ESTIMASI KERAWANAN BANJIR DAERAH ALIRAN SUNGAI WAWAR MENGGUNAKAN SISTEM INFORMASI GEOGRAFI (SIG)

Wawar Watershed is located in Central Java covering Wonosobo Regency, Purworejo Regency and Kebumen Regency with approximately area 761 Km 2 . Land use of upstream watershed dominated for farming activities causing high potential flooding. Therefore, the information of flood vulnerability is needed as a reference for decisions making in determining space using. Geographic Information System aims to determine and map the potential cause of flooding and flood prone areas. Potential cause of flooding determined by the maximum of daily rainfall, watershed shape, gradient streams, drainage density, average slope of watershed and land use. The flood prone areas determined by land form, meandering, river meeting point, drainage and water conservation structure. The map of flood vulnerability obtained based on classification and scoring method, weighting and overlay of meteorological and watershed characteristics that affected the flood. The results show that Wawar Watershed has three classes of flood potential, such as prone (12295,86 Ha), a bit prone (62703,066 Ha) and slightly prone (308.074 Ha). The upstream watershed is an area of potential causes of flooding. The flood prone areas Wawar Watershed consists of four classes, such as prone (27467,78 Ha), a bit prone (3,015 Ha), slightly prone (8378,208 Ha) and safe (39457.997 Ha). The downstream watershed is flood prone areas. Wadaslintang Dam has an important role in flood control. Catchment area of dam is 196 Km 2 (19239,344 Ha) which 4789,204 hectares is prone of potential cause of flooding and 14450,14 hectares is a bit prone of potential cause of flooding. Wadaslintang Dam can control potential cause of flooding in upstream so flood prone areas in downstream can be reduced