Bulkheads are also structurally simple relative to undisturbed shorelines. Bulkheads waterward of OHW eliminate shallow-water refuge and foraging habitat of juvenile salmonids. Bulkheads with large interstitial spaces provide concealment habitat for sculpin, which prey upon juvenile chinook. Chinook fry appear to avoid bulkheads, which may affect their dispersal. Bulkheads interrupt the recruitment and transport of native sediment to lakes, resulting in both local and along-shore erosion.
Piers also disrupt sediment transport.
The amount of reduction is a function of the reduction in light intensity by the structure. Sediment and water contamination can result from leaching of PAHs and heavy metals from treated wood. Hydrocarbon input from two-stroke watercraft engines can be a significant factor in water quality reductions in lakes. However, in urban drainages, and Lake Washington in particular, outboard motors contribute less than 1 percent of PAH input. Chinook smolts exposed to an estuary contaminated with heavy metals and PAHs exhibited suppressed immune responses.