Sediment Environment Assessment System for the Tseng-Wen and Baihe Reservoir Watersheds in Taiwan

本研究以曾文及白河水庫集水區為例，運用易於量化、取得且能反應現況之指標，並建立指標合理變動範圍，希冀從中瞭解水庫集水區土砂環境遭遇問題及評估現況環境，供作保育治理需求參考應用。分析結果顯示，兩水庫集水區境內涉及山坡地範圍之子集水區中，有37 個子集水區屬整治需求區域，其總面積約佔整體水庫集水區之43.2%；可見莫拉克颱風後之治理工作，雖已加速水庫集水區整體土砂環境復育，但仍需嚴防道路無法抵達或採自然復育等區域，坡面上不穩定土砂造成二次災害。建議應進行集水區整體土砂災害處理策略擬訂之水土保持需求評估工作，避免後續災害的形成與擴大。This study completed the assessment of the sediment environment of the Tseng-Wen and Baihe Reservoirs, considering the factors of sediment-related disasters to evaluate the threat of sediment production and plan the requirements of soil and water conservation works for the reservoir watersheds. Case studies suggest the post-typhoon Morakot sediment environment of the Tseng-Wen and Baihe reservoir watersheds in 2014 has recovered well after remediation, but is still in a relatively poorer condition than pre-typhoon Morakot. Further, to limit the occurrence of secondary disasters in disaster-prone creek watersheds, this study suggests a list of watersheds requiring improvement to their sediment environments under the suggested potential sediment production classification. Consequently, there are 37 areas located in the Tseng-Wen and Baihe reservoir watersheds still requiring soil and water conservation works. These observations can serve as the basis for effectively managing reservoir watersheds, planning of disaster prevention work and reducing the risk of rapid sedimentation in reservoirs during the flood season