Study On Dynamic Changes Of Water And Soil Erosion Along Highway Of The Loess Plateau Area Based On RS/GIS

The construction of expressway has a great role in promoting the loess plateau economic development, at the same time, during the highway construction it will cause the destruction to the traffic corridor ecological environment, and the scope of influence is linear distribution. Due to the thousand ditch topography of mountains and valleys in loess plateau, the highway usually is along the channel or river channel, so the side slops along both sides of the the highway are higher, and are easy to cause soil erosion phenomenon. This paper is based on the remote sensing data sources, use GIS and RS technology, researches and analysises the soil and water loss of the expressway between Tong Chuan and Huang Ling on the both sides along the range of 400 metres regions. The paper chooses the remote sensing image before the construction of highway(1995),building construction(2000)and construction completed(2013)three periods to dynamic analysis. By using the remote sensing image data and DEM data as basis data, paper chooses 4 main impact factors of the loess plateau region traffic corridor soil erosion: vegetation coverage,the types of land use,the terrain slope,gully density. According to the “classification of soil erosion classification standard”(SL190-2007),the datas are extracted and divided hierarchy, and the relationship between influence factor and water and soil erosion intensity is confirmed. The paper selects the corresponding weight value to manipulate the image superposition, obtains the composite index of soil erosion, makes soil erosion intensity classification map and uses the datas to quantificationlly dynamic analysis.The main research results are as follows:(1)Analysis on impact factor dynamic changes of water and soil erosion intensity on Tong-Huang expressway along the range of 400 meters:① The area more than 75% of vegetation coverage increased from 7.31km2 in 1995 to 12.79km2 in 2013; the area between 60%~75% of vegetation coverage increased from 15.11km2 in 1995 to 32.32km2 in 2013. So the vegetation coverage of the study area increased significantly.② The area gully density(unit: km/km2) between 2~3 is 17.33km2, accounting for 29.74% of the total area of the study area; the area gully density between 3~5 is 0.55km2,accounting for 52.43% of the total area of the study area. On the whole, gully density distribution is stable and the degree of crushing on study area surface is relatively severe.③ The gentle slope(<5°) area is 14.33km2, accounting for 24.59% of the total area,mainly concentrated in the both ends of the highway(between K0-K10 and K40-K70+20);the steep slope(25°~35°) and steep slope(>35°) areas are 4.72km2, accounting for 8.1% of the total area,mainly distributed in the high elevation area(in K10+80-K30+10).④ forest land in land-use type increased significantly from 10.89km2 in 1995 to 17km2 in 2013;slope farmland is decreasing year by year,it decreased from 20.12km2 in 1995 to 7.79km2 in 2013;with the acceleration of the construction of urbanization,the construction land area increased from 3.71km2 in 1995 to 9.23km2 in 2013;due to disturbance of highway construction on the ecological environment, the bare land area increased from 0.07km2 in 1995 to 2.33km2 in 2000,after the completion of the highway construction, vegetation restoration and slope protection measures of disturbance area, the bare land area decreased from 2.33km2 in 2000 to 0.13km2 in 2013.(2)Impact factor is quantified weight overlapping and using soil erosion index to evaluate soil erosion intensity. The area of trace amounts of water and soil loss and mild water loss and soil erosion is increasing from 1995 to 2013.But the area of other degrees water and soil loss is decreasing.(3)The amount of highway water and soil erosion in the study area was 137895t/a in 1995,and the amount of water and soil erosion was 128290t/a in 2000, the amount of water and soil erosion was 107540t/a in 2013,so it reduced 30355t/a;in 1995~2013, the water and soil erosion intensity was dynamic receded in the study area.