Is Beach Replenishment A Waste Of Money And Natural Resources
Why Beach Replenishment is a Waste of Money and Natural Resources:A look at why it’s necessary to begin embracing newer coastal engineering technology … Written by Dennis A. Schirmer, II
The decision of the Army Corps of Engineers (ACOE) to deny the Southern Delaware Beaches a replenishment due to lack of funding has brought up questions about barrier island geomorphology (the study of the physical features of the surface of the Earth and their relation to its geological structures), as well as whether or not beach replenishment is worth the time, money and resources we put into such a process that must be constantly repeated. This inquiry could be answered best in the form of an educational outreach to the residents of our coastal community.
Rich and I had a discussion a while back about a paper I wrote for a barrier island ecology course I took during the fall 2014 semester at college. The discussion was about whether or not beach replenishments were really worth the money invested trying to save a wave-dominated barrier island from retreating or migrating towards the mainland. Well, after revisiting the discussion this weekend, Rich invited me to guest author this article in an effort to educate the masses. So, here we go…
Let’s first establish that Dewey Beach, Delaware Seashore State Park, the northernmost point of Bethany Beach (at Cove Way and Coastal Highway), the southernmost point of Bethany Beach (at Assawoman Street and Coastal Highway), and throughout Fenwick Island are all part of a wave-dominated barrier island (Figure 1).
Wave-dominated barrier islands are long, narrow barrier islands with typically widely spaced tidal inlets. Because of wave dominance, the capability for longshore sediment (longshore drift) transport is high. Tidal inlets in wave-dominant barrier systems are relatively narrow because longshore drift acts to fill in the inlets and restrict their widths. These changes are not seen at IRI because it is constantly being maintained by the dredging efforts of the ACOE, as well as both jetties that are positioned on the north and south shore. The tidal deltas on the seaward side of the inlets, ebb tidal deltas, also tend to be small because waves tend to limit the distance that ebb tidal deltas can migrate seaward.
Longshore Drift Example Through Animation …
The problem that wave-dominated barrier systems face, is that they are extremely prone to a process called island migration. The belief is that during periods of sea-level rise, barrier islands will migrate inland via erosion and longshore drift, followed by its deposition elsewhere. All of this is enabled by storm-driven wash-over events (Figure 2) , 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 seaward due to reduced erosion and increased near-shore sediment deposition at and just beyond the oceanfront margins.
In attempt to restore what has been lost of the coastline/buffer zone that is protecting our properties and businesses from being further damaged, we have a tendency to stick to what we know, which is widen the beach with another beach replenishment.
Many of us already know what beach replenishment is, but for those who do not, it is the process of pumping sand from elsewhere onto an eroding shoreline to create a new beach or to widen the existing beach. Beach replenishment does not stop erosion; it simply gives the erosional forces (usually waves) something else to “chew on” for awhile. The waves erode the replenished sand instead of destroying houses, roads or parking lots. Because replenishment doesn’t stop erosion, replenishment must be repeated to maintain the beach. It’s helpful to imagine that each replenishment project (i.e., an addition of a batch of sand) has a “lifetime”. The project’s lifetime is simply the time it takes for all the replenishment sand to be eroded away. After that time, the beach would be back to its pre-replenishment width, and would need to be replenished with sand, again.
Beach replenishment is often proposed when beach erosion threatens to remove an existing beach, making it too narrow to be used, and/or when property behind an eroding beach is threatened. Publicly funded beach replenishment is worth considering only if the general public will have good access to the “new” or restored beach, AND when all parties have been informed that this solution is temporary, and will have to be repeated. Publicly funded beach replenishment is foolish if only a few beachfront property owners stand to benefit.
Beach replenishment has some big advantages, for property business owners, but the question is whether or not the advantages outweigh the disadvantages, which is a much longer list. Honestly, I am willing to bet most will say yes, absolutely! However, lets take a closer look. Beach replenishment is probably considered the most gentle approach to shoreline engineering. It restores and widens the recreational beach. Structures behind the beach are protected as long as the added sand remains. When erosion continues, beach replenishment does not leave hazards on the beach or in the surf zone. This is a big advantage when compared with “hard” beach stabilization structures like seawalls or groins. Seawalls may protect structures behind the beach, but they almost always cause the beach in front of the wall to become narrower. If erosion breaches the seawall, then debris from the wall will be left on the beach and in the surf. Since beach replenishment only puts sand on the beach, no debris is left when it erodes.
As far as advantages are concerned, this is all we really have, truthfully. Sure, I’ve heard the arguments about how replenishments keep businesses and homes from becoming flooded during storm surge and overwash events, but when push comes to shove, the property/business owner is still being forced to ante up more money for insurance as their deductibles increase, and in taxes for another publicly funded replenishment project.
Disadvantages of beach replenishment is unfortunately, a much longer list. At the top of the list, beach replenishment sand almost always erodes quicker than the natural sand on the beach. A good thing to remember is that replenished beaches have a tendency to erode two or three times faster than natural beaches. However, erosion rates can differ widely.
The biggest factor for the lifetime of a replenished beach is the number of extreme episodic storm events (EESEs) that affect the beach. As we all know EESEs (like nor’easters and hurricanes) are impossible to accurately predict. Therefore, replenished beach lifetimes are unpredictable as well. The amount of sand added per yard of beach length and the sand placement design determine the new beach width. Wider replenished beaches last longer.
Another disadvantage it that beach replenishment is highly expensive, and must be repeated periodically. Except on very small beaches, the minimum expenditure is usually $1 – $2 million dollars; larger, longer-lasting projects often cost much more (e.g., $100 million – 1 billion). In addition to the disadvantage of expense, sufficient money is never available to replenish the entire beach out to a depth of 40 feet. Thus, only the upper beach is covered with new sand, so that in effect, a steep beach is created (Figure3). As a result of this downfall, the new steepened profile often increases the rate of erosion even more.
In addition to the list of disadvantages, the beach turns into a construction zone during replenishment. Thereby, limiting access to beachgoers.
The most overlooked disadvantage by all of us as coastal residents would be that the process of replenishment damages, destroys or injures marine and beach life by burying/crushing it under bulldozers, changing the shape of the beach, or making the water near the beach too muddy. In recent decades, a variety of plants, insects, turtles, shorebirds, and other animals have become threatened or endangered as a result of human alteration of coastal environments. Many of these organisms rely on EESEs and other natural beach processes (such as dune formation by wind) for the creation and/or maintenance of their habitats. Because of their dependence on natural beach processes, replenishment projects can affect the survival of certain species. For example, beach replenishment can modify a beach by making it too steep and/or too compacted for sea turtles to climb up and bury their eggs. Another example involves filter-feeding marine organisms, such as certain species of clams, that are accustomed to relatively clear water. These organisms can be particularly hard hit by the extreme muddiness produced by replenishment, and can die-off in large numbers.
Lastly, the sand added to the beach is often different from the natural beach sand. It can be hard to find a perfect match. This means that the new material may have smaller or larger diameter sand grains than the natural beach. Such differences in “grain-size” affect the way waves interact with a beach. This will affect surf conditions and bars on the submerged part of the beach, and will also change the shape of the “dry beach”, which is where people spread their towels and go for strolls. Fine-grained sand generally erodes faster than coarse-grained sand, so grain-size influences the replenished beach’s “lifetime”.
The satellite imagery here (Figure 4) 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 National Wildlife Refuge to its South. For the most part, the post-Sandy beach replenishment and addition of groins (shoreline protection structures which extend from the backshore to the surf zone, perpendicular to the shoreline – intended to build up an eroded beach through the entrapment of longshore drifting sediment or to slow beach erosion) have stabilized the developed portion, but for anyone who is familiar with the area, it has come at the expense of the beach (hardening and replenishing a shoreline often accelerates erosion at the beachfront) itself, and many oceanfront homes 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 the information gathered from this image as proof that beach replenishment works, but many experts in the field feel that what some consider a permanent solution is actually a temporary fix (which I previously stated), and likely provides a false sense of security by convincing people to stay-put, actually putting them in harm’s way by providing deceitful reassurance. Bearing in mind that rising waters, EESEs like Sandy, and likely time itself may eventually prove futile the efforts made to nail-down the island where it currently lies.
Originally, I was asked my opinion on the issue regarding the ACOE’s denial of the request for a replenishment in Bethany post-Jonas. Well, I can’t say that this is not an entirely bad thing. Trust me, its not the end of the world. With as many tourists that visit our beaches each summer, the thought of losing money because we weren’t granted a beach replenishment is unnecessary hysteria. We are still going to see the same influx of tourist traffic that we see each year. For many of us that are part of the surfing and surf-casting community, seeing all of the changes in the beach that have happened this winter has gotten a fair amount of us excited for spring and summer. To be honest and add to Mitch King’s comment to Gov. Markell, Secretary Small, and the several representatives that took the time to visit Dewey Beach on the 17th … “Look at the surf, it is perfect to fish, swim and surf, you have to leave it like that, please leave it like that. Rebuild the dunes but leave the surf alone, I haven’t seen it like this since I was a kid…”.He’s right. I’m 35 years old, and I haven’t seen these conditions since I was 13 years old (at the very most). As a matter of fact, I remember a particular beach excursion not a week after a hurricane (I wish I remembered which one it was), but I was in Fenwick, the water was a green-blue hue. There was a sandbar in front of Fenwick Isle at least 150 yards wide. The swell size wasn’t much to write home about, but the break at the leading edge of the sandbar made for a decent sea-kayak ride. Days at the beach like this are what I envision every time I come home, but alas, there have not been days like that in two decades for me.
If we really need to consider another replenishment in an attempt to prevent more damage to beachfront homes and businesses, then why not try considering an alternative. We should be realizing by now that replenishments are meager attempts at shoreline protection in an area where wave-energy is the dominant factor. Because we all need to face it, Mother Nature doesn’t care about our plans to fix a problem that is only a Band-Aid solution to an inevitable fate. Some say seawalls can fix it, but as we have already discussed that’s not much of a good idea either. However, we could turn our heads to the idea of a more sustainable method of attenuating (weakening) wave impact in areas susceptible to erosion. Take for instance, the construction of submerged breakwater structures (i.e. living breakwater), artificial reefs (Figure 5&6), or living breakwater(s) to the stabilize shoreline.
I know that some of you have just begun to pump the brakes on the thought of an artificial reef, go ahead. Sure, it’s going to be a serious investment, maybe even more expensive than a replenishment to construct. However, think about the long-term aspect of a finished product. You’re not having to empty your pockets every 10 years (although that is an exaggerated estimate, 5 years at best), attempting to get the ACOE to put another Band-Aid, knowing good and well that it’s only temporary. Whereas, artificial reef structures are there permanently. I could go through a long list of solid research that backs up the idea that submerged breakwater structures are worth looking at to fix a recurring problem. Talk with any of the surfers and surf-casters who knows a thing or two about how important structure is and you will find that the idea of looking towards a long-term investment (like the placement of an artificial reef) in mitigating the effects of EESEs is not really all that scary.
Dennis A. Schirmer, II