Evaluasi pengendalian genangan dengan kolam retensi Jati Wetan Kecamatan Karanganyar Kabupaten Kudus

Jati Wetan Village frequently experiences inundation problems that require appropriate handling and control infrastructure. This study aims to evaluate the performance of the existing retention pond's flood control system and to plan an adequate infrastructure redesign to optimally accommodate the design flood discharge. The areal rainfall analysis in this study was conducted using the Thiessen Polygon method utilizing data from three observation stations: Kedung Gupit, DPU Kudus, and Tanjung Mojo. Furthermore, the surface runoff simulation to obtain the design flood hydrograph was calculated using the Nakayasu Synthetic Unit Hydrograph (SUH) method. The hydrological analysis resulted in a design rainfall of 214.86 mm for a 10-year return period, with a peak inflow reaching 592.84 m³/s. The evaluation showed that the existing retention pond is no longer adequate. This is evidenced by the volume of water that had to be accommodated reaching 2256402.71 m³, triggering a deficit and resulting in an overflow of 2106402.71 m³ starting at the 3rd hour. As a solution, a system redesign is proposed by expanding the pond area to 70 Hectares and a depth of 10 meters (7000000 m³ capacity), along with increasing the total pump capacity to 250 m³/s through a combination of 5 main pump units. The simulation of the proposed design showed a maximum volume of approximately 6503272 m³ with the highest water surface elevation at 9.29 meters at the 14th hour. Therefore, the storage capacity exceeds the calculated volume (Vcapacity > Vcalculated), completely eliminating the risk of overflow into residential areas.