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標題: A Study on Estimation of Runoff Coefficient with SCS CN Approach for Feitsui Reservoir Watershed
作者: Lai, Yu-sen
關鍵字: Runoff Coefficient
SCS CN Approach
Geographic Information System(GIS)
Remote Sensing Hydrology
出版社: 水土保持學系
摘要: The slope of hill in Taiwan has being been cultivated and used illegally and so that the disasters have been occurred so frequently result from pouring rain for the bellowing reasons: special geographical location, bad morphological and hydrological condition, the increasing population tension, industrial and economical consisting development and the social continuous change. To avoid and prevent disasters occuring, we must set in order to the watershed systematically and build soil and water conservation project in suitable place. Usually, we estimate the design runoff by Rational formula Q=(1/360)*CIA, and the key of successfully estimation of runoff is runoff coefficient C. This study use the image that was collected from the SPOT satellite, first to proceed image, secondary to analyze, and then use SCS CN approach of U.S. Soil Conservation Service, in order to conduct the situation of land use, the water content of soil, and the density of vegetation covering in the watershed. After combining by GIS, we can find the corresponding SCS curve number in every grid, and runoff coefficient of four seasons in the watershed. We found that the runoff coefficient is very high in summer and fall because of the rainfall those caused in West-South monsoon and typhoon. And in winter, result from the East-North monsoon in north of Taiwan, the runoff coefficient is higher than any other places in Taiwan. The results of this study will be available for people to refer when they will design soil and water conservation engineering constructions and to research on remote sensing hydrology.
台灣由於地理位置特殊,地文與水文條件本就不佳,加上人口持續成長之壓力、工商業及經濟持續之發展與社會型態不斷的改變,山坡地常遭非法濫墾與利用,以致每遇豪雨即常發生土砂災害。 因此,為避免及預防災害繼續發生,必須有系統地進行集水區整治並於合適地點施設水土保持治理工程,其設計尺寸則需依各迴歸年降雨強度所對應之逕流量。常用者多以合理化公式 Q=(1/360)*CIA 推估其設計逕流量,而公式中之逕流係數C乃洪峰逕流量估計成敗之關鍵所在。 本研究採用法國SPOT衛星影像經影像處理與分析後,運用美國水土保持局的SCS曲線值法,對集水區內之土地利用、土壤含濕程度與植生覆蓋密度等條件予以掌控,經地理資訊系統(GIS)之整合,以網格化的方式推求出各網格的SCS曲線值,並就春、夏、秋、冬四個季節分別建立整個集水區季節性之逕流係數,由結果明顯呈現出夏秋因受西南氣流及颱風之影響而使逕流係數較大,而冬季則因台灣北部地區受東北季風之影響,逕流係數值也偏高。本研究所得之結果可做為日後集水區整治及工程設計時較為合理且準確之依據,與遙測水文學之研究與發展的參考。
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