STUDI NORMALISASI SUNGAI WELANG-REJOSO UNTUK MENGATASI BANJIR DI KECAMATAN REJOSO KABUPATEN PASURUAN

The Welang River Basin has an area of 361.74 km2 with a length of ± 15,667 km. The condition of the upstream part of the Welang watershed has the potential to cause high intensity rain accompanied by tidal sea water in the estuary. Causing flooding in the downstream area of the Welang River. To prevent flooding in the downstream area, the authors make a normalization study. The purpose of this thesis is to determine the area of influence of each rain station, calculate peak discharge, analyze water level profiles and calculate runoff discharge using the HEC-RAS software, plan flood control buildings. The data needed, among others, rainfall data from the 4 closest stations namely Kawisrejo, Puspo, Panditan, and Ranugrati in 2007-2016 and Welang River geometry. Log Pearson III distribution method to calculate the design rainfall data with a 10-year return period. Nakayasu hydrograph method to calculate flood discharge. Based on the analysis of the broad influence of Sta. Kawisrejo 89,995 Km2, Sta. Puspo 110,372 Km2, Sta. Panditan 116,733 Km2, Sta. Ranugrati 44,640 Km2. Peak discharge at 10 years return 564,204 m3 / s. The water level profile exceeds the cross section of the river along Sta 1 - Sta 102. The flood control building is in the form of a dike and river normalization