Fine sediment transport and management

Evaluation of a simple, inexpensive, in situ sampler for measuring time‐weighted average concentrations of suspended sediment in rivers and streams

“…Second, suspended sediment acts as a transport vector for nutrients and a wide range of contaminants (Horowitz, Clarke, & Merten, ). This transport process occurs because the chemically reactive surfaces of fine sediment particles readily adsorb chemical compounds, (e.g., nutrients, metals, and pesticides), thus concentrating and transporting them downstream (Horowitz, Stephens, Elrick, & Smith, ; D. E. Walling & Collins, ). In the United States, suspended sediment is either primarily, or exclusively, linked to up to 65% of the 126 priority pollutants listed and is considered to be the second highest cause of river and stream impairment, nationally (US‐EPA, , ).…”

“…First, elevated concentrations of suspended sediment contribute to increased turbidity that decreases light transmission through the water column (Newcombe & Jensen, ). Low‐light conditions decrease the productivity and influence the composition of primary producer communities, potentially altering ecosystem structures (Fabricius & De'ath, ; D. E. Walling & Collins, ). For example, disrupted light conditions, from excess fluvial suspended sediment, is causing extensive damage to seagrass ecosystems, on a global scale (Orth et al, ; Waycott et al, ).…”

“…The most common approach to measuring suspended sediment is to collect discrete water samples on a regular but infrequent basis (e.g., monthly) using manual or automated sampling methods. This is insufficient to provide a representative measure of suspended sediment concentration trends in dynamic systems, where changes in sediment concentration occur in unpredictable ways or where traditional sampling methods are impractical (e.g., high flow events, such as, intense rain storms and major floods; Horowitz, ; D. E. Walling & Collins, ). Monitoring regimes that rely on manual discrete sampling by workers, particularly in remote areas, cannot capture all of the high flow events that may occur (due to logistical or health and safety requirements) and will typically generate data biased to lower flow periods with lower suspended sediment concentrations (Horowitz et al, ; M. Perks et al, ).…”

“…Alternative monitoring techniques, such as on‐site automated discrete sampling, can overcome these issues by sampling frequently over a storm hydrograph. However, the high cost of installation, maintenance, and analysis associated with this approach means they can usually only be deployed, in minimal numbers, at high priority sites (e.g., receiving waters with high ecological value; Jordan, Cassidy, Macintosh, & Arnscheidt, ; D. E. Walling & Collins, ). For example, in the 423,000 km 2 of catchments draining into the Great Barrier Reef World Heritage Area, which are the focus of a major water quality management programme by the Australian and Queensland Governments, only 43 automated sampling stations are in operation across the entire area (Wallace et al, ).…”

“…Passive, time‐integrated, in situ sampling techniques, such as that developed by Phillips and coworkers (Phillips, Russell, & Walling, ; Phillips sampler), are more representative than infrequent discrete sampling (i.e., they collect sample continuously over the deployment period) and are more affordable than on‐site automated discrete samplers and turbidity data loggers (D. E. Walling & Collins, ). However, they are primarily designed for qualitative sampling purposes, such as suspended sediment source fingerprinting, rather than for determining suspended sediment concentrations (Phillips et al, ; Smith & Owens, ).…”