Effects of Shorezone Development - Final Report
A Summary of the Effects of Bulkheads, Piers, and Other Artificial Structures and Shorezone Development on ESA-listed Salmonids in Lakes

13 July 2000


This report is a product of a literature review initiated to determine our state-of-knowledge about the impacts of lakeshore development on salmonids, in the context of the Endangered Species Act (ESA).

There is much uncertainty surrounding the impacts of various shorezone structures and activities on salmonids within lakes in the Tri-County area (King, Pierce and Snohomish Counties, WA). Identifying the level of current knowledge, areas of uncertainty, and future research needs could provide a more consistent review and evaluation of shoreline development proposals, and decrease potential impacts to threatened salmon populations if the information is utilized in the course of permit review and assimilated into regulations.

This review was initiated by the City of Bellevue, WA, to provide a digest, a library of pertinent literature, and an annotated bibliography in the form of a Microsoft Access database, detailing the potential impacts of lakeshore development on ESA-listed species. The review is primarily focused on Lake Washington and Lake Sammamish, but most of the information should be applicable for other lakes within the Tri-County area that have threatened salmonid species. Review products will be utilized by decision-makers at the local through federal levels of government to assist in the creation of guidelines and policies related to lakeshore development.

It should be emphasized that, due to time constraints, this "review" is not an exhaustive compendium of all available resources, but rather a measured digest of what was readily accessible in the time allowed. Collection was directed at literature that related directly to shorezone structures and activities in cold, freshwater lakes, but pertinent literature on warmwater, riverine, and marine systems was also included. Despite time constraints, over 350 literature sources were collected and examined, and the salient points from those sources were incorporated into this digest. Primary searches targeted all relevant electronic databases, followed by secondary searches of the references sections of pertinent literature collected during primary searches.

Literature collected includes peer-reviewed journal articles, theses/dissertations, books, and technical documents. The literature collected for the review constitutes the majority of available relevant documents, with only the most inaccessible documents omitted. In addition, personal communications with respected local scientists were included where pertinent, current research was not yet published.

Potential Impacts

Shoreline development may seem innocuous to most people. The average property owner on Lakes Washington and Sammamish has no intention of harming salmonids when they propose to build a pier or bulkhead or otherwise modify their shoreline. The property owner's intention is often to reduce erosion, to develop a tidy shoreline, and/or to improve water access. Thus, it is initially important to define which structures and activities are being analyzed for impacts, and to identify how they may affect ESA-listed species. In Lakes Washington and Sammamish, shoreline development activities and structures that have a federal nexus (i.e., if a federal agency funds, constructs, or permits the proposed project) and are thus subjected to review under the ESA, include those activities/structures that require a U.S. Army Corps of Engineers (USACE) permit.

Specifically, USACE permits are required for the construction, replacement, or repair of piers, docks, boat canopies, boathouses, and shoreline armoring structures (i.e., bulkheads). Adverse impacts on listed species can result from construction or maintenance activities, or from the existence of the structure. Proposed projects having a federal nexus are analyzed for potential impacts at a variety of levels.

Under the ESA, "take," means any potential adverse effects to a listed species that can occur as a direct result of a proposed project, or as an indirect or interrelated result. Direct impacts to a listed species could occur from water quality impacts during construction, or result from increased opportunities for predation from the presence of a new pier. Such a take would be a direct effect. Indirect effects are less obvious. The reduction in water quality that might occur from a fuel spillage during boat fueling at a new residential pier would be an indirect effect. If the pier had not been constructed, the fuel spill would not have occurred.

The following are some specific potential impacts of shorezone structures and activities that have beenidentified through discussions between The Watershed Company and the U.S. Fish and WildlifeService (USFWS) and National Marine Fisheries Service (NMFS) (collectively called the Services)during 1999 and 2000 as part of the Biological Assessment (BA) process of Section 7 of the ESA. TheServices are concerned about potential adverse impacts of shorezone development on juvenile andadult chinook and coho salmon, and bull trout. Despite the Services concern for these ongoing impacts, they can only act on those concerns when an application for a project requiring a federal permit (or with some other federal nexus) is proposed.

  1. Piers, piles, boatlifts, and moored boats may provide cover, shade, and focal points for exotic predators of juvenile chinook (Oncorhynchus tshawytscha) and coho (O. kisutch) salmon such as smallmouth bass (Micropterus dolomieui) and largemouth bass (M. salmoides). Note: native predators such as cutthroat trout (O. clarki) and piscivorous birds may also benefit from shorezone structures, but they have yet to be considered in BAs for proposed shorezone development in the Lake Washington system.
  2. Shading from piers, boat canopies, boathouses, and moored boats may reduce the abundance of prey organisms available to juvenile chinook and coho salmon, and to forage fish of bull trout (Salvelinus confluentus) by reducing aquatic vegetation and phytoplankton abundance. Any reduction in aquatic vegetation may also reduce complex refuge habitat. To date, the Services have made no distinction between native and non-native aquatic vegetation.
  3. The temporary turbidity associated with construction may reduce water quality to the detriment of chinook and coho salmon, bull trout, and forage fish of bull trout.
  4. Pile driving may disrupt the distribution and behavior of, or injure, chinook and coho salmon, bull trout, and forage fish of bull trout.
  5. Piers and/or bulkheads may disrupt the migratory and rearing behavior of juvenile chinook and coho salmon.
  6. The boating activity that accompanies piers could disturb rearing or migrating chinook and coho salmon.
  7. Chemicals used to preserve or clean wood structures, and hydrocarbons from boats and personal watercraft could be acutely or chronically toxic to chinook and coho salmon, bull trout, or prey items of those species.
  8. Pier lighting may facilitate nocturnal predation on juvenile chinook and coho salmon by visual predators like smallmouth bass, cutthroat trout, and piscivorous birds.
  9. The removal of vegetation during bulkhead construction or replacement could eliminate a potential source of cover and food (allocthonous input of terrestrial insects and detritus for foraging aquatic insects) for juvenile chinook and coho salmon, and forage fish of bull trout. Vegetation removed is typically not replaced with native woody species that could provide a future source of woody debris to the lake (see impact # 13, below). Instead, shoreline property owners generally favor lawn or ornamental shrubby species that preserve lake views.
  10. Bulkheads prevent the recruitment of native sediment to the lake, resulting in a loss of heterogeneous substrate, and resulting in shoreline erosion at the toe or along the shore downwind of the bulkhead. This could affect the availability of spawning and rearing habitat, and the forage base for a variety of fish species.
  11. Bulkheads eliminate shallow-water habitat, which is critical as refuge and foraging habitat for juvenile salmonids and other small fish.
  12. Bulkheads reflect wave energy at the shoreline, resulting in the scour of sediment at the bulkhead toe, and creating an inhospitable high-energy environment for juvenile fish.
  13. The permanent removal of woody debris during bulkhead and/or pier construction reduces the availability of complex refuge habitat for small fish, and attachment surfaces for periphyton.
While the above list of identified potential impacts of shorezone structures and activity on ESA listed species is not exhaustive, it does illustrate the intricacy of the problem. There are potentially many ways that the existing and future development of lakeshores could adversely affect ESA-listed salmonids. A significant shortcoming of the above list is the exclusion of non-ESA-listed salmonids such as sockeye salmon, kokanee (O. nerka), and steelhead (O. mykiss).

While the focus of this report is on salmonid species that are listed or considered for listing under the ESA, shorezone development could have the same potential impacts on many other native fish within Tri-County-area lakes. The listing or proposed listing of chinook and coho salmon, and bull trout under the ESA indicates that these species face serious threats to their perpetuation within the region. Such threats are likely being faced by other salmonids as well. Thus, in most cases it would be appropriate to consider all salmonids, and perhaps native non-salmonids, as the subjects of the following discussion of impacts.

The potential impacts identified above of docks and bulkheads provided the focus for the review. For discussion purposes, the above list of impacts has been condensed into six categories: chemical contaminants associated with piers, docks, and bulkheads; disruption of natural physical processes; effects on predation and prey refuge habitat; effects on productivity; effects on migration; and recreation and construction activities.

The following is a summary of the information contained within the collected literature. The summary will begin with a discussion of the salmonid species that are present in the lakes of the Tri-County area, and are listed, or candidates for listing under the ESA. Second will be a discussion of pertinent research regarding the potential impacts. Finally, the summary will conclude with recommendations for best management practices (BMPs), mitigation options, and further study.