Coastal Erosion is the result of coastal process, anthropogenic impacts or often a combination of the two factors, sometimes amplifying each other.
Safe Harbor responds to coastal erosion problems by developing alternative responses. Then we consider each alternative for consequences and linkage to the scale of the problem. The most sustainable response usually responds to the problem and also addresses the cause of the problem. Sustainable responses don’t create shoreline anomalies, because coastal anomalies may generate consequences which can neutralize the response effort.
Winter Storm Erosion: What role does ice play?
Ice may scour intertidal habitat but ice floes absorb wave energy and reduce shoreline erosion.
Winter Storm erosion: What role does wind play? Broken beach steps contributed to near loss of home.
Unfortunately for a property owner with broken beach steps, tenants walked down to the beach over the dune vegetation, killing the beach grass. The winter winds came through the open area for 2 years, creating a blow out big enough to put a small house in.
The blow out was growing several feet each week. At the end of February, we measured the opening in the dune at 55 feet wide, 12-20 feet deep and 80 feet from toe of dune at the beach, to back dune. The foundation posts for the nearest home (not visible here) were 12 feet away. The home belonged to an absentee owner.
After consulting with the home owner and local Conservation Agent, we had a team set up sand fencing until we could develop a restoration protocol. The semi-concentric pattern of fences would slow down the wind. Instead of eroding sand, the wind would now deposit sand.
The erosion was so extreme that we needed to bring in compatible sand to renourish the blow out area. We selected an experienced excavation company (E-Z-Doze It from Wellfleet) with an equipment operator who followed our strict access requirements.
Careful flagging and site management communication, provide clear guidelines for the restoration.
We coordinated sand restoration with replanting beach grass. Early March is perfect but not always balmy.
Sand fencing was re-installed to control wind speed over the restored area. Dennis Minsky, Talilla Schuster, Rachael Sevanich and Meribeth Ratzel take a well deserved moment to admire their efforts. Rachael received Safe Harbor’s Special Recognition Award for her leadership on this project. The beach grass will double it’s stem count each year and in 4-6 years, the system will become sustainable.
Winter Storm erosion: What role do waves play?
The placement of adjacent sea walls redirected wave energy, end scouring this unprotected, beachfront property. End Scour occurs when wave energy gets redirected by a structure and wraps around the corner, transferring energy which erodes the adjacent, unprotected beach.
This neighboring sea wall or bulkhead, creates end scour when waves come from the south (to the left in photo). The structure transfers wave energy northward, eroding the unprotected adjacent beach with end scour.
Petra Mandakova photographs wave driven sand movement in storm conditions. waves come directly onshore, depositing some sand and seaweed as energy is naturally spent on the sloped beach. Note how the wave energy is being reflected by the sea wall, creating turbulence in front of the sea wall. This contributes to erosion in front of the sea wall.
This second sea wall, (above) on the north side of the property, may contribute to a lesser degree of end scour When the wind is northerly. There will be less erosion from that direction because of protection from the Provincetown end of Cape Cod, visible in the distance.
From the combination of construction, wind obstruction and end scour from adjacent sea walls, a significant portion of this beach and coastal dune need restoration.
Portions of the structures have contributed to erosion by inadvertently obstructing, accelerating and redirecting wind energy. In this case, (see following 2 photos) we installed 24″ sand capture fencing, to collect wind blown sand off the beach, during the winter storm season.
Shoreline Erosion, Assessment Tools
Safe Harbor uses satellite imagery to track the history of coastal erosion.
We also utilize Topographic maps to evaluate inter tidal sand deposits.
Close up satellite image of near shore deposits and bottom characteristics.