Over the last many days an extraordinary volume of water has encountered the structural and human density of the fourth largest city in the United States. The Greater Houston metropolitan region has a population of 6.22 million and a population density of 630.3 persons per square mile.
During the month of May over twenty inches of rain has fallen across much of East Texas. In the Houston area on Monday night over ten inches fell in a period of only six hours. Rain continued to fall on Tuesday and Wednesday.
This quantity of rain in a comparatively contained space over such a short period of time would profoundly challenge the equilibrium of most natural environments. The built environment on which humans depend is seldom as resilient. Pack millions of humans into a dense urban environment and whatever our individual resilience, there will be a range of interdependencies that increase everyone’s risk. We can be surprised.
Extraordinary external volume can seldom be entirely avoided. This is true for potential threats beyond precipitation. Denial of service attacks, mass suicide bombings, and uncontrolled oil spills are other examples. Unusual volume, concentrated in time and/or repeating time after time, disrupts and destroys.
Urban population density is a choice, but for the last two centuries it has also been a persistent — and accelerating — choice. There are real benefits. Density is likely to increase in the years ahead.
Given the loss of life, destruction of property, and the extent of human misery caused, I am sure some will be appalled at my lack of apparent empathy, but the floods in Texas and Oklahoma have — among other things — reminded me of some junior high physics problems.
If density and volume are each highly elastic and mostly beyond our control, we seem to be left with mass as the input with which we might still hope to influence outcomes.
In seventh grade I was taught that mass is the property of a body which determines the strength of its mutual gravitational attraction to other bodies and its resistance to being accelerated by a force, such as a volume of water. Generally we protect populations and the built environment by increasing the size and weight of dams, walls, and other “resistance” structures that retain, divert, disperse or otherwise reduce the force of any threatening volume.
At least here on earth, we don’t always give much attention to gravity because there’s not much we can do about it.
Mrs. Holman taught me that gravity is the weakest of the four fundamental interactions of nature, the others being electromagnetic, strong nuclear and weak nuclear. Yet despite its comparative weakness, gravity is absolutely necessary to the universe as we know it. Both gravitation and electromagnetism act over infinite distance to mediate diverse actions.
Both as a matter of physics and as a metaphor for broader application, gravity determines mass through interactions and relationships among multiple bodies. In addition to adding size and weight to strengthen the built environment, what ought we do in regard to interactions and relationships to reduce the risk of volume and density converging?
In the midst of the flooding in Oklahoma and Texas, as in the recent earthquake in Nepal, as in the aftermath of Sandy and Katrina, and in the ongoing recovery from the Triple Disaster in Japan, there has been a tendency to emphasize “weighty” engineering solutions. Good. Great.
But interactions and relationships are also an important part of the formula.