Statistical analysis of the geometrical form of natural rivers meanders

The river meander is an important geomorphologic component of meandering rivers. Study of the evolution of geometrical form and channel migration of river meanders possesses high academic values. Using an integrated platform of Google Earth satellite images and AutoCAD software, a total of 136 mountain meanders and 325 alluvial meanders in eight rivers from different areas are chosen as statistical samples to define and measure geomorphologic parameters of the samples. The statistical result shows that the meander radius of curvatures in mountainous rivers is in the interval 1.7, 14.8, and the value of the curvature radius for alluvial rivers is 1.6, 38.5. Statistically, the mean value and standard deviation of the curvature radius in alluvial rivers are much greater than those in mountainous rivers. There is not obvious skew angle tendency at bend apex in mountainous rivers, showing almost equal opportunity for both upstream and downstream development of bend apex. The number of meanders with 85 degree skew angle and greater in alluvial rivers can account for 65.5% of the total river meanders, indicating a tendency for bend apexes to grow in the upstream direction. There is a good liner relationship between the average width and the width of bend apex in alluvial rivers. A certain extent of positive correlation is found between the average river width and the meander neck width. The relationship between the relative transverse skewness and the curvature appears is also linear. These characters manifest the consistency of the shape of a planer cure in river meanders.