Hysteresis in suspended sediment to turbidity relations due to changing particle size distributions

作者：Landers Mark N^*; Sturm Terry W

来源：Water Resources Research, 2013, 49(9): 5487-5500.

DOI：10.1002/wrcr.20394

• sedimentation
• sediment transport
• turbidity
• streamflow
• particle size distribution

Turbidity (T) is the most ubiquitous of surrogate technologies used to estimate suspended-sediment concentration (SSC). The effects of sediment size on turbidity are well documented; however, effects from changes in particle size distributions (PSD) are rarely evaluated. Hysteresis in relations of SSC-to-turbidity (SSC approximate to T) for single stormflow events was observed and quantified for a dataset of 195 concurrent measurements of SSC, turbidity, discharge, velocity, and volumetric PSD collected during five stormflows in 2009-2010 on Yellow River at Gees Mill Road in metropolitan Atlanta, Georgia. Regressions of SSC-normalized turbidity (T/SSC) on concurrently measured PSD percentiles show an inverse, exponential influence of particle size on turbidity that is not constant across the size range of the PSD. The majority of the influence of PSD on T/SSC is from particles of fine silt and smaller sizes (finer than 16 mu m). This study shows that small changes in the often assumed stability of the PSD are significant to SSC approximate to T relations. Changes of only 5 mu m in the fine silt and smaller size fractions of suspended sediment PSD can produce hysteresis in the SSC approximate to T rating that can increase error and produce bias. Observed SSC approximate to T hysteresis may be an indicator of changes in sediment properties during stormflows and of potential changes in sediment sources. Trends in the PSD time series indicate that sediment transport is capacity limited for sand-sized sediment in the channel and supply limited for fine silt and smaller sediment from the hillslope.

• 出版日期2013-9