A conservation win: How urban green spaces helped save a city from historic floods

The Arkansas River, well above flood stage.

Last month, I had an opportunity to sit in on a forum with the Oklahoma Conservation Leadership Academy, and while there I learned something crucial.

The academy is organized by The Nature Conservancy, a large organization that manages lands across the United States and in dozens of countries for the purpose of returning lands to their natural state and restoring plant and animal species that once flourished in these places before man-made influences became predominant.

The academy’s class is filled with bright people from across Oklahoma who asked intelligent and at times technical questions on the topic of urban conservation, which was the topic of the day. Most of these questions were directed at two panelist speakers, Tulsa Mayor G.T. Bynum and Tulsa Parks Director Anna America.

Both had a lot to say, but something stuck out to me. Both also had detailed stories about how the city’s urban green spaces saved the city truckloads of money and no small amount of grief when the Arkansas River flooded its banks last May.

First, a quick recap: 2019 has been an extraordinarily wet year in northeastern Oklahoma, and never more so than in the spring. Heavy winter and spring rains in Kansas and northeastern Oklahoma saturated the ground and caused the Arkansas River drainage basin to swell. And then May hit.

Day after day of rain-laden squall lines moved across the state, bringing inches of precipitation every day and tornado warnings almost nightly. As the Arkansas River swelled, so did reservoirs built to mitigate flood risks. Chief among those is Lake Keystone, and it held back floodwaters as long as it could. Ultimately, even Keystone Dam had its limits and the U.S. Army Corps of Engineers was forced to increase flows from the lake to near-record levels downstream. At its worst, the dam was releasing more than 287,000 cubic feet of water per second, some four times or more than normal. Such huge releases hadn’t been seen in more than three decades, and that event led to damaging – and deadly – floods in Tulsa and beyond.

As you might expect, it flooded again. Massively. Among the hardest hit places in Tulsa were its parks, particularly the River Parks along the Arkansas River’s banks, and Mohawk Park on Tulsa’s north side. Millions of dollars in damage was recorded, the cleanup and repairs were (and still are) extensive, and at one time, much of the parks were under water.

Floodwaters cover a bike path at Tulsa River Parks.

This would seem to be a sad story for the city, and in some ways, it was. But in truth, the parks did what they were supposed to do. And that helped the city avoid much bigger losses.

America, the parks director, noted that Mohawk Park functioned as designed, absorbing floodwaters that might otherwise have covered neighborhoods, commercial properties and other places where people live, do business, go to church and shop. Mayor Bynum said that the River Parks, being mostly absent of urban development, took the brunt of the flooding inside the city limits while shielding people’s neighborhoods and businesses from harm.

Few people know how vulnerable cities are to flooding just by nature of urban development. Impermeable surfaces like streets and parking lots allow water to flow freely and quickly wherever gravity and the current please. Storm drains in these areas become overwhelmed, and creeks end up flooding, covering roads, causing flash floods and damaging buildings and critical infrastructure like roads, bridges and the like. That’s what makes urban flooding so damaging and dangerous.

But permeable surfaces, where grasses, trees and shrubs grow, absorb and blunt the onslaught of flooding. The city of Tulsa consciously chose to be careful about how much any of the banks of the Arkansas River would be developed. It’s prime real estate that would be perfect for housing subdivisions, luxury apartments and an array of businesses that would make money for the city. But the banks of the Arkansas have a built-in setback of green spaces and are mostly devoid of such development. Spaces like Mohawk Park – a vast tract of parkland that is among the largest of its kind in the country – can serve as a basin to contain flooding before it seeps into populated areas. Both parklands are used almost exclusively for recreation, with minimal use of paved surfaces and other forms of development. But flood mitigation is also part of their purpose.

I live close to the river, and I remember going down to the riverbanks to watch the awesome and frightening power of the river at such an extreme flood stage. The flow of the river reminded me of video footage of what a large tsunami looks like, except in this case, the tsunami was a quarter mile wide and never receded. It just kept going, faster than a man can run or most cyclists can ride, a relentless surge of watery power. It’s remarkable that more damage wasn’t done, especially when you consider what happened to cities and towns downstream of Tulsa that weren’t so fortunate.

The takeaway is that urban green spaces have value well beyond recreation or propping up property values. Green spaces absorb pollution and help scour the air. They provide habitat to permanent and migratory species of all sorts of animals. Wetlands in these spaces act as water filters. And as we saw in the Spring 2019 floods in Tulsa, these green spaces can save communities untold grief when rivers overflow their banks. As climate change advances and more weather extremes like last spring’s rains unfold, these urban green spaces only grow in importance.

Cleaner air, cleaner water, outdoor recreation and flood protection. I can’t imagine a better case could be made for boosting cities with expanded urban green spaces. Not all conservation looks the same, but in the end, conservation works for all of us.

River Parks and Tulsa’s Mohawk Park sustained major damage, but much of the city did not despite historic flooding of the Arkansas River.

Bob Doucette