| As composition basis of natural environment and important part of the natural resources, land is considered to be the most fundamental material basis and environmental circumstance for human survival. However, soil erosion is the main reason leading to land resources degradation and loss, which not only caused massive loss of land resources, but also leads to three aspects of environmental harm:land degradation, potential flood and water pollution. China is one of the countries in the world suffering most serious soil erosion, subsequently, series environment problems occur, such as flood damage of Yangtze River, people’s lives and properties threat from ground hanging river on downstream of Yellow River and serious degradation of the Northeast black earth are all closely related to soil erosion. In Jiangsu province,the landscape type is diversity, the soil texture is loose, the seasonal rainfall is abundant,and human disturbance area is so wide and large,that all of these factors are likely to cause soil erosion.A representative region is Ganyu County, which is the key area of the water and soil erosion management in low hilly land, locates by Haizhou bay in the Northeast of Jiangsu, and nearby the yellow sea,the mountain to the west, Qingdao to the north,Lian Yungang to the southTherefore, in order to control the erosion characteristics and regularity of this region, it is necessary to investigate the characteristics of rainfalls, soil physical and chemical properties, landforms, plant coverage and the measurements of soil and water conservation on the effect of soil erosion. Moreover, trying to establish a regional measurement model for soil and water conservation based on the aspects discussed above will not only provide scientific basis for regional land-use planning, but also significantly promote sustainable development of regional economic society.In this study, Jiagu Hill in Ganyu County was selected as the investigation object. According to the data of soil loss resulted by the different ways of land use under the conditions of20years natural rainfall in Jiagu Hill runoff plot (including tree timber forest area, economic forest area, grass plot area, the slope farming area, standard plot and downs lope tillage area), and the data of stakes monitoring around the slope of Jiagu Hill runoff plots in4years, prediction model for soil erosion was built by Correlation analysis method, regression analysis method and experience model method of soil erosion and sediment yield.Prediction model formula of soil erosion in Jiagu mountainous of Ganyu county is A=R·K·LS·C·PIn the formula, A is the average soil loss amount for many years (t·hm-2·a-1), R means rainfall erosivity factor (J·mm·m-2·h-1·a-1),K means soil erodibility factor (t·m2·h·hm2·J-1·mm-1), L means slope length factor (m),S means factor of grade of stopes(°),C means the factor of Vegetation coverage and crop management, dimensionless, P means Factor of soil and water conservation measures, dimensionless.Based on predecessors’ research results, using the check figure method, the look-up table method and empirical formula method, correlation analysis and regression analysis method, etc.. research to determine various factor of slope soil loss equation calculation method or numerical in the low hilly land.finally build the low hilly land slope soil erosion prediction model, in order to offer scientific basis for prediction of soil erosion in Ganyu county, soil and water conservation monitoring network construction,soil and water conservation planning, watershed management, ecological environment construction.The main conclusions are listed as follows:(1)In the rainfall features,the interactions of30min (I30) maximum rainfall intensity and rainfall time total kinetic energy (∑E) has a significant influence on soil erosion, the larger130and E E, the greater the erosion and the correlation coefficient is0.871, the determination coefficient is0.944, which meet quality characteristics significantly correlated level. So use I30and∑E to show the effect of the characteristics of rainfall on soil erosion. R=I30∑E. In order to calculate the rainfall erosion force promptly and efficiently, the relationship of hypo-rainfall, and the hypo-rainfall intensity was further analyzed, the larger the rainfall (H),the larger the hypo-rainfall intensity, the relationship between them is R=0.214H1.387, determination coefficient R2is0.944,which has reached extremely significant level.(2) According to the soil physical and chemical properties in Jia Gushan clip the K value of Jiagu slope surface was0.36.(3) Terrain factor, which include slope and slope length, has a significant influence on soil erosion. During0-22meters long, the longer slope length, the greater the soil erosion. Define the slope factor L=A/Ao, the relationship between L and λ is L=(λ/22)0.3, the determination coefficient is0.942, which has reached extremely significant level; Within the range of0°to35°, the larger the slope (a), the greater the soil erosion. Define slope factor S=A/Ao, slope factor S and a are power function relationship between the S=(α/5.5)1.21,and the determination coefficient is0.999,which has reached extremely significant level.(4) The impact of plant coverage on soil erosion. different vegetation types, the amount of soil erosion is different; Different vegetation coverage, soil erosion is also different. Use Vegetation coverage and management factor C to express its effects on soil erosion:the C values of arbor, shrub and herbage, grass’C value changes from0.45to0.011, the bushes’ C value is between0.4-0.011, the shrubbery’C value is between0.39-0.007, and dense forest’C value is between0.1-0.001,while the coverage changes from0%to100%; when sweet potato’s coverage is70%in the area, it’s C value was0.232; the relationship between C and e (coverage) of peanut is C=0.933e-0.046x, the correlation coefficient is0.983, which has reached extremely significant level.(5) The impact of tillage measures on soil erosion. P values of different plots were speculated by the results of20years data accumulation in the six regional runoff experimental plots. And the values were0.3,0.24,0.349,1.0,143and0.033for arbor area, economic forest area, pasture area, down slop farming area, standard cell and terraces cell, respectively. From the values,we can find that the average annual soil loss under different land uses were given as following desending order:the slope farming area> the standard area> the commercial forest area> the grass area> the timber forest area> the terrace cultivation area.(6)For red scarf small watershed, and using relative deviation and model coefficient uncertainty to determine the reliability of the model, the results found that soil erosion prediction model used in this study of prediction of soil erosion compared to the red scarf of the actual soil erosion of small watershed, the relative deviation is less than10%, the model of the deterministic coefficient were greater than0.8closed to1, so this research forecasting model is reliable.(7) With Ganyu city clip valley slope surface soil loss prediction model for technical tool, big Wushan (belong to low hilly land) in Lianyungang as an example to carry out the typical survey and forecast soil erosion of annual big Wushan is3540t·km-2·a-1, the soil erosion intensity is moderate, the results agree with soil erosion status chart of Ganyu county, and the Wushan (The area is7km2) annual soil loss is calculated for26700t; With red scarf small watershed as an example, direct how to choose the suitable soil and water conservation measures to manage soil and water loss. |
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