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DESIGN FOR CLIMATE CHANGE: The Flood Proof House, Part 2

Updated: Apr 17, 2023



Flooding is more than just a matter of your carpet getting wet; it presents a range of risks most of which can easily be lethal during a major flood but all of which are typically very expensive.

In Part 1 of my Designing a Flood Proof House article, I summarized the causes of flooding - how nearly any location has the potential to experience a flood. This article reviews the specific dangers of a flood and lists ways a community or a household can best prepare.

Regardless of the cause of the flood, and the drainage piping around the foundation that is designed to carry away water in the soil is overwhelmed. The soil becomes waterlogged, and water basically piles up around the foundation or basement walls, pressing to get in -- this is called hydrostatic pressure. As the water levels increase, this force increases. Foundations are generally not designed for this sideways push, and they may buckle, crack, or collapse.

Water moving through the soil or washing soil away can pull away the earth upon which foundations, utilities, or roadways rest. Burst gas lines can cause explosions and subsequently catch fire. Underground electrical services can become exposed. Roadways can be washed away (as they were along the Coquihalla) and cut off access for supplies or emergency services. Buildings themselves are sometimes floated off their foundations and carried away while being torn apart.

Water will find ways into the buildings - through joints, cracks, vents, drains, or just by osmosis through materials that are not waterproof (e.g. dampproofing and concrete). Standing water in your home can short out electrical circuits and present an electrocution risk to anyone in the water. A hot water heater that suffers flood damage could cost thousands of dollars to replace.

The water can cause flood damage outside of buildings also. Great damage is often the result of large debris (pieces of bridges, boats, vehicles, trees) colliding with structures or sweeping people away. As the flood water infiltrates the sanitary sewer system, water treatment facilities, and processing plants that store chemicals or toxic waste, the contamination of the flood waters by chemicals and diseases becomes insidious and the most difficult to remedy.

People who fail to find suitable shelter on stable, high ground may drown, die by hypothermia, or suffer infection of their wounds.

Community Response

As you can appreciate, developing a strategy to prepare for flooding is more than just adding some waterproofing and involves more than your own house. The flood risk impacts entire communities, so every community should plan some type of response to maximize preparedness.

First, the community must come together to educate itself on the risk of flooding, the dangers, the various measures than can be taken, and also on the resources that the community members have collectively. The best response to any emergency is any response that has a plan. Second, tasks should be delegated to volunteers so that everyone knows what their roles are and what they need to do.

When a flood or similar emergency arises, neighbours should check in on those who are more vulnerable. Organizing this beforehand will speed up getting a status of the situation and determining who may need emergency care. The community should also designate places to gather themselves and emergency supplies if the need arises. This muster approach will likewise speed up the flow of information when communication lines may be disrupted. Utilities and supply routes may be temporarily cut off, so centralizing locations where shared supplies may be available will maximize their reach.

Individual Response

A similar strategy can be used at the household level and would apply to any major emergency or natural disaster. Each family should have a contact procedure which may include a designated family member to whom to rally, a location at which to assemble. An inflatable kayak is a useful last resort to avoid being stranded if your flood defenses are overcome, making your house an island. This small boat takes up very little storage space and can be deployed relatively quickly.

Some or all public utilities are likely to be compromised. You need to have a protected store of drinking water that be adequate for a few days. You should also have some means of sanitary handling - something to fill in safely for not having a working toilet. Backup power by way of a generator - if it's above the flood level - or a battery or UPS (uninterrupted power supply) could provide charging for critical devices or possibly a small amount of heating where required.

In Part 3 of my Designing A Flood Proof House article, I explain the range of dry flood proofing measures that can be taken both on your property and in your house itself. My SAPPHR Strategy includes these techniques. If you would like to discuss what the flood risk is to your house or how your new or remodeled home could include these design features to prepare for a flood, please book a free call with me using the button below.


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