Perencanaan Desain Kolam Retensi sebagai Alternatif Pengendalian Banjir di Kecamatan Medan Maimun

Abstract

Deli River is one of the watersheds in the city. The catchment area of the Deli River reaches 47,748.01 Ha with a river length of 70 km from upstream to downstream. When climate change occurs, where in the rainy season with high intensity, the Deli River often experiences an increase in discharge, causing the river discharge to overflow and inundate residential areas in the Medan Maimun District. This is also triggered by a change in the function of land use where there is the development of residential areas in catchment areas in Medan Maimun District. The purpose of this final project is to reduce the flood discharge that occurred in the Deli River in the District of Medan Maimun and to find out how effective the construction of retention ponds in flood control efforts in the District of Medan Maimun is. The methodology used in this final project is the Nakayasu Synthesis Unit Hydrograph method to prepare a flood discharge plan using analysis of the distribution of probability and rainfall data. Based on calculations using the HSS Nakayasu flood discharge method, it is obtained 200,692 m3/s at the 20 year return period and the river capacity is 80,35 m3/s, and the planned retention volume capacity is 712,500 m3. With the planning of 3 retention ponds in several locations and the planned depth of each pond is 3m, the planned pond area is 237,500 m2 or about 23.75 ha. To drain the flood discharge into the retention pond, it is planned to use a spillway with a width of 43 m and a height of 2m, respectively. While the retention pond draining building is planned to use one sluice gate with a gate width of 50 cm and a height of 1.5m, pool II 1 m and height 1.5m and pool III 1.8 m and 1.5m high.