ASSESSING THE EFFECTS OF LAND USE CHANGE ON RUNOFF IN BEDOG SUB WATERSHED YOGYAKARTA

The study was to assess the effects of land use change on runoff in the Bedog sub watershed.Soil and Water Assessment Tool-Water Balance (SWAT-WB) hydrological modeling was usedto predict runoff for years of 2001, 2006, and 2010. Land use in Bedog has rapidly changedin last few decades due to agglomeration process in Yogyakarta City. Coverage of mixedgarden decreased during period of 2001-2010 despite still as predominant land use in total.On the other side, change detection analysis revealed that there was an increase ofsettlements coverage from 9.51% to 13.79% in the same period. Sensitivity analysis revealedthat soil properties were the most sensitive parameters on runoff generation. Calibration wasperformed for years of 2001, 2006, and 2010 and the result shows an acceptableperformance in runoff simulation. Changes in land use were responsible for an increase inthe annual runoff between 3.42% – 4.67%. This study showed that dynamics of runoff can bepredicted by forecasting and simulating future land use