Quantifying Fine-Grained Sediment Storage in Lowland Headwater Streams of the East Midlands

2015-10-22T14:55:05Z (GMT) by Rosalinde Alison Nicholls
Fine-grained (≤2mm) sedimentation of streams can cause detrimental impacts on ecological quality. However, there is currently little information on the quantity and spatial variability of fine-grained sediment (FGS) stored in river channels. As a result, there are few baseline data available to evaluate the success of any measures designed to reduce FGS supply, and by extension FGS storage (e.g. catchment land management). There is, therefore, a need for a reliable in-stream monitoring technique to quantify FGS storage. This research, which was based in the East Midlands, developed and employed a field-based methodology for determining FGS storage in stream channels. The method used a combination of sampling a given volume of bed material using a McNeil corer, and a resuspension technique using a streambed shear stress achieved with a mixing paddle attached to a cordless electric drill. FGS storage was evaluated in riffles and pools of Stonton Brook (42km2), Eye Brook (61km2) and the Upper Welland (53km2). FGS was found to be dominated by sand-sized particles. The mean average at-a-site storage in the Upper Welland, the Eye Brook and Stonton Brook were 4977±511 g m-2 cm-1, 5710±437 g m-2 cm-1 and 4626±342 g m-2 cm-1, respectively. FGS storage in pools exceeded that of riffles. Surficial remobilisable storage of fines was also higher in pools than riffles. The organic matter content of the FGS was low, and showed little variation between pools and riffles. The baseline data set collected could be used in the future to evaluate the success or otherwise of catchment land management interventions in reducing the quantity of fine sediment stored in the streams investigated.

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