Posted on April 15, 2019
RYE — The Board of Selectmen met with a state Department of Environmental Services representative to review conservation practices to reduce erosion and prepare for impacts of sea level rise on the town’s coast and coastal estuaries.
DES Coastal Resilience Coordinator Kirsten Howard spoke before the board Monday about coastal flooding and the erosion on Rye beaches. She presented data from a DES study spanning the past two years on the volumetric loss of sand on Rye beaches. Rye beaches have lost upwards of 0.72 meters per year of sand on beaches, with an average of 0.25 meters per year.
Citizen scientists and volunteers through the University of New Hampshire helped collect sand loss data through UNH’s Beach Profile system, where small teams gathered monthly data at several points along Rye’s beaches.
Howard stressed the importance of shoreline integrity. Without a robust shoreline, she said, the town would be more susceptible to flooding, storm surge and loss of property and natural resources. She explained most of Rye’s sandy beaches could be lost without proper maintenance.
While sea walls are traditionally the barrier of choice on the New Hampshire coast, research funded by the National Oceanic and Atmospheric Administration suggests they increase erosion in many instances. The hard barrier causes sand below to be swept away. Twenty-three percent of Rye’s coast is already protected by sea walls.
Howard and DES proposed the use of other conservation techniques and suggested the town tailor the approaches to different environmental sites as applicable. An estuary such as a salt marsh would be a better candidate for natural barriers, where a combination of natural and man-made barriers would be important to protect a beach, for example.
The main conservation approach highlighted by DES is living shorelines projects, which create natural barriers and maintain the existing land-water interface. This includes creating sand dunes, planting vegetation, using other biomass such as shellfish, grading slopes and other approaches.
Other possible conservation techniques include beach nourishment, the act of manually adding sand. Grading the beach, dredging and reshaping harbor boundaries are all possibilities that have been used in the past.
DES and national data suggests sea level rise in Rye of two to six feet by 2100.
A Colombia University study conducted in January showed just two inches of sea level rise caused flooding to increase by 260 percent in New Hampshire since 2000 and cost $15 million in unrealized property value.
Sea-level rise and flooding are a concern to the Board of Selectmen, which formed a Conservation Commission in 2014 to assess risk to resources in Rye.
The town of Hampton experienced approximately 60 instances of high tide flooding into roadways along the marsh last year and is engaged with DES to mitigate possible future erosion on their beaches, including dredging its harbor and using the sand to replenish its beaches.
Beach nourishment in Rye remains a challenge because the sediment that would be dredged from Rye Harbor is mostly silt and muck and could not be used for that practice. Instead, the town would have to bring in sand, an expensive endeavor.
Selectman Bill Epperson said beach erosion is naturally cyclical, losing sand during the winter months, and regaining the sand in the summer.
“That’s correct,” Howard said, “but we’re continuously losing sand despite this and will continue to do so at an increasing rate such that it won’t be replenished fully without proper shoreline management.”
DES is partnering with the town of Durham and University of New Hampshire to implement a living shoreline project at Wagon Hill Farm in Durham, abutting the Great Bay tidal estuary. DES hopes the project will encourage other towns to follow suit.
Funding opportunities are available with the National Fish and Wildlife Foundation through the National Coastal Resilience Fund, which is requesting proposals for living shoreline projects. New Hampshire Coastal Resilience Grants will be available to in 2020.
Source: seacoastonline.com
