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Scaling analysis of peak flow and drainage area in nested watersheds
|Authors: ||Nai-Chin Chen|
|Contributors: ||NTOU:Department of Harbor and River Engineering|
scaling relationship;transition break;stream network structure;watershed geomorphology;digital elevation model;kinematic-wave-based geomorphologic IUH model;nonlinearity
|Issue Date: ||2011-06-30T07:51:37Z
|Abstract: ||本研究內容為探討集水區尖峰流量與面積尺度關係之線性與非線性特性，以及考慮不同流域範圍下集水區尺度關係之變異情形。研究中選取俄羅斯地區Komarovka流域與美國密西西比州之Goodwin Creek試驗集水區為研究集水區，應用數值高程模式與運動波－地貌瞬時單位歷線模式，配合統計尺度理論以分析尖峰流量與集水區面積之尺度關係，以瞭解集水區空間尺度變異臨界點發生之機制，及探討不同降雨事件下之尺度關係。 本研究首先迴歸集水區尖峰流量紀錄值與面積之指數關係，初步瞭解尺度關係之非線性關係。而受限於研究集水區水文測站之個數，研究中藉由運動波－地貌瞬時單位歷線模式推估無紀錄地區之尖峰流量以補足各面積尺度之值，並根據研究集水區之河川網路結構，探討尖峰流量與集水面積尺度關係之尺度變異臨界位置的影響，並將模式推估值與紀錄值加以驗證。研究結果顯示，考慮主流河川或是同時考慮集水區內其它主要逕流路徑之尺度分析，其小面積尺度區之尺度指數迴歸值並無太大差異。迴歸曲線之小面積尺度區接近線性關係，而大面積尺度區因樣本數減少與集水區河川網路結構特性，導致尺度關係並不一致。 研究中深入探討集水面積與尖峰流量關係圖上，線性與非線性迴歸線之變異臨界點。研究結果發現，若沿著河川主流往下游逐步計算其上游匯流面積，當有較大次集水區匯入時，因匯流面積遽然增加，其於面積與尖峰流量關係圖產生明顯不連續現象，此亦即是線性與非線性迴歸線變異臨界點之所在位置。此外，研究中亦分別探討不同集水區範圍下尖峰流量與面積之兩段式迴歸關係，結果顯示在不同的集水區尺度區間裡，皆能將集水區尖峰流量與面積之兩段式迴歸關係加以區分，而成為大面積尺度區與小面積尺度區，且其尺度指數分別呈現小於1.0(大面積尺度)與接近於1.0(小面積尺度)之非線性與線性關係。|
The objective of this study is to investigate the nonlinear scaling relationship between peak discharge and drainage area, and to realize the variation of scaling relationship in different basin scales. In this study, Komarovka River basin in Russia and Goodwin Creek experimental watershed in Mississippi of USA were selected as test sites. Analysis was performed based on a digital elevation model (DEM) and the kinematic-wave-based geomorphologic instantaneous unit hydrograph model (KW-GIUH) to investigate the cause of the transition break in the scaling relationship graph. Statistical scaling theory was also adopted to describe the scaling relationship between peak discharge and drainage area from linear to nonlinear. The peak discharges vs. drainage areas for individual rainstorms were plotted together with corresponding regression curves to provide a preliminary analysis of scaling relationship based on available record data. In considering the limited record data, KW-GIUH model was verified with record data and then used to generate peak discharges at ungauged sites. The results indicated that only slight differences can be found in the lower-segment of the scaling relationship regressed line considering either only the mainstream path or the major tributaries runoff paths. The scaling relationship was found approach to linear in the regressed lower-segment region and it was nonlinear in the regressed upper-segment region. The transition break of the two-segment regressed lines from linear to nonlinear on the drainage area vs. peak discharge graph was detail investigated. The results indicated that when a large tributary flowed into the mainstream, an abrupt increase in the drainage area was observed in the graph of drainage area vs. distance to mainstream outlet. The abrupt change corresponded to the transition break shown in the graph of peak discharge vs. drainage area, which was an indication of the two-segment scaling relationship separation. Moreover, in considering different ranges of basin scale, numerical experiments were conducted to investigate the change of the scaling relationships from downstream to upstream along the mainstream. The results illustrated that both the linear and nonlinear relationships could be found for different ranges of basin scale in the Komarovka River basin and Goodwin Creek experimental watershed. The results also showed that the lower segment (for small watersheds) approximates to a linear relationship between the peak discharge and watershed size, and the scaling exponent for the upper segment (for large watersheds) is less than unity.
|Appears in Collections:||[河海工程學系] 博碩士論文|
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