Technical Studies

The project has five main research items in this year. The first item is the review and establishment of river warning stages after the flood of this year, served as the reference of the river warning stage announcement in next year. The second item, the new water stations establish the river warning stages. The third item is the installation of second type 1D hydraulic model of the central authority’s river, model verification and validation that can insert in FEWS-TAIWAN forecasting platform. Fourth ,the installation of 1D sediment model including model verification and validation is performed and applied to the Zengwen river. Finally, the training and transferring of the model is executed. This year project results are summarized as follows:

• 1.According to the river warning stage of the central authority’s river analysis and review results are shown in summary Abstract Table 1. It can be served as the reference of the river warning stage announcement in next year.

• 2.In the warning stage of the central authority’s drainage, using the measurement data of water stage and drainage warning stage analysis results of this year, the 1^st degree warning stages are still applicable and the relevant results and warning stage in next year are described in section 3.11.

• 3.This project installs second type 1D hydraulic model (CCHE1D) for 14 rivers including Lanyang, Fengshan, Touqian, Daan, Wu, Zhuoshui, Puzi ,Bazhang, Zengwen, Yanshui,Gaoping, Donggang, Hualien and Tamsui rivers. Through WRA’s other working group, the model output data can be connected to the FEWS-TAIWAN forecasting platform.

• 4.After the model verification and validation of 1D hydraulic and sediment model (CCHE1D) for the Zengwen River, we compared two model simulation results of the flood level and flood rise rate. The results show that in the sediment model simulation results at the flood level are lower than hydraulic model simulation results. With the simulation time increases, the amount of the erosion of the bed increases in the sediment model, the two model simulation results of the flood level difference also increase.

• 5.The same hydrological conditions are used to compare SOBEK1D, CCHE1D hydraulic models, CCHE1D sediment model simulation results of the flood level and flood rise rate. The different model simulations show the difference on the water level,and the error is primarily due to numerical skills in the model itself.Because the sediment model considers the bed change process, the water level simulation results are also lower than hydraulic model simulations. The reason may come from the increase of flood capacity under the bed degradation.

• 6.To achieve the relevant technology transfer of establishment of river warning stages, we prepared operation manual for running the SOBEK hydrology and 1D hydraulic models, and using the SOBEK model to the establishment of river warning stages. In addition, we also went to Lan-Sheng Bridge, Shang-Gui-Shan Bridge and Sa-Xia gage stations and explained in the field the significance of the establishment of river warning stages to achieve the relevant technology transfer.

• 7.Establishment of river warning stage has its own basic assumptions and limitations. As natural and human-induced environment change, it will result in the question of applicability of existing river warning stages. Therefore, revision of the river warning stage timely can conform to demand of flood prevention.