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Maps mitigate Cincinnati flood damage.

Floods cause more damage, injuries, and deaths in the U.S. every year than any other type of natural disaster. So when a stubborn storm system settled in over the Ohio River Valley in early March 1997, the first thing Cincinnati residents wanted to know was: how high will the Ohio River get?

After a weekend of torrential rain and 100-mph winds, the experts were predicting the storm's 12 in. of rain would swell the muddy Ohio, normally about 26 ft deep, beyond its 52-ft flood stage to a crest of 64 ft by the following Wednesday. That meant the city's Riverfront Stadium would be swamped. Major portions of Cincinnati's riverfront as well as its low-lying residential and industrial riverfront areas could be under as much as seven ft of water.

It was easily shaping up to be the worst flood in 33 years.

This prompted the Cincinnati Metropolitan Sewer District (MSD), the department responsible for some of Cincinnati's flood protection, to summon "all hands on deck" and immediately dispatch crews to assemble the steel gates that protect the openings in the city's 1.5-mile long flood wall. The watertight barriers were designed by the Army Corps of Engineers in the 1940s to help the city withstand a flood of 83 ft.


It also spurred MSD GIS Manager Bob Babbs to contact Shaoli Huang at the Cincinnati Area Geographic Information System (CAGIS) consortium for emergency mapping assistance. "I knew our city was in deep trouble," said Babbs, who has been with the agency for 25 years, "...and that everyone would be asking for maps."

Babbs and Huang spent the next several days and nights putting ARC/INFO and ArcView GIS software (Environmental Research Systems Institute, Redlands, California) through its paces to produce detailed maps of Cincinnati's and Hamilton County's extensive riverfront. Using ARC/INFO's GRID and TIN extensions, CAGIS's Huang created an elevation model for the vulnerable downtown riverfront section, to project what might happen if the river crested at 64 ft. He added in the effect of the MSD's steel flood gates to the projected flood levels to come up with maps that showed exactly which buildings, streets, and railroads in each section of the city were likely to be affected.


By Monday afternoon, the requests started to pour in. Babbs took the files, which had been created using 10-ft contours, and in some critical areas, used heads-up, on-screen digitizing in ArcView to refine the projected flood levels along 2-ft contours. He printed the beautifully detailed, color maps on the MSD plotter and distributed them to his colleagues at MSD. They, in turn, used the maps to inform the public about potential flooded areas, formulate dozens of critical decisions about flood control measures, and implement water safety precautions throughout the following weeks.

The maps, which turned out to be extremely accurate in predicting actual flooding, were so popular that everyone wanted their own sets. "They'd never had such good data to work with," said Babbs. The MSD ended up supplying dozens of sets to local and national disaster relief teams, local government officials, utility companies, the Red Cross, the media, and many other organizations.

The only limitation was how fast the plotter could print them. The MSD plotter ran more or less continuously for several days, with breaks only when a piece of equipment had to be shut down for a few hours to await repairs. During this time, Babbs enlisted the CAGIS plotter and other city agencies to plot additional sets of maps.


Additionally, the disaster relief team had the Public Safety Department's own ArcView setup available, and was able to plot some of its own copies of the maps forwarded via the city's computer network. The maps and underlying intelligence of the GIS data, which contains property ownership information, played key roles in many critical decisions to determine which Cincinnati residents were most at risk, to select the best locations for emergency shelters, to identify hazardous locations, and to ensure public safety.

"We were put to the test in an emergency situation," said Huang. "It used to take departments weeks to generate this information, but we had it for them right away. Now a lot of people know what we can do and we expect they'll ask us to do a lot more."


The software is continuing to prove its usefulness in other ways, according to Huang:

* City and county departments can use maps and data to show the location and ownership of homes, property, and commercial buildings receiving the heaviest damage in an emergency so building inspection teams can be sent there first.

* Planning, economic development, and traffic engineering departments use the data to ask "what if" questions about how a dreaded 100-year flood might affect areas under consideration for future industrial and residential development.

* Businesses will use the information to reroute deliveries and shift storage areas.

* The MSD and other utilities use the software to determine such things as which sewage and water treatment plants would be flooded; what customers would be affected by the threat of raw sewage and unsafe water; and what types of flood protection should be used under differing storm scenarios.

In all, the Flood of '97 inundated 1,000 miles of shoreline, drove tens of thousands of residents out of their homes, and caused 31 deaths in nine days along the Ohio River Valley. High waters disrupted rail service, washed out streets, blocked traffic, closed manufacturing plants, swamped ports and barge traffic, and slowed or disrupted nearly every business unfortunate enough to be located near the banks of the flooded river in Ohio, Kentucky, and Indiana.

Yet despite the killer storm's grim toll, Cincinnati residents have much to be hopeful about. "We're prepared for the next storm," said Babbs.
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Publication:Public Works
Date:Mar 1, 1998
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