台灣上游集水區洪峰流量的產生和計算方法之研究

A Study of the Origins and Determination Methods of Peak Flows for Upstream Watersheds in Taiwan

10.29417/JCSWC.199211_23(2).0003

鄭皆達(J. D. Cheng)；林莉利(L. L. Lin)

洪峰流量 ； 上游集水區 ； 暴雨流出量產生機制 ； 集流時間 ； 逕流係數 ； Peak Flows ； Upstream Watersheds ； Stormflow Generation Mechanisms ； Time of Concentration ； Run-off Coefficient

中華水土保持學報

23卷2期（1992 / 11 / 01）

29 - 39

繁體中文

合理化公式至今仍為世界各地最被廣泛使用來估算無流量資料集水區之洪峰流量的方法。本研究乃從台灣上游覆蓋良好的森林集水區暴雨流出量產生機制的觀念來檢討評估合理化公式應用上的合適性、困難和其修正的必要性，其方法為：(一)比較不同土地利用下土壤渗透率和不同延時及重現期之降雨強度，以探討地表逕流發生的可能性和時地限制。(二)水文流量歷線圖分析的方法驗證以往假設暴雨流出量的來源大都是地表逕流的不合理。(三)評估現有以地表逕流為集流時間計算主要依據的合適性，並作初步改進建議。(四)由實際水文圖分析以算出逕流係數（C）值之大小，以作為選擇C值之參考。分析的結果顯示台灣上游森林集水區之暴雨流出量是由地表和地表下二種途徑流出，故而在估算集流時間時應考慮此二種流出途徑。同時也得分區依實際降雨與流量資料分析求出逕流係數，並將結果按集水區地質、地形、土壤、植生覆盖等因子列表，以作為各地區選擇合適C值的參考。

Upstream forested watersheds in Taiwan are generally characterized by steep slopes, shallow but highly permeable soils and peak flows occuring mainly in the May. October typhoon season in response to heavy rainstorms. Hydrograph analyses, comparison of rainfall intensities with soil infiltration capacities, and field observations all suggest that subsurface stormflows plays at least an equally if not more important role than the infiltration-exceeded surface overland flows in generating peak flows from forested watersheds in Taiwan. Most widely used peak flow estimation methods such as the Rational Method were developed according to the stormflow generation mechanisms that do not recognize the contributions from subsurface flows. Therefore, application of this commonly used Rational Method to forested watersheds n Taiwan require a more realistie determination of values for time of concentration t_r and run-off coefficient (C) with locally available rainfall and streamflow data, and based on the concept of stormflows from mixed surface subsurface pathways.