Lexington County federal flood maps get update

New outlines of flood-prone areas that could guide development in Lexington County for the next two decades were unveiled Thursday.

It’s the first update of flood-prone areas in the 758-square-mile county since 2000. The changes will come into use as soon as spring 2017.

The changes mainly are tweaks instead of radical differences, county officials said. “It’s fine-tuning,” county flood plain manager Christopher Stone said. “There won’t be any big surprises.”

Still, some homeowners in St. Andrews were shocked to learn that their dwellings would be classified in a high-risk location despite years of coping with overflows along Kinley Creek.

The change will mean higher insurance premiums for many homes in Challedon, Whitehall and adjoining neighborhoods.

That factor promises to make selling her father’s home in Whitehall more difficult, Vicki Bates said. “It’s a hindrance,” she said. “You don’t want to be in one of those (high-risk areas).”

The guidelines particularly affect development around Lake Murray and along the Congaree, Edisto and lower Saluda rivers as well as three dozen major creeks.

The maps’ final adoption depends on how many landowners seek adjustments in the boundaries proposed. But any adjustments likely will be minor, state flood plain coordinator Maria Cox Lamm said.

Overall, 14,172 of 131,753 parcels in the county – about 1 of every 9 – tentatively are rated flood-prone, county public works officials say. That’s 1,066 more than previously rated, with many of those added in the largely rural southern third of the county.

It was the first look of its kind at maps for communities such as Batesburg-Leesville, Gilbert, Pelion, St. Andrews and Swansea.

The update is among the first in the state to describe areas susceptible to flooding in a new way. “Flood-prone,” with categories of low, moderate and high, replaces the former terms of flood plain and floodway.

Developers are starting to assess the impact of the new boundaries. Changes will be sought “if we see significant issues,” said Earl McLeod, executive director of the Building Industry Association of Central South Carolina.

Building in flood-prone areas often is allowed. But the new boundaries will be instrumental in determining if extra development requirements apply and open the way for higher insurance bills because of the increased threat of damage.

Some aspects of the plan already are outdated since the study was completed before flooding that damaged 380 homes across the county after record rain Oct. 4.

For instance, no analysis occurred on the impact of the collapse of the Old Mill Pond dam in the center of Lexington that flooded a golf course and a few homes downstream.

The storm last fall was “a rare occurrence” not used in determining areas likely to flood during traditional storms, county Public Works Director Wrenn Barrett said.

Meanwhile, some areas already get extra protection from 100-foot natural buffers required along many creeks that county officials put in place in 2008 for a cleaner environment.

Those landscaped areas are intended to reduce pollution from erosion to meet clean-water standards.

“It’s a side benefit that put structures further away in flood-prone areas,” Barrett said.

The update of flood-prone sites was produced through a partnership of county, state natural resources and federal disaster officials that reviewed terrain using digital technology for the first time.

“It made a world of difference,” Barrett said. “This is so much more accurate.”

While the number of parcels with structures rated as flood-prone increased, 1,481 tracts and 2,209 structures were removed, officials said.

This story was originally published March 31, 2016 at 8:05 PM with the headline "Lexington County federal flood maps get update."