石塊之覆蓋率及嵌入對紋溝間土壤沖蝕影響之研究

A Study on the Effects of Cover Rate and Embedding of Rock Fragments on Interrill Soil Erosion

吳明峰(Min-Fon Wu)

指導教授 ： 范正成

國立臺灣大學/生物資源暨農學院/生物環境系統工程學研究所/博士(2006年)

https://doi.org/10.6342/NTU.2006.00515

摘要

本研究的主要目的在於藉由人工降雨沖蝕試驗探討石塊覆蓋率及石塊放置方式對紋溝間土壤沖蝕之影響機制。沖蝕試驗採用台灣北部地區的紅壤及黃壤土，重模於沖蝕試驗箱，並分別利用天然卵石及人造水泥圓球鋪放在土壤表面模擬石塊覆蓋。覆蓋率於65%以下區分六種比例；石塊放置方式採用全部露出及半嵌入土壤表面兩種。試驗坡度則固定為20%。
試驗結果顯示，石塊覆蓋對於抑制紋溝間土壤沖蝕之效果，因覆蓋率而不同，且與其係完全露出或半嵌入土壤表面而異。完全露出土壤表面之石塊，對於抑制沖蝕之效果，優於半嵌入土壤表面之石塊。至於覆蓋率增加，則非必然可降低土壤沖蝕。本研究尚發現，在相同覆蓋率情況下，石塊半嵌入土壤表面時之沖蝕率與完全露出時之沖蝕率之比例，與覆蓋率具有自然指數關係。另在飛濺沖蝕之影響方面，完全裸露土壤之飛濺沖蝕量縱然不會全部成為進入紋溝的土壤沖蝕量，但在數量上已佔土壤沖蝕量之比例逾三分之一，甚至在低降雨強度時，其數量足以使飛濺成為沖蝕的主因。然而，隨著覆蓋率增加，飛濺沖蝕量所佔總沖蝕量之比例逐漸降低。此外，完全露出土壤表面之石塊底下受遮蔽之土壤表面，在降雨過程中因未封鎖孔隙而具有較高之滲透性。本研究所使用兩種土壤之試驗結果均顯示，經降雨沖蝕之後，石塊下方遮蔽範圍內之入滲率約為裸露土壤表面之2.2倍。

關鍵字

土壤沖蝕 ； 紋溝間 ； 覆蓋率 ； 石塊 ； 降雨強度 ； 入滲

並列摘要

The main purpose of this study is to investigate the effects of cover rate and disposition of rock fragments used as mulch cover on the mechanism of interrill soil erosion by tests with simulated rainfall. There were two kinds of soil used in this study, lateritic soil and yellow soil, and were collected from northern Taiwan. The soil was remolded in a test box. Natural pebbles and motar balls were placed at the soil surface as the mulch cover respectively. The erosion tests were repeated on soil samples at 6 different cover rates under 65%, and two types of surface covers: completely exposed to the soil surface and half embedded into the soil. During the tests, the slope steepness of the erosion boxes was maintained at 20%.
It was found that the effect of reducing interrill soil erosion changed with different cover rates, and with the positions of rock fragments. The rock fragments placed on top of the soil surface were found better for controlling interrill erosion. However, the increase of cover rate did not insure reduced interrill erosion. It was also found that there was natural exponential relationship between the interrill erosion of the soils with rock fragments on top of the soil surface and with half embedded. Aside from these, even though the splash erosion would not totally become interril erosion. For soils without any cover, the proportion of splash erosion to total interrill erosion was more than one-third. At lower rainfall intensity, splash erosion dominated interrill erosion. However, along with the increase of the rates of cover by rock fragments, the proportion of splash erosion to total interrill erosion was reduced. Besides, rock fragments placed on top could protect the underlying topsoil against surface sealing by raindrop impacte, and retained higher infiltration. The results of both kinds of soil used in this study showed that the infiltration rate of the topsoil underlying the rock fragments was 2.2 times the infiltration rate of bare area after rainfall erosion.

並列關鍵字

soil erosion ； interrill ； cover rate ； rock fragment ； rainfall intensity ； infiltration

參考文獻

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