Abstract
Rainfall in Taiwan mainly concentrates in the period of typhoons and torrential storms. In this period the soil severely erodes due to the frail geology, steep gradient and easily weathered parent rock. Currently, the Universal Soil Loss Equation (USLE) is used to estimate soil erosion amount in Taiwan. Although it is regarded as the reference, its results are often inconsistent with the actual situation because the application conditions show great difference. Therefore, an alternative to the USLE is necessary for Taiwan. This study focused on 25 main basins in the mountainous area of Taiwan from which 69 experimental sites were established; 20 in the north, 11 in the center, 21 in the south and 17 in the east. The agency of Soil and Water Conservation Technical Specifications table, soil test in the experimental site and on-site measurements of erosion and redeposition were used to determine soil erodibility index (Km). The results shows that most Km obtained in the north areas were smaller than those from the specification, while Km in the rest of the areas varies without a regular pattern. It was concluded that the Southern areas were more susceptible to soil erosion because of the larger indexes.
Highlights
Taiwan is an island covering 3.6 million hectares, of which, about 2.639 million hectares are mountains, accounting for 73.3% of the total area
This study used the erosion indexes defined in the Technical Code of Soil and Water Conservation, as shown in Table 3, to analyze and compare it with the data obtained through experiment and analysis in this study
It can be concluded that the Southern areas of Taiwan are more susceptible to soil erosion
Summary
Taiwan is an island covering 3.6 million hectares, of which, about 2.639 million hectares are mountains, accounting for 73.3% of the total area. How to control soil loss and reduce soil erosion is a key subject for soil and water conservation when developing these mountainous areas. The soil erodibility is commonly predicted using the USLE nomograph on the basis of five soil and soil profile parameters that include soil particles (% sand, % silt, % very fine sand and silt and % clay), % organic matter, soil structure code and soil permeability class (Schwab et al, 1993) The parameters in this equation were representatives from two-thirds of the eastern U.S As time elapsed, the accumulated data shaped this equation that has been widely employed in today’s research
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