Site Selection for an Earth Dam in Mbeere North, Embu County—Kenya

Choosing a suitable site for dam is a crucial phase in dam construction. A successful outcome of this effort is initiated by taking into consideration some watershed properties and characteristics. This study aimed to investigate hydrological information for dam site selection by integrating GIS with AHP Multi-Criteria Decision Analysis to establish hydrologic characteristics of the region suitable for a dam construction. The method used was based on consideration of seven criteria which included topographic factors (slope), geological factors, soil type, catchment size, land cover, proximity to river and proximity to roads. Data from ASTER GDEM was utilized for generating various topographic parameters while Geological Maps from Kenya Department of Mines were used for depicting rock formation/structure. Soil data from ILRI was used to show the distribution of the various soil categories. Land cover, roads and river centrelines were also used. This data was processed in ArcGIS to generate thematic layers of each criterion, on which weight was assigned depending on the most important factor. Weighted overlay analysis was applied to obtain layers showing suitable sites for dam construction. A final suitability map was established showing four possible sites of highly suitable areas for dam construction, with a capacity of 8.3 million m3 to North East, 14.9 million m3 to West, 26.9 million m3 to North West and 269.2 million m3 to North East of the study area. The larger site was the most recommended due to its narrow formation of contour troughs and ridges allowing for various dam options.