考慮時變性部分集水面積概念之降雨逕流模式

Development of Watershed Rainfall-Runoff Model Based Ontime-Varying Partial Contributing Area Concept

黃仁國(Jen-Kuo Huang) ； 李光敦(Kwan-Tun Lee)

《中國土木水利工程學刊》 21卷1期 (2009/03) Pp. 13-23

https://doi.org/10.6652/JoCICHE.200903_21(1).0002

摘要

早期降雨逕流模式之觀點，認為降雨期間整個集水區均能發生地表逕流，而事實上地表逕流僅發生於河川附近地下水位較高，且土壤水份達飽和之部分集水面積。本研究以即時降水指標為基礎，探討降雨期間土壤水份變化情況，而後利用一指數方程式，建立即時降水指標與部分集水面積之轉換關係，據以推求部分集水面積之時變效應。研究中結合以考慮部分集水面積觀念之運動波－地貌瞬時單位歷線模式，進行颱洪事件之模擬，以評估即時降水指標與部分集水面積轉換關係的適用性。
本研究以臺灣北部地區淡水河流域五堵集水區、中部地區濁水溪流域桶頭集水區為研究集水區，藉由連續小時降雨資料，推算即時降水指標與部分集水面積變化情形，並說明指數轉換關係中相關參數之影響特性。研究結果顯示，結合即時降水指標與運動波－地貌瞬時單位歷線模式，可得到良好的逕流歷線模擬。研究中並發現，部分集水面積比例於降雨初期為最小，而於最大降雨強度或尖峰流量發生時刻達最大值，並隨著歷線退水期而遞減。本研究之結果可提高逕流模式參數之穩定性，有助於執行颱洪期間之逕流預測工作。

關鍵字

部分集水面積 ； 即時降水指標 ； 運動波－地貌瞬時單位歷線模式

並列摘要

In conventional rainfall-runoff modeling, entire watershed was assumed to contribute surface runoff to the drainage network during rainstorm. However, field survey has shown that only the areas near channels or those areas with high groundwater level contribute surface flow. In this study, the time-varying soil moisture content in the study watershed was analyzed based on a current precipitation index (CPI). An exponential function was selected to describe the relationship between the CPI and the partial contributing area (PCA) during storm events. A kinematic-wave-based geomorphic instantaneous unit hydrograph model (KW-GIUH), which can consider PCA concept, was used to simulate watershed storm flow to evaluate the adequateness of the transform functions for the relationship between CPI and PCA.
Hydrologic records from two watersheds, Wu-Tu and Tung-Tou in Taiwan were adopted to validate the proposed analytical procedure for storm runoff simulation. The time-varying CPI and PCA series were generated from hourly rainfall records, and the influences of the parameters in the transform function were detailed investigated. The results show that the KW-GIUH model coupled with the time-varying PCA provides good performances in runoff simulation. Moreover, the PCA ratio was found increasing from the beginning of the rainstorm and attaining to a maximum value at the occurrence of the peak discharge or the maximum rainfall intensity in the storm. Subsequently, the PCA ratio decreases gradually in accordance with the recession of the storm flow. The results of this study are expected to improve the reliability of the rainfall-runoff model parameters to provide a stable model for flood prediction during storms.

並列關鍵字

partial contributing area ； current precipitation index ； KW-GIUH model