The Chicago River ran backward during those crazy rain storms last weekend.

That’s right. It rained so hard, for so long, that the river turned tail and flowed into Lake Michigan.

Take a moment to think about that incredible fact.

More than a century ago, Chicago pulled off an engineering marvel, reversing the flow of the Chicago River so that it would stop dumping dangerous pollution in the lake (and in our drinking water). For hours on Saturday and Sunday, the river returned to its old course, bringing millions of gallons of sewage along with it.

OPINION

While it’s mind-blowing to contemplate the river changing course, this was hardly the first time. In fact, it is happening more and more frequently. But images of a flooded Riverwalk make the phenomenon harder to miss.

You can blame climate change. And infrastructure not designed or built to deal with the changes brought by our changing climate.

For decades, climate researchers have predicted increasingly violent rainstorms for our region. And in recent years, the predicted storms have arrived, dumping an incredible volume of rain in very short periods of time. The region’s stormwater control system, even with massive expansions, cannot keep up. Sewers fill and dump into the river.

As the Chicago River fills with all that stormwater, now commingled with whatever nasty stuff was in the sewer lines, it rises. Pressure builds throughout the system. The water has to go somewhere. Either into the streets or our basements or … the lake.

At such times, the Metropolitan Water Reclamation District and the Army Corps of Engineers open the navigation locks that separate the river from the lake. This prevents the structure from being overtopped and trashed by the sewage-laden flow, and it reduces the risk of flooding throughout the region. And so, this past weekend, billions of gallons of contaminated water flowed out into the lake.

Climate change discussions in the news tend to center around places like Antarctica. The focus tends to be on threats such as rising sea levels. But this is a story of climate change right here at home. The Riverwalk remained closed on Monday, still slick with muddy river sludge. Homeowners still were pumping water out of basements. The river remains perilously high.

What do we do about it?

First, we must address the root causes of climate change. At every level of government, we need to advocate for clean-energy and carbon-reduction policies. The City of Chicago has been a leader in this area for years, and has stepped up even more recently. And the State of Illinois passed the Future Energy Jobs Act, which should spark a renewable energy revolution here while slashing dangerous carbon emissions.

Alas, the Trump Administration has signaled it will eliminate the Clean Power Plan and withdraw from the international Paris Climate Accord. Those actions undercut the nation’s ability to head off the worst impacts of climate change. More weird weather will follow, with more river reversals.

Illinois’ entire Congressional delegation should have toured that Riverwalk mess last weekend and seen it for themselves the harbinger of danger it is. They should take action, regardless of party affiliation.

But we are already feeling the impact of climate change. We cannot pretend otherwise. At every level of government, we need to be advocating for more resiliency in the face of the impact. In every decision on infrastructure, we need to consider wild swings in water level or temperature. In every plan for development, we need to include the same considerations.

A stroll down the Riverwalk should make the urgency clear.

Henry Henderson is Midwest director for the Natural Resources Defense Council (NRDC) and served as the founding Commissioner of the Environment for the City of Chicago.

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