STUDI PENGENDALIAN BANJIR DI SUNGAI WELANG KECAMATAN KRATON KABUPATEN PASURUAN JAWA TIMUR

The Welang Hilir River in the Kraton District, Pasuruan Regency is often inundated with water with a flood height range of 0.1 - 3.88 m. This is due to the discharge that occurs due to changes in land use in the catchment area, tidal impact and a decrease in the capacity of the river which causes the river to be unable to flow. Therefore, it is necessary to study the flood control of the Welang River in Kraton District, Pasuruan Regency, East Java to overcome the destructive power of water and reduce losses caused by floods. This study uses an alternative flood retaining wall design for Q25th return discharge using the Nakayasu Synthetic Hydrograph Unit, analyzing the flow profile of the existing condition using the HEC-RAS 5.0.7 program with the calculated Q25th. From the calculation results obtained a debit of 595,071 m3/sec with the largest runoff as high as 3.88 m. The results of the planning obtained that the height of the flood retaining wall is 5 m, the width of the foundation (B) is 3.5 m and the depth of the foundation (D) is 1 m. Calculation of stability is declared safe under normal and earthquake conditions (overturning, sliding, and soil bearing capacity)