Mozambique

Upscaling nature-based flood protection in Mozambique’s cities: Cost-Benefit Analyses for Potential Nature-Based Solutions in Nacala and Quelimane (January 2020)

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EXECUTIVE SUMMARY

The Consultant conducted a cost-benefit analysis (CBA) with financial support from the World Bank. The CBA will comprise the data and adopt the methodology in the evaluations of the CEADIR activity prepared for USAID. 1 This has allowed the CBA to consider ecosystem services such as carbon sequestration and storage estimations, natural hazards and agricultural production. In addition to further externalities such as climate change impacts over time. (Narayan, Foley, Haskell, Cooley, & Hyman, 2017) The purpose of this analysis was to provide technical assistance to the Government of Mozambique to enhance and upscale the implementation of nature-based solutions for urban flood risk management in Nacala. Flooding and erosion is significantly accelerating in the city which is exacerbated by tropical cyclones. A need for flood risk management and support is apparent. Nacala city is experiencing drainage and significant erosion problems as storm water runoff has washed out several gullies and stresses both natural and man-made channels. Flooding is significantly accelerating in Quelimane which are exacerbated by tropical cyclones. A need for flood risk management and support is apparent. Quelimane city is experiencing accelerated peri-urban growth and mangrove degradation which disrupt natural protection from flooding. This study estimated the costs and benefits of revegetation of land in the less densely populated areas and a combined measures approach for inner city areas which included retention ponds, improved drainage system, toe protection of gullies and small scale revegetation in Nacala city. The consultancy service for Nacala city focuses on nature-based flood protection measures, across 13 previously described catchment areas to reduce erosion of gullies and protect the residents. The analysis used CES data on the economic and environmental costs and benefits of revegetation of land and the combined measures and evaluated it against the cost and benefits of no-project scenario. This study also estimated the costs and benefits of vegetation of land and a combined measure which includes construction of retention ponds, drainage channels, rehabilitation of existing drainage channels, outlets and flap gates, green revetment, dike with green revetment, constructions of protection of bridge abutment and a certain area allocated for the protection and re-growing of mangroves, in Quelimane city. The consultancy service for Quelimane city focuses on nature-based and hybrid based flood protection measures, across 11 catchment areas to reduce flooding risks and protect the residents. The analysis used IL data on the economic and environmental costs and benefits of vegetation of land and the combined measures and evaluated it against the cost and benefits of no-project scenario. W&H conducted the CBA in a Microsoft Excel file that serves as a companion to this report. This file allows users to adjust the assumptions in the analysis and examine additional scenarios.