Consulting firm says modeling behind proposed FEMA flood maps in - WMBFNews.com, Myrtle Beach/Florence SC, Weather

Consulting firm says modeling behind proposed FEMA flood maps inaccurate

Stephen Williams points out a portion of the Pee Dee River he said was not accounted for in FEMA's modeling for new flood maps (Source: Amy Lipman) Stephen Williams points out a portion of the Pee Dee River he said was not accounted for in FEMA's modeling for new flood maps (Source: Amy Lipman)

HORRY COUNTY, SC (WMBF) – The models used to create FEMA’s new flood maps for Horry County have significant discrepancies, according to an appeal filed by The EARTHWORKS Group.

"The goal of a model is to replicate reality,” said Stephen Williams, of The EARTHWORKS Group.

At the end of May, South Carolina's flood mitigation program coordinator said the changes on the proposed flood maps are the result of new studies of the Great Pee Dee River, which has serious effects on the waterways in Horry County.

However, Williams said data shows that’s not really the case.

"We all want to make sure the best possible product is put out there in the community, so that people in the community aren't being forced to pay excessive flood insurance premiums based on data that needs refinement,” he said.

Historically, and as recently as October, Williams said when the Pee Dee River rises 20 feet outside of Marion, the water doesn’t rise nearly as much further downstream.

"By the time that peak translates down here to the Intracoastal Waterway and the Waccamaw River, it barely moves the needle,” he said.

Williams said the water spreads out throughout the swamp from where gages are located, collecting data, and where he said the actual model FEMA used begins.

"They're taking values from 52 miles away and using those peak values down river, and they're not accounting for all of this flood storage that happens in the river swamps,” Williams said.

He said other methods FEMA used in its modeling were not thorough and don't reflect reality.

"In our opinion, it's very hard to deny what the gages are telling us,” he said.

Also, the flood mitigation program coordinator said in May the Great Pee Dee River didn't experience the same 100-year flood Horry County experienced in October, however, Williams said he thinks the rainfall totals in that area qualify it as a 100-year storm.

FEMA's maps were released prior to October, so the October floods were not taken into account, but Williams said he thinks the scale of that flooding shows the proposed maps are not accurate because they are supposed to represent flooding of that same magnitude.

Horry County hired a consultant to help with the appeals process.

The county also requested the ability to file supplemental materials after the 90-day review period, which ends July 16.

FEMA hasn't responded to that request, Spokesperson Lisa Bourcier said.

Bourcier said Horry County has additional opportunities to request map revisions after the 90-day review period ends.

Myrtle Beach Area Chamber of Commerce President/CEO Brad Dean said Congressman Tom Rice is making progress getting the attention of FEMA leaders.

He said FEMA has yet to agree to any problem within the maps though.

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