Water levels in the Great Lakes have reached record or near-record levels this summer. While all that water has been good for the shipping industry, it has caused significant damage along the shoreline and left many residents wondering whether high water levels are the new normal.

Just six years ago the shipping industry was complaining about record low water levels. In the late 1990s, Great Lakes water levels began dropping — quickly. The decreased levels happened because warm lake temperatures led to high evaporation rates, said Drew Gronewold, a University of Michigan environmental science professor and former hydrologist at NOAA’s Great Lakes Environmental Research Laboratory.

That downward turn lasted 15 years. But in 2014, lake levels started to rise — and fast.

That rise has continued into this summer: Lakes Erie and Ontario have reached their highest levels ever recorded, and Lake Superior has set new monthly records.

In the past few years, the city of Duluth, in Minnesota, has learned the hard way just how powerful all that water in Lake Superior can be. In October 2017, 60 mph winds sent huge waves crashing into the shore, shredding seawalls, destroying roads and eroding the lakeshore. Six months later, another big storm caused yet more damage. And then last October, a third storm hit — the biggest one yet.

“It’s been hard for the city to catch its breath, frankly,” said Mike LeBeau, Duluth’s construction project supervisor.

The city’s popular Lakewalk pedestrian and biking path, just blocks from the heart of downtown, was especially hard-hit after being hammered repeatedly by the storms. The boardwalk itself withstood some structural damage, but it didn’t stop there. “It undermined the buried electrical wiring for the lights, tipped over some lights, flipped the boardwalk sections up near the hotels, even,” LeBeau said. And it eroded away acres of land, upending large boulders that had been put in place to protect the Lakewalk and tossing them easily out into the water.

Lake Superior’s gales are legendary. But the high water levels, LeBeau said, have made these recent storms even more destructive. The city has estimated damage from the three storms, in less than two years’ time, at nearly $30 million. It’s a similar story elsewhere around the Great Lakes, where beaches have disappeared, docks are submerged, and lakeshore is eroding.

But for the shipping industry the higher water levels have been a boon. That’s because deeper water allows ships to carry more cargo.

“A great example of this is a vessel like the Edwin H. Gott, which can carry an additional 267 tons of iron ore per extra inch of draft,” said Jayson Hron, spokesperson for the Duluth Seaway Port Authority. “That’s something like $26,000 worth of extra ore per inch, so if you multiply that by 2 or 3 inches of water level, and then multiply it by more than 30 trips over the course of a shipping season, it adds up to some significant benefits,” he said.

The recent spike in water levels has been driven largely by an increase in rain and snowfall, over the Great Lakes themselves, and on the surrounding land that runs off into them, said Lauren Fry, an engineer with the U.S. Army Corps of Engineers’ Detroit district.

“Over the past six years, we’ve had above-average water supply more often than not,” she said, “so it’s been an ongoing building of high water levels, culminating this season.”

Rapid fluctuation between high and low water may be the new normal for the Great Lakes, said the University of Michigan’s Gronewold. “I do think it is prudent for any planning decisions to take a look at the historical highs and historical lows and recognize that at some point in the next couple of decades it’s extremely likely that we’ll continue to oscillate between those two,” Gronewold said.

That puts people who live and work along the lakes in a tough spot. Some landowners have moved their homes farther away from the eroding shore. That’s not an option for the city of Duluth as it rebuilds its Lakewalk trail, said Mike LeBeau. There’s no place to move it. So instead the city designed a more climate resilient Lakewalk. Crews hauled in giant boulders, weighing 3 to 4 tons apiece, for the foundation. They sunk an 18-inch wide concrete wall 12 feet deep in places, and built a thicker paved trail.

“There are places where the solution is retreat,” LeBeau said. “And there was nowhere to retreat here. So, we have to do the best that we can come up with and afford and hope that it lasts a long, long time.”