Seawall – a form of coastal defense constructed where the sea, and associated coastal processes, impact directly upon the landforms of the coast. The purpose of a seawall is to protect areas of human habitation, conservation and leisure activities from the action of tides and waves.
dike or levee – a raised bank of a river. A levee (European name: dike) offers protection against floods.
New Orleans – On August 29, 2005, New Orleans was hit by Hurricane Katrina which destroyed over 80% of the city when the cities levees broke. The special systems built to protect this under water city failed in several ways. Water came over the dikes, seawalls, and levees at six places. The engines on the pumps failed as the water rose above them. It is estimated that more than three quarters (3/4) of New Orleans was under water in early September of 2005. The very deep water caused failure of sewer, phone, electric and fresh water systems.
Galveston Seawall – On September 8, 1900, a hurricane sent an 8-foot high wave crashing into the city of Galveston, Texas. This hurricane killed 6,000-8,000 people and is considered to be the worst natural disaster in U.S. history. After the hurricane, the city asked retired Army engineer Henry Robert to design a seawall that would be seven miles long and seventeen feet high. Robert designed the wall as asked and also raised the city by pumping sand underneath the buildings. In 1915, the seawall was tested by another hurricane. This time, all but 8 people survived.
What’s the problem?
Seawalls are important for protecting coast areas and preventing erosion.
- Ask – How often does flooding occur? How high does the water rise?What makes the water rise – storms, river run-off? What is the seawall expected to do – keep water out? Keep the shore from eroding?
- Imagine – What types of structures are used for seawalls? How effective are these? Is the location of the planned seawall similar to existing seawalls?
- Design, Build – Seawalls may be constructed from a variety of materials, most commonly: reinforced concrete, boulders, steel, or gabions.
- Improve – What other materials could be used that cost less or work better? Additional seawall construction materials may include: vinyl, wood, aluminum, fiberglass composite, and with large biodegrable sandbags made of jute and coir.
- reinforced concrete – concrete with long pieces of metal called rebar inside to make it stronger. Almost all concrete in buildings and roads is reinforced concrete. Reinforced concrete is stronger than normal concrete.
- reinforced concrete, boulders, steel,