Effect of Debris Flow Event on the Affected Areas in Putih River, Indonesia

Debris flow is a natural phenomenon that can cause some damage and fatalities. from Mount Merapi frequently happens through the Putih River, so it necessary to do research. Anticipating occurrence of debris flows be done with predictions reduce number casualties material losses. This research used simulation method based on Ashida, Takashi, Mizuyama equation applied Nakayasu synthetic unit hydrograph modeling SIMLAR V2.1 application by modifying hyetograph pattern rain intensity value. The test result contained flood area, velocity, volume, height, value degradation aggradation happened in each simulated pattern. velocity 56.8 mm one peak 1.36 m/s, two 1.42 m/s. It means parameter increases 4.4%. Based results, concluded very influential impact lava floods. increase also directly proportional velocity. affects areas affected flood. increasing area flooding.