Analysis of run-off potential for flash flood management in Rahakolowu Watershed

Abstract Rahakolowu Watershed is an important and strategic issue area for the South Buton Regency. The characteristic of this region is in the form of hills and having wavy until the very steep slope which is very potential of having high run-off. The purpose of this study was: 1) to determine the potential for surface run-off that occurs in the Rahakolowu Watershed; 2) to map the potential for flash floods that occur in the Rahakolowu Watershed. The approach used in this study was a modified HRU (Hydrological Response Unit) with a run-off occurrence land unit as its unit analysis. Based on the result, the highest run-off water discharge produced in each sub-basin was an average of more than 0.50 m3/sec, both on forest, moor, residentials, mix garden and shrubs. The high slope and the area of each land unit in a flow occurrence is the factor causing the high run-off in the Rahakolowu Watershed. Flash floods occur along the main river channel and become inundation floods when they reach downstream. The accumulation of run-off in the southern sub-basin has more potential as a flood contributor in the Rahakolowu Watershed.