infrastructure - EasyBlog

Minnesota's Changing Climate

Thursday, 10 October 2019

Flooding in a Southwestern MN Ag. Field

Minnesota is one of the states most impacted by climate change. Official precipitation and temperature data has been collected in Minnesota from 1895 through today, showing some striking statistics about our changing climate:

13% increase in the size of the heaviest annual rainfall.
Since 2000, rains of more than 6" are four times more frequent than the previous 30 years prior.
65% increase in the number of 3" rains.
Average temperatures in Minnesota have warmed by 3˚F since 1895.
Overall, Minnesota's climate is warmer and wetter.

These changes are impacting Minnesota's wildlife, forests, water quality, infrastructure, and outdoor recreation (especially winter sports). Below are some links to MN DNR infographic GIFs that shows the change to our 30-year average winter temperature and 30-year average yearly precipitation:

Change in 30-Year Temperature Average

Change in 30-Year Precipitation Average

Sinkhole in Duluth Following a 7"+ Rainfall

As you can see, Minnesota's winters are warming dramatically, with the 9˚ contour moving north by as much as 150 miles. Similarly, the 26" contour for precipitation has migrated roughly 100 miles to the Northwest.

We witnessed the impact of elevated precipitation in 2012 when the most damaging flood in Duluth's recorded history began when heavy rains fell over already saturated ground on June 19^thand 20th. At the Duluth National Weather Service (NWS) the rainfall total for those two days was 7.24 inches. A NWS volunteer observer in Two Harbors recorded the storm's largest value of 10.45 inches in 24 hours.

The aftermath included millions of dollars of insurance losses to repair roads, bridges, homes and businesses. Many homes foundations were damaged extensively and the houses were razed. One state highway (MN 23) was closed for 3 years while it was repaired. The City of Duluth has had to adapt their stormwater infrastructure to withstand events that 30 years ago were considered 500-year events, but now happen regularly. In June 2018, just southeast of Duluth, the area received up to 10" of rain and once again damaged Highway 23.

Here in Anoka County, we've witnessed a similar story in 2019, with all of the monitored lakes, rivers, and streams in the County reaching historic water level averages for the year. This increase in precipitation only solidifies the need for comprehensive watershed management to make sure that our infrastructure and waterways can handle the increased erosion and flow produced by this additional rain.

Interested in learning more? Check out MN Pollution Control Agency's Climate Change in Minnesota webpage or the MN Department of Natural Resources Climate Data

3274 Hits

Tags:

Climate Agriculture infrastructure Water

What in the World is a Rain Garden?

Friday, 04 January 2019

Barbara

Water Quality Rain Gardens

Rain gardens have popped up like weeds throughout the Twin Cities over the last decade to mitigate stormwater pollution in lakes, rivers, and streams. Despite their prevalence, the function and purpose of these little curbside gardens remain a mystery for many folks.

Downspout rain garden

Rain Garden Benefits:

Cities are very dirty. When it rains, stormwater picks up everything from feces to the motor oil that your neighbors spilled on their driveway. Many older neighborhoods were developed without stormwater treatment, so pollutant-laden runoff from roads, houses, driveways, and parking lots makes its way directly into rivers, lakes, and streams. Stormwater doesn't end up in a wastewater treatment facility or septic system like the water that drains out of your bathtub.

When functioning correctly, rain gardens protect natural water bodies from polluted stormwater, reduce flooding, recharge groundwater, and provide habitat for local pollinators. Rain gardens can be built to any size or shape to fit into the landscape of old neighborhoods where space is limited. They are relatively inexpensive to design and construct and can be maintained by homeowners who agree to take on that responsibility.

To treat all of the water in a neighborhood, it may be necessary to pepper the neighborhood with many small rain gardens, or put in a few larger gardens depending on available space and landowner interest. A well-functioning rain garden will dry out within 48 hours after a rain event, which keeps the plants healthy and prevents creation of mosquito habitat.

Rain Garden Types:

There are two basic types of rain gardens, those built to treat water exiting a gutter downspout, and those built to treat road runoff. The first type, called a downspout rain garden, can easily be installed by a homeowner. This type of rain garden can prevent flooding around downspouts and allow rainwater to recharge groundwater.

The second type is called a curb-cut rain garden because an opening is cut into a roadside curb to allow water to flow off the road into the rain garden. When the rain garden has filled to the brim, the stormwater flowing along the curb will pass by and flow into the storm drain as it did prior to installing the rain garden. Curb-cut rain gardens are much larger, more complex, and should be designed and installed by professionals. Curb-cut rain gardens are more cost-effective because they only treat water that would definitely have made it into the stormwater system. For this reason, they are the only type of rain garden for which Anoka Conservation District currently provides assistance.

While traditional curb-cut rain gardens are built with the expectation that water will drain through the soil, some rain gardens are built in conditions that don't allow for water to drain quickly enough. In this scenario, an underdrain would be installed below the rain garden. The underdrain re-directs excess water from the rain garden into the street's stormwater drain to prevent the rain garden from flooding.

Thriving curb-cut rain garden that easily drains within 48 hours

Failed rain garden that does not drain between storms

Rain Garden Pitfalls:

Unfortunately, some rain gardens don't work as intended. Due to poor planning, faulty design, shoddy construction, or a lack of maintenance, some rain gardens fail to properly fill or drain. When done right, rain gardens are an effective and aesthetically pleasing method for combating pollution in lakes and streams, replenishing groundwater, and creating pollinator habitat. However, not every property or every homeowner is ideally suited to have a rain garden. While professionals at ACD can assess whether or not a property is a viable candidate, only the homeowner can decide if they are up to the task of maintaining a rain garden.

6363 Hits

Tags:

stormwater rain gardens home infrastructure