Lake City residents travelled from Alligator Lake to the Ichetucknee River by boat a century ago. Today, people take the same route, but it is called State Road 47.

Tributaries that flowed into the Ichetucknee River also have new names, including County Roads 240, 242 and 341.

The river went underground many years ago, following a series of channels through the limestone, marked on the surface by springs and sinks.

On rare occasions, the underground river fills to capacity.

Then the old riverbed once again becomes a river and the tributaries overflow with rainwater.

People who own homes, businesses and farms suddenly are in the midst of a flood.

Lakes form in low lying areas that long ago had been lakes.

The Ichetucknee Trace is clearly visible on topographical maps. In fact, the old riverbed looks like a river, even when it is dry, because low places are shown in dark green.

Divers still follow the river underground, exploring and charting this natural wonder.

Visit Ichetucknee Underwater, a slide show provided by some of the best underwater photographers in the world.

One of the lowest areas is Callaway subdivision, off County Road 247. Many homes were flooded eight years ago in what has been described as a 100-year event. Some homes were demolished and others had extensive renovations.

Life returned to normal until last month. Relentless rain from Tropical Storm Debby put even more water into the subdivision. This may be designated a 500-year event. There is no guarantee that the next major flood will not happen for another 100 or 500 years.

FEMA National Flood Insurance, which is the only source for flood insurance, designated the area a flood zone. Flood insurance is not mandatory, but banks make it a requirement for a loan or mortgage.

And governments cannot stop people from building houses in flood zones.

"No government has the right to restrict completely the use of someone's property, unless the government wants to buy it, said County Manager Dale Williams at the July 5 commission meeting.

"The law says that all we can do is impose reasonable restrictions. Reasonable restrictions are a moving target and have, for the most part, been established by court law."

County Commissioner Jody DuPree, noted, "In 2006, a preliminary FEMA flood map was presented," DuPree said.

The areas that are now flooded are the ones designated as flood zones on that map.

"Operation and maintenance of that system was by the homeowners association," DuPree said. They were responsible for maintaining storm-water control systems.

"The Homeowners Association disbanded in 2004, abandoning that system," DuPree said.

Suwannee River Water Management, which has standards for storm-water retention ponds and drainage, requires that retention ponds be able to handle an inch of water per hour, DuPree said. Rain from Tropical Storm Debby was far greater than that.

SRWMD can limit use of wetlands. An expensive process called mitigation requires that an area, much larger than the one being used, be restored as a wetland and preserved forever.

Meanwhile, employees of Columbia County and the Suwannee River Water Management District, are using pumps to move the water to an available retention pond, and from there to an area that has drainage.

When the flood is over, homeowners who have flood insurance will collect on their policies and be allowed to repair the houses.

They will have the opportunity to buy the flood insurance, subsidized by the federal government because it would be prohibitively expensive for a commercial company to provide.

And Columbia County will be required to issue building permits, if the applications meet building standards.

One thing may change this year. Columbia County plans to put markers in flood zones, indicating historic high water levels.