New Breakwater Stops Coastal Erosion
September 30, 2013
Every year storm waves erode some 34 hectares of coastal areas in Poland. The costs of protecting the seashore and repairing damage caused by storm waves are high. A scientist from the Maritime University of Szczecin in northwestern Poland has developed a new type of underwater breakwater to suppress sea waves and counteract coastal erosion.
As wind-generated waves enter shallower coastal waters they generally become unstable and break, dissipating much of their energy. However, the remaining energy in the waves can still cause shoreline erosion. Common ways to protect the coast are based on building breakwaters or dikes made of concrete or rocks. These help reduce the amount of wave energy that reaches the shore because they force waves to break and dissipate part of their energy in the process. The disadvantage is that such permanent structures alter the natural appearance of the coastline, make it less attractive to tourists, and are sometimes criticized as not environmentally friendly enough, in addition to being expensive.
Prof. Boles³aw Ku¼niewski from the Maritime University of Szczecin has designed a new, active, coastline protection method different from traditional, passive, protection methods. His method involves suppressing sea waves using their own energy before they reach the shore. Ku¼niewski developed the method by studying the mechanics of water undulation.
The method is based on a breakwater that is fully immersed and mounted a few dozen to a few hundred meters from the shore. The breakwater consists of interconnected, vertically positioned floats made of polyethylene tubes filled with air that inhibit water undulation. Because it is buoyant, the device is tied down with ropes anchored to the seabed to keep it immersed.
The device was designed as part of a research project carried out at the Maritime University of Szczecin between 2008 and 2010 that focused on developing a new way to protect the seashore against waves. The National Center for Research and Development allocated around $1 million to help finance the project, which involved eight researchers.
Wave attenuation studies carried out at the Ship Design and Research Center (CTO) in Gdańsk confirmed that the design was effective and encouraged the researchers to conduct further research in the sea, Ku¼niewski says.
“Coastline protection technology needs to be improved because the force, duration and frequency of storms have increased in recent years,” says Ku¼niewski. Particularly vulnerable to damage are high and steep shores with cliffs, which total about 50 km in length in Poland.
The breakwater developed at the Maritime University of Szczecin is primarily designed to protect small ports and parts of the seashore with cliffs as well as residential buildings and other facilities. In such areas the sea has eroded the coastline for centuries and the new type of breakwater will be particularly useful, especially as classical methods of coastline protection are very expensive there, according to Ku¼niewski.
The new method will help a number of small ports on the Baltic Sea, many of which are completely unprotected. During a storm ships can neither enter these ports nor leave them.
Ku¼niewski invented the breakwater when conducting research in other areas of physics. He thought about the mechanics of wave undulation and found that the energy of sea waves can be used for the protection of the seashore. “This is a versatile device that can potentially work everywhere,” Ku¼niewski says.
The new wave attenuation method was patented by Ku¼niewski last year, on the basis of an application submitted by the Maritime University of Szczecin.
The new method to protect the coastline is environmentally friendly, does not change the appearance of the coastline, and lowers the costs of maintaining it in a state suitable for tourists and recreation. The breakwater is lightweight and portable. It can be easily assembled, disassembled and transported. The estimated cost of producing it is less than that of strengthening the coastline with traditional passive methods, the researchers say.