Flood Hydraulic Characteristics of Rubber Dam on Juwana River, Pati District

Pati Regency, Central Java Province is an area that frequently experiences floods, including tidal floods and flash floods during the rainy season. The Pemali-Juana River Basin Center has planned the construction of a rubber weir which will be built in 2022-2024 to overcome this problem. It is hoped that this rubber weir will be a solution for controlling floods and as a water storage system during the dry season. This research aims to model the hydraulic characteristics of the flow in Karet Juwana Dam under flood conditions (Q10, 20, 25, 50, and 100 years). Modeling of flow hydraulic characteristics using HEC-RAS 5.0.3 software. The modeling results show that when the rubber weir expands, maximum backwater occurs for 2.26 km upstream of the weir. The water level above the rubber weir is 1.0 meters with flow speeds upstream and downstream of the weir threshold of 0.40 m/s and 0.66 m/s respectively. Controlling flood levels against overtopping can be optimal if the water level is 0.60 meters above the crest. Hydraulically, the simulation results show that a deflation speed of 0.2 meters/minute can control overtopping optimally.