The Flash Floods of Fall 2010

 In late September of 2010, southern Minnesota experienced some of the worst flash flooding in recent history. With the ground already saturated from an unusually wet summer, torrential rain fell across the bottom quarter of the state. Rainfall amounts ranging from six to ten inches pounded the northern side of Interstate 90. Roads were barricaded and people evacuated from their homes as rivers rose to dangerous levels and inundated towns in numerous counties, disrupting the lives of thousands of people.

 The summer of 2010 brought more rain to southern Minnesota than is typical for the area. Some towns in the area received over 20 inches of rain over the course of the summer season. According to the Minnesota Department of Natural Resources Climatology Office, September of 2010 was one of the wettest noted in their records dating back to 1861 (Ellison et al.). Tropical Storm Georgette, which originated in the Eastern Pacific Ocean in mid-September, moved to the northeast towards Minnesota. Aided by a low-pressure system that emerged from Kansas, Georgette, along with Hurricane Karl, which moved northward from the Gulf of Mexico, brought moist, tropical air and instability to the area. This warm, wet air mass stalled over a line somewhat parallel to the Interstate 90 corridor (“Significant Flooding and Heavy Rain of September 22-23, 2010”).  The storm dumped copious amounts of rain before heading eastward towards Wisconsin.

 Heavy rain began to fall during the afternoon hours of Wednesday, September 22nd. This rain persisted into the evening hours of Thursday, September 24th, when it finally began to dissipate. The town of Amboy, Minnesota, received the highest 72-hour rainfall total with 10.68 inches (“Heavy Rainfall – September 22-23, 2010”). Zumbro Falls, Minnesota, came in as runner-up with 8.5 inches. Almost the entire southern portion of the state acquired over four inches of rain. Rivers and streams began to rise overnight on Wednesday and didn’t crest for several days thereafter.

 Around 2:00 AM on Friday, water reached the height of the dike in Zumbro Falls, spurring panic as residents attempted to get their belongings to higher ground (“5 Year Anniversary of the 2010 Flood”). The water rose at a rate of about sixteen inches per hour in the little town of less than 200 people, and homeowners had to leave everything behind to evacuate before their homes were completely submerged. Everything from the Post Office, city buildings, bars, hair salons, and the only gas station were totally inundated. The National Guard was called in to help with rescues, as all the main roadways leading out of town were impassable. At one point during the day on Friday, Lamar Johnson and his nephew Matt waded into the floodwaters to rescue four of their horses that were tied up and unable to escape the high water. After being untied, the horses were swept downstream, but eventually made it out of the water alive. Many of the city’s residents started over and rebuilt their homes in Zumbro Falls, but several properties remain empty to this day.

 Although the little town of Oronoco, Minnesota, did not receive quite as much rain as surrounding areas, the damage caused by floodwaters was extensive. Built in 1937, the Lake Shady Dam was located near the center of the city, and the County Road 18 bridge above it connects the north side of town with the south side. The dam failed and the entire north portion of the bridge was washed away on the night of the 23^rd. Lake Shady emptied into the Middle Fork of the Zumbro River, eroding the northern banks and flooding homes downstream. As a result of the damage, the Oronoco Dam Removal and Zumbro River Restoration Project was launched the following year and the dam was replaced by rock rapids (“BALMM to Meet in Oronoco for Zumbro River Project Overview and Tour”

Oronoco Bridge on September 24^th, 2010 (“2010 Flood Photo Gallery”)

 To the north of Oronoco, the small town of Pine Island suffered widespread flooding. The Middle Branch of the Zumbro River damaged over one hundred homes and twenty businesses. Many of the buildings affected had been built on a flood plain and managed to avoid this amount of damage in the past. Water covered the local baseball diamonds, soccer fields, and the school track. Students were not able to return to school for well over a week while the river retreated. Floodwater had entered the basement of the school, which was mainly used for storage and wrestling practice. The school’s bus garage was also overcome with water and all vehicles stored inside the garage were damaged. Total damage estimates to the school’s buildings and sports fields totaled over hundreds of thousands of dollars. Cleanup and recovery efforts were stifled by power outages, and Highway 52 north of Pine Island was closed in both directions, leading to lengthy detours in opposite directions.

Portions of cities to the west had to be evacuated as well. In Owatonna, Minnesota, about seventy homes and several businesses had to be evacuated when the Straight River breached its banks and came into the city. Despite being separated in two by floodwaters, the effects of the flood were not felt as severely as they might have been had the city not taken action to protect its wells after prior flooding in 2007 (“Owatonna Survives 2010 Flood, Raises Wells to Head Off Future Floods”). After the 2010 flooding, even more work was done to prevent damage by future flash floods. In Blue Earth County, the rising La Sueur River caused the sanitary system to fail, and residents of the town of St. Clair were asked to stop using water completely (“Flooding Eases in Parts of Minnesota and Wisconsin, But Some Communities Still Struggle”). Construction of an interchange where Interstate 35 and State Highway 14 intersect in Owatonna was flooded, resulting in the interstate being closed in both the northbound and southbound lanes for several days (Iowa Department of Transportation).

Governor Tim Pawlenty requested a major disaster declaration on October 1, which was then granted by President Obama on October 13^th for 21 Minnesota counties (Ellison et al.). This declaration provided relief funds from the Federal Emergency Management Agency. The damage caused to these counties exceeded 64 million dollars. Many communities have taken action to prevent similar flooding events from wreaking havoc in the future, including the reinforcement of levies, the elevation of wells, water diversions, and the planting of vegetation on flood plains. Both federal and state assistance was provided to victims, and many were able to restore or rebuild their homes in their neighborhoods.

With the recurrence of heavy precipitation events in recent years, memories of this devastating flood remain in the minds of the people for whom their entire lives changed in September of 2010. Tropical air masses carrying vast amounts of moisture will continue to bring large quantities of rain to southern Minnesota throughout the summer and early fall months. As close-knit communities, it is my hope that we will continue to improve our infrastructure and be better prepared for flash flooding in the future.

Works Cited

• “2010 Flood Photo Gallery.” City of Oronoco, Minnesota, www.oronoco.com/?SEC=09D8A12C-2240-4C51-A39C-82055917F924. Accessed 7 July 2019.
• “5 Year Anniversary of the 2010 Flood.” Zumbro Falls Minnesota, zumbrofallsmn.org/5-year-anniversary-of-the-2010-flood/. Accessed 6 July 2019.
• Christopher A. Ellison, Chris A. Sanocki, David L. Lorenz, Gregory B. Mitton, and Gregory A. Kruse. “Floods of September 2010 in Southern Minnesota.” U.S. Geological Survey Publications Warehouse, 10 Jan. 2013, pubs.usgs.gov/sir/2011/5045/.
• “Flooding Eases in Parts of Minnesota and Wisconsin, But Some Communities Still Struggle.” Fox News, 26 Mar. 2015, www.foxnews.com/us/flooding-eases-in-parts-of-minnesota-and-wisconsin-but-some-communities-still-struggle.
• “Heavy Rainfall – September 22-23, 2010.” Home – Minnesota DNR, www.dnr.state.mn.us/climate/journal/ff100924.html. Accessed 5 July 2019.
• “Significant Flooding and Heavy Rain of September 22-23, 2010.” National Weather Service, www.weather.gov/arx/sep2310#rainfall. Accessed 6 July 2019.