What are Floodwalls?

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Floodwalls are flood-control concrete structures designed to block water from rising and seeping into buildings and other structures. These flood barriers help to contain water from lakes, rivers, or other waterways if they rise to abnormal levels.

Floodwalls are usually constructed as cantilever walls, basic I-walls, buttress walls, gravity walls, and sheet pile cells.

This article discusses the features, types, and benefits of floodwalls as flood-control structures.

Features of Floodwalls

• Floodwalls are engineered structures made from concrete, masonry, or steel to prevent encroachment of floodwater. They are constructed mostly in urban/industrial areas where space is a constraint. 
• The main functions of a floodwall are:
  • Provide a barrier against inundation
  • Protect the enclosing area and structure from hydrostatic and hydrodynamic loads
  • Deflect flood-borne debris away from the building.
• Most floodwalls are constructed at a distance away from the building to avoid any structural defects or modifications to the building.
• The location and coverage of floodwalls vary based on the terrain. 
• Floodwalls surrounding the site have openings to provide access to the site. 

Types of Floodwalls

The major types of floodwalls used in flood protection projects and their construction features are explained in the table below:

Type of Floodwall	Construction Features
Gravity Floodwalls	1. Simplest type of floodwall 2. Works based on gravity and self-weight. 3. Constructed at a right angle with the base of the wall larger and heavier than the top to hold on to the ground. 4. The floodwater finds it difficult to move the heavy floodwall structure below the ground.  5. Requires a lot of concrete for its construction.
Inverted T-type Cantilever Floodwalls	1. Cheaper to design and construct. 2. The cantilever of the floodwall is a projecting structure like a beam that is supported at one end and carries a load at the other.  3. Stability is achieved partially from the weight of the soil on the heel portion of the base of the T-type cantilever and its self-weight. 4. Usually made from reinforced concrete. 5. The wall employs cantilever action to retain the mass behind the wall.
I-Walls	1. I-walls are cheaper than T-slabs as no base slab, or cantilever is not required. 2. Sheet pile I-walls, modified I-walls, and Type II I-walls are some of the types of I-walls.
Buttress Floodwalls	1. Consist of a transverse support wall on the heel side. 2. The concrete buttress is located on the opposite side of the retaining water. 3. It is not used commonly as the buttress takes the usable space.
Counterfort Floodwalls	1. Consist of traverse support wall on the side of retaining water.  2. As the supporting walls are hidden under water or soil, it provides extra space on the other side. 3. Hence, it is used widely compared to buttress walls.

Benefits of Floodwalls

1. Protects the area around the structure from inundation.
2. Eliminates structural damage to the building caused due to water pressure.
3. It is a better option compared to relocating or elevating.

Disadvantages of Floodwalls

1. Floodwalls are not a solution for large and long-duration floods.
2. Floodwalls can affect the local drainage, resulting in water-related issues in the areas outside the floodwall.
3. Floodwall construction can violate some of the state codes and regulations.

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