LAND USE SCENARIO MODELLING FOR FLOODS MITIGATION IN BEDADUNG WATERSHED, EAST JAVA']JAVA INDONESIA

The 2019 dry season in Bedadung watershed caused a catastrophic forest fire. The fires caused a significant reduction in forest area in a short period. As a result, there was an increase in downstream discharge when entering the rainy season. This study aims to determine the impact of land use change towards floods and the boundary of optimal land use in the flood management framework, and then it can be used as a basis for designing flood disaster mitigation strategies due to changes in land cover. The land cover map used as input flood model was obtained from the processing of Landsat-8 satellite imagery, meanwhile modeling of flood response to land cover changes was carried out using the SWAT model. After knowing the flood discharge response to land cover, the simulation process was carried out by making several land cover scenarios to find the appropriate and optimal land cover area. The results showed that the calculation of flood discharge after the calibration process resulted in the NSE and R-2 values of 70.7% and 0.709, meanwhile the validation values of NSE and R-2 were 82.1% and 0.88, respectively. The simulation of land-use scenarios shows that the optimal land cover condition of the Bedadung watershed is to use a scenario of 30% forest area of the total watershed area.