河道床面形态对断面法计算冲淤量误差的影响

Effect of riverbed form on error in calculation of channel erosion and deposition volumes by cross-section method

当采用不同断面间距时,计算得到的宜昌—枝城河段2002年10月至2008年10月冲淤量存在较大差异。针对这种差异,采用分形维数对河道床面形态进行量化,对比断面分维数、深泓纵剖面分维数和床面分维数与冲淤量相对误差的相关性,探讨了河道地形起伏程度对冲淤量计算结果的影响。研究表明:冲淤量相对误差与河型无明显相关性,误差的根源在于河道床面起伏程度不同。床面分形维数比断面分维数和深泓纵剖面分维数更能反映出河道地形起伏程度,其与冲淤量相对误差的相关性较好。床面分形维数大的河段,用不同断面间距得到的差异较大,而分形维数较小的河段,差异较小。

Volumes of erosion and deposition in the Yichang-Zhicheng reach from Oct. 2002 to Oct. 2008 were calculated by cross-section method, and they showed significant differences when using different cross-section spacings. To explain it, riverbed form was quantified by using fractal dimensions and comparing the relations between cross-section fractal dimension, thalweg fractal dimension, bed surface fractal dimension, and relative errors of erosion and deposition amounts. Examination at the effect of topographic relief degree on computations of erosion. The deposition shows that the relative computation errors have no clear correlation with river pattern and their root is this relief degree. Relative to cross-section fractal dimension and thalweg fractal dimension, bed surface fractal dimension is a better indicator of the relief degree and has a good linear correlation with the relative errors. In general, a greater relative error corresponds to a greater bed surface fractal dimension, and vice versa.