The federal government must spend up to $12 billion to improve the nation’s flood maps and should do more to steer development out of flood-prone areas, according to two recent studies that warn about increasing flood damage from climate change.

The Federal Emergency Management Agency has produced flood maps covering only one-third of the nation’s 3.5 million miles of streams and 46% of shoreline, the Association of State Floodplain Managers said in a recent report.

The maps show coastal and riverine areas that are most likely to be flooded and help planners and builders determine which areas of a community are suitable for development. FEMA also uses the maps to determine which properties must have flood insurance.

But the absence of flood maps leaves communities “less able to be resilient because the foundational flood data does not exist,” the report says. “Unmapped flood hazard areas present a serious threat to people who may choose to buy or build within them.”

In addition, many of the flood maps that FEMA has drawn “are badly out-of-date,” according to a separate study by the R Street Institute, a free-market think tank in Washington.

The outdated flood maps fail to account for climate change and “do not reflect the degree to which climate change and sea-level rise are expected to heighten the risk of flooding and expand the areas that will be subject to flooding in the future,” the R Street study says.

The National Climate Assessment of 2018 says climate change is intensifying rainfall, storm surges and high tides.

The two studies come as a House committee is set to hold a hearing tomorrow on flood mapping and as President Trump has proposed cutting FEMA’s flood-mapping budget from $263 million this year to $100 million in fiscal 2020. Congress has ignored Trump’s previous proposals to cut federal spending and flood mapping and shift costs to states.

The floodplain association is urging Congress to spend more on flood maps and says it will cost between $3.2 billion and $11.8 billion for FEMA to finish drawing maps for the entire nation. Maintaining and updating the maps will cost $107 million to $480 million a year, the association projected.

But the costs are recovered because flood maps steer development out of risky areas and avoid flood damage, the association said.

FEMA has noted that the overwhelming percentage of U.S. residents live in communities with flood maps. The communities without flood maps are concentrated in sparsely populated regions of the Great Plains and Rocky Mountain West.

But the Wisconsin-based flood association said FEMA’s focus on highly populated areas “ignores lesser populated areas that have considerable flood risk, especially in relation to the local economy, and may have rapidly developing areas with no flood data to guide development.”

And the R Street Institute says that some of FEMA’s most obsolete maps are found “in some of the nation’s most flood-prone communities,” according to the study, written by R.J. Lehmann, an insurance expert.

A November 2017 report by the Congressional Budget Office found that exactly half of the 166 counties with the highest flood risk used flood maps that were more than 5 years old. Forty-two of the counties used maps that were more than 10 years old, the CBO found.

FEMA requires people and businesses that own property in a high-risk flood area to have flood insurance if they also have a federally backed mortgage. FEMA sells almost all of the nation’s flood insurance coverage through its National Flood Insurance Program.

Lehmann says that FEMA should stop selling insurance to new construction in high-risk flood zones, which are defined as areas with a 1% annual chance of being flooded. This policy would reverse a trend of increasing development in the nation’s most flood-prone areas and mark a sharp departure from FEMA’s long-standing policy of insuring any property against flood damage regardless of its flood risk.

Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at