Perhaps because my town is a river town, I find myself regularly thinking in terms of moving waters. I’ve written previous posts on visiting European cities settled on rivers, and about the impact of rivers and canals in shaping our national economic geography.

Avulsion is what geologists call the sudden transformation in the route a river follows over a landscape. These shifts aren’t dress rehearsals: When the river moves to a new channel that provides a steeper decline toward the sea, the move is complete and rapid. The Mississippi River has avulsed about every thousand years, following its current channel since about 900 A.D.

Whether we believe the last few generations represent an anomaly in U.S. land use or not, avulsion strikes me as a suited metaphor for what’s underway today. In the case of rivers, the move to a new channel results typically because sediment has collected around a delta to an extent that the slope of the river channel is not as steep as alternative, nearby channels. In the case of the form of our cities, metro areas and small towns, factors inciting change include: 

  • Growing agreement that uses in many cases do not pay for themselves
  • Fiscal austerity caused by high expectations for public infrastructure and services, matched with little will to contribute to its finance
  • Unfunded liability in the costs of carbon release and climate change
  • In part thanks to austerity, shifting cultural preferences toward residential and commercial places accessible without cars.

As it turns out, as dialogue here and in a growing number of other forums indicates, land use is one thread that ties these factors to each other. We see new links between neighborhoods and land use and public health outcomes. A study released in the last week presents ideas about the connection between zoning, education and social mobility.

Zoning decisions frequently revolve around precedent, and it’s not often easy at the time to perceive how individual cases can move local policy. In addition to decisions on individual cases, we can make communities stronger and more prepared for the future by writing the zoning code with a different future foremost in mind. We may not agree whether Euclidian or form-based codes are superior, but we can agree that zoning powers are a key tool for communities in planning for fundamental shifts ahead. 

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