Project context and challenge
For more than a decade, the Msimbazi basin has been the part of Dar es Salaam hit hardest by flooding, almost every rainy season. Floods cost lives, destroy homes, interrupt traffic, leave behind silt and stagnant, contaminated water, and threaten the livelihoods of many residents.
In the middle basin, flooding has five main causes: river sections that are too narrow, bridges that block the flow and cause water to back up, poor urban drainage and solid waste management, the loss of green areas that once absorbed rainfall, and settlement in the natural floodplain. Without action, flood risk will grow substantially. By 2050, around 70% of the increase in flood hazard is expected to come from urbanisation and 30% from climate change.
Through the C40 Cities Finance Facility, which helps cities develop finance-ready climate projects, GIZ asked CDR to identify and assess flood management options for the middle basin, building on the Msimbazi Opportunity Plan.
CDR’s approach and contribution
CDR led the study together with WEMA and DASUDA. A vulnerability analysis identified four hotspots: the Kawawa Road Bridge, Kigogo ward, the industrial zone and the railway bridge. In online design charrettes, stakeholders helped select and prioritise measures, ranging from wider bridges and river channels to room for the river, resettlement and reforestation.
Sets of measures were tested in a flood model. Based on the results, CDR developed a flood management strategy with a short term component to 2026, focused on removing bottlenecks with wider or raised bridges, wider riverbeds and bank protection, and a long term component to 2050, making room for the river, regenerating urban areas to accommodate resettlement, and regreening the catchment.
An urban strategy, concept designs, a preliminary cost-benefit analysis, a preliminary environmental and social impact assessment and an analysis of institutional and funding options completed the feasibility study.
Result
The study delivered a phased flood management strategy for the Msimbazi middle basin. The short term measures prevent about 25% of flood damage, while the full long term strategy prevents around 75%, with major ecological and social benefits from regreening and planned urban development. In all climate and growth scenarios, the benefits outweigh the costs.
The strategy complements the investments in the lower valley and gives the city a clear basis for further preparation and funding.
