Traffic on Hwy 169 in New Hope June 26th
Flash flooding June 26th in Twin Cities
CHASKA, Minn. -- It may be hard to imagine what kind of event would bring together landscape architects, city planners and climatologists under one roof. But hundreds have gathered at the Minnesota Landscape Arboretum west of the Twin Cities for the Clean Water and Climate Adaptation Summit.
They're not there to debate global warming or whether it's a manmade phenomenon. They're talking about ways to adapt to life in a warmer state, and what that means for land use policies and for future infrastructure needs.
Warmer air aloft, for instance, allows clouds to carry more moisture. And, as the theory goes, people living in a warmer Minnesota would see more more intense downpours when it does rain.
"The climate is a big predictor of what our environment is like, in terms of the size of storm events and what we need to do with the water that falls on the ground from those," Julie Westerlund of the Minnehaha Creek Watershed District told KARE Thursday.
The district, which is one of the summit's sponsors, manages creeks, lakes, wetlands, shorelines and erosion control in the southwest Twin Cities metropolitan area. If the state does become generally warmer, it will become harder to manage storm runoff with traditional drains and pipelines.
"Traditionally we've built these drains and storm sewers to convey that water as quickly as possible, but that allows it to pick up pollutants and move downstream causing problems for our lakes, rivers, streams and wetlands."
And the summer of 2010 has provided ample reminders, in the form of flash floods in the Twin Cities, that the storm drainage system can be overwhelmed already in big storms.
Westerlund said land developers and individual homeowners can take pressure off the municipal infrastructure by paying closer attention to what she calls the natural infrastructure.
"Our parks and open spaces and wildlife corridors, our trails, the things that connect our natural systems together is also a form of infrastructure that we have to invest in," she said, "And take care of and maintain because it's critical for keeping our water and our habitat healthy."
The arboretum itself has plenty of examples of new methods of retaining rain water on site. There are permeable paving systems on display, as well as "green" roofs covered in plants and rain gardens in the buffer strips in the parking lots.
The green zones between lots are dug in so they're lower than the pavement, and they're filled with native plants with deep root structures that allow the soil to absorb more water. Curbs have been removed so that the rain water can run from the parking lot into garden.
"This is is a way for us to treat the water that's coming off of this parking lot and get it soaking into the ground like it naturally would in a natural setting," Westerlund explained.
"And over a short period of time, a couple of days, the water will soak into the ground and the rain garden will be dry again, ready for that next rain event."
That's in sharp contrast to the typical suburban parking area, with grass islands sit above pavement level and drain into the parking lot quickly. Hard curbs then corral the water into storm grates, and it heads into the sewer system.
That water is supposed to be treated before entering rivers and streams, but in a large rain event the system is designed to let storm water bypasses the treatment plants.
(Copyright 2010 by KARE. All Rights Reserved.)