Everything you need to know about flood protection

Flood barriers are protective structures designed to prevent or reduce flooding damage to buildings and properties. They act as physical shields against floodwater, keeping water out of vulnerable areas.

Understanding what flood protection is essential for homeowners and businesses looking to protect their assets against rising water levels and storm surges.

Different Types of Flood Barriers

A flood barrier is a barrier designed to fit within a building opening, such as a door, window, or entryway. Flood barriers are used to block the water in a space that often opens and closes. Static openings, such as a sealed window, often don’t require a flood barrier.

There are several types of flood barriers, each suited for different scenarios and needs:

Temporary Flood Barriers: These are portable and can be installed quickly during a flood threat. 

Examples include sandbags, water-filled tubes, and modular panels. 

They are ideal for emergency use but typically require manual setup.

Permanent Flood Barriers: Built into the property structure, these barriers provide continuous protection without requiring setup each time. 

They include walls, levees, and permanent gates that integrate seamlessly with buildings.

Permanent self-closing Flood Barriers: These innovative flood barriers automatically raise as floodwaters approach, requiring no human intervention or power source. The barrier is recessed below ground in a trough and uses the buoyancy of incoming floodwater to float and lift it into place. Once raised, the barrier locks securely, creating a watertight seal to protect against floodwater. When floodwaters recede, the barrier lowers back into its resting position. This type of barrier is ideal for locations where rapid flood response is critical, such as unmanned sites, urban areas, or railway defences. 

Modular Flood Barriers: These versatile systems combine the benefits of temporary and permanent barriers. They can be pre-installed for quick deployment, but also removed or adjusted as needed. 

Often made from durable materials, modular barriers offer customizable solutions for openings such as doors, windows, and vents.

How do flood barriers work?

Most people imagine floods like a bathtub filling up — calm, static water rising evenly. But in reality, the forces applied to a flood barrier are complex and constantly changing. Understanding them helps explain why proper installation, correct sizing, and robust materials — like Flowstop’s drop-stitch inflatable design — matter so much.

Below are the 5 major forces that act on any flood barrier.

1. Hydrostatic Pressure (The Main Force)

Hydrostatic pressure is the static pressure from standing water. It increases with depth, which is why the bottom of a barrier takes the most load.

Key points:

• Pressure increases ~ 0.43 psi per foot of water

• At 3 ft of water, the pressure is ~ 1.3 psi

The entire wall (door, frame, barrier) must resist this force continuously

This is the primary force every flood barrier must withstand.

2. Hydrodynamic Pressure (Water in Motion)

If water is flowing rather than standing, the barrier is exposed to dynamic forces.

Examples:

• Water rushing down a street

• The wind is pushing water

• Waves generated by cars driving through floodwater

Hydrodynamic pressure acts like a horizontal push, increasing the load on the barrier.

Flowstop system handles this well because the inflatable cushions absorb and distribute impacts instead of passing them directly into the frame.

3. Debris Impact Force

Floodwaters often carry:

• Branches

• Trash cans

• Furniture

• Construction debris

These objects hit the barrier with force, sometimes at speed.

While rigid barriers can crack under sudden impacts, an inflatable design acts like a shock absorber, dissipating energy and reducing structural stress.

4. Buoyancy / Uplift Forces

This force tries to lift or push the barrier upward.

Any barrier that forms a watertight seal must resist buoyancy; otherwise, the water will try to force it:

• upward

• outward

• or diagonally away from the frame

High-quality gaskets and proper inflation pressure will prevent this.

5. Seepage and Micro-Infiltration

Even the best barriers are designed to allow small amounts of seepage, in accordance with international standards such as FM Global or FEMA standards. This isn’t a “force” in the classical sense, but it creates pressure gradients and wetting forces around the edges.

Flowstop manages seepage by:

• compressing the gasket against the frame

• distributing pressure evenly

• adapting to small irregularities

Dry Proofing vs Wet Proofing: Understanding flood protection strategies

Flood protection can be approached through two different methods:

• Dry Proofing involves sealing a building to keep floodwater out entirely. 

It makes the structure watertight using barriers, waterproof coatings, and sealing openings. This method actively prevents water damage and is ideal for protecting valuable interiors. However, dry proofing is only suitable for structures with very strong walls and foundations because the water pressure against these barriers can be extremely high during floods. Buildings with weaker walls may suffer structural damage if subjected to this intense pressure without proper reinforcement. 

We often hear our customers say, “I had 4 ft of water inside during the last flood, therefore I know my wall can withstand that much pressure.” Unfortunately, this is not true.

If floodwater has already entered your home or building, it means the wall or barrier was breached and did not hold back the water pressure. For water to rise several feet inside, the exterior barriers (walls, doors, or other flood protection) must have failed or were not fully sealed. For a wall to successfully withstand hydrostatic pressure from floodwater, the water must remain outside, pressing firmly against the surface but not penetrating through it.

In other words, the presence of water inside indicates that the flood pressure was strong enough to overcome weaknesses, openings, cracks, or gaps, allowing water to flow in rather than being resisted. True pressure resistance means no significant water intrusion at all. So, the fact that water was inside proves the wall could not effectively resist floodwater pressure, contradicting the assumption that it withstood it.

• Wet Proofing allows controlled flooding of designated areas to relieve hydrostatic pressure, reducing structural damage risk. 

It uses flood vents or breakaway walls designed to let water in and out safely. While cheaper and reducing structural risks, wet proofing requires post-flood cleanup and may lead to interior damage.

Custom-made inflatable flood barriers allow for the use of both dry proofing and wet proofing methods, providing flexibility to adapt to specific building needs and flood scenarios.

Are flood barriers enough to dry-proof a house?

In most cases, no. Flood barriers are designed to protect only the main opening and are not enough to fully dry-proof a house. While they are designed to block floodwater from entering through the main openings, there are many other vulnerable points in a building. Water can still seep through outdoor electrical outlets, pipes, cracks in walls, gaps around windows, ect. Even the smallest openings that are not properly sealed can become significant entry points for water due to the immense pressure exerted by floodwaters.​

Additionally, if a flood lasts for an extended period, water can gradually penetrate through the walls themselves, especially if the structure lacks adequate integrity or waterproofing. Over time, hydrostatic pressure builds up against the exterior, leading to infiltration through porous materials or even structural weaknesses. For total dry-proofing effectiveness, it’s crucial to assess and fortify all parts of the building envelope, not just the main openings.

The cost of not protecting your property

Ignoring flood protection can be costly for both homeowners and business owners:

Homeowners face direct costs such as structural repairs, replacing damaged belongings, water extraction, drying, mold remediation, and electrical/plumbing repairs. Severe floods can lead to costs exceeding tens of thousands and may require full home reconstruction.

Business Owners, on the other hand, risk not only property damage but also operational downtime. Flooding can cause lost business days, impacting earnings and customer trust. 

On average, installing flood protection systems such as flood barriers can cost between $5,000 and $20,000, depending on the size and number of openings to be protected. But this investment provides a reusable, durable defense that can prevent costly flood damage.

Indeed, the financial impact of flood damage is significantly higher. For homeowners, flood damage repair costs typically range from $50,000 and over, covering structural repairs, water extraction, drying, mold remediation, replacement of damaged belongings and, relocation. The average insurance claim was $68,000 in the US between 2016 and 2021. Severe flooding may even require complete home reconstruction, where costs can rise substantially.

Business owners face even greater risks with the combined effects of property damage and operational downtime. Therefore, the average cost of flood damages for businesses is well over $100,000 per event, while lost business days due to floods can number in the thousands annually, leading to substantial revenue losses and of course eroded customer trust.

Building Codes and Flood Protection Compliance

Building codes play a critical role in ensuring that structures are adequately protected against flood risks. Many local and national building codes require minimum floodproofing standards, especially in flood-prone areas. These codes specify design criteria for walls, foundations, openings, and barriers to withstand certain floodwater depths and pressures. Compliance with building codes ensures that flood barriers and other protective measures meet safety and durability requirements, reducing the risk of structural damage and water infiltration. Adhering to building codes not only helps protect property but also can be necessary for insurance purposes and legal compliance.

FEMA and FM Global: Industry Standards for Flood Protection

The Federal Emergency Management Agency (FEMA) and FM Global are leading organizations that establish standards and guidelines for flood protection and risk management. FEMA provides extensive flood risk data, building standards, and design criteria aimed at minimizing flood damage in residential and commercial properties. Their guidelines influence local building codes and floodplain management to enhance community resilience. FM Global, a prominent commercial insurance company, offers engineering expertise and loss prevention standards focused on protecting businesses from natural hazards, including floods. Their stringent requirements often guide the design and testing of flood barriers to ensure reliability under high water pressure and severe flood conditions. Choosing flood protection systems compliant with FEMA and FM Global standards helps guarantee trusted performance and may also facilitate insurance benefits.

Why choose FlowStop to protect your property

FlowStop flood protection systems stand out because they combine ease of use, durability, and efficiency. Custom-made, FlowStop barriers effectively seal against water infiltration in various openings, including doors and windows. Their robust gaskets and secure fittings ensure reliable performance in severe conditions, and the modular nature allows for tailored protection adapting to any home’s unique structure, versatile enough to be used for both dry proofing and wet proofing.

In addition, FlowStop has been rigorously tested by Canadian experts under high-pressure water conditions, proving its reliability and effectiveness in real-world flood scenarios (see report here). Choosing FlowStop means investing in peace of mind with proven, premium flood defense solutions.

For expert advice on protecting your home with FlowStop, contact us today to get a quote and keep your property safe.