Dynamic Study On Soil Erosion In Nanchong

Soil erosion is one of the main ecological environment problems in our country, is the result of natural factors and human factors, with economic and social development, regional surface environment change, soil erosion also changed. Nanchong City is located in the middle and lower reaches of the Jialing River, belongs to the subtropical moist monsoon climate, rainfall concentrated, coupled with the special natural geographical environment and the human activity influence, in Nanchong City, soil erosion serious, in recent years, Nanchong City take the some soil and water conservation measures, soil erosion has been improved. In this study, the revised universal soil loss equation, based on the 3S technology, to extract and analyze the effect of soil erosion in Nanchong City of various natural factors, rainfall erosion force factor(R), soil corrosion factor(K), terrain factor(LS), vegetation cover and management factor(C) and soil maintain measures factor(P), generated by soil erosion in Nanchong city natural factor series of grid database and the paper makes a concrete analysis of the soil and water loss in Nanchong city spatial and temporal changes in the state. It provides a certain basis for the development of soil and water conservation work in Nanchong city. The main conclusions of this paper are as follows:First, using Gaoping station in 1952-2014 daily rainfall data, the chapter Wenbo daily rainfall model estimation Gaoping station rainfall erosivity, and use it for reference value to establish the Nanchong City monthly and annual rainfall erosivity simple algorithm model. Again according to the Nanchong City of seven meteorological station 1959-2013 years of years of monthly average precipitation data, using Nanchong City of monthly rainfall erosion force algorithm model calculated Nanchong City for many years the average monthly rainfall erosivity, and the years of monthly average rainfall erosivity accumulated years of average rainfall erosivity. The results show that the Nanchong City annual average rainfall erosion force between 5812.56-8784.19[MJ·mm/(hm2·h·a)], among them, the average value for 6776.73 [MJ·mm/(hm2·h·a)], the biggest difference is 2971.63 [MJ·mm/(hm2·h·a)]. Showed increasing trend from south to north, and the average annual rainfall trend.Second, using the 1:100 000 soil database of China, Nanchong City soil type map extraction and the impact of soil can erosion of sand, silt, clay and organic carbon content of soil physical and chemical properties of spatial distribution characteristics were analyzed, using EPIC model estimation of Nanchong soil erodibility K value, calculation results of unit for [t·ha·h/(ha·MJ·mm)]. The value given type of soil properties, soil erodibility of Nanchong grid map. Analysis of the spatial distribution of the value of soil erosion. The K value of Nanchong city is in the range of 0-0.016885705[t·ha·h/(ha·MJ·mm)], among which, the K value is 0.012239759 [t·ha·h/(ha·MJ·mm)] RGc distribution is the most widely. On the whole, the purple soil of Nanchong city is the main, so the soil of Nanchong city is high.Third, using the 30 m DEM figure of Nanchong, extracted the Nanchong slope length factors. The results showed that the slope of Nanchong city was 0 ° and 65.5923 °, give priority to with low hills. LS value range in 0.0382587 to 40.284, increasing overall from south to north.Fourth, using remote sensing image to extract the NDVI in year 2002, 2014 figure, on the basis of this estimate vegetation coverage. The results show that in 2002-2014, Nanchong City, Southeast and central vegetation covered degree have increased significantly, but the northeastern and northwestern vegetation coverage degree by the decline. So we can see that the vegetation damage increased in the low mountain and hilly areas of Nanchong and the northwest, while the water and soil conservation measures in the central and southeastern regions have achieved certain results.Fifth, the rainfall erosivity(R), soil erodibility(K), slope and length(LS), vegetation cover and management factor(C) and soil maintain measure factor(P) of uniform projection and the grid size, under the support of ArcGIS grid calculator, five factor multiplication, Nanchong City in 2002 and 2014 soil erosion modulus map. In 2014, the maximum erosion modulus increased by 161.088 t/(ha·a) compared with the maximum erosion modulus in 2002, which showed that the soil erosion intensity in the 2014 local area was enhanced. But in 2014 the average erosion modulus decreased by 20.7 t/(ha·a) compared with the average erosion modulus of 2002, which showed that the soil erosion degree in Nanchong from 2002 to 2014 was weakened.Sixth, according to the standard of the Ministry of water resources, the soil modulus of 2002 and 2014 were classified, and the situation of soil and water loss in Nanchong city was analyzed in time and space. The results showed that the average annual rate of Nanchong city and the 2014 year of 2002 were mainly slight erosion, but the proportion was obviously decreased. From the point of various counties(city), langzhong is the most serious soil and water loss and those days; From the perspective of the terrain is the most serious soil and water loss, 400-600 m height; From the point of slope, 5°-15°slope soil erosion area is the most widely; From dynamic change, the high level of erosion intensity to a low level of intensity of erosion accounted for 99.86% of the transfer, new erosion was the main type of micro degree erosion and light erosion, the two accounted for new 92.47% of total erosion, severe erosion of new area is only 0.49km2, shows that the situation of soil erosion is not worse, but a trend of improvement.