上游集水區適用集流時間公式之探討

Investigation of Time of Concentration Equations in Upland Watersheds

李光敦(KWAN TUN LEE) ； 楊銘賢(MING-SANG YANG)

《台灣水利》 46卷1期 (1998/03) Pp. 60-71

摘要

上游集水區水資源工程規劃設計過程中，常面臨的難題之一，便是如何正確估算集水區之集流時間。本文之目的乃在針對本省經常使用之集流時間公式，經由水力學的觀點，以數値試驗方式探討此集流時間公式之合適性。研究發現，角屋公式較能提供合理的集流時間推估值，Kirpich公式與Rziha公式有低估集流時間之情形，而水土保持規範（1996）中所列之公式則有高估集流時間之情形。研究中同時應用運動波理論，配合V型漫地流模型，分析集水區之集流時間值。數值試驗結果顯示，由於此V型運動波集流時間公式已考慮集水區中之幾何因子、糙度因子與降雨強度因子，且將集水區分爲渠流與漫地流不同的逕流機制，因此所推求之集流時間值，能顧及集水區之水文與地文特性。此外，因爲此V型運動波集流時間公式在實際應用上甚爲簡便，所以值得在本省大力推廣。文中並以水里溪流域之次集水區爲例，分別應用不同的集流時間公式代入計算，同時配合以合理化公式推求設計流量，以進一步分析不同集流時間計算方式所導致設計流量之嚴重差異。

關鍵字

集流時間 ； 上游集水區 ； V型運動波集流時間公式 ； 合理化公式

並列摘要

The estimation of time of concentration (t_c) is one of the most difficult problems for water resources design work in upland watersheds. The objective of this study is to investigate the adequateness of the time of concentration equations frequently used in Taiwan. Based on hydraulic point of views, numerical tests were used to demonstrate the reasonability of each time of concentration equation. The results show that the Kadoya equation can, in general, provide a reasonable estimation for the time of concentration. However, the Kirpich equation and the Rziha equation always give a lower estimate, and the Soil Conservation Handbook equation (1996) usually yields a higher estimate. The V-shaped kinematic wave t_c equation is also applied in this study for analysis. The results indicate that the V-shaped kinematic wave t_c equation can adequately account for the watershed hydrologic and geomorphic conditions, because the runoff process has contained the overland-flow state and the channel-flow state, and the equation includes the factors of watershed geometry, roughness condition, and rainfall intensity. The concise operation of the V-shaped kinematic wave t_c, equation is also one of the merits. Therefore, the V-shaped kinematic wave t_c equation is recommended by this study for practical design works in Taiwan. Three subbasins of Shuili watershed in the central part of Taiwan were adopted as examples in the paper. The values of time of concentration determined by using different t_c equations were then combined with rational method to estimate design peak discharges. The differences of these design peak discharges were also detailedly analyzed.

並列關鍵字

Time of concentration (t_c) ； Upland watersheds ； V-shaped kinematic wave t_c equation ； Rational method