How does climate change aggravate street flooding?

Tuesday's storm was something else — or was it?

Cleanup continues in the Twin Cities following Tuesday's severe thunderstorms, and forecasts show there could be more severe weather in parts of the state Thursday. The rain came down hard enough to put some stormwater sewers at capacity.

"Yep, this is what happens in summer in Minnesota," said assistant state climatologist Pete Boulay of the storms.

The rain was intense and caused some minor street flooding. But it was also a welcome relief for gardens and lawns across the Twin Cities.

"This was one of those million-dollar rainfalls. Because the ground was so dry, any rainfall that fell, the ground eagerly soaked it right up," said Boulay.

Though there were certainly exceptions — many streets flooded because stormwater sewers couldn't handle so much rain in such a short period of time.

Boulay says people's reaction to the rain could have something to do with where they were when the storms moved through. Like one of his own relatives.

"She called me on the phone and said, 'this is the worst rain I've ever been in,' and it was because she was in her car at the moment that the torrential downpour was happening."

One of the worst spots in the Twin Cities was the underpass at the intersection of Highway 36 and Fairview Avenue in Roseville. Images of cars stuck in several feet of water made headlines.

The intersection dried out, but nearly a day later evidence of the three to four inches of rain that dumped on the city was still there.

Water was flowing fast out of a stormwater pond just west of Snelling Avenue and County Road C2. Roseville Public Works Director Marc Culver says water coming off of more than 100 homes, plus streets and parking lots that are part of a large commercial and industrial area all send water to this pond.

"The biggest issue, especially in the first-ring suburbs and core of Minneapolis and St. Paul is that our stormwater systems just weren't developed for these events," said Culver.

Many cities have been evaluating how climate change could aggravate the problem in the future. New stormwater infrastructure guidance known as Atlas 14 recommends much bigger pipes than Roseville has, but Culver says it's not feasible to change everything.

"We have literally hundreds of miles of pipe under the ground and to meet those design standards we have to increase those pipe sizes, and that's probably not going to happen," he said.

It'd be incredibly expensive. Plus, there sometimes just isn't room to make pipes bigger in dense urban areas. So instead, cities are finding ways to direct stormwater into the ground such as concrete chambers under park land or constructing basins next to sites that are being redeveloped.

Climate scientists have noted that warming temperatures put more moisture in the atmosphere, leading to heavier rains.

"So far what we've been seeing is fewer days contributing to more precipitation," said assistant state climatologist Kenny Blumenfeld.

Blumenfeld says that means on the days it does rain, we'll get more of it on average. Blumenfeld says this week's storms didn't break any records, but some of the forecasters were impressed by one figure.

"It did occur in an environment where there was an unusually high amount of precipitable water," he said.

That's the amount of water in the atmosphere that could come down as rain, and that fits a trend scientists are seeing in recent decades. If storm conditions had been different during Tuesday's storms, they could have produced a lot more localized flooding.

And now that the ground is wet and less able to soak up moisture, more rain in the forecast could cause even more problems for cities in the days to come.