Flooding, according to Howard County's 2004 Natural Hazards Mitigation Plan, "is the most common natural disaster to impact Howard County."

Flooding is well-documented in the county — moreso than earthquakes or tornadoes, for example — and has taken lives and caused millions of dollars in damages over the years.

Located entirely within the watersheds of the Patapsco and Patuxent rivers, the county is susceptible to swollen rivers and to flash floods at any time of the year and should be prepared for them, the mitigation plan says.

"There's no question it is our top hazard, so we've taken it real seriously," said Ryan Miller, deputy director of the county's Office of Emergency Management.

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Unfortunately, the county learned the hard way.

Forty years ago this month, when Tropical Storm Agnes rampaged through Howard County on June 21 and 22, 1972, there was no comprehensive county plan in place for flooding, officials said.

Many local residents were caught off-guard by the rapidly rising waters that flooded historic Ellicott City, washed out bridges and roadways and caused widespread damage in Elkridge and other low-lying areas of the county. Some were trapped on second stories of their homes, some on roofs.

County roads, sewage treatment services and other resources were overwhelmed — ill-suited and under-equipped to deal with the devastation, local officials recalled.

Members of the professionalized Howard County Department of Fire and Rescue Services, which was in its infancy at the time, recall having little rescue equipment and using rope, flashlights and flat boats not meant for swift currents to perform daring rescues in raging waters.

Data on storm water levels was slow to come in or unreported altogether, as there were relatively few gauges throughout the region's watersheds.

Without many of the early-warning systems of communication in place today, businesses and homes were suddenly flooded with little or no advance warning.

As a direct result of the storm, a flood warning system was instituted for historic Ellicott City, and according to county officials, changes to how the county mitigates vulnerabilities and plans for natural disasters have continued to be rolled out ever since.

The county now prohibits structures from being built in flood-prone areas and has a program for purchasing and demolishing structures already there.

It has a team of storm water management professionals who monitor a series of gauges throughout the two watersheds during large storms and predict rises in water levels at various points throughout the county — allowing them to sound alarms and warn emergency personnel before flooding begins.

The county has a network of contacts in communities that are most vulnerable to flooding, who provide county personnel with critical information and eyes and ears on the ground ahead of and during major storms.

The county also has put together grant funding for business owners in flood-prone areas who want to move their utilities off the ground. It has created NotifyMeHoward, a message alert system to send out early warnings.

The county is also working on a new version of its 2004 hazard mitigation plan, with updated data and information.

In all, Miller said, the county is far more prepared for flooding than it was in 1972.

Still learning

Not that there aren't lessons still to be learned.