Flood maps out of date as sea levels rise
Many US flood maps are out of date because they don't account for sea-level rise projections, according to Frank Mansell, a spokesman for the Federal Emergency Management Agency in California. Flood maps are costly and take three to five years to create, he said. Although some parts of the maps have “phenomenal” accuracy, some may be out of date because flood zones change constantly with new construction and environmental changes. “Sometimes they’re out of date by the time you finish revising,” he said.

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As officials in Washington try to repair the nation’s flood insurance program, scientists in California are grappling with a looming threat that will complicate flooding hazards in the state: sea-level rise.

Creeping ocean waters are already flooding coastal areas more frequently and eroding sea cliffs more rapidly. They’re also worsening damage from extreme weather events like high tides and torrential rains.

Flooding issues will worsen as sea levels rise, Griggs said, both in coastal regions and inland areas.

Scientists can’t predict exactly how much sea levels will rise over time because there are too many unknown factors, particularly how much more climate-warming greenhouse gas humans will produce, said Gary Griggs, a geologist at UC Santa Cruz who studies the coast.

Some parts of the coast will experience greater sea level rise than others. Ocean levels don’t change uniformly along the entire California coast due to geographical variation, but the whole coastline will be affected as sea levels rise.

Griggs and a team of other scientists published a report on California sea-level rise in April. In the most extreme scenario they considered, they projected sea levels could rise over 10 feet by the end of the century.

Flooding issues will worsen as sea levels rise, Griggs said, both in coastal regions and inland areas where water systems will also be impacted by rising ocean levels.

Congress faces a December deadline to reauthorize the National Flood Insurance Program, which provides flood coverage to millions of Americans. The program relies on floodplain maps many criticize as out-of-date. The program is billions of dollars in debt, and congressional leaders have said they plan to overhaul it as part of the reauthorization process.

“Mother Nature doesn’t read flood maps.” — Frank Mansell

When studying flood risk in parts of California, Griggs said he has found some federal maps of flood zones to be “way off” and not reflective of flood risks from sea-level rise.

Flood maps are costly and take three to five years to create, said Frank Mansell, a spokesman for the Federal Emergency Management Agency in California. Although some parts of the maps have “phenomenal” accuracy, some may be out of date because flood zones change constantly with new construction and environmental changes.

“Sometimes they’re out of date by the time you finish revising,” he said, adding that, even when they’re accurate, “mother nature doesn’t read flood maps.”

The maps don’t account for sea-level rise projections because they reflect only current conditions, Mansell said.

At the state level, California lawmakers have had numerous discussions about sea-level rise, but have done little in the way of actual policy.

Opponents say Stone’s bill infringes on Californians’ right to protect their property from ocean rise by building sea walls.

“The Legislature hasn’t really done that much other than worry about it a little bit,” said Assemblyman Mark Stone, a Democrat whose coastal district includes Santa Cruz and Monterey. “It’s going to have a dramatic impact on homeowners along the coast.”

This year, Stone introduced a bill he says is the first major piece of state legislation to adapt the coast to sea-level rise. His bill, AB1129, would give the state more power over sea walls, which can protect properties from ocean rise but can shrink beaches and shift problems to other coastal areas.

The effort has proven to be a “struggle” because changing local land use rules is politically unpopular, Stone said. The bill didn’t make it out of the Assembly, the house where it originated. Stone said he will continue to try to pass the bill next year. It must clear both houses of the Legislature and secure approval from the governor to become law.

Opponents say Stone’s bill infringes on Californians’ right to protect their property from ocean rise by building sea walls.

“We think that it’s unfair to property owners to have the government approve developments, allow people to move in and then turn around and not allow for the protection of those properties from erosion,” a representative from the California Association of Realtors said at a committee hearing on the bill earlier this year. “AB1129 works against communities and property owners trying to protect themselves against rising sea levels”

Moving forward, Stone says the Legislature needs to give resources to local communities to help them address sea-level rise.

Rising ocean levels also threaten major public infrastructure, particularly structures intentionally built at sea level near the coast, such as power plants and sewage treatment facilities. The airports in San Francisco and Oakland that are built on landfill also face catastrophic damage from sea-level rise.

Griggs said he is aware of only a handful of projects to move infrastructure away from the coast. The structures being moved are mostly roads and parking lots in areas with space nearby to relocate them. He described the projects as positive, but “low hanging fruit.” More substantial changes will require greater political will.

“It’s a lot easier to talk about it than it is to take that first step,” Griggs said. “It keeps creeping up on us.”