|Abstract: ||摘要:早期水文模式均視暴雨之空間分布為均勻,藉以推求集水區之降雨-逕流關係,是以此種傳統水文模式,往往忽略暴雨移動特性對集水區出口處之逕流歷線所造成的影響。因此,如何考慮降雨之空間變異特性,以及移動暴雨對逕流歷線之影響,以正確估計集水區降雨-逕流關係,實乃當前水資源工程設計之一重要課題。 Yen and Chow(1969)之移動暴雨模型試驗資料雖已提供部分結果以供參考,但其模型試驗組別甚少,其試驗結果仍不足涵蓋移動暴雨對逕流影響之全部效應。本研究由因次分析著手,分析影響集水區逕流生成之因子;藉由此因次分析所得之結果,確立數值試驗之獨立變數,再以數值模擬方式進行試驗。由於在坡度較陡的中上游集水區,運動波方程式已足以模擬水流的運行,且就目前漫地流數值模擬理論發展而言,已可正確掌握研究中所欲觀察之現象;因此研究中採用線性與非線性運動波有限差分方法,並配合單一漫地流平面模型與V型漫地流平面模型以進行數值模擬。 數值試驗結果得知,當暴雨向下游移動且此暴雨長度小於集水區漫地流長度時,集水區仍會達全區域供水;此外,當降雨延時小於集水區集流時間之情況下,集水區也有可能達全區域供水。此結果有別於傳統水文學認為當暴雨長度等於漫地流長度,且降雨延時大於集流時間時,才會達到全區域供水之現象。研究中亦分別針對不同的暴雨長度與集水區地文因子進行數值試驗,歸納出可達全區域供水之條件,以提供水資源工程規劃設計者之參考應用。|
abstract:In general, the spatial distribution of rainfall is considered uniform in traditional hydrologic models for rainfall-runoff simulations. Thus the influences of a moving storm on hydrographs at the watershed outlet are always neglected. For this reason, the way of considering moving storm effects on watershed runoff needs to be investigated for water resources engineering. Although Yen and Chow (1969) conducted several experimental tests for moving storm, their results were not enough to cover all the influence factors of the moving storm due to the limited number of tests. In this study, the dimensional analysis technique is used to obtain the influence factors for further numerical tests. Since the kinematic wave approximation has been considered acceptable in steep upstream watersheds, linear and nonlinear numerical schemes for kinematic wave approximation are used to simulation the runoff on a single overland plane and a V-shape overland model. The results of the numerical tests indicate that for storms moving downstream, the whole watershed contributed can be attained even the storm length is shorter than the length of the overland plane, and even the rainfall duration is less than the time of concentration of the plane. This phenomenon of the whole watershed contributed is quite different from that in the traditional hydrology. Various storm lengths and watershed geomorphic parameters are used in the numerical tests to classify the flow condition for attaining the whole watershed contributed. The results are expected to be useful for the planning and design of water resources engineering works.