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In the Great Lakes Region, we often feel that we are safe from the extreme weather that often ravages other parts of the country, like hurricanes out east or wildfires out west. And we often have a false sense of security or complacency. The greatest risk to our watershed and region has been, and continues to be, from flooding impacts caused by increasingly heavy and volatile events. Summer floods have become fairly common over the last century, happening every few years. The Milwaukee Journal Sentinel recently featured pictures from summer floods going back to 1928, affecting many of the same areas that were flooded in our recent storm event. Many of those historic storms exceeded what we call the 100-year storm event, which has a 1% probability of happening in any given year; flooding widespread areas after only 3-4 inches of rain in a day.

The rainfall on August 10th was much more significant, with up to 14 inches in some areas! Most of the cities in the lower half of our watershed received well over 8+ inches in only 4-6 hours, making this a 500-1,000 year event. This caused widespread flooding, several bridge/culvert failures, boat damage, sewer backups, and other property damage. Supersaturated soils have also led to a lot of streambank failure and trees falling into the river. We are still assessing much of the damage, and more will become apparent as the Milwaukee River continues to drop. It’s important to note that there is still significant debris in the rivers, so paddlers, fishermen, and other river users should take precaution.

The recent storm also led to the largest combined sewer overflow, of sewage and stormwater, since the Deep Tunnel went into operation in the early to mid-1990s, with over 5 billion gallons discharged into local rivers in the Greater Milwaukee Area. The Northwest Side Tunnel had so much pressure that sewage blew the top off of an access shaft 125 feet above, sending sewage over a portion of the County Grounds into the Menomonee River. It is important to note that there is no sewer system in the country that could have handled the amount of rain that we received. Our infrastructure was not designed to handle 1,000 year storms.

The good news from this storm event is that much of the work done by MMSD, local municipalities, and organizations over the last few decades– to increase stormwater management practices (rain barrels, rain gardens, bioswales, etc.), protect communities from flooding with levees and detention basins, protect and restore floodplains like the Milwaukee River Greenway, and remove dams and concrete channels—undoubtedly minimized the impact of storms. This was especially apparent in the Menomonee River Watershed, where hundreds of millions of dollars have been spent on flood protection and stormwater management efforts (check out this great article from former Board Member Eddee Daniel).

We can hope that this is a rare storm that we will not experience again, but warmer temperatures, increasing moisture in the atmosphere, and weakening wind currents from climate change created a perfect environment for this storm to stall out in our area and dump much more rain than was expected. These storms are hard to predict, and given recent trends, its likely that the magnitude and frequency of these severe weather events will only continue to increase. While we can be proud of all the work we have done in the region to buffer ourselves from the storm, that is little consolation to those still dealing with the aftermath or facing devastating loss of property and even life. We can take comfort in how our neighbors rallied to help those impacted by the storm, continue to provide support to our community members most impacted, and rededicate ourselves to rebuild in a way that will be more resilient to these types of storms in the future while better respecting our rivers.