Analysis of Risk Level Mapping of Flash Flood in the Air Betung Sub-Watershed, Pagar Alam City, Indonesia

This research aimed to obtain a map of flood and inundation distribution in the Air Betung Sub-watershed of Pagar Alam City at an altitude of 200- 1500 meters above sea level. Moreover, the city consists of mountainous and hilly areas, wavy and steep relief, forest areas, and plantations, including settlements and sub-watershed (DAS), characterized by an average annual rainfall of 234.50 mm, with air temperature between 140C-350C. Based on Indonesian Disaster Information Data (DIBI) from National Disaster Management Agency (BNPB) from 2014 to 2019, the Air Betung Sub-watershed has experienced 5 flash flood disasters. These incidents resulted in damage to 1 house unit, irrigation channels ± 50 m, retaining walls ± 25 m, and ± 30 hectares of agricultural land damaged. The method used in this research included Risk Index Mapping to determine the level of flash flood risk by analyzing hazard, vulnerability, and capacity indices. The hazard index was analyzed using Flash Flood Potential Index (FFPI) method, while the vulnerability and capacity indices were evaluated through equations in accordance with Perka BNPP No. 2 of 2012, as processed in the Arc-GIS version 10.4 program. Generally, risk index map research was classified into three classes, namely low, moderate, and high. The results showed that the Pagar Alam Selatan Sub-district had a high index value compared to others in the Air Betung Sub-watershed, Pagar Alam City.