THE HYDROLOGICAL IMPACT OF LANDUSE CHANGES ON RUNOFF IN THE UPPER BUKIT TIMAH BASIN

Abstract

The association between landuse and hydrology has not always been given the attention that it deserves. So far, only two types of landsurface change, that is, major changes in vegetation and urbanization development, have been sufficiently tested to allow prediction of changes expected. This exercise is an attempt (1) to analyse the changing landuse of a selected area, the Upper Bukit Timah Basin, in terms of increase in impervious area over a period of years (1950-1986), and (2) to relate this change to the change in runoff over the same period. The years 1950, 1959, 1973, 1980 and 1986 were chosen on the basis of data availability and the degree and pattern of landuse change between these selected years were compared. Next the changes in run off in terms of peak discharge and time of concentration were analysed using the Rational Formula. Finally such changes were related to the change in landuse. From this analysis of past and present landuse on runoff, any future development in landuse and its effect on runoff can then be postulated.