Identification of flash flood hazard zones in mountainous small watershed of Aceh Besar Regency, Aceh Province, Indonesia

Flash-floods develop at space and time scales that conventional observation systems were not able to monitor for rainfall, stream flow and sediment discharge. This condition resulted in greater casualties and tremendous economic losses. One of the regions in Indonesia affected by the flash floods was Aceh Besar Regency. It was located in Krueng Teungku watershed. The flash floods were recurring events, which occurred in 1987 and 2000. The disaster reocurred on January 2, 2013 at 19:30 P.M. with the huge impact. This study aimed to analyze the factors affecting flash flood hazards and to obtain flash flood hazard zones at the Krueng Teungku watershed. The method used in this study was weighted overlay technique through Geographic Information System (GIS). The result revealed the information about the flash flood hazard zones at Krueng Teungku watershed as the model for the early warning. Through the development of this model, flood forecasting capabilities in the watershed without measuring devices can be improved. This paper provided the review of factors that affect the incidence of flash flooding, including the factors of peak discharge, slope, watershed shape, stream gradient, damming, drainage density, erosion, slope stability and reservoir volume. The information factors were expected as a contribution for research agencies and government (Aceh Disaster Management Agency) to guide the disaster risk reduction (DRR) activities of flash floods.