| 摘要: | 台灣地區地形起伏變化劇烈，地質環境複雜多變，加上坡地開發不當，因此每逢颱風豪雨季節地質災害頻傳，近年來尤以土石流災害最為嚴重。為了瞭解地質分區對於土石流危險程度之影響，與提高危險程度判斷，並供災害防治之參考。本研究選擇大漢溪流域北橫公路大溪至明池段，根據流域與溪流特性選取空間因子，進行變異數分析，萃取出顯著影響土石流發生的土石流誘發因子，進一步利用多變量分析方法將土石流誘發因子進行關聯性組合與分析解釋，討論區域特性對於土石流誘發因子萃取行為與土石流危險溪流判定之影響，並結合多元迴歸分析，求得土石流危險溪流危險度指標，完成室內分析工作，最後再針對防災需要，配合野外調查工作，得到最後危險度等級。研究結果顯示，以往前人評估土石流危險度之影響因子與野外調查方法在沈積岩區可得到較佳的效果，但如果要推演至變質岩區甚至全省其他地區，則需要根據區域特性在影響因子萃取行為上做修正，才可得到較合理與正確的評估。本研究之分析流程對於不同地質環境仍可適用，唯參數分析結果可能不同。在危險度分級上，給予誘發因子權重得到土石流危險溪流危險度指標後，配合防災需要與野外查證，與水保局公佈之土石流危險溪流資料對照，可得到良好的修正效果。 Owing to steep topography, complex geological environment, and improper land use, geologic disasters occur frequently in Taiwan, especially during typhoon seasons. Recently, the disaster of debris flow is especially severe. The purpose of this study is to understand the in influence of geologic zoning in debris-flow hazard and to improve the decision-making in hazard precaution. The study area is located between Tachi and Minchi, North Cross Island Highway, the Da-Han River watershed area, northern Taiwan. Space factors were chosen according to the characteristics of alluvial basins and streams. ANOVA analysis was then performed to choose debris flow-inducing factors with significant effect. Furthermore, multivariate analysis was used to compose debris flow-inducing factors, so as to discuss the influence of debris flow-inducing factors upon the determination of debris flow hazard streams. In addition, the debris flow hazard assessment is classified by combining multiple regression analysis with field studies. Results of the analyses displayed several debris flow-inducing factors in the risk assessment of debris flow. However, field investigation coped well with the analytic result in the sedimentary rock area, but for the metamorphic rock area, the chosen debris flow-inducing factors need to be corrected according to the characteristics of the area. The analytic procedures of the study still can be applied to difference geologic zones, although different parameters might be induced. Finally, the classification of debris flow hazard needs to be coped with the weighting of debris flow-inducing factors, in addition to the double-checking by field studies. The analytic results can be further compared with the debris flow data provided by the Soil and Water Conservation Bureau, to achieve the optimum correction for final results. |
