Abstract
The changes in land use/land cover (LULC) during the process of urbanization have a profound influence on runoff increases and flooding incidents. Narok town, in Kenya, experienced numerous disasters associated with cyclic flash floods that produced human losses and economic damages. Design hydrograph and its peak flow are the key elements to determine hydraulic geometrical properties in designing an adequate drainage system. Due to the continuous occurrence in LULC changes resulting in variability of design hydrograph, this study was carried out to evaluate existing channels geometric properties(conveyance capacity),with field measurements through a ground survey using Real- Time Kinematic equipment at Kakia and Esamburmbur channels of Narok town. To further improve the drainage system in the main channels, the evaluated peak flows under assumed future LULC scenarios were used to design hydraulic geometrical properties (width, depth) for a sustainable urban drainage system. Three geomorphic-based hydrological and hydraulic models (EBA4SUB, Manning’s equation, and Civil3D) were used under different LULC scenarios for computing channel geometry and correspondent water level. Results show that infrastructures such as highway bridges and commercial buildings contributed to narrow the channel downstream. The change in channel geometries was found to obstruct free flow for different scenarios of peak discharge and flow volume. The design conveyance capacity for the two channels considering the evaluated peak discharge from the assumed LULC scenarios can be used in improving the drainage system by local Municipal bodies to mitigate flood hazards.
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