Flooding on State Street in Brewer in 2019. Credit: Linda Coan O'Kresik / BDN

Maine businesses face financial risk from floods that will increase with more frequent and intense storms, with 1 in 7 buildings in commercial centers already vulnerable to a major storm, a study released Monday found.

Bangor has the highest projected damages of the top 20 Maine cities and towns with the most buildings now and in 30 years, according to data from First Street Foundation, a New York City nonprofit that studies flood risk, and Arup, a global commercial engineering firm. Brewer has the highest percentage of commercial properties at risk during that period. 

The heavier storms could put more pressure on already stretched town budgets for flood mitigation. While Maine is not as much at risk as states severely affected by hurricanes, including Louisiana and Florida, about 14 percent of more than 8,000 commercial properties in the 20 major commerce centers already are vulnerable to disabling floods and damage. That share will rise to 18 percent by 2051, the study said.

Businesses in cities near the coast or major rivers are most at risk now, but severe storms are expected to increase flooding even in inland towns that have not yet experienced much overflow from streams and rivers.

It is due to warming seas and atmospheric temperatures creating stronger storms in the southern U.S. that are dropping more rain and moving further north, including inland in Maine. The study, which used federal and other data to determine buildings at risk, covers all 50 states and estimates the risk of floods to retail, office and multi-family buildings and the potential damage cost this year and in 30 years.

Heavier storms already are causing backups in some of Brewer’s stormwater systems and catch basins, resulting in portions of roads being flooded, said Linda Johns, the city planner. She also noted it would cost a lot up front to resize all lines and that Brewer is taking a gradual approach.

“As money and opportunities arise, we will constantly be upgrading the system,” she said.

 Barry Spofford of Bangor Public Works moves leaves to open drainage and relieve flooding on Broadway at Broadway Park in Bangor on Oct. 23, 2019. Many roads are flooded from heavy rainfall and dropped leaves. Credit: Linda Coan O’Kresik / BDN

The city has already stabilized much of the Penobscot River shoreline with riprap rocks and a retaining wall, “so it would take quite a bit of a rise for those properties to be flooded,” she said.

Commercial structures within 1 1/2 blocks of the river face the biggest risk of floods from heavy rains or river overflow, Jeremy Porter, First Street’s head of research, said. The concentration of commercial properties there puts them at high risk relative to properties in other Maine cities.

For example, only 45 of Portland’s 1,030 commercial properties are at risk of damage now, but that is predicted to more than double in 2051, when commercial properties along Route 1 experience increased risk, Porter said.

About 18 percent of Bangor’s commercial properties are at risk now, notably in a stretch of the downtown, making the potential damage from a major or sustained flood event to all of them this year at almost $22 million. Bangor is the most expensive of the cities by potential damage cost.

“The first-floor square footage is a big factor in the amount of damage,” Porter said.

Other Maine cities with high flood risks to commercial properties include Lewiston, Augusta, Auburn, Waterville and Biddeford, all of which have major rivers running through their downtowns.

Nationally, almost 730,000 commercial properties face an annualized risk of flood damage today topping $13.5 billion, a number expected to rise 25 percent in 30 years, First Street said. U.S. businesses stand to lose about 3.1 million days of operation next year, which is expected to rise 29 percent by 2051.

“Flooding that leads to lost days of operation and lengthy repair times for local businesses could have significant broader national and even global economic consequences,” Matthew Eby, First Street’s executive director, said.