Flap gate to prevent floods

Flood-prevention system eliminates need for electricity, human operators

http://ajw.asahi.com/article/economy/technology/AJ201305210056

By DAISUKE SUDO/ Staff Writer

OSAKA--Engineers say they have created a flood-prevention system that runs on the forces of nature, eliminating the risk to human operators and problems caused by power outages.

The “flap gate,” jointly developed by Kyoto University and machinery maker Hitachi Zosen Corp., can be used in sea walls to block tsunami and tidal waves or at building entrances to prevent inundation from torrential rain.

Hitachi Zosen showed the system to reporters at its headquarters in Osaka’s Suminoe Ward on May 20.

The flap gate is essentially a gate affixed to the seabed or ground at the opening of a sea wall or the entrance to a building. In normal times, the board at the base of the gate lies flat.

If a surge in water reaches the sea wall or building, the flap gate’s board automatically rises. Once the board is fully erected, the water pressure and buoyancy keep it in place to block the water.

The board is made of a special resin that is buoyant but strong enough to hold moving cars.

Currently, flap gates can work in spaces with a width of up to 10 meters and a height of 5 meters.

Hajime Mase, a professor of engineering at Kyoto University who specializes in disaster-prevention measures in coastal areas, said the big selling point of the flap gate was safety.

“The new system will not put humans in danger,” he said.

Opening sections of sea walls are usually closed by humans via remote control.

After the Great East Japan Earthquake and tsunami on March 11, 2011, it became impossible to close sea walls by remote control due to a power outage. Many volunteer firefighters tried to close them manually, but they drowned in the towering waves.

Hitachi Zosen aims to achieve sales of 3 billion yen (about $30 million) a year from the flap gates.