Water Storage Flooding and Property Damages

Photo credit: Water Resources Center MNSU – Mankato, 1965 Minnesota River Flood

This area of the Midwest is no stranger to major flooding. There have been many floods of the Minnesota River from past to present day: 1965, 1993, 2002, 2004, 2010, and many more in the past 10 years. (https://libguides.mnhs.org/disasterrelief/floods). These floods are becoming more frequent which is putting a strain on infrastructure across the basin. Many bridges and roads become overtopped, washed out or flooded. There is significant property loss along the rivers’ edge and structural damages to homes and buildings.

Many stormwater systems in Minnesota were put into the ground as early as a century ago. Many are already at the end of their lives. Some cities that have completed upgrades (including rain gardens and tree trenches) are already facing the strain again. (To learn more about stormwater upgrades and BMPs on the MPCA website: https://www.pca.state.mn.us/water/stormwater) According to the American Society of Civil Engineers, Minnesota’s Infrastructure Report Card, both drinking and waste-water are in need of improvement (https://www.infrastructurereportcard.org/state-item/minnesota/). One way to combat this problem is to try to disconnect the rain from the river and create water storage on the landscape.

Property loss from erosion is another significant impact that flooding can have on our towns and farm fields. Soil erosion from water and wind on farm fields is another sediment source to the Minnesota River. A fact sheet from BWSR, produced in 2002, highlights the issue and various solutions: https://www.maswcd.org/Youth_Education/StudyGuides/soil_erosion_BWSR.pdf. However, over recent years, research has shown the source of sediment has shifted from predominantly field to near-channel sources. Learn more from research conducted by Dr. Karen Gran, Dr. Patrick Belmont and others working with the Collaborative for Sediment Source Reduction.

Sediment Sources for the Greater Blue Earth River Basin

Photo credit: Dr. Karen Gran – Hydrology, geomorphology, and the need for water storage: Water Storage Forum presentation on April 4^th, 2019

According to their research, bluff erosion has since surpassed field erosion. Rivers are adapting to this increasing flow volume by increasing in width as well. River widening is well documented in many river systems. The MPCA has documented that even one 20 minute storm can increase the sediment in the Minnesota River: https://www.pca.state.mn.us/featured/protecting-farmland-protecting-water-quality.

One example shown is from the Le Sueur River between 1939 and 2010.

Photo credit: Science Briefing Booklet: Le Sueur River Watershed, p 19: http://lesueurriver.org/wp-content/uploads/booklet_5_30_draft_removed.pdf

While channel change is a normal process as rivers adjust to changing conditions, researchers are documenting much more rapid channel widening in recent decades across tributaries and the Minnesota River mainstem.

More Resources:

News

http://www.startribune.com/muddy-minnesota-swamped-by-water/449125243/ https://www.mprnews.org/story/2017/10/03/increased-water-flow-straining-the-muddy-minnesota-river

Historic Floods

https://www.dnr.state.mn.us/climate/summaries_and_publications/extreme_rainfall_events.html

http://www.gendisasters.com/mainlist/minnesota/Floods

https://www.mankatofreepress.com/news/local_news/glimpse-of-the-past-many-zoo-animals-died-in-flood/article_d9c55c83-a08a-508b-b90d-b734986f5fef.html

https://www.mankatofreepress.com/news/part-flood-brought-devastation-heroics/article_d676cc58-cdd4-11e4-80a3-134a6dc31da8.html

https://libguides.mnhs.org/disasterrelief/floods

https://www.dnr.state.mn.us/climate/journal/1965_floods.html

Flood Mitigation and success stories

https://www.leg.state.mn.us/docs/2018/other/180969.pdf