Pengendalian Banjir Hulu Sungai Juana, Kabupaten Kudus dan Pati, Provinsi Jawa Tengah

Abstract

The Seluna River system consists of the Serang River, the Lusi River, and the Juana River. The downstream section of the Lusi River meets the Serang River before the Klambu Dam. The discharge from the Klambu Dam flows back into the Serang River. Downstream, the Serang River divides into the Juana River and the Wulan River through the sluice gates at the Wilalung movable dam. The discharge from the Wilalung sluice gate is large enough to cause flooding in the Juana River. Previous flooding events indicate that the Juana River's capacity is insufficient to accommodate the inflow from 21 tributaries, so the discharge should not be diverted to the Juana River. Given the conditions and problems that have occurred, flood mitigation efforts are needed in the Juana River. Flood distribution analysis uses HECRAS 2D software. The planned flood discharge calculation uses the Nakayassu Synthetic Unit Hydrograph method. Hydraulic modeling uses the HECRAS 2D program. The discharge used for the upstream flood modeling of the Juana River comes from the release discharge of the Klambu Dam, while the downstream boundary of the Juana River is the Karet Juana Dam when the rubber dam is expanding and when the rubber dam is deflating. Flood modeling of the Juana River with two conditions, namely the existing channel dimension conditions and the planned channel dimension conditions. From the flood events that occurred, normalization planning was carried out with a compound river cross-section at STA 11 + 900 to STA 60 + 900, with a base width of 30 meters, the next cross-section width of 15 meters to the left and 15 meters to the right with a slope of each slope of 1: 2. So that the river cross-sectional area becomes 177.080 m² from the original 33.749 m². This effort can increase the full bank capacity which is proven to be able to reduce flooding. Based on the modeling results, the most critical condition is when the downstream boundary of the Karet Juana Dam is expanding. The results of the flood reduction analysis at a 25-year return period were 13.40%, a 50-year return period was 12.73%, and a 100-year return period was 11.64%.