Protecting a Shoreline

October 29, 2015

Protecting a Shoreline

By Pete Zitta

Picture this: It is Labor Day weekend and we’re driving east on U.S. 50, heading to Lewes, Delaware to spend a couple of days at the beach.  Crossing the Kent Island Narrows bridge in Maryland, we turn north off the highway for a late seafood lunch of anything with Old Bay anything and a few glasses of summer ale at the Harris Crab House (There’s always a designated driver for the post-lunch driving.)  The outside top deck of the restaurant overlooks part of the Chesapeake Bay at Kent Island Narrows and the Chester River.  Just east of the Crab House, across from the marina, is the Narrows Pointe Community – a multi-unit, townhome style, condominium community situated on a linear peninsula that juts out into the Chester River.  It is here that soon a Living Shoreline will be constructed to help protect the community’s shoreline from erosion.  The energy from waves, wind and storms on the Chester River are slowly eroding the Narrows Pointe shoreline.  The shoreline has a long fetch, which is the distance that waves and wind travel unimpeded to that spot. It is the long fetch at the Narrows that is the main contributor to erosion. The longest fetch at Narrows Pointe is 29 miles from the north/northeast bearing of the property.

Narrows Pointe has nearly 2,000 linear feet of shoreline to be protected with a Living Shoreline measure.  Since 2008, the Maryland Department of Environment has required that shoreline stabilization projects use non-structural stabilization measures in tidal wetlands.  Living Shorelines are a non-structural shoreline stabilization method comprised of stone sills (also called stone containment barriers) located just off-shore. The sills are constructed using tightly fit, large, armor boulders weighing between 400 and 1,200 pounds, trapezoidal in shape and interspersed with multiple openings.  The large rocks provide stability to help absorb wave energy from storm surge and flood waters; the openings provide aquatic habitat access.  The top elevation of the stone sills are based upon the storm surge elevation above the predicted water levels of certain storms—for example 1-in-10 year or 1-in-25 year storm events.  Behind the stone sills, stretching landward is a sand-fill layer that extends from the mid-tide elevation at a gentle slope to tie into the shoreline bank above the local mean high-water elevation.  The sand-fill area is planted with Spartina Patens marsh-grasses. High marsh grasses are planted from the high water elevation to the upper edge of the sand-fill. Low marsh grasses such as Spartina Alterniflora are planted from the mid-tide elevation to the high water elevation line.  The grasses and sand-fill area behind the stone sills provide a natural vegetative buffer for protection and aquatic habitat areas, and they help to improve water quality by settling sediment and filtering pollution.

The Narrows Pointe Living Shoreline and similar projects designed to restore and stabilize eroded shorelines, channels and streambanks are small parts of a larger effort to help improve the health of Chesapeake Bay and protect property infrastructure.  This is part of what we do.  At the 2013 Mid-Atlantic Living Shoreline Summit in Cambridge, Maryland, an eastern shore Living Shoreline contractor made a memorable quote:  “When you install a Living Shoreline, you are raising a child.”  You have to maintain things, or entropy prevails.

So, we finish our lunch at the Harris Crab House and head back onto U.S. 50 and drive on to Delaware.  The old Creedence Clearwater Revival song Bad Moon Rising begins to play on the car radio:  “…I hear hurricanes a blowing…I fear rivers over flowing…don’t go around tonight, it’s bound to take your life, there’s a Bad Moon on the Rise – the lyrics make me wonder about another “Super Storm Sandy” type storm blowing through and conjuring up large waves and strong winds.  Pondering the time, the permitting hurdles to overcome and the monies spent and believing that the Narrows Pointe Community will be well protected with a Living Shoreline.

Construction photos can be viewed here http://www.narrowspointewaterfront.com/editor_upload/File/30%20Nov-4%20Dec%20Construction%20Photos.pdf

 


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