The Union of Concerned Scientists is recommending steps to help reduce flood damage that has been increasing due to rising sea levels associated with climate change, with flood insurance rates set to go up Oct. 1.

The rates are slated to rise 25 percent yearly for the next four years, bringing them to an average ranging from about $533 to $10,723, depending on proximity to the highest-risk flood zones, said a panel of four experts in the field of flood risk and climate scientists. They made the recommendations Tuesday in a conference call with journalists.

Locally enforced ordinances should require property owners in areas at high risk for flooding to have flood insurance, rates should be based on “true risk,” and long-term, low-interest loans should be available to property owners to upgrade to protect homes and business. In addition, subsidies should be offered to low-income property owners so they can afford insurance through the National Flood Insurance Program.

“Sea level rise is increasing the risk of destructive events, and flood insurance rates have been set artificially low, so that they do not reflect true risks,” said Rachel Cleetus, senior climate economist at the Union of Concerned Scientists. “We have ignored this for too long, and taxpayers will be picking up the tab” unless reforms in the National Flood Insurance Program are enacted.

Erwann Michel-Kerjan, a University of Pennsylvania-Wharton School professor who studies the flood insurance program, said the nation has $35 trillion in property assets in vulnerable coastal areas.

“America has to realize it’s going to get worse,” he said, noting increases in frequency of severe storms in recent decades. Despite increasing risk in coastal areas, “we’re building too fast and without enough protection.”

He noted that 65 percent of all major disasters from 1960 to 2010 were flooding events.

Ben Strauss, vice president for climate impacts and director of the Program on Sea Level Rise at Climate Central, a nonprofit research group, said rising sea levels “elevate the launch pad” for major storm surges.

“Climate change has aggravated coastal flooding and will continue to do so at an accelerated rate,” he said. Sea levels have risen about 9 inches over the last 130 years, causing flooding to become “bigger and deeper.

“Events we call 100-year storms today would become 10-year events” in many coastal areas, he said.

Setting flood insurance rates more in line with risk, the group said, would not only ease the burden on taxpayers to shore up the program, it would also send a message to property owners about the true risk they face and encourage them to take steps, such as raising the elevation of their homes, that would both reduce their rates and protect their properties.

On the local and state level, “site-specific” measures should be taken to reduce risk of vulnerable coastal areas, including protecting natural flood buffers such as salt marshes and enacting building codes and policies that factor in sea level rise, panelists said. In the wake of major disasters such as Superstorm Sandy, local and state officials and policymakers should take opportunities to encourage “climate resilient rebuilding,” Cleetus said.

“It’s an opportunity to build better and differently going forward,” she said.

j.benson@theday.com