近年來位於太魯閣國家公園內的合歡山遊憩區所面臨的遊憩壓力越來越大，遊憩活動則會對土壤、植被、野生動物與水質造成衝擊。本研究針對太魯閣國家公園內合歡山群峰7條步道，總計14.55公里進行步道土壤沖蝕深度的普查。除了每隔30公尺紀錄步道沖蝕最深深度、坡度與寬度，並針對合歡山地區步道遊客人數做夜間問卷與日間實際遊客人數監測的調查。夜間問卷調查地點在合歡與觀雲兩山莊，日間遊客數監測則是選擇東峰與北峰兩條步道。並且利用20m×20m的數值化地面模型(DTM)來計算步道所經過的邊坡坡度與坡向。 結果顯示，影響沖蝕深度的因素有坡度、坡長與施工遺痕。步道坡度與沖蝕深度的相關係數除了北峰主線與石門山步道沒有相關外，其餘四條步道皆呈現坡度與沖蝕深度的高度相關。北峰主線步道下段是因為植被與土壤的保護所以沖蝕深度與坡度沒有呈現出相關;石門山則是因為有施工遺痕所以在坡度緩的地方有較深的沖蝕深度。坡長方面，經由東峰合歡山莊線單元長度的取樣方式得知，在相同坡長的下段沖蝕情況會比上段更嚴重。合歡群峰有施工遺痕情況的四條步道中，除了主峰武嶺線施工遺痕路線與無施工遺痕路線沖蝕深度沒顯著差異外，其餘三條步道皆顯示施工遺痕路線對沖蝕深度有顯著影響。 步道遊客人數使用的差異會反映在步道寬度上。經比較三條步道的主線與支線寬度，結果顯示三條主線步道寬度皆顯著寬於支線寬度。 根據本研究調查結果，建議對沖蝕嚴重但遊客人數較少的北峰支線與東峰松雪樓線步道暫時封閉，並且對其它步道沖蝕深度超過30cm的路線與坡長太長的路段進行水土保持方面的工作。 關鍵字:土壤沖蝕，步道，合歡山區。 ABSTRACT Trails especially unattended trails in alpine area could cause serious soil erosion problem along the route. Recently, recreation activities at Mt. Hohuan recreation area in the Taroko National Park are escalating alarmingly. Soil erosion along seven trails with a total length of 14.55 km at Mt. Hohuan was surveyed. Each trail path was divided into 30-meter sections and maximum soil erosion depth, path width, and section slope were measured. Impact of visitors on those trails was also estimated based on questionnaire conducted during the night at the Hohuan and Kuanyun lodge. Soil erosion impact caused by seven trail paths around the Hohuan area were assessed based on soil erosion depth, path width, and amount of soil erosion. Sideslope and aspect were calculated by digital terrain model. Relationship of soil erosion, path width, path slope, slopeside, aspect and number of visitors were investigated mainly based on correlation analysis. Survey result indicated that the critical factor that influence trail erosion depth is trail slope. Erosion depth at 4 trails were significantly correlated with trail slope except Mt. North-Major Trail and Mt. Shihmen Trail. There are better vegetation coverage and soil condition along the trail such that the soil erosion problem is somewhat eased at Mt. North-Major Trail. At Mt. Shihmen Trail, however, the erosion depths at flat slope were deeper than expectation possibly due to some past engineering works along the trail. Slope length is another factor that influence trail erosion depth. There are four trails which show traces of engineering works. Among them, soil erosion depth at sections which had traces of past engineering works along 3 trails, except Mt. Major- Wuling, shows deeper soil erosion than those sections without engineering works. Trampling caused by visitors, however, is the primary agent of trail widening. Survey result also indicated that the width of minor trail sections are narrower than that at major sections of trails. Finally, in order to remedy the soil erosion problem at those high mountain trails, it is suggested that Mt. North-Minor Trail and Mt. East- Sunghsueh Lodge Trail could be closed at least temporarily because there are alternative trails available. For trail sections that erosion depth deeper than 30 cm and longer slope length remedial works such as water bars could be installed. Keywords: trails, soil erosion, Mt.Hohuan Area