Updated Floodplain Maps in St. Johns County Give Residents and Emergency Managers Improved Data

St. Johns County, Fla., residents can immediately get a better idea of what their flood risk is but are still urged to buy flood insurance by local emergency management officials.

by Jim McKay / December 14, 2018

New, updated floodplain maps in Florida’s St. Johns County will give residents a much better reading of their flood risk and give emergency management better insight into which areas may present flood problems.

But the message to residents is the same: Please buy flood insurance.

St. Johns County, in northeastern Florida, is composed of 822 square miles — 221 of those are water, around which the approximately 190,000 residents live.

The new FEMA floodplain maps, in the works since 2016 and available for public consumption on the county website, are the first major update since 2004 and offer the latest technology and science used by FEMA, including lidar.

“Tech advancements over the last 15 years have grown by leaps and bounds,” said Floodplain Manager Patrick Doty. “There’s a much higher level of detail, greater input on topography data, and the elevation models, the inundation layers are just a lot more accurate.”

He said property owners will have a much better idea of what their flood risk is, and it provides tools for emergency management to mitigate events like hurricanes Matthew and Irma, which passed through the county in 2016 and 2017, respectively.

“We’ve had those two events, so we have a pretty good idea of what our flood prone areas are, but this shows us some areas that maybe we weren’t aware of that weren’t rated accurately under the old maps.”

The new maps are much more detailed than the old smudgy ones, Doty said. “You look at the 2004 maps and they look like blobs. You can see general areas where we go, ‘OK, we know there’s going to be flood hazard here,’” he said. “Whereas now, if you go to our flood zone viewer it follows the topography of the county, and the interior and boundaries are much more defined.”
The maps were put to use immediately.

“Today we’re supposed to get four inches of rain,” said Kelly Wilson, the county’s emergency management planner. “We can start looking at those areas, so we know where the areas and communities are that are most susceptible.”

But the floodplain maps are different from the county’s evacuation maps, something Wilson says residents sometimes struggle to understand. And the floodplain maps don’t include surge, where hurricanes or tropical storms push the water level above the high tide line in coastal communities. Also commonly, as was the case in Houston after Hurricane Harvey, flooded homes are often outside of the floodplain. 

“We’ve gotten several calls today about it,” she said. “People ask, ‘are we in an evacuation zone now?’ We go, ‘not necessarily, you’re in a flood zone, which is based on freshwater flooding, not necessarily from a storm.’ It’s tough for anybody to understand what a flood map is and why it doesn’t include storm surge flooding.”

She said the main thing for residents is to get flood insurance. During Irma and Matthew, residential homes in areas that weren’t in flood zones ended up with feet of water inside.

“We tell everybody, just because you’re not in a flood zone doesn’t mean your house won’t flood,” Wilson said. “We all have flood risk. If your driver’s license says Florida on it, you need to carry flood insurance because those new flood maps do not include storm surge.”