After days and inches of rain the warnings have popped up all over the Boston metropolitan area. Small stream flooding, major urban drainage problems, more rain to come. In our built environments drainage is an issue that can't be ignored. And this applies whether we live in rain-soaked regions like the northeast United States or in desert-dry localities like the southwest. Pavement leads to floods.
Why is this? In part we can attribute it to the physical properties of water. A sheet of water is an infinite series of interconnected molecules. Water not only "finds its way." It does so as part of a mass flow of molecules. Water collects in sheets on pavement and other non-absorptive surfaces. Once it overflows whatever bounds exist it moves with force.
The more paved surfaces the more force. The more water gathers the more it finds a way to move to another level. "Controlling" water is almost impossible. And the more water you want to control the greater the cost and the harder it is to accomplish. Are there any ways in the built environment to ameliorate the detrimental effects of water?
So-called green roofs are one attempt to "soften" the paved landscape. I've discussed in other posts how they're a not-always-reliable solution. The planning, infrastructure, and maintenance that is needed for green roofs is not an easy thing to accomplish. And the biology of green roofs is still poorly understood. How do we plan for the inevitable change in plant species that occurs on green roofs?
Maybe one way to ameliorate urban flooding is to promote more green spaces in our cities. This can be accomplished through something as simple as individual gardens. In our crowded old neighborhood in the heart of Boston, simple gardens show us the contrast between paved and unpaved when it comes to urban drainage. Asphalt, brick, and concrete surfaces collect water, which moves uncontrollably to places we may not want it. The varied contours and rich variety of a growing garden absorb, store, and ameliorate water. They change water into a resource instead of a nuisance.