ANALISIS ELEVASI MUKA AIR BANJIR PERUMAHAN ALTURA DESA MAMBALAN METODE SHERMAN

Flood Water Level Elevation Analysis Altura Housing, Mambalan Village Sherman Method

Abstract

Altura Housing is located on Jalan Raya Mambalan, Gunug Sari District, West Lombok Regency, with coordinates -8°55'02.36‘S and 116°130'29’E. Benchmark point + 38. The housing area is a potential rice field area. The topography of the housing area is terraced with sandy loam and clay soil types. The analysis aims to determine the flood height in the housing drainage channels according to the flow direction and the Altura Housing Site Plant. The Altura Housing Complex does not yet have a safe point against flooding, whether caused by very high rainfall intensity or flooding originating from the Rainfall Catchment Area (ADT). Therefore, an analysis of the Housing Complex flood level with a 2-year return period using the Sherman Method is required. The results of the analysis of the two-year return period flood discharge using the Sherman method obtained a Q₂Th of 0.878 m³/sec with a maximum rainfall intensity of 175.521 mm/hour and a drying duration of 10 minutes. And the channel construction material was designed using Yudith K225 concrete. The analysis results obtained a primary Yudith base width (B) of 1 metre, a secondary B of 0.8 metres and a tertiary B of 0.5 metres, an average slope of 0.002, a water velocity of 0.777 m/sec, and a water level in the primary channel of 0.4 m. The flood level or flood water elevation (EMAB) of the primary channel is +35.80, the secondary channel is +36.10, and the tertiary channel is +36.60. Therefore, it can be recommended that the Altura Housing Complex is safe from flooding