THE DESING OF TANJUNGWADUNG RETENTION BASIN LOCATED IN TANJUNGWADUNG SUBDISTRICT KABUH

Tanjungwadung Village is one of the villages in Kabuh District, Jombang Regency. This area often experiences flooding in the rainy season and drought in the dry season. In Tanjungwadung Village there is a river, namely the Wadung River, which has the potential to be a water source to meet the water needs of the local population. Therefore, in this area it is necessary to plan a water storage building as an effort to control flooding and provide for irrigation needs.
In this final project, the Tanjungwadung Dam is planned with the position of the weir axle determined in the previous analysis. Planning was carried out by analyzing existing data to obtain a design for the Tanjungwadung Embung. The analysis carried out included hydrological analysis, hydraulic analysis, as well as stability control of all buildings at the Tanjungwadung Embung. Calculations used in planning include planning rainfall calculations using the Pearson Type III Log, analysis of discharge availability using the FJ method. Mock, planned discharge using the Nakayasu hydrograph method, storage analysis using the reservoir capacity curve, analysis of the reservoir body and its stability, and overflow analysis using Microsoft Excel.
From the calculations that have been carried out, it is obtained that the peak flood discharge (Qp-flood) using the Nakayasu method for several 50 year return periods is 64.54 m3/s, the inundation area is 7,602 m2 and the total reservoir volume is 23,302 m³. The embung design uses homogeneous backfill with a width of the top of the embung of 5 meters, a height of the body of the embung of 5 meters, an upstream slope of 1:2.5, a downstream slope of 1:20. The spillway uses the ogee type, the width of the lighthouse is 5 m, the height of the lighthouse is 2.5 m, with the stilling pool type, namely USBR type III.