It’s possible — or at least worth considering — that we have been doing urban planning backwards.
Consider that planners have traditionally focused first on the urban environment they wished to create. Only then do they begin to design the stormwater control infrastructure needed to manage the flow of runoff away from that environment.
The problem with this approach is simple: No one can out-design Mother Nature.
Even the best-designed stormwater management systems are no match for water that is bound and determined to find the downhill path of least resistance. And that can lead, among other things, to sewer overflows, overstressed wastewater treatment plants and stream degradation.
As we look to the future, we can address these problems by rethinking our approach to stormwater management. More simply, we can put water first.
Think about how different our urban areas might look if, instead of developing them using a traditional street grid system, we began by allowing stormwater runoff to follow more natural pathways. These streams and drainage areas could then be incorporated into our urban landscape, with planners designing streets and structures around them.
Changing the Urban Landscape
Many of the water quality and runoff issues cities face today are the result of the impervious surfaces created through urban development. Part of our challenge, moving forward, is to mitigate these changes whenever possible.
Putting more pipes in the ground to move stormwater downstream as quickly as possible is rarely the smartest or most cost-effective answer. Urban environments in the future will likely rely more on stormwater best management practices, also called green stormwater infrastructure, that remove some of these surfaces, capture water where it is and give it a natural place to go.
Urban planning should therefore include more open spaces and drainage areas where rainwater can collect and drain naturally. These environments will also benefit from more multipurpose spaces that, for example, serve as a trail system one day and a detention basin for stormwater the next.
This is a concept that runs counter to the expectations of most city dwellers, who normally associate standing water with flooding. Part of our job as planners is to educate and, in some cases, re-educate those who have long believed it’s our job to eliminate standing water. In the urban environment of the future, we all will have to become more OK with seeing such water ebb and flow as part of the natural ecosystem.
There is, of course, no one-size-fits-all solution to stormwater runoff. Combined and storm sewers will continue to play important roles in urban infrastructure, and many will need to be rehabilitated or replaced as they age.
But where it makes sense to re-establish natural drainage channels, planners should consider doing so. Even in highly developed, highly urbanized areas, we should seek sustainable, green infrastructure solutions whenever practical. These could include everything from subsurface stormwater detention storage and permeable pavers to street trees and plants that absorb stormwater.
Residents can be expected to take an increasingly important role in understanding the causes of runoff and controlling their contributions to it. Our firm recently worked with the City of Grandview, Missouri, after severe, repeated flooding impacted certain parts of the community.
A mapping-based tool we developed now allows the city engineer to map the community’s natural drainage paths. Citizens who report repeated flooding can now overlay a map of their property with that of the natural drainage paths. By considering how water runs through and drains from a given land area, it’s possible to evaluate all the sources that affect water quality and quantity.
In other words, communities like Grandview are taking a watershed management approach to managing their water resources. Urban planners would be wise to follow their lead.