Channel geometry change response to flow regulation on the Langat River

Abstract

This research examines channel geometry change in particular their planform characteristic due to intensive regulation by the Pangson and Semenyih Reservoirs on the Langat River over the last 30 years. GIS-ArcInfo extrapolation analysis was used to quantify the geometry change. Superimposed topographical maps of pre (1973) and post regulated (1985) were successful to determined type and pattern of channel planform change. Examination of planform indices, represented by three-point stations in the upland, intermediate and lowland reaches indicate that in general, channel sections tend to be straighter in the upland and become narrower with more meandering in the intermediate and lowland reach sections. These were proved quantitatively using sinuosity index (SINDX). In the upland reach, the SINDX was reduced to average 1.02 to 0.99 post-regulation while the others demonstrate the opposite trend.