A common misconception is that installing a flood barrier solves the problem. In reality, a barrier only reduces or delays water entering through a specific opening. It does not remove the water that still finds its way inside. In longer duration flooding, that residual water is often what causes the most damage.
A flood barrier is not a complete solution on its own. It is one component in a wider flood mitigation system.
In almost every project we work on, from a simple doorway barrier to full perimeter wall schemes, we explain the same principle:
Barriers reduce incoming water. Pumps remove the water that still arrives. You need both.
Even with a well-installed barrier, water can still appear on the “dry” side. That isn’t a failure. It’s simply how water behaves under pressure.
1. Rainfall inside the defended area
If you defend a driveway, garden, patio or yard, any rain falling inside the protected zone has nowhere to drain during a flood event. The defended area effectively becomes a bowl, and water accumulates surprisingly quickly.
2. Seepage and hydraulic pressure
When floodwater builds up outside a wall or barrier, the external water level rises, and so does the hydraulic pressure. Water naturally moves from high pressure to low pressure. It only needs tiny imperfections in soil, masonry, or service penetrations to find a pathway. This creates seepage beneath or through structures and can raise groundwater levels inside the defended area. This occurs even with reinforced walls, tanking systems, or deep foundations.
3. Backflow through drainage
During flooding, sewers and surface water systems can surcharge. Water can rise back through drains unless non-return valves (NRVs) are fitted. NRVs stop reverse flow, but they do not remove the water that still collects internally.
4. Ingress through building fabric
In property-level protection schemes, barriers may seal doors and openings, but water can still enter through walls, floors, and service routes. Measures like repointing or tanking reduce this, but rarely eliminate it entirely.
A barrier holds water back.
A pump actively removes water.
Without pumping provision, the protected area can simply fill from the inside.
Pumps are installed on the dry side of the barrier so that any water entering can be removed faster than it accumulates.
Across hundreds of flood risk surveys and resilience schemes, the same pattern appears:
• Small volumes of water become major damage if left unmanaged
• Groundwater levels rise inside defended zones during prolonged flooding
• Rainfall inside protected areas accumulates faster than expected
• Some seepage through walls and ground is almost always present
This is why reports often state:
“Regardless of barrier type, pumping provision is recommended.”
Because resilience is not about stopping every drop, it’s about controlling what happens when water inevitably appears.
Safeguard test data illustrates this clearly. At a floodwater depth of 0.6 m, a single-skin Fletton brick wall can permit approximately 12.5 litres per square metre per minute of water ingress. While repointing and masonry treatments can significantly reduce this, it demonstrates why pumping provision remains essential even where walls appear solid.
Pump selection depends on the site and how flooding occurs.
• Puddle pumps are popular for temporary deployment. They require no sump and can be stored ready for use.
• Automatic sump pumps in Packaged Pump Stations are better where flooding is frequent or occurs with little warning.
A key principle in all flood defence schemes is redundancy; installing more pumping capacity than the minimum required. This ensures protection if inflow is higher than expected or if a pump fails.
Where barriers are installed on properties, some internal water ingress should always be assumed. Buildings should be designed to recover quickly (for example, tiled floors instead of carpets) and pumps used to keep water levels low and damage limited.
Barriers + Pumps = Resilience
For further information on flood barriers please visit: Aluminium Flood Barrier – FPS Barrier®
What is a packaged pump station and when are they used? This article explains how pump systems can form part of a wider flood resilience strategy, using a real Flood Risk Assessment example from a property in Flood Zone 3.
What started as a routine pump enquiry became a bespoke engineering review. This real project shows the difference between buying a pump and designing a pumping system – and why that distinction protects performance, reliability and long-term cost.
A sump pump is an automatic water pump installed in a chamber at the lowest point of a property to collect and remove water when levels rise. Used for flood control, basements, garages and pumped drainage where gravity outfall is not possible, a correctly sized and installed system becomes a reliable, low-intervention water management solution.
