Most floodproofing systems have openings that need to be closed and watertight during a flood. A panel closure is any flat, firm sheet of material used to block one of these openings. It may be plywood, aluminum, steel, wood planking, Plexiglas or any rigid material. It can be permanently attached or designed to be set in place quickly in an emergency.
An opening that needs a closure may be completely clear, such as for a driveway. It may be partially blocked with a door or window that needs additional protection; water may leak between a door or window and its frame or between the frame and the wall.
A panel should be...
- Strong, but not brittle. It should resist the impact of floating debris.
- Durable when wet. It should not dissolve or come unglued in water. If you’re using plywood, choose an exterior grade. Don't use particleboard.
- Weather resistant. The panel should be painted, galvanized or otherwise sealed to prevent weakening by rot, rust, sunlight or corrosion.
- Resistant to termites, wildlife and pets, if permanently installed.
- When floodproofing systems fail, it is often because the closures were improperly designed or installed. In a system designed to hold back 3 feet of water, the panel closure itself must be strong enough to hold back 3 feet of water.
- The force from water against a panel is transferred to the frame. In addition to using panels with sufficient strength, be sure the frames and mountings are strong enough to support the panels.
- If a panel covers a door or window, the building must be strong enough at that point to resist the force transferred to the wall from the panel. If a building is structurally inadequate or weakened by decay or termites, you risk damaging it even further by attempting to floodproof the structure itself. When in doubt, choose a method that holds water away from the building completely.
- Floodgates can be hinged so they swing into place. Heavier gates may be installed on tracks so they glide into position. Either type can be designed to close and seal automatically to protect property from flood damage when no one is home.
- Another type of panel closure resides underground and floats into place when its storage compartment fills with water.
Things to Remember
- Panel closures must be equal in strength to the strength of the rest of the flood protection system.
- The supporting frame must be strong and securely mounted, because it will have to bear the full force exerted on the panel.
- Never use closures and pumps to create a difference of more than 3 feet between inside and outside water levels unless an engineer certifies the structure's ability to withstand the unbalanced forces that will be generated on the walls.
- Install panels so water pressure tends to push them closed, not open. Use gaskets between hard surfaces to improve the seal.
- Permanently mounted panels are more likely to be used than stored panels that must be found, transported and installed.
- Removable panels that fit into permanently mounted frames provide better protection than panels with no special framing.
- Panels that position themselves automatically can protect the building when you're away or asleep.