If you haven’t noticed, I’ve been narrowing the focus of my blog posts to an interlocking set of topics: transportation, land use, energy, environment and infrastructure. Each of these themes is inextricably bound with the other. We’ll never make sense of any one of them until we understand how each relates to the others.
A case in point comes from an article published in the June 2008 edition of the American Water Works Association Journal written by Ridge Schuyler, Piedmont program director for the Nature Conservancy. In “Reducing the Effects of North America’s Hardened Landscapes,” he traces a fascinating flow of causality.
When Virginia was wilderness, the forest acted as a natural buffer for rainwater. The forest canopy, low-lying vegetation and leaf litter slowed the flow of rainwater into rivers and streams. Much of the rainwater was absorbed into the water table, and the run-off was gentle when it hit the tributaries. Over the decades, the clearing of farmland and then the construction of roofs, roads, parking lots and other impermeable surfaces has destroyed much of this buffer. There is more run-off these days, and it hits waterways with greater velocity.
Schuyler cites a U.S. Department of Agriculture study that estimated the amount of soil deposited from an eroding stream bank in North Carolina into the stream: Researchers found that over the course of one year, a mere 100 feet of stream bank deposited 500 tons of soil into the waterway.
Virginia’s geology and hydrology are very similar to North Carolina’s. The spread of hardened landscapes explains the tremendous erosion of our stream beds and the consequent increase in sedimentation. Charlottesville, Schuyler points out, relies upon a reservoir that is slowly filling in from sedimentation. “Over the next 50 years,” he writes, “it is expected that roughly half the reservoir’s storage capacity will be lost to dirt.”
Even though Virginia is blessed with abundant rainwater, increasing populations will demand more clean drinking water. That may be hard to supply if our reservoirs are silting in.
What are the options? Dredging our reservoirs? (Is that even possible?) Building new reservoirs? (Talk to the City of Newport News to see how many decades that can take.) Traditional engineering solutions will cost large amounts of money — money that could be spent on other pressing priorities.
Schuyler discusses a short-term solution: “rainwater harvesting.” The idea is to capture rainwater in barrels or cisterns as it runs off roofs and release it slowly, using it for such indoor things as toilet water or outdoor applications such as watering the garden.
That’s good as far as it goes. But long-term, the answer is adopting more compact human settlement patterns (and creating appropriate storm water management systems), reforesting more acreage and re-instituting nature’s storm water buffers. Until we make the systemic changes needed to restore the health of our streams, we’re just drawing down our natural capital. Ultimate destination: Haiti.
(Photo credit: American Water Works Association Journal.)
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