| Summary: | Models are needed to describe how nonpoint source area of a watershed affect the
rainfall-runoff process in tropical region, yet little spatially distributed data exist to
develop such models. Hence, a coupled GIS-event base storm runoff model in a variable
source area is developed. The model use grid-formatted map data supported by the
Geographical Information System (GIS) and generates distributed results for runoff
depth, discharge and coefficient of saturated area fraction. The GIS grid-based distributed
CN-VSA method was evaluated for two (W1= 2.29 Km2
, W2 = 0.88 Km2
) small
watersheds located in tropical region in Malaysia. The average Nash-Sutcliffe (1970)
efficiency for predicting saturated area fraction and runoff within and outlet of the
watershed (W1) using verification between observed and model simulated data for fifteen
storm events were (R2
=0.99) and (R2
=0.86), respectively. Coefficients indicated a good
efficiency for model prediction. Since, the model proposed was found to be suitable for
prediction of saturated area fraction (Af) and sources area of runoff, the proposed model
was applied for unmonitored sub-watersheds W11, W12, W13 (of watershed W1) and
watershed W2, respectively.
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