Soil erosion evaluation and prediction approach using <sup>137</sup>Cs,RS,and GIS in Xiaojiang River basin of China

Abstract

It is difficult to evaluate and predict soil erosion and its related effects in mountainous areas without sufficient observation data． This study aimed to estimate and predict changes in soil erosion using 137Cs，ＲS，and GIS techniques and propose an a pproach for soil erosion evaluation in mountainous areas． Using the erosion modulus calculating models based on 137Cs concentration， the annual average soil erosion modulus of forest lands，shrub lands，grasslands，farmlands，and uncovered land were obtained． The values were 356—1531 t /( km2·a) ，330—1709 t /( km2·a) ，886—3885 t /( km2·a) ，5197—12454 t /( km2·a) ， and more than 1 5000 t /( km2·a) ，respectively． Then，erosion zoning was done by combining erosion rates and land use data by interpreting remote sense images from 1987 ( Landsat TM) ，1995 ( Landsat TM) ，and 2005 ( Landsat ETM) ，and these were overlaid with 1∶ 50000 DEM data． The results showed that the eroded land changed very little from 1987 to 2005，accounting for about 66%—67． 3% of the total; however，the erosion intensity significantly rose from 1987 to 1995，up to 30% for some land use types． The eroded land， with the erosion modulus of 2500—5000 t /( km2·a) ， 5000—8000 t /( km2·a) ， and 8000— 15000 t /( km2·a) rise 30%，23%，and 26%，respectively． The soil erosion amount in the Xiaojiang Ｒiver basin was 7． 51 × 106 t / a，8． 19 × 106 t /a，and 8． 18 × 106 t /a in 1987，1995，and 2005，r espectively． Moreover，the zoning and amount of soil erosion for 2015 was predicted using a Markov-Cellar A utomata Model，which was established using the data from 1995 and 2005． The predicted result，8． 17 × 106 t /a，was very similar to that from 2005． This study provides a valuable solution to evaluate and predict soil erosion for mountainous areas in southwest China．