One Year Later: July 22 Flood Effects Can Still Be Felt
Meteorologists explain the perfect storm that led to massive new control efforts.
One year ago today, July 22, 2010, at just after 5 p.m., the skies blackened, huge swirling clouds rolled over the north metro Milwaukee area, and torrential rain began to pour down.
The water came so fast that even areas of high ground were swamped. That water simply could not run off nearly as fast as it was coming down.
The flood that followed will remain a powerful memory for the thousands whose homes and businesses were swamped and for those who were caught out in it, trapped in cars for hours on inundated freeways and city streets.
The flood also wrought permanent changes in Milwaukee and its suburbs. Soon afterward, the Milwaukee Metropolitan Sewerage District, under fire from the whole north half of its service area, announced a 10-year, $150 million plan to repair and upgrade sewer systems including leaky private laterals.
That plan calls for expenditures not just by MMSD but also by every affected municipality within the district. Some of those funds can go to private citizens willing pay part of the cost of repairs on their properties, said Kevin Shafer, executive director of MMSD.
Among other major projects already being undertaken by MMSD is the construction of a mammoth pumping station astride the Wauwatosa-Milwaukee boundary at 6000 W. State St. on the Menomonee River. That project can be heard and felt as pile drivers pound daily at old concrete foundations and bedrock.
As described by MMSD officials, the huge pumps will suck stormwater out of the main combined sewer line at that location and literally force the water into the river.
At the State Street location, they said, a main feeder comes down from the historic watershed of Schoonmaker Creek, falling rapidly in elevation down the bluffs, but then encounters and crosses the broad floodplain at a lower angle.
In major floods, the river there rises so fast and with so powerful a current it pushes water back up the existing sewer line. The pumps are designed to be so potent they will overcome the force of a river in flood.
Before last year's deluge, back-to-back floods in 1997 and 1998 and again in 2008 and 2009 had already set Milwaukee area residents on edge, and had also produced their own versions of the future of flood control, including the detention basins on the County Grounds and the remaking of Hart Park, related projects in Wauwatosa that also cost between $120 and $150 million.
But it was the July 22 storm that caused the entire community to explode with indignation that such things could keep happening.
So what exactly happened that day, weather-wise?
According to meteorologist Chris Kuhlman of the National Weather Service in Sullivan, several clear characteristics of the main weather front contributed to what would have made for a memorable rainstorm in any case, but some less predictable ones made it enormous.
"To begin with, at that point in the season, you just have a ton of moisture available in the atmosphere," Kuhlman said. "So much so that as conditions for thunderstorms develop, you can expect some very strong ones with high hourly rain rates and hail, and of course the possibility of tornadoes.
"But while hourly rain rates of 3 to 4 inches or more are not unusual, it is unusual for them to last an hour. Most summer thunderstorms blow through and are gone in 15 minutes.
"This one stopped and just sat on top of Milwaukee for an hour. We had the maximum rain rates we usually see at the height of a brief thunderstorm, but continuing for an hour, with as much as 7 inches of rain falling in that time.
"That is seldom seen, but it isn't unprecedented. A few years ago, we had a system that produced 13 inches of rain over a couple of hours in Dane and Dodge counties."
What Kuhlman describes can be seen on a radar animation included with the NWS report on the storm. A massive storm line moves rapidly across the state from northwest to southeast, but when it arrives at Milwaukee, it pauses for an hour, the heaviest, widest area of precipitation in the whole system settling like a suffocating sponge on the north side of the metro area.
As it happens, a student meteorologist working at Sullivan that day was given the task of dissecting the cause for the pause, but his findings did not get put into the NWS report. However, meteorologist Jake Wimberley was able to locate it.
"What he found," Wimberley said, "is that what is called a 'strong low-level jet' formed and intersected the path of the storm, and that affected its motion – slowed it down.
"A low-level jet is a line of strong wind that moves from south to north at about a mile above the ground, which is right where a storm front is getting its motion. It's warm and also moisture-laden, so it can not only slow a storm, it can strengthen it.
"North Milwaukee just got lucky that day – or very unlucky, I should say."
It's a very uncertain thing, Wimberley said, to say where and when two such events will form and then meet. Low-level jets are entirely unrelated to the Jet Stream. They are localized and short-lived, moving through an area in one to three hours.
So, the odds say it is unlikely that what happened last summer will happen again in the same place any time soon.
And yet, well it might – or something like it.
According to some of the world's most noted climatologists at the University of Wisconsin-Madison, in a recent report called the Wisconsin Initiative on Climate Change Impacts, the weather in our area has been getting wetter and more severe for quite some time and will continue to do so at an increasing rate.
"From 1950 to 2006, Wisconsin as a whole has become wetter, with an (average) increase in annual precipitation of 3.1 inches. This observed increase in annual precipitation has primarily occurred in southern and western Wisconsin," the scientists found.
That 3.1 increase is the average across the state. For Milwaukee County, the increase in annual precipitation has amounted 6 to 7 inches over those 56 years.
The report also says that the number of 2-inch or greater rain events per year has also increased over that time and is forecast to continue, with up to three more large rain events per year expected by mid-century, a 25 percent increase over the 12 we now experience on average.
"Our state is likely to see changes more pronounced than what we have seen so far," the report says. And the odds say Milwaukee could see changes more pronounced than much of the rest of the state.