Table 1. Ambient Sedimentation Rates Derived from Published Sources

ERDC TN-DOER-E19

March 2005

However, effects ranges are usually expressed in responses to total suspended solids or

particulate concentrations (mg L-1). It is clear that for some taxa of concern, the thickness of

sediment accumulation may be critical and accumulation is not the same as water column

concentration (see below). It is also important to understand the range and timing of natural

sedimentation events in each region or habitat. An additional confounding factor for spawning

grounds is that most monitoring programs and water quality regulations for streams are

expressed in turbidity (often with a narrative description, e.g., cloudy, free from color or

turbidity, reduced light transmission), which may be used as a surrogate for suspended sediment

concentration or siltation (Gray and Glysson 2003).

An initial estimation of ambient sedimentation rates derived from published sources is presented

in Table 1.

Table 1

Ambient Sedimentation Rates Derived from Published Sources

Habitat

Sedimentation Rate

Concentration Near Bottom

0.1-100 mg L-1

Spawning grounds (for attached eggs,

Unavailable

gravel, sand)

0.1-0.3 cm yr-1

10-100 mg L-1

Estuarine SAV

0.3- 1.0 cm yr-1

100 20000 mg L-1

Turbid estuaries Fluid muds

Minimum levels of sedimentation known to have an adverse impact on early life stages of

fish. Available data on sedimentation expressed as concentration in the water column (potential

sedimentation) do not appear to be sufficient to provide prediction of impacts on early life stages

of fish. There is a need to determine relevant scales of sediment thickness and bulk

characteristics prior to larval or egg settlement and deposition of sediment after attachment or

settlement. The effects of increased sedimentation resulting in "embeddedness" (fine sediment

filling in gaps between gravel in streams) on hatching of salmonid eggs has been described

(Waters 1995) and has resulted in guidelines based on percent fines and other variables

(Lotspeich and Everest 1981, Caux et al. 1997).

In the Great Lakes, Walleye (Stizostiderm vitreum) eggs and larvae also appear to be affected by

sedimentation, but laboratory dose-response data are unavailable (D. Clarke 2004,

http://www.glc.org/dredging/scoop/DougClarke.pdf). A small number of direct observations and

studies indicate that attachment of non-salmonid fish eggs to benthic substrata can be inhibited

by siltation. Pacific herring eggs appear to require virtual absence of fine sediment layers to

allow attachment to the substratum (Stacey and Hourston 1982, Haegele and Schweigert 1985,

Barnhart 1988). Winter flounder eggs were observed to be affected by thin layers of deposited

sediments in laboratory conditions.1

Additional

related information is available on the effects of both sediment transport and

suspended

sediment concentrations on the early life stages of fish. Lisle and Lewis (1992)

provide a

useful model of salmonid embryo survival based on streamflow and sediment

transport.

They were able to incorporate long-term streamflow records (6 years), bedload

Personal Communication. 2004. D. Nelson, National Marine Fisheries Service, Milford, CN.