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Ridge Schuyler's talk on excessive sedimentation before Charlottesville City Council on 3/03/08
Thank you, Mr. Mayor and Members of Council.
This is my third installment in a series, discussing the work of the Nature Conservancy in this community.
As you may recall, I left off last week with how the Conservancy, using a scientific process, identified the Rivanna watershed as one of the finest freshwater river systems in the Southeastern United States.
Tonight, I wanted to address the overarching threats facing the health of this watershed.
Before I do that, however, I wanted to say that I know — by personal experience — that there are at least two other residents, other than me, who watch this station. I’ve had two people approach me to say they saw me on TV, but before my head could get too big, they told me that I talk too fast. So rather than discussing the two major threats to the Rivanna, I thought I would discuss them one at time — one tonight and one the next time we meet.
Working with over three dozen experts over a couple of years, we determined that one of the great threats to our watershed is excessive sedimentation; sediment is literally choking the life out of our rivers and streams.
To understand the cause of that excessive sedimentation, you need to travel back in time. Long, long ago, the Rivanna watershed, like the rest of the Piedmont, was blanketed in forest. Our rivers and streams coursed through those forests.
As the rain fell, it would hit the tops of the trees and slow down, then it would hit the redbuds and dogwoods in the understory, and finally the leaf litter on the forest floor, where it would slowly infiltrate into the ground, recharging the groundwater and slowly moving toward the lowest points, which were the stream valleys.
When the watershed was converted from a forested environment to a non-forested environment, there were no longer trees to slow the energy of the water. There were no longer trees to hold the soil. As a result, much of our topsoil ran down toward the stream valleys, creating a floodplain that was vulnerable to erosion.
As we have hardened the landscape, through rooftops and roads, we have accelerated the flow of water. Now, streams are handling volumes and velocities of water that they were not “designed” to handle and all that energy — seeking a place to go — acts as a scouring force against the streambanks and streambeds. To give you an idea of the erosive force of that water, USDA conducted a study in the Piedmont of North Carolina, to estimate the amount of soil deposited from an eroding streambank into a stream over the course of one year. They determined that the one hundred foot length of stream they studied, over the course of one year, deposited 500 TONS of sediment.
All of that sediment ends up in our streams, slowly suffocating the life out them. That’s one threat. Next time, I’ll talk about the other overarching threat, and then I’ll end with a series of cheerier notes about strategies we are employing to address those threats.
Our Committment to Sustainable Waters
Learn about the Conservancy's commitment to conserving freshwater ecosystems for people and for nature.
Review the Conservancy's work to address fresh water issues in key sectors:
Explore freshwater conservation sites around the Conservancy.
Nature picture credits (top to bottom, left to right): Photo © Mary Porter (Landscape view of the south fork of the Rivanna River.); Photo © Allan Gates (Piedmont program director, Ridge Schuyler with his son, Charlie); Photo © TNC (Diane Frisbee working in Meadow Creek).
