The Twin Cities received record rainfall in 2014, but that was just the start of what experts predict will be more extreme weather for the metro area in the future.
As a result, two cities in Hennepin and Carver counties — one large, the other small — are taking a fresh look at ways to manage flooding, as part of a federally funded study.
The study, conducted by the Minnehaha Creek Watershed District and the cities of Minneapolis and Victoria, shows the various ways in which each city may be prepared or not for the kind of heavy rain that fell in the summer of 2014.
“This is an issue that is going to continue posing problems for communities,” said Telly Mamayek, spokeswoman for the watershed district.
In 2014, the wettest June in Minnesota history resulted in flooding statewide after a winter of heavy snow. In the metro area, Lake Minnetonka surged to all-time-high levels.
Across the watershed district, which covers 181 square miles of the west metro from Minneapolis’ Chain of Lakes to Minnetonka, 47 roads were flooded and shut down. Flooding caused $1.2 million in damage to six streams in the watershed district.
It’s considered part of a trend of more extreme weather events that are increasing across the country.
‘Not the norm anymore’
Even before the 2014 flooding, the watershed district along with Minneapolis and Victoria, Syntectic International, Antioch University New England and the University of Minnesota had wrapped up the two-year study funded by a $300,000 grant from the National Oceanic and Atmospheric Administration (NOAA).
The results and community guide (which can be found at minnehahacreek.org) were released last week.
The study simulated worst-case scenarios, showing that certain areas are more prone to flooding, such as dense, hard-surfaced parts of south Minneapolis, which also has undersized stormwater pipes.
In contrast, the small suburb of Victoria (pop. 8,500), which hasn’t yet fully developed, would likely only see flooding in some parks and recreational space, no matter how much rain fell.
“It helped us understand that our approach to planning as the city develops … has been an effective one,” said Cara Geheren, Victoria’s city engineer.
The study reaffirmed, she added, that the city needs to continue to preserve green space to hold extra water as development continues, with 100 to 150 new homes being built every year.
Unlike other cities, Geheren said, Victoria preserves wetlands and buffers as public property rather than easements to better protect the land and prevent flooding.
In Minneapolis, the study results reinforced the need for increasing the size of stormwater pipes and providing for more water storage when new projects come up, said Lisa Cerney, Minneapolis’ director of surface water and sewers.
Planning also should include worst-case rainfall levels. “We don’t typically look at off-the-charts events,” she said.
Over the years, the city’s flood management program has built more stormwater ponds, increased the size of stormwater pipes and redirected water in areas where flooding occurs often.
Now other cities may use the study results, Mamayek said, as a call to action, re-examining stormwater systems before major flooding recurs.
“Our weather is changing,” she said. “It’s not the norm anymore.”