terrace therefore also remain dry during these extreme events, which supports the envisioned residential and commercial urban activities planned at this terrace. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 59 Flood depths at 12 hours of T10yr event Flood depths at 24 hours of T10yr event Flood depths at 36 hours of T10yr event Flood depths at 12 hours of T100yr event Flood depths at 24 hours of T100yr event Flood depths at 36 hours of T100yr event 2 1.5 Remains dry throughout T10yr event, Flooddepthin[m] 1 and is inundated for a couple of hours 0.5 with a maximum inundation depth of 0 50cm during T100yr event. 0 10 20 30 40 50 60 70 80 Ͳ0.5 Timeinhours PORALG Maximum flood depths at Mkunguni, first terrace level location 2 1.8 1.6 1.4 Flooddepthin[m] 1.2 This floodplain location gets inundated 1 0.8 in both events, with a maximum 0.6 0.4 inundation depth of 70cm for T10yr 0.2 0 and 150cm for T100yr. Ͳ0.2 0 10 20 30 40 50 60 70 80 Timeinhours PORALG Maximum flood depths downstream of Jangwani Bridge at Suna 2 1.8 1.6 1.4 Flooddepthin[m] 1.2 This floodplain location gets inundated 1 0.8 in both events, with a maximum inun- 0.6 0.4 dation depth of 50cm for T10yr and 0.2 0 120cm for T100yr. Ͳ0.2 0 10 20 30 40 50 60 70 80 Timeinhours PORALG Maximum flood depths Upstream of Jangwani Bridge 2 1.8 1.6 Remains dry throughout T10yr event, 1.4 Flooddepthin[m] 1.2 and is inundated for a couple of hours 1 0.8 with a maximum inundation depth of 0.6 0.4 20cm during T100yr event. 0.2 0 Ͳ0.2 0 10 20 30 40 50 60 70 80 Timeinhours PORALG 5 0.3 m flood depth 0.9m flood depth 1.8m flood depth 10 Terraces(T10yr) 11 Terraces(T100yr) 5 0 3 m flood depth 0 9 m flood depth 1 8 m flood depth 10 Terraces (T10yr) 11 Terraces (T100yr) Maximum flood depths at Msimbazi Bondeni, first terrace level location 60 Modelling results of situation with Terraces during T10yr and T100yr Flood depths at 48 hours of T10yr event Flood depths at 60 hours of T10yr event Flood depths at 72 hours of T10yr event Flood depth (m) N 0 250 500 1000 meters Flood depths at 48 hours of T100yr event Flood depths at 60 hours of T100yr event Flood depths at 72 hours of T100yr event ! Terraces – Rainfall return ! period T10yr and T100yr After the peak there is barely any areas anymore that remain inundated for a longer period, which means that ! the channel, floodplain and terrace formations convey the storm water to the ocean. The T10yr results ! show that most of the first level ! terraces (which are about 1 meter ! higher than the floodplains) remain dry throughout the event, whereas during the T100yr event the first level ! ! terraces get inundated. The second level terraces remain dry throughout ! both T10yr and T100yr events. Terraces Zones Flood depth (m) Flooddepth in [m] 0 0 - 0.3 ¸ 0.3 - 0.9 0 250 500 1,000 Meters 0.9 - 1.8 > 1.8 Figure 57: Terraces at T10yr and T100yr comparison Maximum flood depth in 72 hours of the T100yr event Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 61 62 3.4.1 Location Specific Elements This section offers a closer look at the various elements of the Detailed Plan. Elements of the core of the City Park, wet- lands and mangroves and the urban development areas are 3.4 highlighted and further explored. Within the scope of these Detailed elements many special places in the design can be found as illustrated on this map. Plan Elements Mangroves Mkunguni / Hananasif terraces with lower density residential development Hananasif terraces with medium density residential development Wetland park / confluence Sinza & Msimbazi river Park and sport facilities at terraces of Idrisa and Suna River maintenance depot Wetland with agricultural plantation New urban developement at terrace of Suna Wetland and Mangrove visitors centre New Jangwani Bridge Public Amphitheatre Mwinyimkuu Lower density residential developments Jangwani Lookout Hill (and potential BRT bus depot) Wetland park / confluence Kibangu & Msimbazi river Jangwani Playgrounds and Sportspark Central Market Place New mixed use higher density commercial development River maintenance depot Mbuyuni lower density residential development Boulevard and park Msimbazi Bondeni with mixed use higher denisty residential development N 0 50 100 150 200 250 500 meter Figure 58: Map with overview of various places in the Msimbazi City Park in the Lower Basin Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 63 Figure 59: Aerial view of exisiting situation at location section A (in Figure 60: Aerial view of exisiting situation at location section B opposite direction) Figure 61: Aerial view of exisiting situation at location section C Figure 62: Aerial view of exisiting situation at location section D 64 3.4.2 Cross sections The variety of spaces in the Detailed Plan are shown here by sections of the valley. The terraces concept with its various levels makes many uses and identities possible, depending on the time of year and amount of water in the basin, and gives the whole area a lively character. Some cross sections are examined more closely to assess the different opportunities. In this section four locations have been chosen to compare the existing with the proposed situation in sections of Mwinyimkuu to Msimbazi Bondeni (A), Mwinyimkuu to Mtambani A (B), Hananasif to Suna (C), Mkunguni B to Charambe (D). D C B A Figure 63: Overview map of cross sections Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 65 New Existing Figure 64: Section A: Mwinyimkuu to Msimbazi Bondeni in dry conditions; Between the two river streams of the Msimbazi and Kibangu Rivers a River Management Depot is created. On both sides of the flood plain terraces will create a new urban edge New Figure 65: Section A: Mwinyimkuu to Msimbazi Bondeni in flood conditions Existing 66 New Figure 66: Section B: Mwinyimkuu to Mtambani A in dry conditions; Terraces, park space with areas Existing that can inundate and areas that will stay dry and safe for new housing development. In the existing situaton the bus depot is situated in the middle of the flood plain and the Jangwani Playgrounds are the lowest point of the section New Figure 67: Section B: Mwinyimkuu to Mtambani A in flooded conditions Existing Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 67 New Existing Figure 68: Section C: Hananasif to Suna in dry conditions; The existing flat and lowest area in Suna is now partly abandoned. In the new situation part of this area will be raised with terraces New Existing Figure 69: Section C: Hananasif to Suna in flooded condition 68 New Figure 70: Section D: Mkunguni B to Charambe in dry conditions; Terraces at Mkunguni B side with a park edge lining the revitalized mangrove forest, public access from designated points, and defining the Existing edge between flood plain and secure dry edge with new housing New Figure 71: Section D: Mkunguni B to Charambe in flooded condition Existing Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 69 B D C 70 3.4.3 The core of the City Park The core of the City Park is the central area of the Lower Basin where most functions and activities for people are concentrated. It is envisioned as an accessible, wide green space that is well connected to the surrounding areas and urban fabric. The second terrace is much wider in this part than elsewhere in the basin. This additional space will not only provide for protection against floods and guidance of the river water, it will also offer a rich selection of desired community and urban functions. The core of the City Park does not have strict borders and will not be fenced off. The main access to the City Park is to the north on Morogoro Road. There is a large wetland area with paths leading farther north (towards the mangrove forest). To the East is the current line of formally planned buildings (A) in Mtambani. All existing streets will connect to a new boulevard (B) that borders the park and provides access to it. To the South a new urban neighbourhood will be developed at Msimbazi Bondeni. Here there will also be a new boulevard (C), a renewed Jangwani Road, that will be the border and main access to the park. The park continues toward Kawawa Road Bridge, but A becomes smaller and there tend to be fewer community and urban functions. To the West a natural boundary is made by the Msimbazi River (D). Although some crossings for pedestrians will be added, the park has a distinct character on its west side, which fits the individual neighbourhoods located here. Walking Walking Walking Sports Real Nature and wetland experience Sports, Playgrounds Estate Agricultural by-use Leisure Festivals Concerts Figure 72: Principle section of the levels of use in the Core of the City Park N 0 50 100 150 200 250 500 meter Figure 73: Illustrative design for the Core of the City Park in the central area of the Lower Basin Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 71 The Central City Park Overview We Wetl tlan and d an Mang and Ma gro rove ve vis isit or o itor ent rs ce re tr e New Ne Jang ngw w Jan wa a ani ni ridg ni Bri ge dg St Stag ge Stag Publ Pu blc A Publ Ammp ph ithe hit ea tre at Floo Fl plai ood pl ain ai n/w weetl t an etl pa nd p k ark F rs Firstt te t rr rrac ace leve e le l vel 72 Jang Ja ngwani wa Loo o ko kout ill ut Hil l Ja angwa ng Jang wan gwa nii Pla layg roun ygro ds und s Ol Jangwa Old Ja i roa w ni o d Ne Ma N wM ark rke et ace t Pla e Seco Se ond n ter erra er r ce vel e lev l M Ms mb sim ba azi Boule evaard va d rd New mixe Ne mixe mi xed us use ur urba urba ban de ban velo deve men lopm ent Figure 74: The Central City Park overview Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 73 Figure 75: Facet map of the three ground levels: floodplain (lightest green), first terraces (light green) and second terraces (dark green). Marked is the area seen as the Central City Park Figure 76: Special places with views over the water and wetlands Figure 77: Example of a formal and designed park at the highest are planned for at the flood plain level terraces along the newly developed urban edge Figure 78: Boulevard lined with trees along the road and the edges of the terraces Figure 79: The City Park is a park of trees where in most places a canopy provides shade 74 The Core of the City Park has functions on all elevated levels from floodplain wetlands to the highest terrace. The lower parts are less landscaped with fewer hard surfaces. With the exception of walkways, most is left as natural habitat. Additional explanation is provided on the planting and the typical pathways in the wetlands (paragraph 3.4.4). From a functional perspective it is important that the area is walkable and visitors can reach the riverside to enjoy the floodplain landscape. With benches or special spaces at the water level (Figure 76) the wilder, natural area of the central space in the park becomes an attractive asset, inviting people to walk from highest levels all the way down to the water’s edge. In contrast, the slopes of the highest terrace of the park will be more sophisticated with hard surface footpaths, special plantings and grass lawns (Figure 77). Formal designs will establish the quality of this part of the park as a central asset for the Mega-City of the future. This is also where the newly (to be) developed urban areas and the formal park edge will meet at a tree-lined boulevard (Figure 78). Trees are an important feature of the park, creating a green canopy that provides shade and cool spaces interspersed with open grass fields (Figure 79). In the central area the pathways are refined with good material, implementation detail and hard surface (Figure 80). Sports are key in the park, not only on the Jangwani Playgrounds, but also along the boulevard where there will be space for clubs and for public sports amenities, with green, tree-lined sports fields (Figure 81). The Amphitheatre is a special landscape that is terraced and shaped, large enough to hold thousands of people and the ideal spot for festivals, public gatherings and concerts (Figure 82). Figure 80: Examples of quality pedestrian path and bridge in the central part of the park Figure 81: Sport fields in a green framework of trees and part of the City Park Figure 82: The Amphitheatre and its stage for festivals and gatherings for all citizens Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 75 Figure 83: Facet map of the river and wetlands Figure 84: Facet map of potentially inundated areas and mangrove forest Figure 85: Variations in vegetation and footpaths to enjoy Figure 86: Example of an eco wetland park in the context of a city nature in town Figure 87: Rehabilitation of the wetland areas with typical wetland species like Matete, Papyrus and Water llilies, and wetlad grasses and reed. Figure 88: Palm tree plantations as agricultural supplement 76 3.4.4 Wetlands & Mangroves In the lowest areas of the Lower Basin are the wetlands, which are envisioned as a park space that includes the river channel and floodplains, and is part of the City Park (paragraph 3.4.3). A system of footpaths and footbridges will facilitate public access. In the downstream area of the wetlands some elevated paths could prolong periods of accessibility during periods when water covers ordinary footpaths. Such elevated paths, made of wood and lifted above the surface, could connect an entrance from Morogoro Road towards the mangroves. The wetlands will need to be shaped and maintained according to the river dredging and maintenance plan. An important function of the area is to allow for inundation with higher water levels without damage to its assets. The biodiversity and eco-services of the natural species in the wetlands also need to be enhanced, therefore supporting the integration of new planting areas. Regular maintenance within the wetlands will be required; the small natural pools and ponds and the flood plain surface can be supported by the recurrent dredging works. Figure 89: Principle section: Wetland Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 77 Figure 90: The mangroves will both extend upstream and Figure 91: A zoom-in of the mangrove area in the illustrative design map downstream: Upstream because salt water will come further into the valley again, downstream because the shallow bay is more protected against waves by the new Selander Bridge Figure 92: Clean and vital mangrove forest as an attraction to sail through by small boat or walk on a raised boardwalk through the tree canopy and experience nature in the heart of Dar es Salaam Figure 93: Boardwalks through the forest 78 The area reserved for the mangrove vegetation (forest) and for the saline wetlands can cover the major river plain area between Selander Bridge and Jangwani Bridge. Dredging a wider and deeper channel will remove some of the existing mangrove trees, but this will also allow the sea at high tide to penetrate further into the basin. This will improve the habitat for new young natural stands of mangrove trees upstream, resulting in an extension of the mangrove forest by natural regeneration. Downstream the forest can also expand if the protected area is extended to the ocean side of Selander Bridge, where the natural habitat is conducive for mangroves. Together with the wetland area, the mangrove forest can be an asset that attracts interest from visitors and becomes a must-see when coming to Dar es Salaam. A full grown, well maintained and clean environment is a prerequisite for such a development. Special attention therefore is needed in the implementation stage of restoration of the wetland area after the capital dredging and during the maintenance dredging works. Highly specialized expertise will be required to support preparation of implementation plans for physical works in and around the mangrove area. Figure 94: Visitors centre for eco-tourism in the city Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 79 80 3.4.5 Urban Development Areas The terraces create a safe level where new functions can be located without flood hazard. Some of those locations connect directly to the existing urban fabric. The second terrace creates an opportunity to make a new urban front towards the valley and the new City Park. These new urban development areas are divided into three categories: ● Residential development in lower density (3.4.5.1) ● Residential development in medium density (3.4.5.2) ● Mixed use development (in higher densities) (3.4.5.3) The residential categories have a subcategory of existing functions and buildings that can remain although they are situated within the boundary of the Special Planning Area. The map on the left shows that there are also valley edges that have no development or regeneration marked in the plan. All other non-park areas are intended to be redeveloped over time. Some of those areas will first need to be elevated by construction of the terraces. Other parts targeted as newly planned urban areas are already at a flood safe elevation but need redevelopment in order to align with surrounding neighbourhoods in terms of quality, services, streets or the typology of functions. Adjustments in these existing neighbourhoods might be needed in order to match and merge existing and new. Figure 95: Principle section: Urban Development Area In the following section the principles and guidelines are explained for the three different types of urban development areas. This includes the elements that will shape future Urban Development Detailed Precinct Plans in the next stages and the principles on which the proposed design must be based. N 0 50 100 150 200 250 meter Figure 96: Facet Map Urban Development Areas with the three different levels of urban development Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 81 From Lower Basin Detailed Plan to Urban Development Precinct Plans The Detailed Plan for the entire Lower Basin provides a broad vision for all development areas. More specific layout designs and development codes for building and public space are required for particular environments of the three typologies identified for the urban development zones. Prior to the roll-out of each new development area, an Urban Development Detailed Precinct Plan must be drawn up for that area and phase. The Precinct Plans must also indicate more detailed designs for street, block and plot levels. Precinct Plans must, at the minimum, address the following aspects: • Detailed street and block or plot layout • Detailed street profiles with (underground) infrastructure definition • Detailed urban design guidelines per street or block that address the relationship and interface between buildings, access, pedestrian movement and the relation between public environment and public spaces • Building typologies and volumes Figure 97: Examples of various housing typologies in existing urban neighbourhoods in Dar es Salaam 82 Implementation and enforcement of building code The Dar City Council Project Implementation Unit (PIU) for the Msimbazi Special Planning Area will require sustained technical assistance from PO-RALG and development partners to oversee the implementation and enforcement of this Detailed Plan, the Precinct Plans to be made for each urban development area, and the associated design codes . Before the physical implementation of each Precinct Plan the following designs must be in place: • Detailed specifications/designs for all streetscape elements (paving materials and street furniture, etc.). This will be done for the first Precinct Plan of each category and that will become the standard for similar category neighbourhoods. • Technical designs for individual public open spaces (streets, squares, parks, etc.) which incorporate all aspects applicable, such as engineering, urban, landscape and architecture. • Site development plans for individual plots addressing issues such as site layout, conceptual building design, conceptual site landscaping plans, arrangements with neighbouring properties in the block layout, and building plans for the construction of individual structures. Responsibility for the preparation of the plans/designs will vary. Some will have to be developed by the Msimbazi PIU (such as detailed specifications/designs for all streetscape elements), while others may be the responsibility of either the PIU, the responsible Municipality or individual developers (such as Precinct Development Plans and technical designs for individual public open spaces). Others, such as site development plans and building plans will solely be the responsibility of individual developers to prepare. All plans and designs must be then submitted to the PIU for approval before they may be submitted to the Municipality, or any other statutory local authority, in accordance with Tanzanian law. Density and degree of mix Density, building typology and the degree of mix of uses are important factors in how these areas can be developed. With the current rapid growth of Dar es Salaam, urban regeneration can only be realistic when at least medium density and mixed use are enhanced in development plans. Urban development should offer enough housing opportunities for the whole range of income groups within society. This is the guiding principle for the urban development areas within Lower Basin. The aim is to be efficient with space in order to house a significant number of people, to have adequate space for commercial uses, to accommodate traffic and to provide adequate parking. The goal is not simply maximizing the total square meters. All three categories of urban development defined in the plan are based on liveability and contextual principles. Realizing density increase in the built environment is an objective for each developer, but there is no square meter quota. Liveability and quality of space are as important as reaching an optimum in densities. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 83 4) 3) 2) Figure 98: Example urban design: Part of Mkuguni B; from bottom to 1) top: 1) Block layout with green and valley edge; 2) streets and parking; 3) commercial volumes; 4) residential volume 84 3.4.5.1 Lower density residential areas Figure 99: Location of example urban design Land use The proposed land use for some of the urban development areas at the edge of the valley basin and connected with the existing lower density is now mainly single storey and mostly informal/unplanned housing areas. The Detailed Plan proposes to change that for some areas in order to raise density, raise the provision of variety of typology of housing and offer new housing for people confronted with resettlement. In this paragraph the areas with the Lower Density Residential typology are explained. Street profiles All streets have a clear similar structure comprised of a central carriageway (6 meter wide), with parallel parking spaces (2 meter wide), and wide sidewalks on both sides of the street (2 meter wide). Small trees line both sides of the street, placed between the parking spaces. There is no parking on the streets at the edge of the park. Streets perpendicular to the park have an access footpath into the park. Main streets will also be lined with bicycle lanes to stimulate a multi-modal transport system and emphasize non-motorized transport for liveability. Bicycle paths may connect with main paths leading through the park. All streets will have public street lights on at least one side. The technical design of the Precinct Plan need to be informed by an underground infrastructure analysis on required leeway for sufficient storm water drains, sewerage, water supply, telecommunication cables and electricity. Division of Public and Private Space Public Private 32% 68% Figure 100: Bird’s eye view on an abstract model of the example layout Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 85 Figure 101: Example layout to test unit sizes and mix Figure 102: Aerial view from above the mangrove forest, overlooking the new Hananasif Bridge, the terrace edges and the new housing at Mkunguni B. The tower in the back is an existing apartment building 86 Building typology Building size Detached housing, duplex and small apartment buildings. and Density Building heights • Normal street blocks: - Minimum 2 storey / maximum 3 storey • Street block parallel to bridge: - 50%: Minimum 2 storey / maximum 3 storey - 50%: Minimum 3 storey / maximum 5 storey Floor Area Ratio7 • Minimum 0.58 • Maximum 0.89 Maximum footprint of the buildable area: 40% • 60% of the perimeter block is for green courtyard and alleys for pedestrians • Footprint of the ground floor will be used for - 8% retail and commercial use - 92% residential use Residential density • Average unit size: 40 m2 • Mix of housing typologies in the range of: - Bedsitters from 15 m2 - Studios from 25 m2 - 1 Bedroom houses and apartments from 30 m2 - 2 Bedroom houses and apartments from 60 m2 Range of number of units per ha: 145 - 210 Interface with the public realm Distance from the street boundary: • There should be a sidewalk directly along the façade to a maximum of 2 meter from the façade. Types of boundary barriers: • Hedges • Low wall (no higher than 0.75 meter from sidewalk level) Ground floor use: • Commercial uses should only be at the corners with consumer attractions, using maximum 8% of ground floor area. Openings on the front façade and architectural articulation11 of the front façade: • All commercial functions have doors at street level and need to be open/active at daytime. • Residential units on the ground floor should have windows large enough for actual visual contact with the street. Vehicular access to the property 10 FAR: gross floor area divided There is no parking in the buildings, or on private property, only in the parking spaces on the by buildable area streets. 11 Attractive side of the building Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 87 4) 3) 2) 1) Figure 103: Example urban design: Part of Suna; from bottom to top: 1) Block layout with green and valley edge; 2) streets and parking; 3) commercial volume; 4) residential volume 88 3.4.5.2 Medium density residential areas Figure 104: Location of example urban design Land use In this section the typology of the Medium Density Residential areas are explained. Some of these medium density residential developments are neighbouring existing urban areas characterized mainly by single storey, informal/unplanned housing. The difference in land-use needs to be bridged in the concrete design proposal for each location. Street profiles All streets have a clear similar structure. A central carriageway (6 meter wide), parallel parking spaces on both sides of the street (2 meter wide) and sidewalks (minimum 2 meter, maximum 5 meter wide) on both sides. All streets have trees of various sizes on both sides in between a series of parking spaces. At the edge of the park the street profile has no parking. There is a continuous sidewalk on the park side. The streets perpendicular to the park have an access footpath into the park. Main streets will also be lined with bicycle lanes in order to stimulate a multi-modal transport system and emphasize non-motorized transport for liveability. Bicycle paths may connect with main paths leading through the park. All streets will have public street lights on at least one side. The technical design of the precinct plan need to informed by an underground infrastructure analysis on required leeway for sufficient storm water drains, sewerage, water supply, telecommunication cables and electricity. Division of Public and Private Space Public Private 40% 60% Figure 105: Street profile principle Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 89 Figure 106: Example layout to test unit sizes and mix in a perimeter blok in Suna. From left to right: Buildable perimeter with unbuilt area in yellow; ground floor with commercial and residential; typical floor with residential layout of various units 90 Building typology Building size Apartments in small and larger buildings with a variety of sizes, layout and building and Density configurations and ground floor options of mixed use. Building heights Note: The 3 storey buildings are located border-ing the park sides • 25%: Minimum 3 storey/ maximum 3 storey and where a link with the existing • 40%: Minimum 3 storey/ maximum 4 storey lower buildings needs to be made. The maximum 4,5 and 8 • 25%: Minimum 3 storey/ maximum 5 storey storey buildings are arranged so • 10%: Minimum 3 storey/ maximum 8 storey that many apartments have the opportunity to overlook the park, have roof terraces and avoid Floor Area Ratio blocking neighbouring buildings. • Minimum 1.25 • Maximum 1.76 Maximum footprint of the buildable area: 70% • 30% of the buildable area should be used for courtyards, alleys and back alleys • Footprint of the ground floor will be used for: - 70% retail and commercial use - 30% residential use Residential density Note: Focus on the mix of typolo- gies should be in the range from • Average gross unit size: 55 m2 bedsitter to 1 bedroom apart- • Mix of housing typologies in the range of: ment for the socio-economic target groups in most of the - Bedsitters from 16 m2 Medium Density Residential ar- - Studios from 25 m2 eas identified in the plan. - 1 Bedroom apartments from 30 m2 - 2 Bedroom apartments from 60 m2 Range of number of units per ha: 190 - 270 Figure 107: Aerial view of the example of urban development of Suna. The section shows lower buildings near the existing housing and near the park edge, and higher buildings in the middle overlooking the park edge. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 91 Figure 108: Layered representation of a typical block tested on building heights, functions and position in the neigbourhood 92 Interface with the public realm Distance from the street boundary: • Sidewalk along the façade minimum width of 2 meter to maximum 5 meter from the façade. Types of boundary barriers • Façade is the boundary, when built at the plot boundary. • Some of the alleys to the courtyards can be closed off because of the privatized status of these spaces. In such cases the boundary barrier can be a wall or fence in between the building façades with a setback of 1 meter. Ground floor use: • Up to a maximum of 70% of the ground floor is for commercial use (small shops, workshops, social facilities, etc.). • The commercial spaces are located at the block corners and span to the middle section of the block. • Minimum of 30% is for residential use at ground floor. • The residential units on the ground floor are located in the centre of the block and span outwards to the commercial functions at the corners. Openings on the front façade and architectural articulation of the front façade: • All commercial functions have doors at street level and need to be open/active at daytime. • Residential units on the ground floor should have windows large enough for actual visual contact with the street. Vehicular access to the property Places for car parking are located on the streets around the perimeter block. No parking within the plot of the private domain between the buildings (alleys and courtyards) is allowed. When the amount of residential units for socio-economic target groups of which an increase in car ownership is expected, the parking facilities can be incorporated in the built volume at the ground floor, but not visible from the front façade. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 93 4) 3) 2) 1) Figure 109:: Example urban design: Part of Msimbazi Bondeni; from bottom to top: 1) Block layout with green, boulevard and valley edge; 2) streets and parking; 3) commercial volume; 4) residential volume 94 3.4.5.3 Higher Density Mixed Use areas Figure 110: Location of example urban design Land use The Higher Density Mixed Use development is neighbouring some existing urban areas characterized mainly by single storey housing. The difference in land-use need to be bridged in the concrete design proposal for each location. Therefore specific locations at the edge of the Higher Density Mixed Use area may require special modifications. For all other building activities the following set of guidelines apply. Street profiles The area has an internal street pattern with more or less identical street profiles characterized by a central carriageway (6 meter wide), parallel parking spaces on both sides (2 meter wide), and sidewalks on both sides(5 meter wide). All streets have large trees on both sides in between a series of parking spaces. At the park edge there is the special street profile of the Msimbazi Boulevard with a wider profile, as it will accommodate 2x2 lanes for car traffic (or public transport), parking only on the building side, a double row of trees, and a footpath at the park side. Main streets will also be lined with bicycle lanes in order to stimulate a multi-modal transport system and emphasize non-motorized transport for liveability. Bicycle paths may connect with main paths leading through the park.All streets will have public street lighting on both sides, and the Msimbazi Boulevard has extra lighting along the footpath on the park side. Division of Public and Private Space Public Private 55% 45% Figure 111: Street profile principle for the Msimbazi Boulevard (left) and for a typical street (right) Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 95 Figure 112: Example layout to test a mix of unit sizes in a perimeter block in Msimbazi Bondeni, the Mixed Use area. From bottom to top: Buildable perimeter with underground parking in yellow; ground floor with commercial, housing entrances and parking garage entrances; typical floor with residential layout of various units in the mix 96 Building typology Apartments and offices in larger building blocks and towers with a variety of sizes, layout and building configuration, but all on a plinth with commercial space. Building size and Density Building heights Note: The structure of the • Building blocks along the boulevard building blocks and the ability to vary in layout on the buildable - 20%: Minimum 5 storey / maximum 5 storey sites is equal for all, the building - 60%: Minimum 8 storey / maximum 10 storey blocks along the boulevard are simply higher to maximize the - 20%: Minimum 8 storey / maximum 20 storey built programme overlooking the • Building blocks (all behind the boulevard front) park. - 50%: Minimum 4 storey / maximum 5 storey - 25%: Minimum 4 storey / maximum 8 storey - 25%: Minimum 4 storey / maximum 10 storey Floor Area Ratio • Minimum 1.53 • Maximum 2.91 Maximum footprint of the buildable area: 80% • 20% of the buildable area should be used for courtyards, alleys and backalleys • Footprint of the ground floor will be used for: - 80% retail and commercial use - 20% entrances for residential and car park garages Residential density Note: The mix of typologies • Average gross unit size: 70 m2 should include 1 bedroom apart- ments to 3 bedroom apartments • Mix of housing typologies in the range of: for most of the higher density - Studios from 20 m2 mixed use areas identified in the plan. - 1 Bedroom apartments from 30 m2 - 2 Bedroom apartments from 60 m2 - 3 Bedroom apartments from 80 m2 Range of number of units per ha: 150 - 300 Figur 113: Aerial view from above the park seeing the example section of Msimbazi Bondeni in cross profile with higher blocks near the park edge overlooking the park Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 97 Figure 114: Layered representation of a typical block tested on building heights, functions and position in the neigbourhood 98 Interface with the public realm Distance from the street boundary: • Sidewalk along the façade (minimum width of 5 meter). Types of boundary barriers: • Façade is the boundary, when built at the plot boundary. • Some of the alleys to the courtyards can be closed off because of the privatized status of these spaces. In these cases the boundary barrier can be a wall or fence in between the building façades with a setback of 1 meter Ground floor use: • Up to a maximum of 80% of the ground floor is for commercial use (retail, shops, small shops, workshops, social facilities, restaurants, etc.). • The commercial spaces are the dominant factor and form the plinth of the building blocks. The only other functions on ground floor level are car park garage entrances, residential entrances and hallways. Openings on the front façade and architectural articulation of the front façade: • All commercial functions have doors at street level and need to be open/active during the day. The contact with the street of all these functions make it a vibrant city environment. • Offices, hotel or leisure functions, and residential upper storey façades are open and focused on the views. The high-rise building façades are consciously designed without glass in directions that receive too much direct sunlight, with shading constructions and cantilever terraces or balconies. • The buildings with car park solutions at the first floor and higher need to have a smart façade that allows natural ventilation, does not heat up the internal space or block the view. Vehicular access to the property The extent of square meters of development, the type of mixed use functions and the location in the city are all certain to attract car traffic and create the need for parking. Therefore a parking strategy is included which adds to the parking spaces in the street profiles of this area. • Parking garages below ground floor level are a possible measure or parking above the ground floor level from level 1 upwards. No parking at ground floor level. • An important quality aspect is that parking floors should not hinder other functions in the building or neighbouring buildings. • An estimated figure would be that 3% to 6% of the total gross floor area of perimeter block need to be for parking. This may vary due to the typology of housing, and the amount of retail and/or offices. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 99 Volume B: Detailed Plan for the Lower Basin Path Forward for the Lower Basin 4 The Msimbazi Opportunity 4.1 Implementing the Detailed Plan will require: 4.1.1. Resettlement 4.1.2. Channel opening 4.1.3. Bridge interventions 4.1.4. Implementation of terraces Immediate Actions 4.1.1 Resettlement 4.1.1.1 Resettlement The proposed interventions in the Detailed Plan area have implications for land owners, house owners, business owners and tenants. The number of Project Affected Households (PAHs) and small business that have to resettle is tentatively estimated at 3,00012. Resettlement is needed because the PAHs currently occupy areas identified as high risk by the flood modelling, and/or they occupy locations where new terraces will be constructed to create a safe zone for the city park functions. The PAHs will be eligible for compensation. Resettlement Action Plans (RAPs) for Project Affected Households/Persons, businesses and other asset categories are the main legal instruments to guide resettlement in Tanzania. The Strategy and Management Framework (Msimbazi Opportunity Plan, Volume A), contains a specific Resettlement Strategy developed by PO-RALG based on good international practices. Importantly, one of the features of this strategy is that the Resettlement Action Plans will include tailor made Livelihood Restoration Programs (LRPs) where needed. RAP The RAPs will offer the affected people (Household Heads), and business owners compensation different options: (i) replacement housing within the MSPA (high-rise buildings and/ or low-rise buildings); (ii) cash payment; (iii) in-kind compensation of land outside the options Msimbazi Basin, inclusive of community shared facilities like public services, water for Project points, playgrounds; and (iv) voluntary relocation with its associated negotiations on replacement rates and quantities. Affected Households Livelihood “The purpose of the LRP is to as much as possible restore livelihoods of the displaced and all those people affected to a level prior to their displacement or the start of the Restoration program or even enhance the livelihoods above that level. The LRP is not the same as Programs the compensation for lost properties and assets but goes well beyond the compensation to support livelihoods revival for those that have had this upheaval”10. 4.1.1.2 A staged approach It is proposed to align the resettlement implementation stages with the phased development of the terraces. For technical reasons, the engineering works will start downstream at Selander Bridge and work upstream. Detailed engineering will have to define the phasing with a likely time frame of a five-year work period. The first year of implementation could cover the area between Selander Bridge and Jangwani Bridge; and in the next four years the works would 12 See Msimbazi Opportunity, cover the area between Jangwani and the Kawawa Bridges. Volume A, SC № 6 13 PO-RALG, 2018 102 Over this period nine new terraces will be constructed; • Year 1: Mkunguni A; Mkunguni B, Hananasif/Kawawa Bridge, and Suna/Idrisa, • Year 2 to 5: Mwinyimkuu (2x), Msimbazi Bondeni, Mtambani, and Ilala Kota and in the upper section of the Lower Basin. This phasing is technically driven by the soil balance of the infrastructure works. It is foreseen that households will be resettled in the specific year that the works will affect their assets. 1. Land Acquisition: The terrace design for the Detailed Plan implies that all buildings on the river valley floor will have to be vacated; and all lands, if in private hands, Implement a- will need to be acquired by DCC or the Municipalities for the project. tion priorities Housing Development: The highest terraces will be developed for mixed housing. 2. The Detailed Plan provides for 14,500 apartments, including at least 2,000 as compensation for Households that need to resettle and choose to remain in the Lower Basin. 3. Resettlement: Only the PAHs displaced during the first engineering works, who opt for resettlement in the Lower Basin itself, will have to be resettled temporarily to another location until the first new terraces at Mkunguni A, B and Suna become available. The next group of PAHs from the larger areas upstream at Msimbazi Bondeni can be accommodated directly in apartments which are built on the first three new terraces. 4.1.1.3 Management and priority actions The actions outlined here are taken from Strategy Component №6 in Volume A, Chapter 3, where more detail is provided. Priority №1. Estimate the Resettlement Strategy cost and mobilize funding The PIU/DCC takes the lead on the resettlement action. The PIU, together with MLHHSD, physically mark the boundaries of the flood safe and unsafe zones within the boundaries of the MSPA and Lower Basin. PO-RALG defines the Resettlement Strategy principles applicable to the Msimbazi Special Planning Area; undertakes the surveys necessary in the Lower Basin to produce an informed estimate of the number of PAHs and the RAPs, and mobilizes necessary finance. Priority 2. Finalize the Resettlement Strategy and make the detailed plans PO-RALG engages the Charrette stakeholders team to design the Resettlement Action Plan content and implementation procedures, and determines the compensation options. . Priority 3. RAP/LRP preparation and community sensitization PO-RALG in consultation with DCC-PIU appoints a RAP/LRP development team, and implementation support facility. The team is available to make tailormade Livelihood Restoration Programs (LRPs) for the eligible households and/or businesses. Priority 4. RAP/LRP implementation The PIU gives RAP priority to people whose houses were demolished in 2015/16 and households most vulnerable to flood risk in 2018/2019 and 2019/2020. The next implementation steps follow the phased development of the terraces. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 103 4.1.2 Channel opening Establishing enhanced discharge capacity from the Lower Basin to the ocean by means of Intervention A and C is essential to reduce flood hazards (lower flood levels, shorter inundation periods). A balance needs to be struck between enhancing the discharge capacity of the lower basin into the ocean, and minimizing sedimentation after capital works. In this project the channels have been designed and tested numerically at a conceptual design level, but are subject to detailed design. The fundamental next step is to make detailed designs of these interventions in which channel characteristics like depth, gradient, width, side slopes are verified and optimized (Section 5.5). Figure 115: Flood Intervention A: Figure 116: Flood Intervention B: Figure 117: Flood Intervention C: Dredging a wider and deeper channel between Widening and raising Jangwani Bridge Dredging a wider channel from Jangwani Bridge Jangwani Bridge and Selander Bridge. further upstream. 4.1.3 Jangwani bridge intervention Based on the Charrette process, including the flood modelling that has been performed, it is strongly advised to construct a new bridge at Jangwani, Morogoro Road. This new bridge design needs to be aligned with the design of the dredging interventions, the overall Detailed Plan as well as the proposed future relocation of DART bus depot. An integral design that takes these aspects into account and anticipates the various development stages of the surrounding area is ultimately required. The new bridge should therefore provide both i) sufficient/acceptable hazard reduction with the DART bus depot in its current location, and ii) sufficient/acceptable hazard reduction when the DART depot is relocated, and the terraces are implemented. An intermediate measure, such as jacking up the existing bridge, would not make optimum use of financial resources and would ultimately not provide a sustainable solution for the bridge intervention and the integration with surrounding planned changes. 104 4.1.4 Implementation of terraces The phased construction of the terraces (Figure 5.1.4.1) should be integrated with the capital and maintenance dredging, and excavation works in the channel and the floodplain. Based on the soil balance, the capital dredging and excavation works would provide a large share of the total required fill material for the terraces in the lower section of the Detailed Plan area. In the upper section the soil balance shows a terrace volume fill deficit of over 1.2 million m3. This implies that for the upper section the terraces need to be filled over time, with soil that becomes available through maintenance dredging and captured in silt traps (Figure 112 for potential locations of silt traps) (Figure 111 for details on soil balance). Sediment traps and controlled sediment mining Maintenance dredging depots Figure 119: Potential locations to capture soil from sedimentation stream Figure 118: Soil balance map for two levels of terraces Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 105 4.2.1 Time 4.2 Construction should ideally be undertaken during the dry season (May – September) for all proposed interventions. Timing in the dry season is particularly important for implementation of Interventions A and C as works can be undertaken more efficiently and with less uncertainty Resources for around potential morphological change of the river. The terraces can also be filled during the Interventions dry season, anticipating enough time to protect terrace edges against erosion before the onset of the ensuing rainy season. Year 2019 2020 2021 2022 2023 2024 Quarter Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Intervention A Intervention B Intervention C Terraces lower section RS and RAP lower section Resettlement terrace Mkuguni B Resettlement rest of lower section Terraces upper section Resettlement upper section Surveys & Monitoring Detailed Design Interventions DRS and RAP Surveys and procurement Resettlement Monitoring Construction Interventions Table 2: Time line for implementation 106 4.2.2 Equipment to be deployed Within the Detailed Plan area, the dredging and excavation works can be done by a combination of excavators and small cutter suction dredgers. During construction of terraces, suitable logistics should be assessed for transporting the excavated/dredged material to the envisioned terrace locations, as different methods may be required for different terrace sites. When using cutter suction dredgers the material can be pumped directly to a stockpile or to the planned terrace locations. When using excavators, transport of excavated material can be done by dumper truck to locations where the material can be stocked, or directly dumped at terrace locations. These stockpiles/sand depots are indicated at two locations in the Lower Basin (Chapter 3.3.3 Robust design of terraces). An important consideration is whether the transport from the sand/silt depots takes place directly across the valley, over the valley floor, or transport takes place via existing roads to the neighbourhoods on top of the ridges. From the ridge, material could then be tipped into the valley. Consideration should be given in the technical detailed design stage if transport via water by barge may also be possible, requiring another re-handling step to offload the sand ashore. Among others, important evaluation criteria include: i) accessibility/bearing capacity of the flood plains, ii) transport and the costs of rehandling material, and iii) environmental and social impact. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 107 4.2.3 Financial outline An outline of the cost breakdown of the Detailed Plan is provided in Table 3 • The Lower Section has higher costs than the Upper Section, mainly because the Jangwani Bridge is included as part of the Lower Section interventions. • Without the Bridge intervention the lower section has lower costs than the Upper Section. • The initial available 20 million USD covers the main Bill of Quantity items (e.g. 1, 2, 3 and 4) of the Lower Section interventions, even when contingencies are included. Section Item Description Cost (USD) 1 Soil for Terraces 7,030,000 2 Rock for Erosion and Scour Protection 740,000 3 City Park Landscaping 3,360,000 4 Mangroves 700,000 Lower Section 5 Displacement & Resettlement 4,370,000 6 PIU - 2 years 1,000,000 7 Capacity Building, Studies, Advisors - 2 years 2,000,000 8 Rebuild Jangwani Bridge 25,000,000 Subtotal 44,200,000 Contingencies 40% on Items 1,2,3,4 4,732,000 Contingencies 25% on Item 8 6,250,000 Total Lower Section 55,182,000 9 Soil for Terraces 14,740,000 10 Rock for Erosion and Scour Protection 500,000 11 City Park Landscaping 7,700,000 Upper Section 12 Displacement & Resettlement 10,520,000 13 PIU continued - 4 years 2,000,000 14 Capacity Building, Studies, Advisors - 4 years 4,000,000 Subtotal 39,460,000 Contingencies 40% on Items 9,10,11 9,176,000 Total Upper Section 48,636,000 Total Detailed Plan Area 103,818,000 Other related 15 Reforestation for 10 years 10,000,000 costs 16 Sedimentation trap 500,000 Total Other related costs 10,500,000 Grand Total 114,318,000 Table 3: Outline costing of Detailed Plan 108 Real Estate Development in the Lower Basin The Urban Development guidelines present three bandwidths of total units per land use Indication category. The average of the three bandwidths is 160 to 260 units per hectare depending of potential on the level of maximizing the development potential. At the upper bandwidth the total urban development areas for regeneration and redevelopment as defined in the Lower Revenue Basin within the Special Planning Area boundaries is 57 ha. This would provide over and added 14,500 units across a range of typologies, sizes and places throughout the plan. Economic As benchmark for a calculation an average gross floor space of 60 m2 per unit for 14,500 Resources housing units could realize 870,000 m2 of additional housing in the Lower Basin. The current market compliant square meter price of 850 USD for an apartment in the City Centre leads to the estimate of nearly 740 million USD in potential revenues in housing development. As the area will also offer space for shops, malls, offices, and parking garages, this is only one part of the expected economic benefits. The land value of newly created urban area itself should also be considered. With 200 USD per m2 for prime urban locations in Dar es Salaam, the renewed 57 ha will represent an estimated value of 114 million USD. In the Lower Basin one can also expect real estate values in the surrounding areas to rise substantially. 4.2.4 Continuation of stakeholder and community participation and engagement Participation by many stakeholders has been key to arriving at the results of this Detailed Plan for the Lower Basin. This effort of collaborating to make a plan for an integrated approach for a complex urban challenge was a new approach for most of the participants. For some, it was uncomfortable at first, but eventually the process was embraced by all, from government officials to community members. This Detailed Plan could be seen as an end result of that process, however the messages that emerged during the last stages of the Charrette were clear: the top priority moving forward to the much needed implementation of the plan, was to continue the valuable stakeholder and community participation and engagement. Many participants have been very consistent in their attendance throughout the Charrette process. They have put in the effort to deliver content and develop knowledge together. In the final session many individual statements endorsed the plan and offered a personal vision on their further contribution (Volume C). The concrete nature of these statements resulted in an array of potential contributions for implementation stages. It is strongly recommended to use this body of knowledge and to continue to engage this group of ambassadors of the plan. They are the best insurance for ownership, quality and purpose of the interventions on the way to fully implementing the plan. Volume B: Det ailed Plan for the Lower Basin The Msimbazi Opportunity 109 The Msimbazi Opportunity Volume B: Detailed Plan for the Lower Basin