Climate variability and anthropogenic impacts on a semi-distributed monsoon catchment runoff simulations

Recent studies has showed that the modification on land use have an impact to hydrology particularly flood and global climate variability. Therefore, the major factor decided to the effect of hydrological responses in contributing flood disaster in this research, is land use changes as well as climate variability. This study tries to provide a framework mainly to apply a semi-distributed hydrological model in a monsoon catchment and to quantify the relative contributions of physio-environment (i.e. land use change and climate change) effects to hydrological response and flooding in the River Kelantan catchment. The HEC-HMS hydrological model was utilized to show that land use change, predominantly deforestation for agricultural purposes, has potentially caused some increases in hydrological response over time (i.e. 16 years) in the upstream area. However, the predicted effect of precipitation change was about three-to-four times greater than that of land use change in the upstream area. In the downstream area land use change was predicted by the model to have led to a very small decrease in hydrological response between 1988 and 2004 compared to the precipitation change. It is plausible to suggest that during the monsoon season, with heavy precipitation and the large area involved, the effect of land use change on the hydrological response may reduce and allow precipitation to become the dominant factor in causing changes in peak discharge and runoff volume.