坡地崩塌對集水區沖蝕量及產砂量影響之研究

坡地崩塌是集水區沖蝕及產砂量大幅增加的主要原因之一，為探討崩塌對集水區沖蝕量及產砂量之影響，本文應用所發展之地文性土壤沖淤模式進行不同颱洪事件對集水區考慮崩塌之沖蝕量及產砂量影響之模擬演算，研究結果顯示，崩塌面積影響之沖蝕量與產砂量均明顯高於未崩塌影響，且分別高於未崩塌影響之1.1至7.7倍及1.3至9.1倍，沖蝕量與產砂量增加之趨勢與流域崩塌面積（崩塌率）變化趨勢相符。崩塌與未崩塌影響之沖蝕區域分佈雖有相似之趨勢，但考慮崩塌衝擊下之沖蝕之深度有更加劇之趨勢。依各級距沖蝕深度之面積統計，崩塌影響之沖蝕深度小於0.5公分的沖蝕面積相對於未崩塌影響是減少，而沖蝕深度大於0.5公分之沖蝕面積均為增加，且崩塌率愈大、累積雨量愈多之洪水事件，其沖蝕深度較大的面積增加較多。沖蝕總面積並未增加，而是沖蝕深度增加，即是沖蝕量之增加來自於沖蝕深度的增加。此結果提供集水區管理單位研擬相關土砂災害防治策略之參考。

關鍵字

崩塌；崩塌率；地文性土壤沖淤模式；土壤沖蝕；產砂量

並列摘要

Landslides are one of the main reasons for the soil erosion of a watershed and increases in sediment yield. To explore the effects of landslides on soil erosion and sediment yield, a physiographic soil erosion-deposition model was used in conjunction with a Geographic Information System to simulate soil erosion and sediment yield caused by the typhoon rainfall events and heavy rainfall. The results indicated that the soil erosion and sediment yield of landslide areas were both significantly higher than those of areas without landslides by 1.1-7.7 and 1.3-9.1 times, respectively. The trend of increasing soil erosion and sediment yield is consistent with change in the trend of the landslide ratio in the watershed. Although the distribution of soil erosion areas had a similar trend in areas influenced and not influenced by landslide, the depth of erosion in landslide areas was more severe. According to area statistics on erosion depth, compared with the area without landslide, the area of erosion depth of ＜0.5 cm is reduced; landslide ratio and erosion depth increase with an increase in accumulated rainfall. The total area of erosion did not increase, but the erosion depth increased. The results from the study will aid management units in the development of reference adaptation strategies.