Technical Studies

Typhoon Morakot occurred in 2009 had an extreme discharge with the peak near 35,000cms at Kao-ping weir, which exceeded the design discharge (26,800cms). The flood over-topped the embankment, and resulted in severe facilities and property damages. After typhoon Morakot, the meandering pattern of Kao-ping River changed and sediment concentration increased obviously. To ensure the stable water supply, South Region Water Resources Office, WRA studied on the channel migration and stable water supply countermeasures of Kao-ping weir reach. A two dimensional mobile-bed model (CCHE2D) was adopted to simulate the channel migration and deposition of Kao-ping weir reach. The study reach is from the upstream Li-ling bridge to the downstream Kao-ping bridge. Inflow sediment concentration, bed-material grain size and cross-sections of Kao-ping River were surveyed and analyzed. These basic data are used to calibrate and validate the numerical model. Meanwhile, short-term, mid-term and long-term stable water supply plans at Kao-ping weir are proposed. The stable water supply countermeasures of Kao-ping weir contain four main strategies, e.g., stabilize the flow path, improve the weir operation, enhance the embankment and homeland security, and develop the alternate sources of water. At the present stage, all the stable water supply countermeasures proposed in this study are planned within the powers and responsibilities of the WRA. In the simulation of stable water supply plans, scenario 4.1 (heighten the base of rubber weir about 1 m, heighten the concrete weir to EL.18.5m, and setup the diversion dike near the weir No.1 and concrete weir) was suggested. In comparison with the existing case, scenario 4.1 shows the velocity has an increased trends near the intake of Kao-ping weir, the bed elevation also has an erosion trend, and the flow path will shift toward the intake after the long-term simulation.