The Effects of Rock Fragment Mulch Cover Simulated Using Mortar Ball on The Mechanism of Interrill Soil Erosion

本研究的主要目的在於探討石塊覆蓋方式對紋溝間土壤沖蝕之影響機制。本研究之沖蝕試驗採用台北縣新店山區的黃壤土，並利用特別設計之試驗箱及人工降雨機進行試驗。試驗箱的坡度固定為20%。利用人造之水泥圓球鋪放在土壤表面作為試驗之覆蓋物，並改變其覆蓋率與覆蓋方式，於兩種強度的人工降雨下進行沖蝕試驗。覆蓋率分別為0%、10%、20%、30%、40%及50%等共六種；而覆蓋方式則採用全部露出土壤表面及部分嵌入土壤中兩種，其埋入率分別為0%與50%；降雨強度則分別為40mm/hr與90mm/hr。 試驗結果發現，有石塊覆蓋之試體，在低降雨強度且覆蓋率低於40%時可降低土壤表面之逕流率；石塊全部露出土壤表面時，對降低逕流沖蝕、飛濺沖蝕，及總沖蝕率之效果較石塊部分嵌入時理想，但在覆蓋率10%時對降低逕流沖蝕及總沖蝕率則是石塊部分嵌入時較好，但兩種覆蓋方式皆能有效降低沖蝕。對降低沖蝕效果而言，當石塊全部露出土壤表面、低降雨強度下且覆蓋率大於40%時效果最好。經迴歸分析結果發現，沖蝕量與覆蓋率、覆蓋物的埋入比率及降雨強度有不錯之關係。The main purpose of this study is to investigate the effects of rock fragments used as mulch cover on interrill soil erosion. The soil used in the soil erosion tests was collected from a mountainside at Sindian, Taipei County. Erosion Boxes and a rainfall simulator were specially designed and fabricated for this study. During the tests, the slope steepness of the erosion boxes was maintained at 20%. Mortar Balls were placed at the soil surface as the mulch cover. The rate and type of cover were changed, and two different rainfall intensities were simulated and applied in this study. The erosion tests were repeated on soil samples at the cover rates of 0%, 10%, 20%, 30%, 40% and 50% and types of completely exposed to the soil surface and partially embedded into the soil (i.e. the embedded ratio was 0% and 50%), and rainfall intensities of 40 and 90 mm/hr. It was found from the test results that while the rainfall intensity was low and the cover rate was less than 40%, the runoff rate decreased. While the rock fragments were completely exposed to the soil surface, the runoff erosion, splash erosion and total erosion rate were found less compared to that while the rock fragments were partially embedded into the soil. At the cover rate of 10%, it was found that while the rock fragments were partially embedded into the soil, the runoff erosion and total erosion rate were found less. Nevertheless, both the two types of cover could effectively reduced the erosion. It was also found that while the rock fragments were completely exposed to the soil surface, the rainfall intensity was low and the cover rate was greater then 40%, the reducing effect of soil erosion was the best. After regression analysis, an equation was proposed to relate soil erosion, cover rate, embedded ratio and rainfall intensity. The relationship were found very satisfactory.謝誌 Ⅰ 中文摘要 Ⅱ 英文摘要 Ⅲ 目錄 Ⅴ 圖目錄 Ⅷ 第一章 前言 1 第二章 文獻回顧 3 2.1紋溝間土壤沖蝕發生機制 3 2.2雨滴撞擊因子 3 2.3 土壤特性因子 4 2.4 坡度因子 6 2.5 覆蓋及處理因子 7 2.6 實驗室之沖蝕試驗設備 11 2.6.1 沖蝕試驗箱 11 2.6.2 人工降雨機 12 第三章 研究方法 15 3.1 試驗材料與試驗設備 16 3.1.1 土壤 16 3.1.2 覆蓋物 18 3.1.3 沖蝕試驗箱 18 3.1.4 人工降雨機 21 3.1.5 實驗相關設備 26 3.2沖蝕試驗箱上方之降雨強度率定 26 3.3 沖蝕試體製作 30 3.4 人工降雨沖蝕試驗 34 3.4.1 試驗說明 34 3.4.2 試驗步驟 42 第四章 試驗結果與討論 44 4.1 人工降雨機之降雨強度率定結果 44 4-2 人工降雨沖蝕試驗結果 44 4.2.1 逕流率與覆蓋率之關係 46 4.2.2 逕流沖蝕與覆蓋率之關係 48 4.2.3 飛濺沖蝕與覆蓋率之關係 52 4.2.4 總沖蝕率與覆蓋率之關係 55 4.2.5 逕流沖蝕與飛濺沖蝕所佔沖時之比例與覆蓋率之關係 60 4.2.6 逕流沖蝕/飛濺沖蝕與覆蓋率之關係 62 4.2.7 逕流沖蝕與逕流率之相關性 66 4.3 綜合性試驗結果與比較 69 4.4 石塊覆蓋對紋溝間土壤沖蝕之影響機制推論 71 4.4.1 石塊覆蓋對於紋溝間土壤沖蝕之影響效應 71 4.4.2 石塊覆蓋率對紋溝間土壤沖蝕之影響機制 73 4.4.3 石塊覆蓋方式對紋溝間土壤沖蝕之影響機制 74 4.5 試驗數據之迴歸分析 75 4.5.1 迴歸模式的建立 75 4.5.2 迴歸分析結果 78 第五章 結論與建議 81 5.1 結論 81 5.2 檢討與建議 83 參考文獻 84 附錄A 人工降雨沖蝕試驗數據 91 A.1 人工降雨沖蝕試驗原始數據 92 A.2 迴歸格式化後分析用資料 94 A.3 統計迴歸分析用資料 96 附錄B 沖蝕試驗結束後之土壤表面圖 97 B.1 土壤表面受沖蝕之情況(一) 98 B.2 土壤表面受沖蝕之情況(二) 99 B.3 土壤表面受沖蝕之情況(三) 10