November 23, 2010

LSU’s Coastal Mechanics Lab, headed by Dr. Heather D. Smith, recently participated in a laboratory study with Oregon State University’s Dr. Dan Cox and Dr. Denny Albert and Kyoto University’s Dr. Nobuhito Mori at the O.H. Hindsdale Wave Research Laboratory in Corvallis, OR. The Hindsdale laboratory houses the largest Tsunami wave simulator in the world and the largest full-scale wave flume in North America.

The goals of the project are to quantify the reduction of incoming offshore wave energy by increasing turbulent dissipation through the vegetation, and investigate the effects on sediment transport through the vegetation. Use of vegetation to dampen wave energy and maintain sediment is both a cost effective technique as well as an ecologically sustainable solution to the high wave energy induced wetland loss encountered in southern Louisiana.

The research group, including LSU graduate students Agnimitro Chakrabarti and Getnet B. Agegnehu, obtained detailed measurements of the free surface elevation and sub-surface velocities in the flume for different densities of locally-harvested bulrush (Schoenoplectus pungens) obtained in Tillamook Bay, OR. This species of bulrush has close relatives which are native to both the Gulf Cast and the Great Lakes.

This is one of the first experiments where live, natural vegetation has been used in a controlled laboratory environment. A variety of wave conditions were tested, including regular and irregular waves, different wave periods, and different wave heights. The wave height was increased to simulate a storm scenario in an attempt to quantify plant damage under storm conditions. To the teams’ surprise there was little or no destruction of stems even under these destructive waves.

Finally, an advection and dispersion study was conducted using salt water as a proxy for contaminants to quantify the transport under waves through the vegetation. In the upcoming months, the research team will be analyzing the data obtained over the three-week long experiment.

This project is funded by the National Science Foundation, the Louisiana Board of Regents, and the Louisiana Water Resources Research Institute.

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Article by Julie Mueller, Department of Civil & Environmental Engineering, 225/578-9170, jmueller@lsu.edu



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