1 JulCoastal Erosion Solutions
Coastal erosion is a constant battle for shore communities and oceanfront developers. Wind, waves and sea level rise erodes coastlines and threatens the survivability of beachfront properties.
There are many solutions for coastal erosion. Some coastal protection systems are artificial and manmade while others focus on strengthening the natural beach environment.
Two Types of Coastal Erosion Solutions
Most coastal erosion solutions fall under one of two categories: hard armor and soft armor. Hard armor structures are physical man-made structures that protect the coast. Soft armor solutions, on the other hand, are more closely aligned with nature.
Both coastal erosion solutions have several advantages and disadvantages. It’s important to weigh those options and how it will affect your coastline. What works for a shore town in New Jersey might not work for a North Carolina beach. That’s why experts recommend picking a coastal protection armor that is site-specific to the natural needs of your beach.
Hard Amor Coastal Protection
Hard armor systems protect the coast from erosion. These artificial structures are the traditional coastal erosion solution. In fact, hard armor has been in use since the Romans constructed a sea wall to protect their harbor.
Hard armor structures are designed to:
1. Protect upland property
2. Trap and retain sand
The following are examples of hard armor coastal protection systems.
Seawalls are one of the oldest hard coastal protection structures. These man-made walls deflect wave energy in order to protect coastal property.
Seawalls are popular because of their longevity and strength. These solid structures are typically made of concrete which means they can withstand a lot of wave energy.
Seawalls are often topped with a walk way or boardwalk which means they also can double as a sight-seeing locale.
The Charleston Battery, for example, is one of the most popular destinations in Charleston, South Carolina. This seawall was originally built in 1909. The Battery was built to protect the city from high tides and strong waves. It is an added benefit that it now doubles as a scenic walkway.
Seawalls are expensive to construct and require extensive permitting. Years of exposure to wind, waves and salt water can potentially lead to scouring, cracking and deterioration. Charleston’s seawall is currently undergoing repairs in order to correct these issues.
Seawalls might protect upland property but they also often cause erosion of adjacent beaches.
Lastly, seawalls are artificial structures which means they take the place of a natural coastal habitat. Many studies have been published recently that indicate natural solutions like living shorelines are more successful coastal protection systems.
Breakwaters are stone structures that protect the coast and harbors from wave erosion. These revetment systems stand in the water. Breakwaters can be parallel or perpendicular to the shoreline.
Breakwaters that are parallel to the shore are often found in the water outside of small harbors and beaches. They protect these vulnerable environments from erosive wave energy.
Perpendicular breakwaters also protect harbors and beaches from waves. These breakwaters are typically attached to land and deflect incoming waves. Naturally, they trap sand as wind and waves push the sediment into the rock structure.
The Virginia Institute of Marine Science has a Breakwater Database that catalogs the Chesapeake Bay’s breakwater structures. You can find that database and the resulting case studies here.
Breakwaters can result in adjacent beach erosion just like the seawall. When sand accumulates in the rock structure, coastal erosion often occurs on the other side of the breakwater.
Additionally, breakwaters can be expensive and time consuming to construct. If not built properly, a major storm can weaken the structure resulting in costly repairs.
Geosynthetics for breakwater construction
Incorporating geosynthetics into the design of breakwaters results in a more stable and dependable hard armor structure. Geosynthetics stabilize the base of breakwaters. Geotextiles have mechanical and hydraulic properties that improve the structure of the hard armor system.
For example, on the Poplar Island Expansion project, high strength geotextiles acts as a mattress for the breakwater. The geotextile absorbs the load of the rip rap and stabilizes the structure on the soft sand. The strength of the fabric prevents shifting that would compromise the foundation.
At the same time, the fabric allows water to flow through the tiny pores in the geotextile which protects the system from hydrostatic pressure. Geotextiles specified for use on breakwater systems have a specific Apparent Opening Size (AOS). The AOS determines the size of the fine that would be able to pass through the opening. You want some fines to pass through the geotextile but too many particles could compromise the geotextile’s function.
Soft Armor Coastal Protection
Many developers, engineers and governing agencies are implementing soft armor coastal erosion solutions because they are not as invasive as the hard armor alternatives. Soft armor controls erosion by mimicking and strengthening the natural coastline.
This coastal protection strategy does not incorporate conventional materials like stone and concrete. Instead, soft armor utilizes natural solutions that improve vegetation, create natural wildlife habitats and control wave energy.
Sand bags are a very common coastal erosion solution. Stack them along the coastline to protect property from crashing waves and sea level water rise.
Sand bags are typically an inexpensive and accessible coastal erosion solution. They are manufactured in many colors but most coastal communities favor white or beige because it is more natural.
Although natural in appearance, sand bags are still a synthetic material. Sand bags are typically filled on location and require man power to stack them into place. If the sand bag is punctured, its strength will be severely compromised.
Geotubes are high strength sandbags made from geotextile fabric. Various geotextiles are used to manufacture geotubes. The fabric chosen dictates the strength and porosity of the coastal erosion solution. Geotubes are filled with a variety of material, stacked in place, and covered with sand and vegetation.
Geotubes provide structure and stability on the shoreline. They increase the surface strength of the sand and dissipate wave energy. Geotubes can be planted with native plants which strengthens the coastline and creates a more natural environment.
Even when geotubes are covered and vegetated, it is possible that they will be re-exposed over time or after a storm. Although this does not necessarily compromise the function of the product, it is less appealing for coastal communities that desire a natural shoreline.
It is important to note that geotubes require equipment to be filled and placed, while sand bags can be filled and placed by hand.
Dunes are the most natural line of defense against coastal erosion. That is why many communities prohibit trespassing on dunes and have laws that prohibit deconstructing beach dunes.
Although naturally occurring, dunes can be strengthened with careful management. Install Sand Fence to control wind erosion and fortify the natural soft structure. Stabilize dunes by planting native species that would naturally exist in the coastal habitat.
Always consult local laws and officials before undertaking any action with beach dunes, even if the dune naturally exists on your property.
Sand Fence is a thin wood slat fence connected by wire. It is not as intrusive as a seawall or bulkhead and is much easier to install. Sand Fence works with wind and waves rather than against them. Wind carries sand and deposits it at the base of the fence. Sand can still blow through the slats but the fence decreases the wind’s strength. As a result, the dune grows in size. When large enough, dunes can protect property from waves and storm surge.
Vegetation is the most natural form of erosion control so dune plantings further strengthen a fortified dune.
Even a reinforced dune can be destroyed when storm surge is strong enough. Additionally, years of wind can bury sand fence which means you might need to install a new line of fence.
More Coastal Erosion Solutions
The examples we’ve outlined for you are just a sampling of coastal erosion solutions. Other solutions include bulkheads, jetties, groins, sand replenishment, salt marshes and oyster beds. If your community is battling coastal erosion the most important thing is to choose a solution that works for you.
Contact us to learn more about how we can help you fight coastal erosion on your beach.