Revised flood maps bring data right down to the property lines

Find out what the hydrologists believe. A new set of flood-risk hazard maps - complete with property lines - have been posted on the Internet.

To find a map of your property, go to www.floodsmart.gov and type your address on the "One Step Flood Risk Profile." The Web site will estimate your flood risk and annual flood insurance costs and provide you with names of insurance agents who can provide coverage.

To see the actual flood-insurance rate maps, visit to the Federal Emergency Management Agency's Web site at www.fema.gov and click on "Flood Insurance, Maps, and Information" on the right side of the page. That move will take you to a new Web page, where you should click on "Map Service Center." Enter your address in the box in the upper left corner. The Web site will show you a map of your neighborhood. Zoom in to see the property lines.

New maps

Tennessee is the first state in the nation to provide maps detailed enough to include property lines, said Stan Harrison, special projects director for the Tennessee Department of Economic and Community Development Community Assistance Program. Harrison works with the National Flood Insurance Program in Tennessee.

Tennessee had already started digital base mapping in conjunction with property assessments, which gave Tennessee an advantage over other states. A variety of maps can be overlaid onto the property-line maps. "Because Tennessee had the initiative under way, it's not costing Tennessee any additional funds" to get such detailed maps, Harrison said.

Congress decided in 2003 that the nation's flood insurance maps should be updated. The effort was funded in 2004 with $200 million a year for five years. The mapping update is 80 percent federally funded and 20 percent state funded.

Tennessee decided to re-map the most populated counties first. The updating process on the last 20 counties began in May. Harrison said it takes about 18 months to update the maps.

Preliminary versions of Dyer County's updated maps were completed on July 27, 2007. The final maps went into effect on Oct. 16.

Dyer County Building Inspector Daniel Cobb said the updating process didn't result in any major flood zone changes.

The older maps were created in 1974 and only the areas with the state's highest growth rates had been updated. While the older maps had fairly accurate stream and flood zone data, Harrison said the street locations weren't always right.

The new maps also put more emphasis on elevations, reducing the 20-foot contour lines in the old maps to 7- or 10-foot contours today. Harrison said that is especially helpful in East Tennessee, where the terrain varies more.

The revised maps feature several flood hazard designations. In Dyer County, Harrison said there are three primary designations: AE, A and X.

"AE" zones estimate the elevation of a 100-year flood, or a flood that has a 1 percent chance of being equated or exceeded in any given year.

"A" zones are flood-prone areas were no base flood elevations have been established.

"X" zones are areas outside of the flood hazard areas. Harrison said flood insurance may be purchased at lower rates for buildings in this zone.

Flood regulations

With two of West Tennessee's major river systems passing through Dyer County and the Mississippi River on the county's western edge, some flooding is inevitable here.

Building Inspector Cobb estimated that 15 percent of the county is located in areas of "special flood hazard." These areas are governed by special regulations dealing with everything from building a home to parking a recreational vehicle.

Dyersburg and Dyer County recently revised their Flood Hazard District regulations - a step that had to be taken if the city and county were going to continue to be a part of the National Flood Insurance Program.

The new regulations, like the new flood maps, are more detailed.

For all new or substantially improved houses in a special flood hazard area, the lowest floor must be at least 1 foot above the base flood elevation. If the base flood elevation has not been established, the lowest floor must be elevated or flood-proofed to a level at least 1 foot above the highest adjacent grade.

For non-residential construction and mobile homes, the lowest floor must be elevated at least 3 feet.

Recreational vehicles that remain parked for more than 180 consecutive days must be elevated 3 feet above base flood elevations, too. RVs also must be anchored so that they don't float away during a flood. All RVs must be licensed and ready for highway use.

New and replacement sanitary sewage systems must be designed to minimize or eliminate infiltration of floodwaters and discharges from the systems into floodwaters. While that may sound impossible, Harrison said it is easily accomplished by placing flow-preventer valves between the home's discharge pipe and the septic tank and between the septic tank and the field lines. These valves, which are commonly installed in septic systems, are pressure operated, he said. The valves are open most of the time, but when fluids try to move from the field line to the tank or from the tank to the house, the flap closes. The valves keep floodwater from filtering into the system.

Insurance benefits

Flood insurance is usually required for anyone seeking a mortgage on flood-prone property, Harrison said.

Homeowners may buy up to $250,000 coverage on their house and another $250,000 on the contents. Flood insurance is a rider that is added to the homeowner's policy.

Dyer County landowners have benefited from the National Flood Insurance Program in the last 30 years, Harrison said. He noted:

* A total of 176 flood insurance policies are in force in the unincorporated areas of Dyer County. These polices provide $14,122,500 of insurance coverage. The flood insurance program has paid 35 claims totaling almost $350,000 since 1978.

* A total of 164 flood insurance policies are in force in Dyersburg. These polices provide nearly $17,900,000 of insurance coverage. The flood insurance program has paid 25 claims totaling about $172,000 since 1978.

* The statistics for Newbern aren't as clear. Harrison said Tennessee actually has two Newberns listed and the computer system sometimes lumps them together. However, he said the computer showed one flood insurance policy for Dyer County's Newbern. It provides $210,000 worth of insurance coverage. No claims had been reported in the last three decades.

* The computer listing showed no current flood insurance policies for Trimble.

Dyer County has a "pretty high" number of flood insurance policies, Harrison said. The abundance of waterways and floodplains put Dyer County at a higher risk of flooding. However, flash flooding is possible just about anywhere.