合理化公式應用於台灣集水區適應性之研究－以翡翠水庫集水區為例

Abstract

合理化公式Q=CIA為設計集水區系統時推估最大洪峰流量之常用方法，由於此法屬經驗公式且考量參數簡單，故常有無法因應各地實際洪峰流量之情形發生。 本研究以翡翠水庫集水區內六個雨量站，自西元1988~2006年連續19年之雨量資料，以對數皮爾森三型分佈法分析不同回歸年之最大日雨量。再利用以實測時雨量資料修正物部式K值，推求出最大時雨量作為合理化公式之降雨強度(I)；另以GIS相關軟體對集水區做空間分析得各子集水區面積(A)及集水區特性因子；最後再由多場單一降雨事件與最大洪峰流量相對應關係，即可決定出翡翠水庫集水區之洪峰逕流係數(C)。研究成果如下： 1.翡翠水庫各雨量站經修正之物部式K值範圍在0.556~0.593之間。 2.翡翠水庫4個子集水區內逕流係數皆與洪峰歷線上升前之累積雨量 呈高度相關。代表土壤臨前濕潤條件對逕流係數影響甚大。 3.翡翠水庫內4個子集水區之集流時間為2~4小時。

The rational formula, Q=CIA, is possibly the simplest flood estimation technique available using rainfall-runoff relationships. The many criticisms regards it’s too over- simplification, and sometimes it could not fit the different watershed. The annual maximum daily rainfall data of the six rainfall stations in the Feitsui Reservoir Watershed between 1988~2006 inclusive (19years) were made using the log Pearson Type III distribution method. We analyzed the rainfall intensity (I), based on the data for hourly rainfall from 1988~ 2006, and modified the parameter-K in Monobe formula; Then used the GIS software to do the spatial analysis for the four sub-basins. Analyzed the many single rainfall events to find the correlation with the peak flood flow, and decided the runoff coefficient (C) in the Feitsui Reservoir Watershed. 1.The Monobe formula’s parameter K is 0.556~0.593 in the Feitsui Reservoir Watershed. 2.The runoff coefficient in four sub-basins of Feitsui Reservoir Watershed is highly related with the accumulate rainfall before the hydrograph start to rise. 3.The concentration time in the four sub-basins of Feitsui Reservoir Watershed is 2~4 hours.