A wide swath of Long Beach, including the port, peninsula, Naples Island and other low-lying residential areas, could see chronic flooding of streets and beaches from rising sea levels in just 13 years, decades earlier than previously predicted, according to a report released this week.

The non-profit Union of Concerned Scientists released a report and interactive tool Wednesday that forecasts what parts of the country are likely to see regular flooding from rising oceans and how soon.

“To my knowledge this is the first that explicitly does it by time increments and drills down by community level to see how much land is at risk,” said Kristina Dahl, a climate scientist with the group who co-authored the report. “We wanted to develop a tool to give communities an idea of how much time they have.”

In addition to Long Beach, the communities projected to experience frequent flooding by 2030 are northern parts of Huntington Beach as far inland as the city’s Central Park, the peninsula in Newport Beach, Balboa Island and the Seal Beach Naval Weapons Station.

Fifteen years later the chronic flooding is expected to extend inland as far as Warner Avenue in Huntington Beach, a low lying part of the city.

“When you have a very low-lying area even a small rise in the level of the sea can propagate far inland,” Dahl said.

In their research, the scientists used high resolution topographic maps, sea level rise projects and tide gauges. The Union of Concerned Scientists predict the number of U.S. communities facing chronic flooding will increase by 83 percent, to 167 communities by 2035. That number is expected to grow to nearly 500 communities by 2100, with many of the most affected areas in Florida, New Jersey and Louisiana. By 2035, some areas here and elsewhere could experience flooding on an yearly average of every two weeks, the report says.

The scientist group said it hopes to encourage cities and the federal government to adopt policies that will discourage building in flood-prone areas and enhance federal policies to support communities that will be forced to cope with rising sea levels.

Some experts cautioned that the report doesn’t account for flood control investments that could reduce the effects of rising sea levels.

“This is a tool to increase awareness about low areas along coastlines that are vulnerable to increasing flooding,” said UC Irvine civil engineering professor Brett Sanders, who works on the FloodRISE project that illustrates flooding from Orange County to Baja California.

But he noted there are infrastructure plans in place to mitigate some of the effects of sea water overrunning parts of Southern California’s shoreline cities.

“The fact is the developed world lives behind flood protection systems. What’s missing from a lot of these analyses is the role the infrastructure is going to play,” Sanders said. The new report, and others like it, help identify weaknesses and what areas need to be protected, he said.

Sanders and Dahl agree not all places can be protected. Some places will be abandoned, such as Holland Island in the Chesapeake Bay, that once had 360 residents but is now entirely underwater at high tide.

“We are not going to be able to protect every community along the coast,” Dahl said. “As individual communities, as regions, as a nation we need to be thinking about how we’re going to handle that. There are going to be places that are going to be unlivable, and yet those are going to be home to people. We need to think of strategies to help communities that are in that situation.”