Warmup has cities rethinking water ways

  • Article by: BILL MCAULIFFE , Star Tribune
  • Updated: May 20, 2012 - 11:44 PM

An increase in storm water spurs communities to evaluate how they use, value or move it.

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Normal annual rainfall for the Twin Cities is 4.25 inches greater than it was in the 1980s. At left is Minnehaha Creek, shown after several days of steady rain.

Photo: David Joles, Star Tribune

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Communities across the metro area and beyond are putting their heads together to figure out how to handle the increases in storm water that a warmer climate is expected to bring.

Public works officials, hydrologists, water quality monitors and others have embarked on a study to find where vulnerabilities exist and devise new solutions in the face of increasing -- and increasingly intense -- rainfall that has been both documented and projected by climate analysts.

The work is funded in part by $300,000 from the National Oceanic and Atmospheric Administration and coordinated by the Minnehaha Creek Watershed District. It will continue into the summer of 2013.

The effort promises to cast climate change in local and practical terms, outlining effects on sewer systems, property tax bills, urban design and even quality-of-life attitudes. Do citizens want bigger, more expensive sewer pipes, porous pavements, surface ponds, more wetlands and rain gardens, or none or all of the above?

In Minneapolis, for example, leaders and citizens may have to determine what kind of effects from excess rainfall they're willing to accept in the city's iconic lakes and creeks, said Lois Eberhart, the city's water resources administrator. They might also have to review a long-standing preference for dry residential landscapes.

"There might have to be changes in behavior, such as accepting more standing water in our streets and yards," she said.

The study project, called WET, for Weather-Extreme Trends, also will encourage joint solutions among cities, since rainfall and floods don't respect municipal boundaries. Most of the participants are from the 27 cities and two townships in the Minnehaha Creek Watershed District.

The project will focus on storm water issues facing Minneapolis and Victoria. Both are in the Minnehaha Creek watershed but have dramatically different storm water concerns. Minneapolis has a crowded urban infrastructure and a sewer system with some 140-year-old parts, and it even has cleared away housing to create storm water retention ponds.

Victoria has plenty of open space, lakes and ponds and has never experienced flooding. But community development director Holly Kreft said the city will have to figure out ways to keep expanding wetlands from threatening existing property and also will probably have to explore using more on-site water retention and design strategies that could reduce storm water buildup and flow.

By focusing on the two different cities, the project, ideally, would provide storm water management options for a wide range of other communities, said Latham Stack, CEO of Syntectic International, an Oregon-based climate consulting firm that is a funding partner in the project.

Researchers will "downscale" widespread climate trends to the local level and provide the information to participants and the public in a series of workshops. But they'll also review trends that are already in place.

"Our infrastructure, utilities, our health systems are designed to suit how climate treated us in the past," University of Minnesota Extension climatologist Mark Seeley told nearly 70 participants at a kickoff session Tuesday. "Now climate is treating us differently than it has in the past."

Seeley noted that annual precipitation in parts of south central and southeast Minnesota has increased up to 15 percent in recent years; normal annual rainfall for the Twin Cities is 4.25 inches greater than it was in the 1980s. Statewide, Minnesota's average rainfall topped 34 inches in 2011 for the first time in 121 years of record-keeping. The Upper Midwest saw a 31 percent increase in "intense" rainfalls -- the statistical 1 percent events -- from 1958 to 2007, over previous decades, according to the National Climactic Data Center. An increase in intense rainfall is regarded as one of the signature trends of a warming climate, due to warm air's ability to hold more water.

The goal, Stack said, is to "help communities prepare for what seems to be the fairly certain risk that's coming."

Bill McAuliffe • 612-673-7646

  • 15 percent

    more precipitation in parts of southern Minnesota

    31 percent

    increase in "intense" rainfalls

    4.25 inches

    more normal annual rainfall in Twin Cities than in 1980s

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