圖書典藏及影音數位平台

後龍溪下游段歷經921地震，加上近年颱風頻仍且挾帶強大豪雨，造成後龍溪流域諸多災害。由於地震及颱洪之作用，產生大量鬆散之砂石，河川輸砂特性因子改變，對於河道穩定產生極大之影響。後龍溪河道沖淤問題已成為河道穩定與防洪安全之關鍵要素，輸砂資料為河床沖淤變化與河川治理之重要參考依據，因此極有必要針對後龍溪水文及輸砂量進行量測，並據以推導研究河段之ㄧ般沖刷水深推估式，供防洪構造物設計及災害預警參考，以達防洪興利減災之目標。

Parametric data on hydrodynamic and sediment transport collected on-site during the study period were matched with hydrological events for a simultaneous full flood process measurement of the amount of sediment transported (suspended load) in Houlong River and in existing hydrological sites. The hydrological events of the primary and secondary tributaries were extrapolated from the inflow hydrograph. Sediment trap constructed at the sites during the flooding season were used to block sediment indirectly. Using the existing scouring tiles installed at the sites, hydrological sediment data, the sediment volume in the sediment trap, and normal river erosion information were collected during the typhoon season. The observed hydrological and hydrodynamic parameters were used as reference to assess the applicability of various sediment transport equations for estimating the volume of the sediment transport in the Houlong River. In addition, this study also used on-site hydraulic model testing to supplement numerical hydrological hydrodynamic analysis to verify the reliability of the results. With the analysis results, we can develop equations for native type sediment transports for the studied river section and obtain the basic information of river sediment transports. Subsequently, we can promote the flood control structures designed by other river bureaus in Water Resources Agency as reference when developing early disaster warnings to reduce disasters through flood prevention. In the mainstream of the Houlong River, a few appropriate observation sites were selected to survey the on-site hydrodynamics, sediment transport characteristics, and changing riverbed erosion patterns during the typhoon and rainy season. The main tasks of this study included using domestic and international sediment transport equations to measure the amount of sediment transport by employing instruments designed to collect and consolidate data from appropriate water flow stations (a minimum of two stations) located midstream and downstream. During the typhoon and flooding season, we conducted a full flood measurement of the hydrology and suspended load of the river to construct an on-site sediment trap for indirectly measuring the river bedload. Before and after the typhoon, topographic measurements using GPS positioning (a minimum two-point position) were conducted to determine the location for burying scouring bricks, and topographic erosion measurements were used to determine the flow of sediment from the inflow hydrograph during the hydrological event. These measurements were then applied to establish the Schoklitsch flow-type bedload formula and the revised Bagnold sediment transport empirical formula, which were used to measure the Houlong River channels. We conducted these processes in an effort to develop more suitable measuring instruments and methodology (field instruments installation program, communicating, observation personnel, measurement location and time, river characteristics, and financial assessment) for Taiwan.