CALIBRATION AND VALIDATION OF SWMM MODEL IN A SUB CATCHMENT IN ELDORET TOWN, KENYA

Flooding in Eldoret town has been occurring during heavy downpours resulting loss of property, live and interruption transportation systems. This study aimed at determining the catchment characteristics for calibration validation SWMM5 model. model was developed by US Environmental Protection Agency. The evolving from Version 1 1971 to 5 2005 called SWMM5. It can simulate runoff quantity any given catchment. Rainfall measured using rain gauge while discharge current meter. Digital Elevation Model area also obtained. results showed that drained an approximately 696.5 hectares with a total 23 sub catchments. average slope found be 2.57% mean imperviousness 25.72%. drain base flow 0.002 m3/s. However, prolonged rainfall, increased up 32.4 maximum rainfall observed period mm which resulted 0.131m3/s overflow drain. Calibrated had N-Imperv 0.45, Dstore-Imperv 2.5 Dstore-Perv 8. ISE values 1.9 1.4 were validation, respectively. NSE 0.97 0.99 meant excellently simulated rainfall-discharge relationship used final design engineers. Future is required calibrate based on more measurements their discharges