FLO-2D數值模式應用於土石流之分析-以南投縣頭坑溪為例

Application of FLO-2D Numerical Simulation Model in Debris-flow Analysis for Toukeng Creek, Nantou County

蔡旻霖(Min-Lin Tsai)

指導教授 ： 林基源

朝陽科技大學/理工學院/營建工程系碩士在職專班/碩士(2011年)

摘要

本研究利用FLO-2D二維數值模式，配合雨量資料及數值地形資料來模擬土石流流動狀態，包括流動深度、流動速度及堆積範圍，另分析頭坑溪土石流匯入和社溪主流短暫形成堰塞湖後，其主流流路變化及水位抬升之反應，亦探討堰塞湖流潰對兩岸與下游河道危害影響情形；同時藉由已蒐集之現地調查結果，驗證數值模擬之正確性。

本研究主要分為二部份，第一部份利用FLO-2D二維數值模式，進行莫拉克颱風實際降雨量於頭坑溪之土石流境況模擬，並藉由土石流災後航照圖，進行模擬結果及數據比對之判勢，結果大致符合。為了解FLO-2D模式應用於現地案例時數值參數對模擬結果之影響程度，改變模式演算方法。分別以不同降伏應力、黏滯係數、體積濃度與比重等參數進行模擬，以瞭解參數值對模式之影響性，作為後續模擬分析時優先修正之參數及調整量大小之判斷原則。

第二部分利用FLO-2D二維數值模式進行頭坑溪之土石流匯入主流和社溪，使主流流路改向及水位抬升之反應及其對兩岸與下游河道進行分析，再利用瑞士災害程度分類之方法，進行土石流危險區域危險度之等級分類，主要由影響強度與發生機率兩種參數構成，劃分為三種等級，並將災害模擬之結果繪製成危險區域分佈圖，以作為土砂防治工程之參考依據。

關鍵詞：土石流、FLO-2D、匯入、影響強度、發生機率。

關鍵字

土石流 ； FLO-2D ； 匯入 ； 影響強度 ； 發生機率

並列摘要

A two-dimensional numerical model FLO-2D was used to simulate debris flow for Toukeng creek in this study. Input the DTM (digital terrain model) data, hydraulic data and the rainfall data for Typhoon Morakot, the simulation results of debris flow including flow depth, flow velocity and deposition area were obtained. Besides, Toukeng creek debris-flow event in Tyohoon Morakot forms debris dam in Heshe River for a short time. The main-flow and water level changes in Heshe River were also simulated. The debris flow and debris dam caused the damages along Toukeng creek and downstream river hazards in Heshe River were discussed and compared with the field investigations. These results verify the accuracy of the numerical simulations.

This study comprises two main parts. The first part focused on the FLO-2D model, through inputting rainfall data during Typhoon Morakot to simulate debris-flow event in Toukeng Creek. Then, comparing the simulation results with aerial photograph taken after Typhoon Morakot, and it generally has a good match. Sensitivity of parameters was also proceeded to understand the impact of parameters on the FLO-2D simulation results. Five important parameters were chosen to discuss the sensitivity including, yield stress, viscosity, concentration of volume, and sediment specific gravity.

The second part focused on the effect of debris dam in Heshe River, caused during Typhoon Morakot for debris-flow event in Toukeng Creek. Toukeng Creek is a branch of the Heshe River that when the debris flow deposit in Toukeng Creek will affect the conditions of the main flows. These situations and water level changes in Heshe River were also simulated and discussed. This study also used the method of the Swiss to classify the hazard degree of debris flow in risk assessment, mainly by considering the influential intensity and occurrence probability. Finally, the analysis results were divided into three levels, and plotted the results of disaster simulations of the regional distribution of risk map, as a sediment control works of reference.

Key Words: Debris-Flow, FLO-2D, Debris Dam, Influential Intensity, Occurrence Probability.

並列關鍵字

Influential Intensity ； Debris Dam ； FLO-2D ； Debris-Flow ； Occurrence Probability

參考文獻

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