Bank erosion and accretion along the Ningxia-Inner Mongolia reaches of the Yellow River from 1958 to 2008

摘要

We studied bank erosion and accretion in the Ningxia-Inner Mongolia reaches of China's Yellow River. The study was based on topographic maps of 1958 and 1967, which had been derived from aerial photos and a field survey and from satellite imagery of 1977,1990,2000, and 2008. We determined the area of bank erosion by comparing sequential changes in the position of the banks in these years. We found 229 stretches where bank erosion (> 10,000 m2) occurred, of which 110 were found along the left bank and 119 along the right bank. The total area of bank retreat from 1958 to 2008 equaled 518.38 km2, of which 257.29 km2 occurred on the left bank and 261.09 km2 on the right bank. The total area eroded along the entire section we studied amounted to 242.21 km2 from 1958 to 1967, 121.61 km2 from 1967 to 1977, 96.89 km2 from 1977 to 1990, 30.80 km2 from 1990 to 2000, and 26.87 km~2 from 2000 to 2008. The annual rate of bank erosion from 1958 to 1967 averaged 26.91 km~2/y, and decreased to 12.16 km~2/y from 1967 to 1977,7.45 km~2/y from 1977 to 1990, and 3.08 km~2/y from 1990 to 2000, then increased slightly (to 3.35 km~2/y) from 2000 to 2008. The Bayan Gol-Hekouzhen section experienced the most intensive bank erosion and bank collapse. The Shizuishan-Bayan Gol section sustained minimal bank erosion. We have also analyzed the estimation error for bank erosion area and the causes of bank erosion.