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“Reference” and Enhanced Rates of Suspended-Sediment Transport for Use in Developing Clean-Sediment TMDL's
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.orgCitation: Pp. 151-162 in Total Maximum Daily Load (TMDL) Environmental Regulations: Proceedings of the March 11-13, 2002 Conference, (Fort Worth, Texas, USA) 701P0102.(doi:10.13031/2013.7543)
Authors: Andrew Simon, Roger Kuhnle, Wendy Dickerson and Mark Griffith
Sediment is listed as one of the principle pollutants of surface waters in the United States,
both in terms of sediment quantity (clean sediment) and sediment quality due to adsorbed
constituents and contaminants. We can view sediment-transport rates and amounts as (1)
natural or background, resulting from generally stable channel systems, (2) impacted, with
greater transport rates and amounts, reflecting a disturbance of some magnitude and more
pervasive erosion, and (3) impaired, where erosion and sediment transport rates and amounts
are so great that biologic communities and other designated stream uses are adversely effected.
Impairment of designated stream uses by clean sediment (neglecting adsorbed constituents) may
occur through processes that occur on the channel bed or by processes that take place in the
water column. Fully mobile streambeds, and deposition of fines amidst interstitial streambed
sands and gravels can pose hazards to fish and benthic macro-invertebrate communities by
disrupting habitats, degrading spawning habitat, and reducing the flow of oxygen through gravel
beds. Although lethal or sub-lethal thresholds are unknown at this time, high concentrations of
suspended sediment, perhaps over certain durations can adversely affect those aquatic species
that filter and ingest water. It is critical, therefore, to clearly identify the potential functional
relation between an impact due to sediment and the sediment process so that appropriate
parameters are analyzed.