| 摘要: | 本研究選取火炎山區域、泉州寮、番婆夾坑以及水土保持局公告之土石流潛勢溪流:投縣DF226、高市DF018、新北市平廣溪及中市DF080 (含中市DF080-1及海風缺)作為研究區域。研究採用ESRI開發之地理資訊系統(Geographic Information System, GIS)軟體ArcGIS，分析數值地形模型(Digital Elevation Model, DEM)，並萃取高程、集水面積、坡度等地貌參數，藉此探討各集水區的地形特徵與土砂災害潛勢。
首先利用集水區險峻值(Melton Ratio, MR) 進行初步分類，將主流上任一點的MR值與其對應的集水面積無因次化，以分析其沿程變化趨勢，據此歸納集水區類型，並進一步將高程差(∆H)、坡度(S)及形狀係數(F)無因次化後與險峻值比較，分析不同類型集水區在各項地貌指標間的對應關係。
為更細緻解析各集水區地貌發展與侵蝕潛勢，本研究進一步採用多種輔助分析方法，如測高曲線(Hypsometric Curve)與統計矩參數、坡度與集水面積關係(Slope - Area Relationship, S-A)、集水面積機率分布以及實際溪流起點的分布特徵等。測高曲線統計矩顯示火炎山1、3、5號坑以及投縣DF226呈現出較高的侵蝕程度，坡度-集水面積(S-A)關係顯示礫石層地區較易集中水流、促進侵蝕與河道化，相對地，以頁岩與砂岩為主的區域則需更大集水面積與能量才能切入地表。集水面積機率分布顯示所有集水區均遵循冪律，並在不同集水面積偏離，在溢流點處又會遵循另一種冪律。此外，研究發現200個網格面積作為溪流起點門檻與實際溪流起點的比較顯示，在砂頁岩互層河川具有適用性，但對於如礫石堆積等特殊地形，仍應輔以坡度、地質與地形等參數判釋，以提升精確度。
;This study examines the geomorphic characteristics and sediment hazard potential of selected watersheds in Taiwan, including the Huoyanshan area, Quanzhouliao, Fanbojia Keng, and several debris-flow-prone streams designated by the Soil and Water Conservation Bureau: DF226 (Nantou County), DF018 (Kaohsiung City), Pingguang Stream (New Taipei City), and DF080 (including DF080-1 and Haifengque, Taichung City). Using ArcGIS and digital elevation models (DEMs), key topographic parameters—elevation, drainage area, and slope—were extracted to assess watershed features and potential erosion risk.
The Melton Ratio (MR) to classify watersheds. MR values along the main channels normalized by corresponding drainage areas to analyze spatial trends. Additional dimensionless indicators—elevation difference (∆H), slope (S), and form factor (F)—were compared with MR to explore interrelations among watershed types.To further evaluate erosion potential, the study employed hypsometric curve analysis, slope–area (S–A) relationships, drainage area probability distributions, and stream initiation point mapping. Results show that Huoyanshan Pits 1, 3, 5, and DF226 have higher erosion potential. Gravel-rich terrains promote flow concentration and channel incision, while bedrock-dominated areas require larger drainage areas for erosion. Drainage area distributions generally follow power-law patterns, with noticeable deviations near critical thresholds. The commonly used 200-cell threshold for stream initiation is suitable for shale–sandstone terrains but may need adjustment in gravel-accumulation zones due to complex geology. |
