Northwest Harbor / Bates Masi Architects. Image courtesy of Bates Masi Architects
Flooding is a serious problem for buildings around the globe, including architectural treasures such as the Farnsworth House, which have been repeatedly affected by the issue. One-third of the United States is at risk from flooding this spring, particularly in the Northern Plains and Upper Midwest. The April 2019 floods that decimated large parts of Mozambique and Zimbabwe left behind tens of thousands of people displaced. Although architecture can’t prevent or solve the worst floods, it is possible and necessary to take protective measures that could reduce damage and save lives.
First, identify if the area in which the building or home is being built is at risk of flooding. This can be done by checking flood maps widely available online, including this site run by the U.S. Federal Emergency Management Agency. If it is, the client and architect can decide whether they want to move or stay in their home and take the appropriate protective measures. We have listed nine measures for those who opt to stay and take the necessary protective steps.
Lift Above the Flood Level
In order to minimize flood damage, architects must build the structure at the flood level. FEMA offers a Flood Level Viewer online that allows you to find the elevation of floodwaters in specific locations. This information can be used by architects to determine how high and what method to raise the building. The most common method of elevating a structure is to build it on stilts or columns. The solid foundation can be raised higher in other cases. For more information, architects can assess the climate and flood history in their area and consult this guide on coastal construction.Guadalupe River House/ Low Design Office. Image by Casey Dunn
Use Flood Resistant Materials to Build
Materials that are flood resistant can withstand flooding for 72 hours without sustaining significant damage. Floodwater can be either hydrostatic (standing water), or hydrodynamic (flowing waters). In most cases, it will cause scouring, displace foundation walls, collapsed structures and floating fuel tanks. Significant damage refers to damage that requires more than cleaning or cosmetic repairs at a low cost, such as painting. Flood resistant materials should be strong and resilient to extreme humidity to prevent such damages. Concrete, glazed bricks, closed-cell insulation, foam insulation, steel hardware and pressure-treated plywood and marine-grade plywood are some examples. Ceramic tile, water-resistant glue and polyester epoxy paint are also available.
Use sealants, coatings, and waterproof veneer
There are two types of floodproofing. Floodproofing that is dry prevents flood waters from entering the house, while floodproofing that is wet allows flood waters to enter. Waterproof veneer, sealants, and coatings are all part of the latter. They prevent water from getting inside the house. A waterproof veneer is a layer made of brick, backed by a waterproof membrane. It seals exterior walls from water penetration. For interior walls, architects should use washable closed cell foam insulation below the flood level. You can also apply sealants and coatings to the foundation, walls and windows to stop flood water entering the house through cracks. These openings are not designed to withstand flood loads and are often watertight. Flood of the River Trave, in the historic Old Town of Luebeck (Germany). Image (c) Maren Winter / Shutterstock
Restore or Floodproof HVAC Equipment, Mechanical, Plumbing, and Electrical Systems Components
Generally, service equipment located above the flood protection level will protect it best. These equipment include heating, ventilating and air conditioning, plumbing appliances and fixtures, duct systems and electrical equipment, including service panels, meters and switches. These components can be severely damaged if they are submerged in floodwater for any length of time. Short circuiting can cause fires in electrical equipment. These components should be raised above flood level. However, if flooding is a concern, waterproof enclosures, barriers or protective coatings may be used to prevent any damage. For more information, architects can consult the municipal codes.
Anchor Fuel Tanks
Flood waters can easily move unanchored fuel tanks, which could cause damage to property and drive them into walls. Buoyancy can push even buried tanks to the surface. It is important that fuel tanks be anchored. This can be done by attaching them concrete slabs that are strong enough to withstand flood water forces or by running straps and attaching them ground anchors.
Install foundation vents or a sump pump
One example of wet floodingproofing is the installation foundation vents. These allow flood water flow through the house and not pool around it. This solution, while it may seem counterintuitive due to the potential damage to the property’s interior, actually serves as an outlet for flood water and reduces the pressure on windows and walls that flood water causes. The interior of a basement is usually prepared with flood-resistant materials, hydrostatic openings and protected key equipment. However, damage to the walls and windows can be minimized. A sump pump pumps water from basements that are subject to flooding. To ensure that they continue to function even if the power goes out, sump pumps with battery backup should be highly recommended.
Construct Permanent Barriers
Flood waters can be prevented from reaching the structure by constructing a permanent barrier. These barriers can be made using either concrete floodwalls or masonry or using a levee of compacted soil layers with an impervious core. This may seem the easiest or most obvious solution, but floodwalls and levees both require significant maintenance and levees require a substantial amount of land and soil materials to construct.
Install sewer backflow valves
Backflow valves stop sewage from backing up in a home by preventing it from being flooded. This issue can be dangerous to the health of occupants and difficult to fix in flood-prone areas. Gate valves are preferable to flap valves due to their better resistance against flood pressure.
Grad the Lawn away from the House
An architect can also grade the lawn away form the house to reduce flooding damage. Rainwater will pool around your home if the lawn is tilted towards the house. Tilting it inward will direct rainwater away. The lawn should be made of a rich soil with clay and sand to allow the rainwater to drain into a better place like a street gutter.