By Virginia Sea Grant Science Writing Intern Sarah Ruiz
On summer afternoons recreational boats slice through the waters of the Chesapeake Bay, leaving behind only their wakes. Although boat wakes may seem inconsequential in the grand scale of the bay, the ripples they generate join the rhythm of the natural waves that lap against the shore, increasing their intensity. With that increase in energy, may come an increase in the rate and severity of shoreline erosion.
In order to explore both the potential impacts of boat wake erosion on shoreline habitats, as well as possible policy options to manage those impacts, the Scientific and Technical Advisory Committee of the Chesapeake Bay Program commissioned a comprehensive report. The result, published this May, was a collaborative effort between scientists at the Virginia Institute of Marine Science (VIMS) and policy experts at the Virginia Coastal Policy Center (VCPC) and included authors from The Chesapeake Bay Trust, the National Oceanic and Atmospheric Administration (NOAA) and Old Dominion University.
The science section of the report focused largely on investigating the association between boat wakes and increased shoreline erosion.
According to Pamela Mason, Senior Coastal Management Scientist at VIMS and one of the authors on the report, this association is one that largely hasn’t been scientifically explored.
“There isn’t that much in the scientific or peer reviewed or gray literature,” Mason says. “There are some studies that are sort of few and far between, and so it was up to us to drill down and look for that information.”
To collect this information, scientists at VIMS conducted a review of the available literature, as well as analyzed the data from several monitoring stations around the Bay. In order to determine if recreational boating was significantly impacting erosion scientists examined turbidity, a measure of the cloudiness of the water which indicates suspended sediments in the water column.
“We looked for signatures to see if, in times that we would have expected high boat usage, like on the weekends, that there would be an uptick in the sediment that was observed,” Mason says.
The report did find these increases in turbidity, indicating an association between boat activity and erosion, but noted that there wasn’t enough data currently available to provide any precise quantitative information on just how much boat wakes were actually contributing to erosion.
“We have not really as a scientific community gone out and looked for that effect,” Mason says. “One of the recommendations of the report is to make a stronger effort to monitor for some of those changes, and to look if we can develop some numbers, and see just how much shoreline erosion can be attributed to boat wakes.”
Despite the gaps in data, the report still notes that actions should be taken to mitigate boat wake impacts because initial indications are that wake action does negatively impact shorelines. One of the most feasible options for mitigation would be to instigate no-wake zones, especially in shallower and narrower water bodies where the wakes have less room to dissipate before hitting the shore.
Video: Daniel Diaz-Etchevehere
