What Is Hard Stabilization?

eHow
July 13, 2011

Hard stabilization includes various man-made measures to prevent shoreline erosion. Shorelines are constantly changing as waves and wind erode rock and deposit sediment on a continual basis, and this movement brings water closer inland and weakens structural foundations. Two methods of shoreline protection are soft stabilization, the process of adding back natural materials to combat effects of erosion, and hard stabilization, building permanent structures like groins, jetties, breakwaters and seawalls to support shoreline structures.

Stabilizing Sediment
Two methods of hard stabilization are used to stabilize sediment: groins and jetties. They are built at right angles to interrupt the flow of sand along the beach, confining it to its designated area. Groins, built perpendicular to the beach, are thin walls extending out into the ocean. As the force of the waves push sand along the beach, it piles up along the barrier of the groins. When enough sand builds up to leak around the groin, the shoreline stabilizes in that area, but at the expense of beaches down the coast. Jetties, like groins, are built perpendicular to the beach. They are placed in pairs at harbor entrances to prevent sand from seeping into the harbor. Jetties protect the harbor’s depth for ship safety, but do little to protect the coastline. Sand builds up, unable to spill over the long structures, and continues to erode down the coast.

Interrupting Waves
Two other methods are used to interrupt the force of waves: seawalls and breakwaters. They are built parallel to the coast to deflect the force of the waves from the beach and coastal structures. Breakwaters are long, thin walls built out at sea parallel to the coast. Like jetties, breakwaters are built to protect harbors from crashing waves. This protects ships, but they also impede the flow of sand down the beach. Sand fills up the space between the breakwater and the shoreline, making the harbor too shallow for ships. Seawalls are built parallel to the coast to protect beach structures. Seawalls need regular maintenance as the force of waves erodes them as it does the beach on either side of the walls. Waves also erode the beach in front of the wall and underneath it, risking collapse.

Problems with Hard Stabilization
Hard stabilization is considered permanent because the structures stay in place for years. In some respects, though, they are quick fixes and can damage the surrounding beach. While these structures protect buildings, harbors and other coastal infrastructure, they destroy the recreational beach by deflecting erosion to the remaining sand. This has dire consequences on the ecosystem as it threatens habitats and nesting grounds. Aside from being aesthetically unpleasant, hard stabilization structures are also very costly to initially build and to continually maintain.

Compared to Soft Stabilization
Adding sand, building dunes and planting vegetation to anchor sediment are all methods of soft stabilization to combat erosion. These methods widen the beach and temporarily protect structures while protecting the aesthetic integrity of the coast and its recreational value. Soft stabilization also has disadvantages. It is costly to maintain and must be replenished regularly. Erosion elsewhere diminishes the sand supply needed for these projects. Transplanting non-native sand can also have adverse effects on marine life.

References
El Camino College: Beaches and Hard Stabilization; T. James Noyes
University of Puerto Rico-Mayaguez: Living with the Puerto Rico Shore
Tulane University: Coastal Zones; Stephen A. Nelson