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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #207875

Title: Magnitude, frequency, and duration relations for suspended sediment in stable ("Reference") streams in the southeastern united states: metrics for linking with aquatic health

Author
item Simon, Andrew
item KLIMETZ, LAUREN - UNIVERSITY OF MISSISSIPPI

Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2008
Publication Date: 10/1/2008
Citation: Simon, A., Klimetz, L. 2008. Magnitude, frequency, and duration relations for suspended sediment in stable ("Reference") streams in the southeastern united states: metrics for linking with aquatic health. Journal of the American Water Resources Association. 44(4):1-14.

Interpretive Summary: Sediment is listed as one of the leading causes of water-quality concern in surface waters of the United States yet little information exists that functionally links sediment-transport rates to aquatic health. To address this problem, historical flow and sediment-transport data from hundreds of sites in the Southeastern United States were analyzed to develop parameters (metrics) such as frequency and duration of sediment concentrations that could be used by aquatic ecologists to develop functional links between sediment and biologic response. Stable sites in the region were used as "reference" sites. The frequency and duration that a given concentration was equaled or exceeded was then calculated to produce a frequency distribution for each site. "Reference" distributions were created for the stable sites in each ecoregion by averaging all of the distributions within an ecoregion. This study presents a method for analyzing historical sediment-transport data from the southeastern United States that can be used to quantitatively evaluate thresholds for aquatic health in cases where sediment is believed to be the impairing water-quality parameter.

Technical Abstract: Sediment is listed as one of the leading causes of water-quality concern in surface waters of the United States. In many cases, the prescribed designated use is aquatic health, indicating that TMDL targets for sediment should be functionally related to this use of surface water. TMDL targets for sediment transport have been developed for many Level III ecoregions over the past several years using suspended-sediment yield (load per unit drainage area) as a metric. Although one can use this methodology to differentiate between sediment-transport yields between stable and unstable streams in a given ecoregion, one cannot state that if a stream exceeds the target range, the aquatic ecosystem will be adversely impacted. To address this problem, historical flow and sediment-transport data from hundreds of sites in the Southeastern United States were re-examined to develop parameters (metrics) such as frequency and duration of sediment concentrations that could be used by aquatic ecologists to develop functional links between sediment and biologic response. Sites determined as geomorphically stable from field evaluations and from analysis of gauging-station records were sorted by Level III ecoregion. Mean-daily flow data obtained from the USGS were applied to sediment-transport rating relations to determine suspended-sediment load for each day of record. The frequency and duration that a given concentration was equaled or exceeded was then calculated to produce a frequency distribution for each site. "Reference" distributions were created for the stable sites in each ecoregion by averaging all of the distributions at specified exceedance intervals.