Abstract:
Retih River is one of the rivers that comes across Kemuning Sector where flood usually
takes place every year. The study of flood prevention and tackling on Retih River has
objectives to know the main cause of flood and to find out the alternative ways to prevent and
tackle the flood.
Flood analysis runs with analyzing the river capacity and comparing it with the
discharge calculated by using Nakayasu method. The analysis of Retih River capacity was
calculated by using HEC-RAS 4.1.0 software. Rain input was calculated based on two years
time period, twenty five years time period and fifty years time period. Profile analysis
performed on the existing condition and the plan condition.
Research findings show that the area of Retih River that is usually struck by flood is the
area where the research performed. On existing condition for the debt of two years time
period, the maximum depth is 1.59 meters. The flood occurred because of bottle neck
constriction is more dominant than the meander. It was proved by the result of the analysis
by using HEC-RAS for two years time period, with 8 meters river width normalization,
0.0002 channel declivity and bank declivity (talud) V(1):H(0.5) is decreased 100% from the
maximum flood height. By creating waterway diversion on the meander, it will give effect of
flood deficiency only about 1.26% from the maximum flood height. So, the effective flood
prevention and tackling effort on Retih River is by applying the river normalization.
