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Development of watershed rainfall-runoff model based on partial contributing area concept
|Authors: ||Chin-Hsin Chang|
|Contributors: ||NTOU:Department of Harbor and River Engineering|
partial contributing area;GIUH;kinematic-wave;surface flow;subsurface flow;digital elevation model
|Issue Date: ||2011-06-30T07:30:53Z
|Abstract: ||傳統水文學中，颱洪流量之模擬通常是以直接逕流概念推衍集水區降雨逕流關係。直接逕流概念是將集水區內地表逕流與地表下逕流之水流運行機制視為相同，並假設在降雨逕流過程中，集水區內每一個位置點均有地表逕流產生。然而，由於地表下逕流為水體入滲至地面下後，經上層土壤流動至河川，其水流運行機制與地表逕流並不相同；並且在實際降雨逕流過程中，集水區內地表逕流往往僅發生於河川附近地下水位較高，且土壤水份達飽和之區域。因此若以傳統方式進行集水區降雨逕流模擬，將因無法反應集水區內水流之真實流況，而造成逕流模擬之誤差。 本文應用地表逕流僅發生於部分集水面積之觀念，先探討部分集水面積之形成因素，並配合數值高程模式以推算部分集水面積之分佈範圍，而將集水區內水流之運行區分為地表逕流與地表下逕流兩種不同區域。研究中並建立以部分集水面積觀念為基礎之運動波-地貌瞬時單位歷線模式，應用運動波理論配合曼寧公式與達西公式，分別模擬地表逕流與地表下逕流之運行，以推衍集水區降雨逕流關係。 本研究以臺灣北部大漢溪流域之橫溪與三峽集水區為模式應用集水區，藉由數值高程模式推算以部分集水面積觀念為基礎之運動波-地貌瞬時單位歷線模式中，所需之各項地文特性因子，並以實際颱洪事件進行逕流模擬分析。研究結果顯示，應用本研究所建立之降雨逕流模擬方式，不論尖峰流量或逕流歷線上升段與退水段之模擬，皆能得到良好的模擬結果。研究中並探討部分集水面積範圍對集水區降雨逕流模擬與地表糙度係數檢定之影響，以供水利工程師進行集水區降雨逕流模擬之參考。|
For conventional hydrology, the direct runoff concept was usually adopted for rainfall-runoff simulations in storms. According to the direct runoff concept, mechanisms of surface flow and subsurface flow were assumed to be the same and the entire watershed was assumed to contribute surface flow into the drainage network. However, field investigation showed that only areas near channels or those areas with high groundwater level contribute surface flow. Rainfall generally infiltrates into soil in the far stream region, in which the groundwater level is low, and then flows slowly into channels as subsurface flow. Since the subsurface-flow mechanism is different from the surface-flow mechanism, runoff analysis only based on the surface-flow mechanism cannot adequately simulate field runoff processes. This resulted serious errors in conventional rainfall-runoff simulations. In this dissertation, the partial contributing area (PCA) concept was employed and influence factors of the PCA phenomena were investigated. Based on the PCA concept with a use of a digital elevation model (DEM), the size of the PCA during storm was determined. Consequently, the watershed area could be divided into surface-flow regions and subsurface-flow regions. A modified kinematic-wave based geomorphic instantaneous unit hydrograph model (KW-GIUH) was used to simulated runoff processes. While considering the PCA concept in the KW-GIUH runoff simulating, the surface flow could be simulated by Manning’s formula and the subsurface flow by Darcy’s law, in contrast to both surface and subsurface flows simulated by Manning’s formula conventionally. Heng-Chi watershed and San-Hsia watershed of Ta-Han River basin in northern Taiwan were used to validate the proposed model. The required geomorphic factors of the KW-GIUH model were obtained by using a DEM. Storm records were used to verify the model performance. Results showed that significant improvements were found in the simulation of the rising and recession limbs of the hydrographs. The influences of the PCA on the rainfall-runoff simulation and the calibration for overland-land roughness coefficient of the study watersheds were detail discussed and carefully analyzed for providing reliable information for practical rainfall-runoff simualtions.
|Appears in Collections:||[河海工程學系] 博碩士論文|
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