Real-Time Control of Inflatable Dams ::
A New Technology to Alleviate the Effects of Levee Failures

By Bill Clayton

ON AUGUST 29, 2005, Hurricane Katrina slammed into the southeastern United States. Winds topped 140 miles per hour. Water surged 20 feet above sea level, breached the levees separating Lake Pontchartrain from New Orleans and covered 80 percent of the city, leaving 1,400 dead, tens of thousands homeless, and damages totaling $100 billion.

Katrina was horrifying - but not a complete surprise. In 2001, the Federal Emergency Management Agency reported that a major hurricane hitting New Orleans ranked among the three most serious threats to the nation. The other two were a terrorist attack in New York City and a large earthquake hitting San Francisco.

Theoretically, taller, stronger levees could have saved New Orleans, but such levees have become too expensive to maintain adequately or to rebuild. Some engineers suggested deflecting floods instead of just blocking them. Others opted for designing storm-resistant levees. But Michigan Engineering's Nik Katopodes and his team of investigators chose to develop inflatable dams with real-time controls - a novel technology that has the potential to mitigate flooding and possibly prevent the collapse of levees altogether.

As sensors detect the oncoming flood wave, the
dam inflates automatically to stem the surging water.

Katopodes, professor and chair, Civil and Environmental Engineering, was working on real-time control of inflatable dams long before Katrina crushed New Orleans. He said the technology relies on sensor arrays that are installed at strategic locations in levees to spot changes in their structural integrity. "The sensors detect the water level adjacent to the levee, instant by instant," he said. "They also read digital images to detect structural changes in the levee. A transmitter sends this information to a predictive control model that creates optimal-operation scenarios for computer-controlled gates that are installed at strategic locations - along a river basin, for example."

The system identifies the optimal time and location for emergency flow diversions, then activates inflatable dams - rubber bladders filled with air - that create storage pools and suppress wave activity that might otherwise damage levees. As water rises and falls, the system's actuators adjust the levels of the dams.

"The final product of this research project will provide a powerful tool to regulatory agencies," Katopodes said. "They'll use it for planning and making critical decisions during times of emergency. It'll yield objective information on whether or not it's possible to take active measures during a flood in order to minimize the potential for disaster. Active flood control can lead to designs that are considerably more efficient than passive ones. Furthermore, since active flood control doesn't require an increase in the height of existing levees, it'll minimize the costs associated with maintaining existing levees and building new ones. And this technology will have a remarkably positive effect on the environment because flood mitigation that's continual can do damage - much more damage than flood controls that are activated only when they're needed."

Sensors located along the levee monitor the water
level and, when a significant change occurs suddenly,
the sensors open gates to release water in a
controlled fashion.

To grasp the potential of this work, it's important to note that the devastation which Katrina unleashed is possible in coastal cities other than New Orleans, which lies 10 feet below sea level. New York City, for example, is about 10 feet above sea level - this includes the perimeter of Manhattan's business district, the lower east and west sides of the city, and the shores of the upper East River. NASA scientists at the Goddard Institute for Space Studies in New York City have predicted that with climate change and global warming, the sea level in this area will rise as much as an additional one and a half feet by 2050. And climatologists say the question is not if a catastrophic hurricane or northeaster will hit New York, but when. This puts New York City, New Jersey and Long Island at great risk.

Katopodes' work on the active control of inflatable dams has the potential to save lives, protect property, limit the costs associated with flooding and create an environment in which peace of mind makes day-to-day life a whole lot easier. -E