Abstract

Morphology and specifically slope have an important effect on water losses due to infiltration and obtained runoff from rainfall. Approximately all of infiltration models survey infiltration in the large scale region (like a basin) and through a vertical column. In other words, they work with this assumption that slope is equal to zero. There are few infiltration models such as modified green and Ampt model which use the slope as an input factor. But, since this parameter is the average slope of whole catchment, it cannot be really accurate. This paper is a raster-based investigation of slope effect on infiltration by considering land use which is one of the most important parameters in this case. For this purpose, geographic information system (GIS) has been used to divide Johor river basin in the south of Malaysia to 1436200 separated pixels (10 × 10 m) and study on each pixel as an independent catchment. To corroborate the suitability of the obtained results, eighteen different type of slope has been studied. The correlation coefficient indicates that the square cosine of slope is the most suitable function of slope which can be used for infiltration calculations.

Key words: Malaysia, infiltration forecasting model, surface slope, geographic information system, land use, digital elevation model.