Research On Soil & Water Loss Caused By Exploitation Projects In Fujian

In course of the accelerated economic development, soil and water loss caused by exploitation projects increased meanwhile. Though it has existed for a long time, it has received little attention. The soil loss caused by exploitation projects is so large that it could fill up rivers and reservoirs, lower the longevity and flood control efficiency and aggravate the flood. Compared with normal form of soil and water loss, the losses induced by exploitation projects are characterized by diversity, abruptness and severity. Due to complexity existed in the formation, style and process of soil and water loss in exploitation projects, prevention and control of this erosion is more difficult. Further, recent research on this respect are scarce in China, thus studies on the mechanism and control measurement of erosion caused by exploitation projects are important and urgent, which will favor eco-environment improvement and sustainable development of society and economy.The regional pattern of soil and water loss caused by the exploitation projects in Fujian was studied through an integrate survey on loss area, intensity and types. Based on this, the erosion mechanism of loosely piled soil was studied in the runoff plot scale. In addition, the marked stake method was applied to assess the effects of the makeup of discarded soil on soil loss.The erosion area caused by exploitation projects in Fujian is up to 17623hm2, being 1.18% of the total erosion area, and the Sanming City is the first contributor. The erosion area caused by the mineral, urban and traffic projects is 9785hm2, 3419.5 hm2 and 3232.2 hm2, the first culprit of which is Quanzhou City, Fuzhou City and Sanming City, respectively.The erosion intensity of the soil and water loss caused by exploitation projects is usually higher than the hard-erosion class, and can be ranked as traffic projects (2.57x104t/km2)>mineral projects (2.23x104t/km2)>urban projects (1.93x104t/km2). The loosely-piled discarded soils has the highest erosion intensity (6x104t/km2), followed by the digging-induced side slopes and the level-up lands.Sanming City had the highest amount of soil erosion in Fujian, followed by Quanzhou City. The mineral, traffic and urban projects had an amount of soil erosion of 223.3, 84.4 and 66.5x104t, respectively, being 56.3%, 21.3% and 16.8% of the total soil erosion that caused by the exploitation projects.The common characteristics of soil erosion that caused by exploitation projects are: a) high soil erosion that differed between the construction and carry-outstages; b) large incidence inside and outside of an area; c) complexity in erosion substrate; d) diversity in erosion pattern; e) dominance of induced-erosion; and f) serious destruction of water resources.The annual erosion and runoff of loosely-piled discarded soils was up to 4.414xl04t/(km2 a) and 762.9 mm, being 3.0 times and 1.7 times as high as those of intact bare-land (1.470xl04t/(km2 a) and 443.8 mm), respectively. When loose-piled soil is covered with grass, water and soil loss decreased significantly, with decreased proportions of 75.8% and 55.5% for amount of soil loss and runoff respectively.The soil erosion of loosely-piled soil occurred mainly during March to September, and July to September are the most risk period of erosion. As for the loosely-piled soil with seeding treatment, 99% of the annual erosion occurred during the period before grasses fully-covered the land, that is, 3 months after seeding.Amount and intensity of rainfall are two key factors influencing soil and water loss. Relation between rainfall amount and soil loss are more significant in uncovered land than that in covered land. Compared with the relation between rainfall amount and soil loss, the relation between rainfall intensity and soil loss is more significant. This holds true for the relation between soil loss and uncovered and covered lands respectively. Soil erosion caused by a rain event can be ranked as: downfall > rainstorm > medium rain > sprinkle. The minimum erosive rainfall are in the...