Series: After the Flood The Challenge of Rebuilding as the Climate Changes

In recent years, Americans have witnessed the destructive power of floods again and again, from the damage inflicted on coastal New York and New Jersey by Hurricane Sandy in 2012 to the devastation wrought by overflowing rivers in Colorado just a few months ago.

Yet as ProPublica has reported, the Federal Emergency Management Agency (FEMA) has flood-risk maps of questionable accuracy for many U.S. counties and lacks maps altogether for some.

This has left property owners in a dangerous state of uncertainty. FEMA’s maps govern whether home and business owners are required to buy flood insurance. They also guide communities’ decisions on where they should -- and shouldn’t -- allow development.

The issue of flood mapping is at the heart of a number of legislative battles currently taking shape.

Last year, Congress passed the Biggert-Waters Act, a law designed to eliminate the subsidies many homeowners have received for years through the National Flood Insurance Program. Because of damage from Hurricane Katrina in 2005 and Hurricane Sandy, the program fell about $25 billion in debt and Congress decided it could no longer support the subsidized rates.

But on Friday, Sen. Mary Landrieu, a Louisiana Democrat, announced that there will be a vote on a bill, delaying the Biggert-Waters flood insurance rate increases until FEMA has “implemented a flood mapping approach that, when applied, results in technically credible flood hazard data.” The bill also requires FEMA to conduct a study of the affordability of the rate increases.

If the measure advances, it could leave the flood insurance program in limbo for an extended period.

There’s still much work to be done to update the nation’s flood maps. Some parts of the country still use flood maps drawn in the 1970s, shortly after the flood insurance program’s inception. In other cases, paper maps from the '70s and '80s have been digitized but not improved using modern technology for measuring topography and modeling storm surge.

Complicating the effort, Congress has slashed funding for upgrading FEMA’s maps by more than half since 2010.

As we said in our story earlier this month, new maps for New York and New Jersey aren’t expected to be finalized until 2015.

The “final preliminary” version of those maps — which are still drafts and won't dictate insurance rates until they become effective — were released on December 5. They include a new storm surge analysis and sophisticated, modern topographic data -- two characteristics earlier maps lacked and that experts have told us are the biggest factors in flood map accuracy.

The rest of the country is slowly getting new maps, too.

New Orleans still relies on paper maps drawn in 1984 while FEMA revises maps to reflect the city’s post-Katrina flood protection measures. New Orleans received preliminary versions of its new maps in January. Boston, Mass. is slowly winding through the preliminary process to replace its decades-old maps, and is expected to get new ones in 2015.