Barrier Island Migration

Harvested from Google Earth, this image speaks volumes on the issue of barrier island migration.  The principle is that during periods of sea-level rise, barrier islands will “migrate” inland via erosion and long-shore transport of sediment followed by its deposition elsewhere.  All this is facilitated by storm-driven wash-over events, such as those that occurred during Superstorm Sandy, that “push” (the actual mechanism is more akin to disassembly and reassembly) the barrier island back towards the mainland.  Conversely, during periods of sea-level fall, barrier islands will relocate sea-ward due to reduced erosion and increased near-shore sediment deposition at and just beyond the ocean-front margins.

Google Earth screen-grab of the Holgate-Forsythe border

The image here is the south end of Long Beach Island (LBI), showing the populated, and “hardened”, area of Holgate in Long Beach Township and the preserved natural area of the Forsythe Reserve to its South.  For the most part, fortification has stabilized the developed portion, but for anyone who is familiar with the area, it has come at the expense of the beach (hardening a shoreline often accelerates erosion at the beach front) itself, and many ocean-front houses exist under a constant state of threat by waves and surge, while the preserved natural area has been allowed to follow the natural path of Westward migration and thus has self-maintained a healthier beach profile.

 

Some may take this information as proof that fortification/hardening of the beach front works, but many experts in the field feel that what some consider a permanent solution is actually a temporary fix, and likely provides a false sense of security by convincing people to stay-put, actually putting them in harm’s way by providing erroneous reassurance.  Bearing in mind that rising waters, storms like Sandy, and likely time itself may eventually prove futile the efforts made to nail-down the island where it currently lies.

 

Another interesting point to note is that, while the Forsythe Reserve area did indeed experience over-wash and breaching during Sandy, these breaches have filled in via natural sediment transport, requiring no human intervention, since the event.

Adding some perspective to “The Dune Debate”

I just got back from a business trip to South Carolina.  A sight observed during a walk down to their beach puts into perspective the chatter and debate about the small engineered dune systems (translation: small piles of sand with a little dune grass planted on top) being reconstructed and/or newly-considered (and in some cases protested) on beach fronts in my home state of NJ versus more expansive and robust natural dunes (pictured) such as those in the Pawley’s Island area that were embraced and incorporated in their development.

 
Some may debate, with validity, whether the development shown in this photo is too close to the ocean, but it can’t be debated that dunes such as these provide far better protection than the little piles of sand we call dunes in NJ. Except for some preserved areas (such as those in Sandy Hook, Island Beach State Park, Barnegat Light, Forsythe, etc.), dunes such as these are the exception, rather than the rule, in NJ, which is a shame as they provide far better protection to that which lies behind them, be it natural habitat, wildlife, or people and their possessions such as homes, businesses, and infrastructure.

 

As you can see, there are multiple tiers and elevations to this dune, the vegetation is far denser and more diverse than what we see on ours, and if you click through to the full-size image you can see how elevated walkways were constructed over the dunes rather than cut through them, which would weaken their integrity during storm surge events with significant wave action.

Something to consider in the ongoing debate.