Restoration of Tidally Restricted Salt Marshes at Rumney Marsh, Massachusetts
Low-lying coastal floodplain environments often experience extreme tidal events. When such high water conditions threaten improved property and highways, the property owners and government agencies often construct a system of earthen dikes, drainage pipes
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Restoration of Tidally Restricted Salt Marshes at Rumney Marsh, Massachusetts Balancing Flood Protection with Restoration by Use of Self-Regulating Tide Gates Edward L. Reiner
Low-lying coastal floodplain environments often experience extreme tidal events. When such high water conditions threaten improved property and highways, the property owners and government agencies often construct a system of earthen dikes, drainage pipes, and tide gates in an effort to exclude damaging tidal flood waters from the protected area while providing for the discharge of storm water from the upland watershed. Tide gates are simple gravity-operated mechanisms typically mounted on pipes through dikes and used to control the flow of water in coastal environments. Conventional tide gates have a weighted valve or one-way gate that is hinged at the top, allowing the discharge of runoff from a protected inner area when interior water levels are greater than exterior water levels, while preventing the return flow of incoming tides. When used in estuarine environments, these gates drain upstream wetlands, obstruct fish migration, increase sedimentation by blocking the scouring action of tides, and decrease salinity. This exclusion of the tide often leads to favorable conditions for the colonization of salt marshes by Phragmites australis (common reed). Dense stands of Phragmites pose fire hazards near developed property, can impair drainage, and result in increased freshwater flooding and mosquito breeding upstream of conventional tide gates. Installing bidirectional-flow tide gates, such as the self-regulating tide gate (SRT), can improve drainage conditions, increase saline tidal flow, help control Phragmites, decrease fire hazards and mosquito breeding, restore normal salt marsh biotic assemblages, and protect adjacent development from flooding. The SRT has a top-hinged buoyant valve that opens with an incoming tide to allow saltwater to flow into the protected area and restore tidal wetlands. The buoyant valve is counterpoised with adjustable back floats whose greater buoyancy counteracts the buoyant valve so as to close the gate at a predetermined adjustable
C.T. Roman and D.M. Burdick (eds.), Tidal Marsh Restoration: A Synthesis of Science 355 and Management, The Science and Practice of Ecological Restoration, DOI 10.5822/978-1-61091-229-7_21, © 2012 Island Press
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communicating restoration science
Figure 21.1. Self-regulating tide gate (SRT), Route 1A in Revere, Massachusetts, adjacent to the Pines River. Unlike conventional flapper tide gates, which provide drainage flow only through a top-hinged structure, the SRT is a float-actuated water control valve that uses a bottom float to open the gate on incoming tides. A second set of adjustable floats (the round floats in this photo) on the valve allows the gate to close for flood protection. (Photo courtesy of Edward Reiner).
water level for flood protection of interior areas. Similar to conventional tide gates, on ebb tide the hydraulic force of the water pushes the gate open
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