Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

First Salish Sea-wide shoreline armoring study shows cumulative effects on ecosystem

20.04.2016

Bulkheads and seawalls along the shores of Puget Sound help ease erosion and stabilize bluffs to protect waterfront properties.

But these walled structures also shrink beaches, reduce habitat for invertebrates and spawning fish and, indirectly, degrade conditions for iconic species like salmon and orcas. Many studies have shown this pattern at seawall sites around Puget Sound.


This is a seawall along Harbor Avenue Southwest in the West Seattle neighborhood in Seattle, Washington.

Credit: Hugh Shipman

A new University of Washington study shows that impacts at individual armored sites can scale up to have cumulative, large-scale effects on the characteristics of Salish Sea shorelines and the diversity of life they support. It is the first study to analyze sites broadly within Puget Sound and offers the most comprehensive look to date at the impacts of shoreline armoring on the Salish Sea ecosystem.

"Given the incredible variety and complexity of shorelines in the Salish Sea, to pick out patterns we had to go very broad and step back and squint, if you will," said lead author Megan Dethier, a research professor of biology at the UW's Friday Harbor Laboratories.

"The huge challenge was searching for patterns in the noise. The shorelines are impacted by hundreds of different things and we were trying to see patterns driven by just one thing -- armoring."

The paper appeared online this month in the journal Estuarine, Coastal and Shelf Science.

When researchers looked at sites from south, central and north Puget Sound, the data showed that armored beaches became slightly narrower and steeper over time, and larger pebbles replaced finer-grained sediment and sand. Additionally, in stretches of shoreline that were more heavily armored, even the unarmored areas showed similar impacts -- less sand and more larger sediment on the beach.

"Changes to the shape and texture of a beach are subtle, slow to happen and can take decades," Dethier said. "It took a big sample size and a range of beach types to see that geomorphic signal. To me, this is the big punch of the study."

Of Puget Sound's 2,500 miles of shoreline, more than one quarter are currently armored. Shorelines range from heavily armored, concrete-covered commercial ports to pristine, sandy beaches.

Erosion from bluffs and banks is a natural process and if left alone, most bluffs will erode and replenish the beaches with sand and gravel. Armoring stops or dramatically slows erosion, and gradual-sloped, wide, sandy beaches over time give way to pebbly, steeper shorelines that aren't desirable to beach-spawning fishes -- or humans.

"This new report by Megan and her team provides crucial information on shoreline armoring impacts that will be highly valuable in improving our management approaches to Puget Sound shorelines," said Randy Carman, who works with the nearshore habitat program at the Washington Department of Fish and Wildlife.

"While we have often relied on conceptual models and studies conducted in other locales, we now have concise empirical data on armoring impacts from a large geography of Puget Sound."

In addition to identifying cumulative effects, this paper also confirmed previous studies and observations that armoring impacts the ecology and structure of shoreline habitat in Puget Sound.

Specifically, armored beaches generally have fewer drift logs, algae, seagrass and other organic debris that naturally washes ashore than their unarmored counterparts. This vegetation provides a daily feast for crustaceans and insects, and indeed, fewer invertebrates were present at armored sites. Sandy beaches, which provide habitat for surf smelt and other forage fish to spawn, were replaced by coarser sediment in armored areas.

Ultimately, all of these changes in nearshore habitat probably alter the feeding and migration patterns of juvenile salmon in the Sound.

In designing the study, Dethier and her collaborators identified 65 pairs of sites around the Salish Sea. Each pair included one site with no shoreline armoring and another close by that had some degree of armoring such as bulkheads, seawalls or wood pilings. Additionally, each pair was within a distinct unit of shoreline, called a drift cell, and the percentage of armored shoreline in each drift cell varied.

They collected detailed data from each site, including the amount of natural debris (seagrass, algae); the number of logs deposited on shore; the presence of invertebrates such as insects and sand fleas; the size of beach sediment, ranging from sand to cobble; the amount of vegetation hanging over the shoreline; and the slope of each beach.

They found the effects of armoring were cumulative, because in shoreline drift cells that had a higher percentage of armoring, even unarmored sites showed impacts, including less sand and more larger sediment.

The data collection was exhaustive, Dethier said, and a single day in the field generated about three weeks of processing specimens in the labs -- all before data analysis even began.

Because the effects of armoring are cumulative, it follows that reducing the number of bulkheads and seawalls throughout Puget Sound would improve the overall health of the ecosystem. Replacing concrete walls with softer, greener materials like logs, or replenishing armored beaches manually with truckloads of sand and gravel are options to lessen the impacts.

Even moving a seawall higher up on the shoreline would allow space for forage fish to spawn and natural tides to bring valuable nutrients to shore.

Many scientists agree the best option is to avoid putting in any new bulkheads and seawalls, which is what Hugh Shipman, a coastal geologist with the state's Department of Ecology, advocates in his work with landowners. Current laws for new armoring are set by the Department of Ecology under the Shoreline Management Act, and local governments are in charge of regulating and approving projects, with additional permitting from Washington Department of Fish and Wildlife.

"We want to assure that more restrictive bulkhead policies are supported by the best science we can possibly have," Shipman said. "This is the most significant paper we've seen that looks at the impacts on Puget Sound."

###

Other co-authors are Wendel Raymond, formerly at Friday Harbor Laboratories and now at the University of Alaska, Fairbanks; Jason Toft, Jeffrey Cordell and Sarah Heerhartz of the UW's School of Aquatic and Fishery Sciences; Andrea Ogston of the UW's School of Oceanography; Aundrea McBride of the Skagit River System Cooperative; and Helen Berry of the Washington Department of Natural Resources.

This research was funded by Washington Sea Grant and the U.S. Environmental Protection Agency, through the Washington Department of Fish and Wildlife.

For more information, contact Dethier at 206-543-8096 or mdethier@uw.edu. She is teaching at Friday Harbor Labs this quarter but has availability on Monday and Tuesday for interviews.

Additional sources:

Hugh Shipman: hugh.shipman@ecy.wa.gov or 425-649-7095

Coastal ecologist at Department of Ecology. Can talk about physical changes to shorelines from armoring.

Randy Carman: randy.carman@dfw.wa.gov or 360-902-2415

Nearshore habitat program at Washington Department of Fish and Wildlife. Can talk about biological impacts of armoring.

Related paper: http://www.sciencedirect.com/science/article/pii/S0272771416301007

Read more in the Encyclopedia of Puget Sound's series on shoreline armoring: https://www.eopugetsound.org/magazine/shoreline-armoring

Media Contact

Michelle Ma
mcma@uw.edu
206-543-2580

 @UW

http://www.washington.edu/news/ 

Michelle Ma | EurekAlert!

Further reports about: Ecosystem Wildlife ecology forage fish insects seawalls

More articles from Ecology, The Environment and Conservation:

nachricht Joint research project on wastewater for reuse examines pond system in Namibia
19.12.2016 | Technische Universität Darmstadt

nachricht Scientists produce a new roadmap for guiding development & conservation in the Amazon
09.12.2016 | Wildlife Conservation Society

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

Im Focus: Newly proposed reference datasets improve weather satellite data quality

UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration

"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...

Im Focus: Repairing defects in fiber-reinforced plastics more efficiently

Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.

Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Multiregional brain on a chip

16.01.2017 | Power and Electrical Engineering

New technology enables 5-D imaging in live animals, humans

16.01.2017 | Information Technology

Researchers develop environmentally friendly soy air filter

16.01.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>