In 2014, the Twin Cities saw the wettest first half of the year since modern day record keeping began in 1871. Coupled with a long winter and late snowmelt, this extreme precipitation led to record water levels and more than $1 million worth of erosion damage along the six main streams in the Minnehaha Creek Watershed District (MCWD). For 83 consecutive days, Gray’s Bay Dam was unable to control water levels on Lake Minnetonka or Minnehaha Creek because of the high-water levels. On June 23, 2014, Lake Minnetonka reached a record elevation of 931.11 feet above sea level, more than seven inches higher than the previous record, and Minnehaha Creek achieved a record flow of 889 cubic feet per second.
The erosion caused by flooding in 2014 had devastating effects on Minnehaha Creek. The eroded soil added nutrients to the creek, destroyed critical wildlife habitat, and impacted public enjoyment of the creek. As part of MCWD’s assessment of the flood damage in the watershed, an application was submitted to the Federal Emergency Management Agency (FEMA) for funding assistance for creek repairs. MCWD was awarded approximately $250,000 from FEMA for repairs along Minnehaha Creek in Minneapolis, which are now underway.
Over the next several months, crews will repair 10 sites along Minnehaha Creek where sections of streambank and trails were eroded by the high water of 2014. Seven of the sites are located downstream of Minnehaha Falls. The other three sites are east and west of I-35W.
The Minnehaha Creek repairs are being coordinated with the current Minneapolis Park and Recreation Board’s master planning process for the Minnehaha Parkway Regional Trail and the Southwest Service Area, in addition to the City of Minneapolis’ Southwest Harriet Flood Study. The partners and a citizen advisory committee are exploring potential improvements to make the Minnehaha Creek park corridor more resilient to our changing climate and to ensure it meets public needs over the next 20 to 30 years. More information about the master planning process can be found on the Minneapolis Park and Recreation Board’s website.
Since the flood of 2014, we have partnered with the National Weather Service (NWS) to better anticipate rain events. The NWS’ customized weather forecasts have helped us proactively manage the Gray’s Bay Dam, preventing flooding in 2016, 2017, and 2018 in spite of record-setting precipitation.
The information provided by NWS allows MCWD to lower dam discharge before large rain events. This results in less water flowing into the creek, preventing flooding in downstream communities where the creek is also impacted by runoff from the landscape primarily through stormwater pipes. As soon as the creek is able to handle additional water, discharge is increased to prevent flooding on Lake Minnetonka. During dry periods, MCWD lowers dam discharge to prevent Lake Minnetonka’s water level from dropping too low, while maintaining water in the creek.
By continually improving our management of the Gray’s Bay Dam we aim to create the best possible outcomes for all communities around Lake Minnetonka and Minnehaha Creek.