Revitalizing Seawalls: An interview in AIA Forum Magazine

17 01 2011


by Dennis Haskell, FAIA

An Interview with AIA Seattle Travel Scholarship recipient Cristina Bump Assoc. AIA, LEED AP

The seawall at McMahon’s Point in Sydney was designed with the intent of providing habitat, in addition to protecting the land. The wall features sandstone blocks with holes that provide shelter for some species, and the omission of a few choice, non-structural blocks create tide pools that serve as habitat.


Why did you select this topic for your application?

After following the Alaskan Way Viaduct redevelopment, I was surprised that the seawall was not a critical consideration: the future of the waterfront relies heavily on improvements to the water’s edge.

Did you do significant research before submitting?

I conducted interviews with several organizations, including SDOT, UW School of Aquatic and Fishery Sciences, Army Corps of Engineers, AIA Seattle, People for Puget Sound, and Puget Sound Partnership, which gave me invaluable information on the current development of the waterfront. After finding limited examples of environmentally friendly seawalls in urban settings, I chose to investigate Australian habitat research in Sydney, Melbourne, and Brisbane.

What were the significant discoveries from your travels?

In Seattle, there are three locations where shallow water development will be considered (Pier 48, the Aquarium, and the Olympic Sculpture Park). The rest of the seawall to be replaced will be vertical due to bathymetric depth and utility locations. For this reason, I focused on studying vertical walls in urban settings and comparing them to the Seattle environment.

Tell us about Sydney

At McMahons Point in Sydney, steel I-beams were hammered to bedrock, then tied back to concrete anchors installed underground. L-shaped precast concrete panels were attached to the steel beams. Sandstone blocks were laid on the bottom section of the L and built vertically. Several non-structural blocks were omitted for environmental purposes. A rock armor was used along the bottom of the seawall to protect against an abundance of wave action. The North Sydney Council asked the University of Sydney’s School of Biological Sciences to design sandstone blocks with inlets that could act as rock pools; holes were drilled into the surface for animals and plants to find shelter.

Salmon, a major part of the Pacific Northwest ecosystem, are a concern as Seattle looks to redevelop its waterfront. According to Jeff Cordell, lead research scientist from the Aquatic and Fishery Sciences Department at the University of Washington, salmon are genetically hardwired to seek horizontal, shallow water habitat. In an urban environment where these shallow water areas have been replaced with vertical, deep water habitat, salmon struggle to find food or refuge. In Seattle, most of the new seawall’s structure will be set in deep water, but a non-structural, environmental component— such as Sydney’s sandstone block tide pools—can be hung off the primary structure at whatever shallow depth will best encourage desired species. This would provide a continuous fish migration corridor along our seawall, providing food and refuge for juvenile salmon swimming out of the Duwamish River.

I learned from Ross Coleman, Director for the Centre for Research on Ecological Impacts of Coastal Cities at the University of Sydney, that if the structural complexity of a seawall is increased, the biodiversity in that habitat will also increase.

What can we learn from Melbourne?

Melbourne went through a period of industrial trade and commerce on the Yarra River. The city effectively turned its back on the river– allowing its banks to become lined with parking lots—and the river soon became contaminated. Birrarung Marr Park, completed in 2002, has transformed the river’s edge, providing an urban place, a public arts space, a pedestrian connection between major city landmarks, and a revitalization of the downtown core. The park reflects the landscape and geology of Australia and celebrates its aboriginal roots.

While Birrarung Marr did not implement an environmentally friendly seawall, it provides an example of smart urban planning and revitalization along a river’s edge.

And Vancouver?

The new Vancouver Convention Centre West incorporates a bioengineered habitat skirt that uses a series of permanent, stepped, pre-cast concrete benches. The five-tiered underwater structure looks like a set of bleachers, consisting of 76 concrete frames weighing more than 36 tons each. The top surface of each bench has a wave pattern of exposed aggregate. A central trough closed at both ends runs along the length of each bench to mimic tide pools.

This variety of surfaces and tidal elevations is expected to encourage initial colonization and long-term use of the bench habitat by a broad range of marine flora and fauna that seek the intertidal zone.

Have you been able to get directly involved in the City of Seattle’s process?

Several City Council members have visited the Smart Seawall exhibit. Tetratech, the seawall consultant team, has used images and information from the same. I was also interviewed by the History Channel in their new show airing in November 2010 about America’s infrastructure. I was encouraged at the City of Seattle’s Seawall Open House and pleased that environmental factors are at the forefront of their planning, and that the UW is still monitoring their seawall test panels.

I am involved in the AIA Viaduct Taskforce and the Peoples Waterfront Coalition. My goal is to stay involved in the Seattle seawall process and raise awareness about this once-in-a-lifetime opportunity to make an incredible waterfront.

What other ways are you going to share your experience?

I created a travel blog which outlines my adventure in Australia and follows the political process in Seattle.

I conducted a waterfront tour with the Seattle Architecture Foundation (SAF) where we examined the past, present, and future of the Seattle waterfront with the help of local experts. SAF is picking up the tour for their regular schedule:

AIA Seattle is sponsoring a model, video, and print exhibition about my research and findings called “Smart Seawalls: A Travel Study on the Future of the Seattle Seawall”. Of special interest will be large-scale physical models of the different “smart” seawalls studied and how they could be applied to Seattle’s habitat, ecosystem, and tidal patterns. This exhibit will then travel to several other venues including Mithun and the Seattle Aquarium to reach a wider audience. The exhibit is now at the Seattle Aquarium.

Cristina Bump Assoc. AIA is a designer for Mithun and 2009 recipient of the AIA Seattle Emerging Professionals Travel Scholarship.





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