Sediment yield mapping in a large river basin: the Upper Yangtze, China

A number of studies have mapped sediment yield at global or regional scales using sediment load measurements from rivers. However, the suitability of the limited mapping methods has not been fully addressed, particularly for large river basins where the sediment load data were obtained from a hierarchical river network. This study examines some of the issues related to the mapping approaches using long-term sediment load data obtained in the Upper Yangtze basin, China. The sediment yield data are treated as point values and interpolated using the kriging function in Arc/Info GIS. Barriers have been incorporated into the interpolation procedure to confine the interpolation points to the same major flow systems. The incorporation of barriers causes sharp changes of the interpolated values along the barrier lines, and significantly increases interpolation time. Scaling ratios relative to a standard size of drainage area have been developed for major drainage basins to remove effects of drainage sizes on sediment yield. By incorporating the scaling ratios the sediment load data from various sizes of drainage areas can be adjusted to what they would be if the drainage areas were the same and a less biased sediment yield map can be obtained as compared to using the original dataset.