Soil Erosion Monitoring In Changting County Based On USLE

Soil erosion threats the ecological security seriously. This study conducted the monitoring and evaluation of the soil erosion changes using 5-year remote sensing images, from 1988 to 2013 in Changting County. The main research is given as follows.(1)Image classification of land use/land cover. We applied an object-based method to classify TM remote sensing images using spectral characteristics for sake of the monitoring of soil erosion. The classification accuracy for water and forest with high vegetation coverage are both larger than 90%. Due to the high heterogeneity of spectral characteristics, the classification results show a low accuracy for farm lands, residential lands, and forest with low vegetation coverage. To improve the classification accuracy of these categories, we interactively processed the classification results of them. The results also show that Changting was generally of high vegetation coverage as it was mainly covered by forest. The middle region was characterized with low vegetation coverage, where the vegetation coverage, farm and residential lands were gradually increased since 1988.(2)Estimation of vegetation coverage using remote sensing images. We conducted the estimation of vegetation coverage by means of dimidiate pixel model using the Topography-Adjusted Vegetation Index (TAVI) to eliminate the topographic effects. The estimation results produced by TAVI performed better than those from Normalized Difference Vegetation Index (NDVI). Particularly, the TAVI was used to effectively eliminate the discrepancy between the shady and sunny slopes, and improved the estimation accuracy for the shady slopes. The monitoring of vegetation coverage in Changting from 1988 to 2013 was carried out. The Changeting area was generally of high vegetation coverage particularly in the west and north regions. Specifically, the medium and low level of vegetation coverage was concentrated in the middle region of Changeting, particularly in both sides of Ting River. From 1988 to 2013, the vegetation coverage with respect to the medium and low level was increasingly transformed into high level, in the middle region of Changeting. The vegetation coverage (i.e.>0.8) increased 1298.98 km2, equaling to 41.92% of the whole area, by 2013.(3)Dynamic monitoring of soil erosion. We applied the USLE model to monitor and evaluate the soil erosion of Changting from 1988 to 2013. The results show that the soil erosion was mainly in a slight level, and distributed mainly in the middle region of Changting as well as several towns in the east region. However, the two sides of Ting River were badly eroded. According to the monitoring results from 1988 to 2013, the soil erosion was improved gradually, leading to a decrease of the total area of soil erosion equal to 431.74km2 during the past 25 years. It was decreased by 283.94km2 for the middle region, where the Hetian town contributed to the largest part and the Sanzhou town had the most evident rate of the soil erosion. The decrease of soil erosion can be closely related to the control of soil erosion performed by the national and regional governments, particularly in Hetian and Sanzhou towns.