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標題: 二仁溪集水區降雨-逕流歷線模式建置之研究
Establishment of Hydrograph Simulation Model for Erhjin River Watershed
作者: 劉志宇
Liu, Chih-Yu
關鍵字: 降雨-逕流模式
Rainfall-runoff model
Normalized Difference Vegetation Index
Geographic Information Systems
Runoff coefficient dynamic model
Modified rational algorithm for predicting hydrograph
出版社: 水土保持學系
摘要: Erhjin river watershed is located in Southern Taiwan. Frequent flood events occurred each year during the period from June to August cause heavy casualties and serious property losses. Normalized Difference Vegetation Index derived from SPOT image coupled with Geographic Information Systems was used in this study to establish the rainfall-runoff model for runoff hydrograph simulation at the given point of channel. The correction coefficient (,) and the revised recession curve (R) calibrated from the observed data can be as the index of watershed characteristics. The correction coefficient α represents water conservation capability; the β-value can be employed as the index of sediment concentration in runoff. The model improved the limitation of rational formula in large watershed and used distributed concept for runoff coefficient calculation in runoff hydrograph simulation. The results show a highly correspondence for single and double peak event and poor agreements for multi-peak hyetograph patterns. To examine the variation of correction coefficient in different watershed, the Erhjin river basin shows minimum variance of  and  because of low infiltration rate in the watershed. About thirty creeks with highly potential debris flow in Chen-yu-lan basin results in a maximum variance of  at Ne-mao-pu station, while the maximum variance of  appears at the Jieshou bridge station due to the antecedent precipitation.
二仁溪中、上游集水區開發甚早,早期地表未被破壞,林相完整,後因大量開墾,造成表土嚴重流失。二仁溪集水區多屬泥岩惡地,區內植被為銀合歡、相思樹、竹林等人造次生林;集水區雨季集中於六~八月,泥岩裸露地區,水源涵養能力差,地表沖刷嚴重,雨水挾帶泥沙,向下宣洩,於下游地區往往造成重大水土災情。為保護民眾生命財產安全,建置降雨-逕流歷線分析系統,供集水區整治及防災參考極為重要。 本研究以常態化差異植生指標(Normalized Difference Vegetation Index;NDVI)結合地理資訊系統(Geographic Information System;GIS),考慮空間及時間分布因素,建立二仁溪流域之逕流係數變動模式,再利用網格式之降雨強度資料及配合集流時間之集水區面積參數,以等集流時間之概念,修正合理化公式之限制,提出合理化公式-流量歷線修正式。透過監測站實測流量資料,推求合理化公式-流量歷線修正式之(洪峰到達時間修正係數)、(洪峰值修正係數)校正係數及退水修正式R,建置二仁溪流域降雨-逕流模式。研究結果顯示模式模擬單峰暴雨時極佳,其效率係數可達0.96;雙峰暴雨之模擬效率稍低,但其效率係數亦達0.85以上;對於多峰或離散型降雨之模擬較不佳。 另外將北部地區之基隆河,中部地區之濁水溪、烏溪與南部二仁溪所求得α、β值做比較。因陳有蘭溪集水區內土石流潛勢溪流多達30條,易使集流時間估算產生誤差,造成內茅埔站α值之變異係數最大;而基隆河流域介壽橋站受前期降雨的影響,造成其β值之變異係數較大,而二仁溪流域則因上游集水區屬泥岩地區,水源涵養能力差,校正係數較不受降雨影響,故變異係數最低。
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