Rising ocean waters will inundate coastal land areas in the future. Scientific research has repeatedly shown this to be an inevitable result of a changing climate.

A new report takes a close look at the impact of swelling waters in California and projects the coast could see a rise of a half-foot by 2030 and up to seven feet by 2100. Severe storm events and high tides will produce even higher increases.

"Even though sea level rise feels like a threat that is really far off, it’s coming sooner than we think," said Rachel Ehlers, a policy analyst with the California Legislative Analyst's Office and lead author of the report "Preparing for Rising Seas: How the State Can Help Support Local Coastal Adaptation Efforts."

For Bay Area residents, the piece of the report that's most intriguing is a map revealing land areas expected to flood if a 10-year storm happens around 2050 when sea levels are projected to have already risen by about two feet. The combination of the storm and the sea-level rise would result in a total water-level increase of more than four feet. (Note: A 10-year storm is an event with a severity level that happens once every 10 years on average.)

The map was created using an online tool from the Bay Conservation & Development Commission and shows what would happen if the Bay Area doesn't take steps to prepare for rising seas. (Find the map from the report and additional maps created using the tool to see close-up views of land areas around the bay.)

The map shows extreme flooding at locations along the coast and bay front; Foster City, the Oakland International Airport and the toll plaza for the Bay Bridge in Oakland are all underwater.

"I think the scenario we picked is pretty conservative," said Ehlers. "It is a really plausible scenario. It's not outer-limits, doom-and-gloom, sky is falling threat. It's a very plausible scenario. Two feet of sea level rise is within the projection of the next 30 years and it's a 10-year storm, meaning a one in 10 chance."

The report offers suggestions for communities to prepare for the future, including building buffers and seawalls, planning future development farther away from ocean waters and constructing buildings that can withstand flooding.

"I think part of the message is local governments will need to use all three of these different strategies and there are tradeoffs with each," she said. "Some may be more practical for coming years, like building up sand dunes or wetlands for buffering waves, and that could hold the waves back for a while. If it can work for a decade or two, that can buy time to prepare for the more drastic situation, like relocating public infrastructure.

"It may be hard to change the way existing buildings are built, but if we're thinking of building for the future, we need to think about how might we change our ways. I think local government will need all their tools in their tool kit."

Amy Graff is a digital editor with SFGATE. Email her at agraff@sfgate.com.