Coastal Engineering is the Civil Engineering specialty that deals with the effects of erosion on our beaches and other coastal areas. Since the end of the last ice age, the level of the sea has been gradually rising.
Working together with the natural action of waves, this is constantly eroding shorelines, from recreational beaches to harbor facilities; even cliffs along the coastline are attacked by this constant eroding action.
Coastal Engineers not only needs to understand the principles of civil engineering, but also of nearshore oceanography and marine geology. These three specialties combine towards solving problems caused by a combination of wave action, storm and the flow of rivers. The combination of these different forces creates great challenges for the Coastal Engineer.
Coastal Engineering for Erosion
Worldwide, about half of the population lives within a short distance of the coast, making this the most prized real estate on the planet. Yet, these same coastal areas are under constant attack by the sea, eroding the very land where many people live and build their businesses.
While erosion is a major concern to Coastal Engineers, safety of the coastlines are just as important. Hurricanes, tsunamis and the normal waves caused by storms can wreck havoc on entire regions, destroying cities and displacing the lives of millions of people. In 2006, Hurricane Wilma totally eroded away Cancun, Mexico’s famous sugar-white beaches in a matter of hours. Coastal Engineers develop systems of defense to prevent destruction caused by both erosion and storm waves.
While there are a number of systems that Coastal Engineers use to prevent damage caused by waves, the most common are breakwaters, sea walls, revetments and gryones. These are all structures built out of concrete, sand and stone to help dissipate the force of waves and control erosion.
• Breakwaters are artificial barrier islands placed a distance from the shore. The force of the waves is dissipated on these barriers, preventing it from affecting the shoreline.
• Sea Walls are concrete or rock walls, built at the back of a beach, to protect a settlement from the effects of erosion. While the beach may erode, the settlement behind it will remain protected.
• Revetments are most easily understood as armor plating the beach with rock or concrete. While the wave force still strikes the beach, it doesn’t carry away the sand.
• Gryones can be made out of wood, stone or concrete and extend out perpendicular from the beach. They work to impede the lateral drift of sand from wave action.
Many times, these “hard techniques” are mixed with “soft techniques” such as beach replenishment, where sand is dredged from the sea bottom and deposited on the beach to replace sand that has been washed away by the waves.
Coastal Engineering and Flood Control
Hand in hand with the problem of erosion is the problem of flooding, especially in storms. Coastal engineers design defenses to protect coastal communities from the ravages of storm flooding. With properly designed and constructed defenses, the effects of the storm are minimized and flooding is prevented.
Venice Italy faces one of the biggest flooding challenges to coastal engineers in the world. Venice is actually an island, fully contained within a natural harbor on the northeast coast of Italy. Since the city is already operating in a state of flood, with canals for their major streets, it takes very little to cause a flood.
Due to its makeup the city of Venice has suffered a constant history of flooding. New work by coastal engineers may be bringing this to a close though. The Venice Tide Barrier Project consists of 80 hinged barriers, which will close off the three inlets to the harbor in the case of high tides or storms. This massive project by Coastal Engineers could save Venice from destruction.
Coastal Engineering and Harbors
Natural harbors are rare, much rarer than are needed for international commerce. For a harbor to be effective, it needs to provide easy access for the entrance and exit of shipping, with enough water depth that the ships can’t run aground. Even more importantly, the harbor must protect the ship from wind and wave action in the event of a storm.
Coastal Engineers create new harbors by adding breakwaters and other underwater structures, making a safe haven for ships, where there is no natural harbor. These man made structures absorb the force of the waves, preventing it from being expended upon the ships at anchor in the harbor.
One of the greatest artificial harbor projects ever undertaken was as part of the Normandy invasion in World War II. The initial troops to invade the Normandy beaches used drop-ramp assault craft to reach shore. However, the huge amount of men, material and vehicles needed for the invasion couldn’t all reach shore by these boats. Instead, two mobile harbors were created, which were brought in once the beaches were secured. The breakwaters for these harbors were floated in and sunk in place, forming the necessary protection for anchoring and offloading ships.
Coastal Engineers and Dredging Operations
Another important aspect of maintaining shipping operations is maintaining a deep enough channel for ships to travel through. Just as waves erode the coastlines, water flowing down rivers carries dirt and silt, eroding the riverbed and watershed. This dirt and silt is deposited at the river mouth, creating what is known as a river delta.
Without dredging operations to remove the river delta, many waterways would soon become impassable by ocean going ships. Natural harbors in those rivers would become unusable and the cities that those harbors support would lose their revenue.
By dredging rivers and their mouths, coastal engineers are able to maintain a safe channel for the movement of shipping into and out of these rivers and harbors.