The Federal Emergency Management Agency’s new flood insurance rate maps became effective Aug. 15 — a change that means thousands of residents now find their homes in floodplains.
Under the new flood maps, more than 3,700 homes will fall in a 100-year flood zone, up from 1,265 homes under the 1999 maps, a 295 percent increase, officials said.
And more than 7,370 homes will fall in a 500-year flood zone, up from 4,245 under the 1999 maps, or a 173 percent increase, officials said.
The council approved changing the city’s ordinances to reflect the new maps, a requirement for continued participation in the National Flood Insurance Program.
A 100-year storm has a 1 percent probability of happening in any given year, while a 1,000-year storm has a 0.1 percent probability of happening in a given year, officials with the National Weather Service in League City said.
While weather scientists initially described Harvey flooding as a 500-year event, some have amended those assessments, calling it a 1,000-year flood.
Hurricane Harvey dropped more than 50 inches of rain on some parts of Galveston County and flooded more than 8,000 homes in League City.
Galveston County and other local governments have waited for years for FEMA to release new risk maps. The maps advise homeowners and buyers about the risk of a property of being flooded. People living in certain high-risk flood zones are required to buy flood insurance.
Some preliminary maps have been published for years. But in some cases, the preliminary maps conflict with other, local maps and cause confusion about which risk category a particular property is in.
Out-of-date maps might have also contributed to losses during Hurricane Harvey. About 60 percent of Galveston County residents did not have flood insurance in August 2017, the month Hurricane Harvey made landfall.
Draft flood maps were first published as early as 2013.