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標題: Application of Grid Rational Algorithm for Predicting Hydrograph (GRAPH) Model for Runoff Simulation of Ba-zhang Creek Watershed
作者: 鍾亦婷
Chung, Yi-Ting
關鍵字: Runoff coefficient;逕流係數;Rainfall-runoff model;Ba-Zhang river;降雨-逕流模式;八掌溪
出版社: 水土保持學系
本研究選取八掌溪軍輝橋及義竹橋上游之集水區為研究範圍,應用網格式合理化法(GRAPH),以等集流時間之概念,利用常態化差異植生指標(Normalized Difference Vegetation Index, NDVI)計算集水區內每一網格之初始逕流係數,建立八掌溪集水區逕流係數變動模式,配合降雨資料建立合理化公式-流量歷線修正式,再透過監測站之實測流量資料,推求合理化公式-流量歷線修正式之、校正係數,建置八掌溪集水區降雨-逕流模式,為調整洪峰到達時間之係數,為調整洪峰流量之係數。

Flood hazards frequently attack riverine areas and cause casualties on the Ba-Zhang River watershed both in steep headwaters and downstream alluvial floodplains. After the 921 Earthquake, the loosened soils and rocks are easy to collapse. Massive landslides and debris flows are regularly induced by storm events. The human lives and properties are under threatened. In order to prevent watershed hazards, a systematic watershed control and management is an appropriate suggested method. The watershed analysis system simulates real-time data to predict hydrograph. The calculate results can provide critical information for hydraulic routing, sediment transport estimation, and emergency rescue measures.
The Junhui Bridge and the Yizhu Bridge as the outlets for the Ba-Zhang River sub-watersheds were used in this study. Combining the concepts of isochrones for time of concentration and raster runoff coefficients derived form Normalized Difference Vegetation Index (NDVI), the dynamic simulation model for the Ba-Zhang River watershed was established. Using precipitation data, the revised rational formula method for predicting runoff hydrograph was employed to simulate real-time flow discharge. The  and  correction coefficients were proposed to modify the predicted hydrograph. The rainfall-runoff simulation model for the Ba-Zhang River watershed was established successfully. The proposed  and  values are the correction coefficients of peak arrival time and peak flow.
From the simulated results, a better model efficiency was obtained for the single-peak rainfall pattern. The model acquired lower accuracy for excessive sensitivity in raising limb and recession segment reactions during low discharge or multi-peaks rainfall patterns. The proposed α correction coefficient represents water resources conservation capability. Because the disturbed downstream watershed may decrease the time of concentration, the larger area is simulated; the lower α value will be obtained. The β-value can be regarded as the index of sediment concentration.
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