Runoff and sediment yield are greatly affected by the type of land use. The paper studies the influenceof agriculture, husbandry, mining and urban development, demonstrates the law of variation in sedimentyield during the processes of land use changes. Land use changes from forest to agriculture, grassland tofarm field and slope plough land to terrace field exhibit the same law influencing the sediment yield.During the transforming period the sediment yield is higher than those of either land used and is provedto be equal to he sum of the sediment yields of the two types of land use. This is named thesuperposition law of land use transtbrmation. The correlation between the percentage of forest coveragewith the runoff and sediment yields indicates that the runoff yield reduce to the minimum and thesediment yield is nearly zero if the coverage is higher than 60%. Whereas the runoff is doubled andsediment is tripled for 10% reduction in the forest coverage if the coverage is between 30-60%. Miningand urbanization increase the sediment yield in the development period.
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