Resilience Scanner

Community-Led Participatory Flood Risk Mapping Using Open-Source Tools

Solution Overview

Community-led resources mapping represents an effective and replicable model for Lagos to strengthen preparation against flood management challenges.[1][3][4] This participatory approach draws from successful international implementations, particularly the Ramani Huria community-driven mapping project in Dar es Salaam, Tanzania, which began in 2015 to train locals and students to collect and digitize data on infrastructure and flood-prone areas using tools like GPS, drones, and OpenStreetMap.[7][1] The methodology proves particularly relevant for Lagos, where the city's low-lying topography—with most land elevated less than 15 meters above sea level—makes flooding especially problematic.[1]

Technical Components

The technical infrastructure relies on open source tools that can be operated by anyone with an Android smartphone.[2] Data collection employs Open Data Kit (ODK) and Open Map Kit (OMK), while map production utilizes QGIS and Java OpenStreetMap (JOSM), all of which are open source software platforms.[2] Community members, university students, and local government personnel receive training to use JOSM and Field Papers for mapping their communities.[9] The Dar es Salaam implementation collected drainage data with smartphones using this community mapping approach during 2017–2019.[8] Data collection encompasses roads, building footprints, flood plains, drainage systems, and key infrastructure including schools, hospitals, and markets.[9] The Humanitarian OpenStreetMap Team with its local partner Open Map Development Tanzania was contracted by the Tanzania Urban Resilience Program of the World Bank to collect large amounts of risk identification data using this methodology.[8]

Implementation Details

The Community Participatory Flood Management initiative in Lagos will organize communities around each of the 57 Local Government Areas and Local Council Development Areas (LGAs/LCDAs) to implement the program.[1] The initiative comprises four components: training communities to carry out comprehensive flood risk assessment, co-producing comprehensive flood risk assessment with trained community members, co-creating flood hazard plans including response protocols, and accessing inputs from the State Government and its partners to implement the flood hazard plans.[1] Potential partners include the Ministry of the Environment and Water Resources, the Ministry of Health, and agencies under primary actors.[1] The World Bank served as the main financier of the Dar es Salaam project, with the Humanitarian OpenStreetMap Team (HOT) as the primary organization managing projects and OpenMap Development Tanzania (OMDTZ) as the primary local organization carrying out activities.[2] The Ramani Huria project commenced in 2015 to address the consequences of floods in Dar es Salaam.[2]

Benefits and Impacts

The Dar es Salaam implementation achieved substantial geographic coverage, mapping 49 out of 90 wards—approximately 50% of the city—comprising about 450,000 buildings and 1,700 schools since 2015.[2] The project mapped 29 wards covering 93 square kilometers for a population exceeding one million people, identifying 1,254 kilometers of waterways and 3,396 kilometers of roads.[9][7] University students completing their industrial training demonstrated the scalability of this approach by mapping 228 sub-wards within seven weeks, with nearly 500 students conducting field mapping to create a community asset and threat inventory.[2] The data collected proves reliable through its participatory approach that incorporates local knowledge.[2] Communities and government utilize the resulting maps for contingency planning, disaster risk reduction, and urban planning and service delivery.[9] The Resilience Academy partnered with Delft University of Technology to investigate whether community-mapped drainage data was suitable for creating an urban flood model, validating the technical applicability of this methodology.[8]

Climate Adaptation Relevance

This approach directly addresses Lagos's acute flood vulnerability, which was demonstrated by the 2022–2023 flood event that resulted in USD 262,500 in damages and displaced 8,000 residents in Lagos State.[10] The comprehensive mapping of drainage systems, waterways, flood plains, and building footprints enables communities and government agencies to develop targeted flood hazard plans and improve disaster risk reduction strategies.[9][1] The methodology's proven effectiveness in Dar es Salaam—another coastal city facing similar flood challenges—demonstrates its suitability for replication in other flood-prone urban environments using the same open source technology platform.[2]

Business Analysis

The open source nature of the technology platform significantly reduces implementation costs, as all mapping and data production software can be accessed without licensing fees.[2] The model leverages existing community capacity and university student participation, creating a cost-effective workforce structure demonstrated by the Dar es Salaam project's ability to deploy nearly 500 student mappers simultaneously.[2] The World Bank's financing of the Tanzania implementation establishes a precedent for international development bank support for similar initiatives.[2] The project's suitability for replication in other cities facing floods using the same open source technology creates opportunities for standardized implementation frameworks and knowledge transfer.[2] Government partnerships spanning multiple ministries and agencies provide institutional support structures, with the Lagos initiative engaging the Ministry of the Environment and Water Resources, Ministry of Health, and agencies under primary actors.[1]

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