OpenStreetMap User's Diaries
Legacy Project for HOT CWG Mentorship 2025 by Mr. Yakubu Enoch & Mr. Alex Muruthi
Flood Risk Map of Kenya using GIS
For the doc version: Kenya Flood Risk Map
Abstract
The Republic of Kenya has recently witnessed a series of devastating hydrometeorological events, transitioning from a severe multi-year drought to catastrophic, El Niño-enhanced flooding between 2024 and 2025. These events have underscored a critical need for high-resolution spatial data to inform disas
Flood Risk Map of Kenya using GIS
For the doc version: Kenya Flood Risk Map
Abstract
The Republic of Kenya has recently witnessed a series of devastating hydrometeorological events, transitioning from a severe multi-year drought to catastrophic, El Niño-enhanced flooding between 2024 and 2025. These events have underscored a critical need for high-resolution spatial data to inform disaster risk reduction and humanitarian response. This research, produced as a Legacy Project for the Humanitarian OpenStreetMap Team (HOT) Community Working Group (CWG) Mentorship 2025, presents a comprehensive national-scale flood risk assessment for Kenya. The study employs a Geographic Information System (GIS) and Multi-Criteria Decision Analysis (MCDA) framework to synthesize six influential factors: rainfall intensity, elevation, slope, Land Use/Land Cover (LULC), distance to water bodies, and distance to road networks. Utilizing a weighted overlay methodology, the study reclassifies these parameters based on their hydrological and anthropogenic influence to produce a final flood risk map categorized into five classes: Very High, High, Moderate, Low, and Very Low. The analysis reveals that high-risk zones are predominantly concentrated in low-lying river basins and informal urban settlements, where high rainfall accumulation coincides with poor drainage and high exposure. The findings provide a strategic foundation for the OpenStreetMap community and disaster management agencies to prioritize anticipatory actions, refine field data collection, and enhance the resilience of vulnerable populations.
Keywords
flood, Kenya, flood risk, mapping, GIS, Multi-Criteria Decision Analysis, OpenStreetMap
Introduction
The Kenyan Paradox: Historical Context and Emerging Flood Dynamics
The geographical and climatic landscape of Kenya is defined by extreme variability, a characteristic that has become increasingly pronounced in the context of global climate change. In the years leading up to 2025, Kenya experienced what has been described as a “climatic seesaw,” swinging from the worst drought in forty years to unprecedented deluges that submerged vast sections of the country. This volatility is not merely a localized weather phenomenon but a manifestation of broader regional shifts in the East African climate, influenced by the Indian Ocean Dipole and the El Niño Southern Oscillation (ENSO).
Historically, Kenya has navigated recurrent cycles of droughts and floods, but the events of 2024–2025 reached a threshold that challenged both national infrastructure and community resilience. The March-April-May (MAM) long rains of 2024, intensified by El Niño patterns, resulted in flooding that affected 40 out of 47 counties. By June 2024, official reports from the National Disaster Operations Centre (NDOC) indicated that 293,200 individuals had been displaced, and approximately 250,000 learners were out of school due to the destruction of educational facilities and the use of schools as temporary shelters. The fatalities recorded during this period exceeded 290, with many individuals still missing as of late 2024.
The economic impact of these floods is equally profound. The agricultural sector, which provides the livelihood for a significant portion of the Kenyan population, suffered immense losses. Over 65,000 acres of cropland were damaged, and 11,000 heads of livestock were lost, exacerbating food insecurity in regions that were already struggling to recover from the preceding drought. Critical infrastructure, including 68 roads and 45 health facilities, sustained heavy damage, creating logistical barriers to humanitarian aid delivery. This report addresses the need for a predictive and diagnostic tool that identifies the spatial distribution of these risks, allowing for more efficient resource allocation and targeted disaster preparedness.
The Role of Open Mapping and the HOT CWG Mentorship 2025
This research project is situated within the institutional framework of the Humanitarian OpenStreetMap Team (HOT) and its Community Working Group (CWG). The HOT CWG Mentorship Program was established to foster peer-to-peer learning and knowledge exchange within the humanitarian open mapping space. By pairing experienced geospatial professionals with emerging mappers, the program aims to build local capacity in priority countries, ensuring that those most affected by disasters are equipped with the tools to map their own vulnerabilities.
As part of the “Audacious Project,” HOT has committed to mobilizing one million volunteers to map areas home to one billion people by 2025. This ambitious goal is predicated on the belief that maps and data, while not directly saving lives, provide the essential infrastructure for those who do. The transition from project-based work to a community-centered approach is vital for the sustainability of these efforts. This Legacy Project, authored by Yakubu Enoch and Alex Muruthi, represents a bridge between academic research and community-driven action. It utilizes open-source software and humanitarian datasets to create a reproducible model for flood risk assessment that can be adopted by OSM communities across Sub-Saharan Africa.
The mentorship program emphasizes professional development, open geospatial skills, and data in humanitarian work. This project specifically addresses the “Open Geospatial Skills” and “Data in Humanitarian” focus areas by demonstrating how advanced GIS techniques, such as Weighted Overlay Analysis, can be applied to real-world crises. By publishing this work on the OpenStreetMap diary, the authors contribute to a global repository of knowledge, encouraging transparency, public reflection, and the continuous improvement of data quality within the OSM ecosystem.
Aim
To produce a Flood risk assessment map of Kenya.
Objective
a. Criteria Dataset gathering.
b. Map creation and analysis using weighted overlay/raster calculation.
c. Flood risk data interpretation.
Study Area Map of Kenya.
The study area encompasses the entire landmass of the Republic of Kenya, located in East Africa, spanning approximately 580,367 square kilometers. Kenya’s geography is marked by its diversity, ranging from the low-lying coastal plains along the Indian Ocean to the high-altitude Central Highlands, divided by the Great Rift Valley.

Literature Review
GIS and Flood Risk Assessment in Kenya
The application of Geographic Information Systems (GIS) and remote sensing in flood management has undergone a revolution in the past two decades. In the Global South, where ground-based meteorological stations are often sparse, these technologies provide a vital alternative for risk delineation and vulnerability analysis.
The Evolution of Flood Risk Modeling
Flood risk is traditionally conceptualized as the product of hazard, exposure, and vulnerability. Early models relied heavily on hydraulic and hydrological simulations that required extensive localized data. However, recent research has favored a multi-parametric approach using Multi-Criteria Decision Analysis (MCDA) and the Analytical Hierarchy Process (AHP). Studies in areas like the Eldoret Municipality have demonstrated that combining factors such as rainfall distribution, elevation, slope, and soil type can produce reliable risk maps with high validation accuracy.
In the Western Region of Kenya, particularly the Budalangi sub-county, research has shown a strong correlation between altitude and flood risk. Analysis of Landsat satellite images reveals that 90% of flood risk zones are located below 1,144 meters above sea level. These zones are often covered by natural vegetation or farmlands, while “safe zones” are predominantly occupied by human settlements and administrative centers. This settlement pattern suggests a degree of historical adaptation, but the rapid expansion of populations into marginal lands is eroding these traditional safety margins.
Challenges of Data Quality and Uncertainty
A recurring theme in the literature is the challenge of data quality and uncertainty in flood prediction. The accuracy of flood maps is entirely dependent on the quality of input datasets, such as Digital Elevation Models (DEMs) and satellite rainfall estimates. Overlooking data uncertainty can lead to significant errors in estimating the intensity and timing of floods, resulting in misleading policy decisions. In Kenya, studies in the Lake Victoria Basin have utilized Satellite Rainfall Estimates (RFE) to overcome the lack of ground data, finding that while daily accumulations may vary, the products are effective for detecting rainfall occurrence and seasonal surges.


For the doc version: Kenya Flood Risk Map
AbstractThe Republic of Kenya has recently witnessed a series of devastating hydrometeorological events, transitioning from a severe multi-year drought to catastrophic, El Niño-enhanced flooding between 2024 and 2025. These events have underscored a critical need for high-resolution spatial data to inform disas
Flood Risk Map of Kenya using GIS
For the doc version: Kenya Flood Risk Map
Abstract
The Republic of Kenya has recently witnessed a series of devastating hydrometeorological events, transitioning from a severe multi-year drought to catastrophic, El Niño-enhanced flooding between 2024 and 2025. These events have underscored a critical need for high-resolution spatial data to inform disaster risk reduction and humanitarian response. This research, produced as a Legacy Project for the Humanitarian OpenStreetMap Team (HOT) Community Working Group (CWG) Mentorship 2025, presents a comprehensive national-scale flood risk assessment for Kenya. The study employs a Geographic Information System (GIS) and Multi-Criteria Decision Analysis (MCDA) framework to synthesize six influential factors: rainfall intensity, elevation, slope, Land Use/Land Cover (LULC), distance to water bodies, and distance to road networks. Utilizing a weighted overlay methodology, the study reclassifies these parameters based on their hydrological and anthropogenic influence to produce a final flood risk map categorized into five classes: Very High, High, Moderate, Low, and Very Low. The analysis reveals that high-risk zones are predominantly concentrated in low-lying river basins and informal urban settlements, where high rainfall accumulation coincides with poor drainage and high exposure. The findings provide a strategic foundation for the OpenStreetMap community and disaster management agencies to prioritize anticipatory actions, refine field data collection, and enhance the resilience of vulnerable populations.
Keywords
flood, Kenya, flood risk, mapping, GIS, Multi-Criteria Decision Analysis, OpenStreetMap
Introduction
The Kenyan Paradox: Historical Context and Emerging Flood Dynamics
The geographical and climatic landscape of Kenya is defined by extreme variability, a characteristic that has become increasingly pronounced in the context of global climate change. In the years leading up to 2025, Kenya experienced what has been described as a “climatic seesaw,” swinging from the worst drought in forty years to unprecedented deluges that submerged vast sections of the country. This volatility is not merely a localized weather phenomenon but a manifestation of broader regional shifts in the East African climate, influenced by the Indian Ocean Dipole and the El Niño Southern Oscillation (ENSO). Historically, Kenya has navigated recurrent cycles of droughts and floods, but the events of 2024–2025 reached a threshold that challenged both national infrastructure and community resilience. The March-April-May (MAM) long rains of 2024, intensified by El Niño patterns, resulted in flooding that affected 40 out of 47 counties. By June 2024, official reports from the National Disaster Operations Centre (NDOC) indicated that 293,200 individuals had been displaced, and approximately 250,000 learners were out of school due to the destruction of educational facilities and the use of schools as temporary shelters. The fatalities recorded during this period exceeded 290, with many individuals still missing as of late 2024. The economic impact of these floods is equally profound. The agricultural sector, which provides the livelihood for a significant portion of the Kenyan population, suffered immense losses. Over 65,000 acres of cropland were damaged, and 11,000 heads of livestock were lost, exacerbating food insecurity in regions that were already struggling to recover from the preceding drought. Critical infrastructure, including 68 roads and 45 health facilities, sustained heavy damage, creating logistical barriers to humanitarian aid delivery. This report addresses the need for a predictive and diagnostic tool that identifies the spatial distribution of these risks, allowing for more efficient resource allocation and targeted disaster preparedness.
The Role of Open Mapping and the HOT CWG Mentorship 2025
This research project is situated within the institutional framework of the Humanitarian OpenStreetMap Team (HOT) and its Community Working Group (CWG). The HOT CWG Mentorship Program was established to foster peer-to-peer learning and knowledge exchange within the humanitarian open mapping space. By pairing experienced geospatial professionals with emerging mappers, the program aims to build local capacity in priority countries, ensuring that those most affected by disasters are equipped with the tools to map their own vulnerabilities. As part of the “Audacious Project,” HOT has committed to mobilizing one million volunteers to map areas home to one billion people by 2025. This ambitious goal is predicated on the belief that maps and data, while not directly saving lives, provide the essential infrastructure for those who do. The transition from project-based work to a community-centered approach is vital for the sustainability of these efforts. This Legacy Project, authored by Yakubu Enoch and Alex Muruthi, represents a bridge between academic research and community-driven action. It utilizes open-source software and humanitarian datasets to create a reproducible model for flood risk assessment that can be adopted by OSM communities across Sub-Saharan Africa. The mentorship program emphasizes professional development, open geospatial skills, and data in humanitarian work. This project specifically addresses the “Open Geospatial Skills” and “Data in Humanitarian” focus areas by demonstrating how advanced GIS techniques, such as Weighted Overlay Analysis, can be applied to real-world crises. By publishing this work on the OpenStreetMap diary, the authors contribute to a global repository of knowledge, encouraging transparency, public reflection, and the continuous improvement of data quality within the OSM ecosystem.
Aim
To produce a Flood risk assessment map of Kenya.
Objective
a. Criteria Dataset gathering. b. Map creation and analysis using weighted overlay/raster calculation. c. Flood risk data interpretation.
Study Area Map of Kenya.
The study area encompasses the entire landmass of the Republic of Kenya, located in East Africa, spanning approximately 580,367 square kilometers. Kenya’s geography is marked by its diversity, ranging from the low-lying coastal plains along the Indian Ocean to the high-altitude Central Highlands, divided by the Great Rift Valley.

Literature Review
GIS and Flood Risk Assessment in Kenya
The application of Geographic Information Systems (GIS) and remote sensing in flood management has undergone a revolution in the past two decades. In the Global South, where ground-based meteorological stations are often sparse, these technologies provide a vital alternative for risk delineation and vulnerability analysis.
The Evolution of Flood Risk Modeling
Flood risk is traditionally conceptualized as the product of hazard, exposure, and vulnerability. Early models relied heavily on hydraulic and hydrological simulations that required extensive localized data. However, recent research has favored a multi-parametric approach using Multi-Criteria Decision Analysis (MCDA) and the Analytical Hierarchy Process (AHP). Studies in areas like the Eldoret Municipality have demonstrated that combining factors such as rainfall distribution, elevation, slope, and soil type can produce reliable risk maps with high validation accuracy. In the Western Region of Kenya, particularly the Budalangi sub-county, research has shown a strong correlation between altitude and flood risk. Analysis of Landsat satellite images reveals that 90% of flood risk zones are located below 1,144 meters above sea level. These zones are often covered by natural vegetation or farmlands, while “safe zones” are predominantly occupied by human settlements and administrative centers. This settlement pattern suggests a degree of historical adaptation, but the rapid expansion of populations into marginal lands is eroding these traditional safety margins.
Challenges of Data Quality and Uncertainty
A recurring theme in the literature is the challenge of data quality and uncertainty in flood prediction. The accuracy of flood maps is entirely dependent on the quality of input datasets, such as Digital Elevation Models (DEMs) and satellite rainfall estimates. Overlooking data uncertainty can lead to significant errors in estimating the intensity and timing of floods, resulting in misleading policy decisions. In Kenya, studies in the Lake Victoria Basin have utilized Satellite Rainfall Estimates (RFE) to overcome the lack of ground data, finding that while daily accumulations may vary, the products are effective for detecting rainfall occurrence and seasonal surges.

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