APPLICATION OF THE TRRL FLOOD ESTIMATION MODEL IN HYDROLOGICAL FORECASTING FOR CATCHMENTS WITH LIMITED DATA A CASE STUDY

The Transport and Road Research Laboratory (TRRL) East African flood model is a method of hydrological forecasting originally developed by TRRL of the UK. The method was an attempt to predict surface runoff resulting from floods for small catchments with limited hydrological data available. This method was tested by the Kenya Railways in the process of re assessing its Mombasa Nairobi mainline crossing structures. Flood froecasting calculations were also conducted using a rational method. The results showed disparities of varying magnitudes. Some of the disparities are attributable to normal computational errors brought about by subjectivity of the various parameters involved. This is especially so because the rational formula tended to forecast high peak flows that are not supported by historical records. On the other hand, the TRRL method was found to be in conformity with the known history of flooding. However, further research needs to be conducted in order to confirm the applicability of this model with actual floods. There also exists scope for adopting the model in other parts of the African continent.