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Decision Tree: Expand the Marsh, Use a Sill for Marsh Toe Protection
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5a(2). EXPAND THE MARSH, USE A SILL FOR MARSH TOE PROTECTION
Moderate and high fetches (longer than ½ mile) support the formation of larger, potentially erosive waves. Although the existence of a marsh at the site indicates that conditions are appropriate for marsh growth, the larger waves may be eroding the leading edge of the marsh and/or the width of the marsh may not fully reduce the wave energy, resulting in upland erosion. Placing a sill at the channelward edge of the newly expanded marsh should provide long-term protection for the marsh, allowing the marsh to provide greater protection to the upland. Placement of offshore structures should take into consideration the existence of other resources such as submerged aquatic vegetation (SAV) and oyster reefs, and avoid impacting them where possible. Where there’s a conflict, placing the sill against the toe of the existing marsh or constructing an onshore revetment may be more appropriate.
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This is an example of a constructed marsh area with a sill for an area with a relatively narrow marsh with moderate fetch. |
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