The Best Of Both Worlds: Reconciling Land And Sea With Soft Engineering

Posted on: 13 March 2015

Seawalls have been built for centuries to protect seaside dwellers from the force and unpredictability of the sea. They can be highly effective in preventing land erosion and deterring floods when the sea level rises. Many countries around the world, including Japan and India, have found seawalls to be especially effective in minimizing the effects of natural disasters. However, many environmentalists worry that seawalls will eventually ruin coastal ecosystems and reduce seaside wetlands. Beaches and shallow water dwellings are disturbed when massive seawalls are built. However, more and more marine contractors are aware of this issue, and are looking into options that provide both a measure of protection and preservation.

So, why are seawalls necessary?

The waves that roll onto shore are powerful forces of erosion. As the waves continue to beat the shore, the water slowly removes land mass. Soon, infrastructure, like houses and roads are in danger of toppling into the sea. Seawalls act as giant retaining walls that hold the land back and protect it from the crashing waves.

Because seawalls have a such a big job, they understandably require large amounts of strong materials and intensive planning. The seawalls themselves are also not immune to the pull of the ocean, so they need to be regularly maintained by experts to make sure that they stay strong for when they will be needed. 

What's the harm?

When seawalls are constructed, portions of the land have to be dug out, and the gradual shoreline of oceans and lakes is removed as the walls are positioned deep into the ground. Therefore, shallow water dwellers like sea urchins, shellfish, starfish, some corals, and other wildlife are not able to survive. Shallow water plants, including seaweed, lily pads, and algae, also may struggle to survive. While massive seawalls are sometimes needed, especially in urban settings, engineers are looking for ways to help preserve the suburbs of the sea.

Also, as seawalls are constructed, beaches eventually disappear, because the shoreline erodes until the point of the seawalls. Some seawalls are designed to alter waves, which can change the shape of the sea floor as the stopped wave must dissipate it's kinetic energy. Many engineers recognize these side effects, but still realize the need for seawalls for protection. So, they have been devising new ways to reduce shore erosion.

How can soft engineering help?

The challenge facing most marine construction designers today is to prevent erosion while trying to keep shallow ecosystems alive. Some newer methods of "soft" seawalls include:

  • using boulders or rocks to build up a shoreline. Often, a cement barricade is not needed. Using rocks for a shoreline helps to protect the softer, more vulnerable dirt underneath. Rock shorelines are best for lakes and shallower ocean areas, where wave height is not a hazard and where smooth water is needed for recreation and shipping. 
  • artificially building up the land that will erode. Usually, this means that a "fake" mound of rocks, dirt and clay will be used to build a fence around the shore line. This way, a beach can be fully preserved, but if the waves come in during a storm or high tide, there is another line of defense waiting to take the force of the blow instead of crucial land mass. 
  • using gradual wave dissipation with angled seawalls instead of vertical ones. Some seawalls can be still be built from concrete and be friendly to the beach. It will take some time for the ecosystem to re-establish itself, but a gradual, man-made beach with curves and a "roll back" design at the tops can preserve natural wave shape, and reduce the impact on the sea floor. Pockets for linger water during low tide can provide places for water dwellers, just like on a regular beach.

Erosion control is a tough problem to tackle, especially because nobody can hold the power of the ocean back. However, some construction experts have realized that it is better to work with the sea instead of against it. Continued development will continue to be made in this area as marine construction becomes even more prevalent and necessary.