Flood defences - Retaining walls

Flood defences
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Flooding is becoming more of an issue with climate change.
The images show the problem that a customer had. I will go through the case study later.
First of all, let’s look at flood wall design issues.
A flood walls will fail in the standard retaining wall failure modes, overturning slippage and shear, but they can also fail from seepage and piping. Seepage is water slowly getting under the wall to the dry side, and piping is when the flow is faster.
The amount of seepage will depend on the soil porosity. Gravel/sand soil will have a porosity, and clay-type soil will have a slow porosity.
Seepage can be controlled by designing a dry side drainage system using a sump and sump pumps. A drainage scheme will depend on the porosity of the soil.
We prefer to use hollow block Stepoc walls for flood defence. The cavity concrete seals up the block joints and connects the wall to the foundation for a cantilever design.
The walls are constructed dry and can be built using a local contractor with some guidance.
You can see the foundation down-stand. This is to help slow down seepage.
You can learn more about Stepoc retaining walls on the Stepoc page.
Back to the case study.
On this slide, you can see the topographical survey. We use the survey to determine the wall heights and lengths, then draw them into a schedule.
This slide shows a 3D sketch of the wall surrounding the house.
This slide shows another example of a flood defence wall for a substation.