GIS Application in Evaluating Land Use-Land Cover Change and its Impact on Hydrological Regime in Langat River Basin, Malaysia Study Area The area of interest for this study is Langat River Basin, that has a total catchment area of 2271km2. Fig 1 shows the diversity of Langat’s LULC for 1984, 1990,1995 and 1997. This river basin located at southern part of Klang Valley, which is the most urbanised river basin in Malaysia, and it is believed that the Langat will compensate the virtue of ‘spill-over’ development from Klang Valley. Hydrometeorologically, the basin experienced two types of monsoons, i.e. the North East (November to March) and the Southwest (May to September). The average rainfall is about 2400mm, and the highest months (April and November) show rainfall amount above 250mm, while the lowest is in June, about the average of 100mm (Noorazuan, 2001). Topographically, Langat basin can be divided into three geographic regions, i.e. the mountainous area of the north, the undulating land in the centre of the basin and the flat flood plain at the downstream of Langat river. A wide range of landforms and an equally wide diversity of surface features and cover are found in the basin. Methods This study makes use of the digitally GIS-based land use maps of 1984, 1990, 1995 and 1997 (Figure 2a to d). The study of landscape patterns and spatial statistics were carried out using GIS ArcView 3.1 with Patch Analysis extension, and SPSS 11.0. In this study, the urban built-up component shall be highlighted and its relationship to hydrological impact. The Langat land cover diversity index will be analysed by using the Patch Analyst extension. Among the spatial statistic of landscape and classes levels involved are Shannon’s Diversity Index (SDI), patch density and edge density. SDI is a index to measure the relative patch diversity within a watershed. Historical mean hourly and daily streamflow data from the Department of Irrigation and Drainage (DID) stream gauge 2816441, of Dengkil station, were obtained for each year from 1984 to 1997. The reason is to study the change of the flow behaviour within the years of land use is mapped.
The hourly and daily rainfall records coincident with streamflow records were acquired from DID rainfall station at Kajang, station number 2917001. For the built–up and streamflow relationship study, only the urban areas above the gauging station will be used in the analysis, which comprises area of 1549km2. Among the analyses that will be used to test the relationship between streamflow and built-up were the surface runoff and streamflow response value. The streamflow response value is a conceptual tool for analysing the rainfall-runoff relationships (Bedient & Huber, 1988). |
