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標題: The Mechanism of Overland Flow Erosion And Rill Formation in Fine Sediment
關鍵字: Fine sediment;Overland flow;Rill erosion;細粒土壤;坡面流;紋溝沖蝕
Project: 水土保持學報, Volume 49, Issue 2, Page(s) 2065-2082.
Researchers have been interested in rill erosion for long times, building lots of empirical or semi-empirical models, such as Universal Soil Loss Equation (USLE), Revised Universal Soil Loss Equation (RUSLE), and Modified Universal Soil Loss Equation (MUSLE). However, the applicability of the empirical models relies heavily on the localized database of the input parameters. The soil used in this study was the mudstone in A-Gong-Dian Reservoir. The soil was oven-dried before being crushed and passed through the #40 sieve. The sieved soil was used to carry out basic geotechnical tests such as specific gravity, Atterbreg limits, moisture content, organic matter, particle size distribution, and pH value and conductivity of the pore water. As the results, the soil is classified as loam in soil texture triangle, and ML or OL based on Atterbreg limits with fine sediments (size range from 0.001~1mm) and low organic. The specific gravity of soil ranged from 2.38 to 2.74. Then the overland flow erosion experiments were carried out using an erosion box which was 0.82 meters long, 0.25 meters wide, and 0.21 deep. The soil was filled in the box with a predetermined bulk density of 1.35 g/cm3 . Prior to the erosion experiments, different slope gradients and flow rates were adjusted and calibrated; specifically, this research conduct the rill experiments under two flow rates (0.4 and 0.8 L/min) in constant water heads and three slope gradients (<0.01%, 5%, and15%) for ten hours. And then measure the amount of eroded soil and the dimensions of rills to qualify relationships(SL=30.76*Q2.23*S0.13、SL=-14.52+0.62S+37.82Q、SL=0.011Atotal.rill 1.09、 Atotal.rill=898.58*Q1.13S 0.16,in which SL(kg) is soil loss in 10 hrs; Q(L/min) is required flow rates; S(%) is slope gradients; Atotal.rill(cm2 ) is total rills area after experiment finished), which can be applied in overland flow erosion analysis and disaster remediation.

坡面流沖蝕研究已有多年歷史,發展出許多經驗或半經驗公式,例如著名的通用土壤流 失公式(Universal Soil Loss Equation, USLE) 及其修正版本如 RUSLE 和 MUSLE 等(劉青泉 et al. 2014)。然而,經驗公式多受的域限制,需針對特定的區及其氣候條件或沖蝕類型進行研究, 調查校正每個參數,建立完整資料庫予以支持。本研究以沖蝕箱進行細粒土壤之坡面流沖蝕試 驗,探討坡面紋溝形成過程與機制,並找出紋溝發生之沖蝕臨界條件、物理參數與量化關係式。 本研究採用阿公店水庫的區土壤,其土壤性質屬於泥岩,顆粒細小。現的土壤經過篩處理後, 先進行土壤特性基本試驗,如比重、阿太保限度、含水量、有機質含量、粒徑分佈及孔隙水 pH 值和導電度等。接著進行坡面流沖蝕試驗,以預設容積密度將土壤分層填入沖蝕箱(0.82 m×0.25 m×0.21 m),以定水頭點源方式進行不同流況與坡度之十小時之沖蝕試驗,觀測未飽程土體, 在坡面流沖蝕下之紋溝發展過程。實驗結果指出,土壤粒徑介於 0.001~1mm 之間,質的屬於 壤土且有機質含量低,比重介於 2.38~2.74 之間,依阿太保限度分類屬於 ML 和 OL。藉由紋溝 之發展過程與沖蝕量測量,得找出細粒土壤坡面紋溝發生之臨界條件及其物理參數,探討土壤 物 化 特 性 對 沖 蝕 臨 界 條 件 之 相 關 性 與 影 響 程 度 , 並 找 出 量 化 關 係 式 , 其 關 係 式 為 SL=30.76*Q2.23*S0.13、SL=-14.52+0.62S+37.82Q、SL=0.011Atotal.rill 1.09、Atotal.rill=898.58*Q1.13S 0.16, 其中 SL 為沖蝕十小時的土壤流失量,單位為公斤;Q 為原預設之流量,單位為 L/min;S 為原 預設之坡度,單位為%;Atotal.rill 為實驗結束後之紋溝總面積之合,單位為 cm2。可應用於坡面 流沖蝕分析與災害防治。
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