The US Midwest has experienced record flooding levels in recent days, and this emphasizes the importance of designing buildings for extreme weather. In order to provide a reliable shelter, a building not only needs structural strength; it must also keep suitable indoor conditions for occupancy as long as possible.

One of the main challenges during a flood is keeping building systems in operation, since power grids are often disrupted by extreme weather. Also consider that many buildings have important equipment in their ground floor or basement, which is not designed to operate underwater.


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Ensuring an Electric Power Supply During Floods

Many buildings rely on diesel generators to ensure a power supply during blackouts, but a flood poses two main challenges. Diesel deliveries may become impossible, leaving the building without power once the local fuel supply is depleted. Also, the generator itself can be covered by water if located in the lower floors.

One option to ensure a power supply during an extended blackout is a natural gas generator or microturbine. If the unit is installed above the reach of floodwater, it can continue operating as long as the gas supply is available. Consider that natural gas lines are much sturdier than power distribution systems, and they can continue delivering gas to properties under extreme weather conditions.

The reliability of natural gas distribution systems was demonstrated when Hurricane Sandy struck New York City in 2012. While 20% of the population was left without electricity, natural gas interruptions were rarely reported.

Keeping Suitable Conditions for Building Occupancy During Floods

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Although a natural gas generator can keep building systems in operation, doing so for an extended period is expensive. Therefore, the building should also be designed to conserve adequate indoor conditions as long as possible.

Many buildings are designed with the assumption that mechanical ventilation will always be available, and openable windows are limited in number or inexistent. A building without ventilation quickly becomes unsuitable for occupancy, and the recommendation is having enough openable windows to achieve natural ventilation during emergencies.

If the weather is very hot or cold during an emergency, good insulation conserves suitable indoor temperatures for longer. In this case, having the windows open is not the best option, and triple-pane low-emissivity glass helps keep a suitable indoor temperature.

Plumbing Considerations: Potable Water and Backflow Prevention

As previously mentioned, a building that relies on a booster pump may be left without a water supply if the unit and its control system are flooded. An effective prevention measure is having a secondary water supply that meets the following conditions:

  • Independent from the main booster pump.

  • Accessible from floors above the reach of floodwater.

The potable water supply of a building is vital during extreme weather, since bottled water deliveries may become impossible in flooded areas. If a building relies on a pumping system that is susceptible to flooding, it may become unsuitable for occupancy even if there is a backup power system.

During a flood, preventing sewage backflow is extremely important, or the conditions inside a building can become very unhealthy in a short time. To improve flood resilience, a building must be equipped with adequate backflow preventers.

Conclusion

The flood resilience of buildings can be improved with smart design decisions. A natural gas generator or microturbine beyond the reach of floodwater can provide a power supply, since gas distribution lines are highly resilient. The property can also be equipped with a secondary potable water supply, while backflow preventers keep sewage out. Effective insulation can help conserve suitable indoor temperatures if there is an emergency during hot or cold weather, and openable windows can provide natural ventilation if air handlers are not operational.

 

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