DESIGN FOR CLIMATE CHANGE: The Flood Proof House, Part 1

Updated: Jun 27


While not everyone lives in a high-risk area, everyone lives in a potential flood zone. However, we can design a flood proof house to withstand the next British Columbia flood event. Modern architecture can avail itself of the advances in building design, but we must first understand the dangers.


Flooding can occur for several reasons to nearly any location, and typical house construction is terribly susceptible to major damage or destruction by flooding. Whether you live on the coast or the BC interior, your home will very likely face a flooding event of some sort and severity in the near future, and it's at risk of damage or destruction.

Most scientists agree that the world's climates are changing. For a variety of environmental reasons, storms are stronger and more frequent, dry weather periods are more severe, and the average sea level is rising. Areas that historically have had a low flood risk will experience stronger storms that can result in severe flood damage or the destruction of your home if you're underprepared. Learn multiple ways in which how your house may be at risk of flooding and a wider variety of techniques to design to withstand and survive a flood event.


Causes


The risk of flooding is typically based on historical records of flooding. Usually, city or regional governments in flood-prone areas publish a 'base flood elevation' (flood level) or in some cases 'flood maps' for which infrastructure and buildings must be designed. However, to develop adequate flood protection, we must recognize that:

  1. flooding is caused by a variety of factors,, and

  2. those factors have been changing for at least the past century


The average sea level is rising and threatening oceanfront buildings. High tides are beginning to flood features previously constructed above the high water mark. During a hurricane or typhoon, the storm surge pushes water further inland to neighbourhoods unaffected in the past. However, severe flooding is a threat not only to the ground floor of a beach house but also to any building anywhere inland.




Warmer weather patterns are occurring over the oceans and is bringing more moist air inland in short periods, creating "atmospheric rivers", derechos, and stronger hurricanes and typhoons. Many locations around the world have experienced intense rainfall in ancient history, but the risk is new to most others. Climate change is causing rain to be concentrated into shorter periods separated by periods of drought. A month of rain may fall in one or two days as it did during each of the 2021 European Floods, the 2021 Henan Floods, the 2021 Pacific Northwest Floods, the 2021 floods cause by Hurricane Ida, the 2022 KwaZulu-Natal floods of South Africa, and the 2021 South India Floods.



In addition to rain, abrupt and erratically warm weather melts snow packs in short periods of time and contribute large quantities of meltwater. The increased volume of water suddenly accelerates the erosion of the shoreline or riverbank. Rivers swell, spill over their banks, and flow across the drainage basin, flooding all the buildings in the area. The Sumas Prairie flooding was a perfect example of this, but neighbourhoods that are built on mountainsides are also at great risk as water drains down the mountain.

Sustained, intense rainfall will saturate soil. Drought and wildfire both reduce the soil's ability to absorb rain, and the soil is saturated more easily. Flood water will literally rise up out of the ground and into buildings. The waterlogged soil becomes unstable and can wash away;. this can include the earth around or under your building's foundation which can lead to collapse. Saturated soil is also the cause of most landslides -- torrents of mud that rush downhill and bulldoze buildings and other structures in their path.


Flooding may also occur without extreme weather. Depending on your location, a tsunami can raise water levels where the flood defenses are overwhelmed. As the sea level rises, a tsunami will continue further inland.


In Part 2 of Designing A Flood Proof House, I present the variety of specific risks that flooding creates, and I offer strategies for surviving a flood by coordinating the efforts of your community. My SAPPHR Strategy includes these strategies. If you would like to discuss the flood risk to your house or how your new or remodeled home could include these techniques to prepare for a flood, please book a free call with me using the button below.