Flood Wall Design

Good flood wall design is important. There are temporary flood protection walls that can be constructed during a flood as the flood water begins to rise. And there are permeant flood protection walls in areas that have a high risk of flooding.

The design principles are much the same as we are dealing with basic physics.

Basic Design Principles

This is a simple explanation of the principles of retaining and flood protection wall design.

The diagrams below show the core functions and the design criteria for a retaining wall. The following failure criteria are encountered while designing a retaining wall.

- Overturning

- Bearing capacity

- Sliding

- Slope stability

- Shear

- Seepage

Piping

Overturning – The material being retained creates a force (moment) that causes toppling of the wall. The weight of a gravity retaining wall resists this moment.

Bearing capacity – The weight of the wall and earth is supported by the base. The ground bearing capacity needs to be checked to ensure any settlement is within limits.

Sliding – The material being retained creates a horizontal force that can cause the retaining wall to slide. This is resisted by the friction between the wall and earth beneath and the embedment of the wall.

Stability – The earth around the wall requires adequate strength to avoid an overall slip failure.

Shear – The blocks can shear at the base or between courses. We introduce a kicker at the base and interlocking buttons to resist these forces

Seepage – Water seeping underneath the foundation

Piping – When seeping become faster and flowing this then becomes piping that can cause the wall to slide and rotate. The solution is to build a cutoff. This is an extended to, see the sketches on the next page.

Flood Protection Walls

We have a number of designs using interlocking concrete lego blocks. The walls are built in two skins of 300mm wide blocks with the inner vertical joint water proofed. For heavy duty wall the cavity is wider and filled with water proof concrete. This can then be reinforced for additional strength and stability. To lean more about the design download our flood defence design and build guide.