AN INTEGRATED GEOINFORMATICS TECHNOLOGY WITH HYDROLOGICAL MODEL TO IMPACT ASSESSMENT OF LAND USE CHANGE ON RUNOFF IN THE UPPER LAM TA KHONG WATERSHED

摘要

The main objective of this study was to evaluate the impact of land use changes on surface runoff in upper Lam Ta Khong watershed, headwaters watershed. The land useduring 1993,2001 and 2009 were classed by visual interpretation methods based on LANDSAT imagery data. The monthly surface runoff simulation by using hydrological SCS-CN model integrated with GIS. Model calibration and validation were performed by comparing observed and simulated results at the M.43A (upstream watershed) and M.89 (downstream watershed) during the water year 1993,2001 (model calibration) and 2009 (model validation). The impact of land use change on surface runoff was evaluated with scenarios model and simple linear regression. The model was conducted for each land use map in three time periods (1993,2001 and 2009). The study revealed that 1) the land use type during 1993 -2009 founded that the forest and agricultural land were decreased, while the urban and built-up area has been continuously increasing. 2) A calibrated model shows that satisfactory of the coefficient of efficiency (E) is 0.39 and 0.45 and coefficient of determination (R~2) is 0.36 and 0.48 at the M.43A and M.89, respectively. 3) The decreased of forest and agricultural land, while urban and built-up area was increased have a negative impact on surface runoff due to decreasing of infiltration and increasing of surface runoff Especially, urbanization was the strongest contributor to the increase of surface runoff. The results of this study indicate that the changing of land use types from natural surface to impervious surface has a significant impact on surface runoff. This study will provide quantitative information for stakeholders in land use plann ingand water resource management in the study area.