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Lake Austin bulkheads damaging environment, city scientist says

Wednesday, May 27, 2009 by Bill McCann

Using global positioning system (GPS) units for measurement, city scientists have discovered that man-made vertical walls, or bulkheads, block almost half of Lake Austin’s shoreline. That’s a problem, according to a City of Austin scientist who reported his findings to the Environmental Board last week.

Property owners build the bulkheads to reduce erosion from floods and watercraft wakes. But Andrew Clamann, an environmental scientist with Austin’s Watershed Protection and Development Review Department, says, “It is an environmental problem. It is apparent that we need to make changes (in city rules) to protect Lake Austin.”

These bulkheads are detrimental to the lake’s ecosystem, and there are questions about their long-term value in controlling erosion, Clamann said.

In March, city researchers, motoring up and down the lake with GPS units in hand, found that about 42 percent of the shore is lined with vertical bulkheads. Most are made of smooth stone or concrete or corrugated steel.

Bulkheads alter the natural shape of the shore, eliminating wetlands and habitat for animals such as fish, shorebirds, macroinvertebrates and mussels, as well as microorganisms and plants that can process pollutants, Clamann told In Fact Daily. The bulkheads denude the shoreline, which often serves as a nursery for juvenile fish, thereby affecting fish populations by reducing protective cover and food, he said.

Lake Austin is a 20-mile-long lake that was created by damming the Colorado River at Tom Miller Dam. Lakeside residents have been installing bulkheads for years with city approval to protect their shore property from the wakes of boats and personal watercraft and from the occasional floods that can return the lake temporarily to a fast-moving river.

Bulkheads are regulated by city code guidelines and criteria, according to Clamann. However, based on existing lake and shoreline conditions, it has become apparent that the language may not be sufficient, he said.

“Historically, applicants (to the city) have proposed bulkheading to protect their property from shoreline erosion. At the time, these were the best solutions available,” Clamann said. “However, we are now more aware of the negative impacts of bulkheading. Higher waves from increasing boat traffic have exacerbated the erosion at the same time the number of bulkhead applications has increased.”

With development of new methods of erosion control, city staff has determined that some changes are warranted to protect the natural shoreline and still prevent erosion and property loss, Clamann said. As a result, the city is developing new bulkhead application guidelines, he added.

“We are catching up with standard practices for these projects on Lake Austin by taking them one at a time and reviewing the circumstances and situations of each site.”

Research by several cities and natural resource institutions, including the City of Seattle, the State of Washington, and the Center for Coastal Resources Management, indicates that vertical bulkheads may not be effective long-term solutions to erosion control. In fact, they may transfer erosion in front of and below the bulkhead, Clamann said.

Fortunately, there are available alternatives that use natural materials, native vegetation, and engineered slopes to manage shoreline erosion, Clamann said. These alternatives support water-quality benefits that natural shorelines provide, he continued. Many of these alternatives are described in technical manuals from the U.S. Army Corps of Engineers and the U.S. Department of Agriculture’s Natural Resources Conservation Service, he said. 

It is difficult to generalize costs because every project is different, Clamann said. Alternatives could be more expensive initially than standard corrugated steel bulkheads, for example, but alternatives have the potential to be cheaper in the long run because of lower long-term failure rates and associated costs, he added.

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