Interactive: Pinellas County flood maps are changing. Here’s what’s different.

Some areas are now designated as high risk for flooding while others are now zoned as lower risk.

The Federal Emergency Management Agency is getting closer to finalizing a new coastal flood map for Pinellas County, the first update since 2003. Introduced to residents late last year, the new map is meant to better reflect the risk that some areas of the county face from flooding during storms.

Once approved, the new maps will help determine flood insurance rates and standards for new construction in areas considered risk- prone from storm surge or during heavy rains.

The next phase of review, still to be scheduled, will allow 90 days for challenges to the study’s methodology and results. It would enable the public, for instance, to point out a parking lot or new development that wasn’t taken into account in determining flood risk. Local governments will then get six months to update local rules that spell out what can be built where and under what conditions.

It’s a process playing out throughout Florida, with residents in Hillsborough County recently getting a first look at flood map adjustments there. Pasco County held open houses for the public to view maps and ask questions last year, while Hernando County did the same in January.

“What we saw (in Pinellas County) is very similar to what we’re seeing along the coast of Florida,” Mark Vieira, senior engineer at FEMA. “Some areas’ flood elevations went up, and some areas’ flood elevations went down.”

Here are five major changes between the old and new Pinellas County maps. Scroll down to the bottom for an interactive map of the changes.

1. The new map expands areas at risk from waves

Counties are divided into flood zones based on how severe flooding could be. The zones range from low-risk (“X”) to high-risk (“A” and “V”). The highest-risk zone is “VE.”

In prior years, “VE” zones reflected areas where buildings were considered susceptible to wave damage from storm surge. But that assumed the waves would be a minimum of 3 feet tall. New data shows that waves as small as 1.5 feet also cause significant damage.

So FEMA drew a line on the new flood maps to show where those smaller waves are expected to start. Anything between that line and the “VE” zone is now called something new — a coastal “AE” zone. In practical terms, it means new construction on those properties must be built to more stringent standards than in areas not expected to see waves hitting buildings.

2. That zone means new buildings in some areas could become much more expensive to construct

Those new building standards could affect future construction in several areas along the eastern shore of Pinellas County, such as portions of Snell Isle.

“From a construction standpoint, it astronomically changes the cost of construction to build a new house,” said Jake Holehouse, owner of HH Insurance. Holehouse helps residents in St. Petersburg and St. Pete Beach understand how their insurance is affected by the flood zone they are in.

In “AE” and V zones, it could require raising the finished flooring of new buildings by a few feet more than was required for older buildings. It could also require features such as breakaway walls that absorb some of the blow from incoming water.

As of late March, Bonnie Hargrett, president of the Snell Isle Property Owners Association, said she hadn’t heard of any residents who expected any imminent effects from the re-designation.

3. Parts of southern St. Petersburg were moved from low-risk to high-risk zones

Portions of southern St. Petersburg are newly in high-risk zones under the new preliminary flood maps. Areas in green are the current "A" and "V" zones, while areas in red are communities that would now be in the "A" and "V" zones on the preliminary map. Yellow areas are currently in "A" or "V" zones, but would no longer be under the preliminary map. For an interactive version, scroll down. [LANGSTON TAYLOR | Times]

A smattering of areas east of 12th Street S and south of 54th Avenue S moved from a low-risk designations to a high-risk zone in the new map, while some portions of the Pink Streets on the southern tip of the Pinellas peninsula switched from zone “AE” to the very high-risk zone “VE.”

If you’re in one of those areas, don’t panic about flood insurance rates, Holehouse said. Homes built after 1975 that were already in a flood zone and got moved to a riskier zone can get grandfathered in for the risk rating when it was built (so long as it was built to code).

According to Lisa Foster, floodplain coordinator for Pinellas County, residents have a year from when the maps go into effect to get that grandfathered rate. She encouraged residents to act on this sooner rather than later.

“They’ll have a year, but the rates are lowest now,” she said.

4. More of Oldsmar is zoned for greater risk of flooding

Several portions of Oldsmar now would be rezoned for the special flood hazard areas. Areas in green are the current "A" and "V" zones, while areas in red are communities that would now be in the "A" and "V" zones on the preliminary map. Yellow areas are currently in "A" or "V" zones, but would no longer be under the new maps. For an interactive version, scroll down. | [LANGSTON TAYLOR | Times]

Coastal areas of Oldsmar, too, are rezoned in the new map, with two substantial areas in the southwestern and eastern areas of the city moving from low-risk zones to high-risk “AE” zones. Several strips of property directly on the bay are newly designated as “coastal AE” zones in the preliminary map.

5. Some areas would be re-zoned for less risk

Other areas, such as portions of Tierra Verde and a large area west of the Gandy Bridge, moved into lower-risk zones. According to FEMA’s Vieira. That happens because of more precise mapping technology that wasn’t available 16 years ago.

“You may not have known the exact ground level,” he said. “Topographic maps are a lot better (today).”

Below is an interactive map of the changes between the current flood map and the preliminary flood map for the highest-risk zones – "A" and “V.” Note that a parts of Pinellas Park and the Gateway areas also would see their flood risk downgraded.