Analysis of parameters sensitivity and sub watershed delineation when flood modeling with spatially distributed unit hydrographs

Abstract

Occurrence of flash floods is a major problem faced by Sri Lanka, today (Hettiarachchi, 2011). Damages to properties, loss of human lives and displacement of people were frequently observed in consequence, during recent period. Changes expected in rainfall patterns due to anticipated climate change (Misra & Ghosh, 2010) and land development due to urbanisation (Hettiarachchi, 2011) are indicated as the major causes of this. There is a possibility of reduction of flood damages, identification of safer locations and directing people to such locations, with a proper flood forecasting system, but urban watersheds being smaller causes such systems have been less effective. Accurate flow estimations and suitable drainage designs therefore, become more important and representative stream flow estimations are essential in flood forecasting. For this, it is important to use representative models to ensure best estimates of watershed responses for a given rainfall (Khaleghi, Gholami, Ghodusi, & Hosseini, 2011).