Tuesday, November 19, 2013

Resilience in the Midwest: How does nature buffer high speed winds?

Those of us who live in the American Upper Midwest have it pretty good. 

Although we rarely take the time to acknowledge it, comparatively to other more vulnerable regions in the globe, we are living in an ideal location. We live in the breadbasket and grow more than enough food to feed ourselves. We’re well above sea level, so we will not be affected by anticipated sea level rise. And we have the world’s largest accessible freshwater body – the Great Lakes – in our back yard. But, we still have our own forms of adversity with which we need to contend - and the tornado that flattened homes outside of Peoria, Illinois, this weekend proves that even inland areas must adapt to the challenge of increasing storm intensity.
Chris Walker, Chicago Tribune, Nov. 18, 2013
According to the Chicago Climate Action Plan, it is likely our region will experience a variety of disturbances, including stronger, but infrequent, storms causing wind damage, widespread flooding and/or intermittent drought. In the wake of the recent tornado that wrecked communities across Illinois, let’s start with wind damage – how can we make our homes and infrastructure more resilient to damaging wind speeds? As an architect and biomimic, I believe the answer can be found by looking at how our neighbors, the native organisms that have occupied this land long before we have, solve the same challenge. We can start by asking nature!

How does nature...buffer high speed winds?

Every time there is a large storm event, we see absolute devastation of our human habitats. There are no metrics to measure the wildlife populations before and after strong storm events, such as tornadoes, but it's safe to say that native populations have adapted themselves to survive and thrive through a variety of disturbances. By looking to native organisms and patterns found in nature, we can begin to think of new and innovative ways of surviving high wind speeds in our built infrastructure. Some patterns we find in nature include:

Zbigniew Bzdak, Chicago Tribune, Nov. 18, 2013
Find Safe Shelter.
Many animals, such as birds and bees, can sense barometric pressure changes in the wind and instinctively move to the relative safety of their nests and colonies. Just as we go into our basements to escape a tornado, burrowing animals retreat to their homes below grade and leverage the safety of the ground to protect themselves from flying objects. 

All buildings in the Midwest should incorporate a safe place within the structure for building inhabitants to take evasive measures to protect themselves. These areas of refuge should have structure reinforced to provide protection from torsional wind stresses without collapse. Structural best practices that protect the safety of inhabitants must be written into the building codes and retrofit guidelines must be widely available.

Be Flexible. 
Native trees and prairie grasses cannot outrun a tornado, so they found a way to bend or adapt to the wind rather than fighting against it. Trees incorporate torsional flexibility into the structure of the trunk to lessen the need for the structure to bend (bend too far and it breaks). Grasses also have high torsional flexibility so that they can be "whipped around" by the wind, not blown over, which risks breakage. 

Architects and structural engineers could take cues from the trees to design flexible structures that are nimble and can move with the wind rather than fight against it. Or, do the opposite: emulate a stone and build a concrete bunker that deflects wind up and around it. 

Build Smart (and Temporary?) Structures
Shelter in nature is ephemeral - it is very often here one season and recycled the next. While the idea of building temporary (and readily recycled) homes and buildings will be hard to construct given our economic system, there are instances where building an ephemeral enclosure (for example, inflatable stadiums or pop-up shading for plazas) is more efficient, resilient, and economically viable than spending the resources to build permanent enclosure. 

When a structure must be as permanent as possible, consider the branching design of a tree that lessens breakage by tapering in size as you move up to adjust for the force of the wind caught by the leaves. Trees build up and protect the trunk on which they depend, but the smaller, taller branches are often a sacrificial layer that can be lost as long as the central core remains intact.

Of course, no strategy is 100% foolproof. Very often, components of even the most resilient systems will fail because the disturbance is just too great. And just because individual components fail, as long as there are backups and different options (functional redundancies and diversities), the system will emerge resilient to disturbance. Ecosystems, in fact, are stronger after disturbance and destruction because of all the new shelter, nutrients, and ecological niches that open up after the storm. Our communities and structures can be the same. 

By leveraging disturbance as an opportunity to rebuild in more resilient ways, we can create buildings and communities that truly emulate nature: by building on what works and recycling what didn't. 

To learn more about resilience as applied to human systems, check out our "BEND, Don't Break" Naturally Inspired Resilience Workshop at http://www.b-collaborative.com/resilience.html.

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