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

• Main Authors: Min-Fon Wu, 吳明峰
• Other Authors: Jen-Chen Fan
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/05518332182715142848

博士 === 國立臺灣大學 === 生物環境系統工程學研究所 === 94 === 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.