Effect of spatial scale on suspended sediment concentration in flood season in hilly loess region on the Loess Plateau in China

Suspended sediment concentration is a major variable influencing soil erosion and loss, study on which at different spatial scales is of great meaning to understand soil erosion mechanism and sediment transport process. Based on data from 4 sloping surfaces and 7 basins ranging from 0.0003 to 187 km² in area, the suspended sediment concentration in flood season (SSC) with drainage area is studied. With increasing drainage area on the slope surfaces, the mean suspended sediment concentration in flood season (MSSC) enhances continuously until a peak value of 685 kg m⁻³ occurs at the whole slope surface No. 7 runoff plot resulting from harder and harder erosion forms downslope. Entering basin systems, the diluted action of subsurface water on the toeslope on MSSC and small water flow power Ω make a minimum MSSC value of 568 kg m⁻³ occur in the first-order basin system Tuanshangou basin at an area of 0.18 km², and then from Tuanshangou basin to larger basins, the positive feedback function among drainage density, water flow energy, and hyperconcentrated flow as well as its reduction of settling velocity of coarser particles generates continuously increasing MSSC with drainage area.