Seawall Habitat Shelves: Science and Urban Design

The seawall project has a variety of habitat enhancements demonstrating the city’s environmental stewardship efforts to improve the lost nearshore environment on Seattle’s waterfront. One of the key enhancement features is the introduction of habitat shelves – protruding shelves attached to the vertical wall face that will serve as the future home to marine life.

Installation of habitat shelves near Pier 57

This week, Seawall Project crews installed the first of these habitat shelves along the face of the new seawall near Pier 57.

Workers install stainless steel rods in the face of the seawall to support the new habitat shelves.

Workers install stainless steel rods in the face of the seawall to support the new habitat shelves.

Prior to installation, stainless steel threaded rods are inserted into the wall face to support the shelves, which can each weigh up to 2,685 pounds. The shelves are suspended by a crane, and then lowered into place and hung on the rods. The shelves are then bolted to the wall and grouted in place.  When the project is complete, 430 habitat shelves will be in place at various locations throughout the project area.

  Habitat shelves are installed in front of Pier 57. The cobbled surfaces promote growth of vegetation and marine invertebrates.


Habitat shelves are installed in front of Pier 57. The cobbled surfaces promote growth of vegetation and marine invertebrates.

The science behind the design

When developing the design for the habitat features of the new seawall, the City partnered with the University of Washington School of Aquatic and Fishery Sciences. Researchers with the university installed shelves and panels on the old seawall with several types of surface features and textures at various locations along the waterfront. They monitored the installation for four years, with the goal of identifying which designs provided the greatest benefit to habitat and could be incorporated into the new seawall.

Researchers from UW tested various shelf features over four years to determine which designs provided the best habitat development. Photo courtesy UW School of Aquatic and Fishery Sciences.

Researchers from UW tested various shelf features over four years to determine which designs provided the best habitat development. Photo courtesy UW School of Aquatic and Fishery Sciences.

The study found that features with high-relief elements, like shelves, had more mussels and algae present than did flat surfaces. In addition, the inclusion of cobbled texture, like those found on the new seawall face panels, appeared to encourage the recruitment of young mussels. Mussels and algae are known as “ecosystem engineers” because they provide additional refuge and food for a variety of small invertebrates that are important food sources for juvenile salmon and other small fish.

A computer-generated model of habitat shelves and face panels designed to enhance texture on the new seawall face. This is one of several textures that will be installed as part of the new seawall.

A computer-generated model of habitat shelves and face panels designed to enhance texture on the new seawall face. This is one of several textures that will be installed as part of the new seawall.

The findings from the study resulted in the design of the habitat shelves that were installed this week, and the cobble textures that have been incorporated into the new seawall face panels.

Learn more!

For more information about seawall construction, visit the Seawall Project website. If you have questions, email (seawall@waterfrontseattle.org) or call the 24-hour hotline (206.618.8584).