Hydrological Approach for Flood Overflow Estimation in Buleleng Watershed, Bali

Abstract

The Hydrology of a watershed, encapsulated within the biogeophysical characteristics of upstream, midstream, and downstream regions, governs the peak discharge. Notable flooding issues have been observed in the downstream region of the Buleleng Watershed, largely attributed to land use transitions from vegetative to built-up areas. This study seeks to delineate the flood overflow zone within the Buleleng River Basin, influenced by factors such as rainfall, land use, and soil texture. Data employed in this study encompass land use maps, an 8-meter resolution Digital Elevation Model, annual rainfall records, soil texture information, and river network maps. The adopted methodology involved field survey data collection, satellite image analysis, and hydrological approach computations. Peak discharge values for the Buleleng Watershed, derived for periods of 5, 10, 25, and 5-100 years, were determined to be 426334.44, 568445.88, 603035.31, and 617379 m3/s respectively, set against a river capacity of 312748.13 m3/s. Given the substantial overflow discharge from the Buleleng River, the watershed is susceptible to flooding. The study findings indicate a progressive annual increase in flood overflow predictions, necessitating targeted interventions such as drainage management, surface runoff control, and a review of spatial permits for settlement usage, particularly within watershed conservation areas.