Geologists Say Rivers Will Change Course With Flooding
09/07/11 5:50PM By Jane Lindholm
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(Host) Nearly every river in southern Vermont adjusted course or experienced severe erosion in the flooding caused by Tropical Storm Irene.
VPR's Jane Lindholm explains that much of the destruction was caused by Vermont's geology, coupled with a couple hundred years of human intervention.
(Lindholm) To understand why Vermont's rivers flooded the way they did last week means stepping back to when our modern landscape was formed.
(Becker) The major river courses-valley courses, let's put it that way, were carved long ago, even before the glaciers.
(Lindholm) State Geologist Larry Becker says the glaciers deposited new materials on our valley floors. Rivers carved these glacial deposits into riverbeds and formed floodplains to spill into during major rainstorms.
During the industrial revolution, we harnessed the power of the rivers for energy and commerce, populated the surrounding floodplains with homes and businesses, and built roads alongside riverbeds to move people and products from one place to another. And we straightened and diverted rivers when their paths were too meandering for our liking.
Mike Kline is the River Management Director for the state of Vermont.
(Kline) "Many activities that went on for over a couple hundred years involved moving the river slowly but surely out of the way of our human activities in these valleys."
(Lindholm) But rivers are oblivious to human desires, and, Kline says, when Tropical Storm Irene hit, rivers reverted to their natural patterns.
(Kline) "Well now here what we've seen is, in 48 hours, many of these stream channels have gone all the way through the evolutionary process, completely eroding both banks, recreating this huge depositional feature that will one day turn into a new floodplain for these systems. And it just happened overnight."
(Lindholm) Overnight and over roads, bridges, and into people's homes. In some towns, residents who say they couldn't even see the local river before Irene, now find it flows through their backyards.
What does this mean for landowners?
(Donegan) Well, from an insurance point of view it's an interesting question because there's not much your insurance is going to do to help you recover from that."
(Lindholm) Susan Donegan is Deputy Secretary of BISHCA, the state department that regulates insurance. Donegan says figuring out property rights is going to be a tricky legal issue.
(Donegan) "Those are going to be questions that are going to have to be legally answered through a look at what's called riparian rights. Lawyers are going to have to probably get into the picture. And perhaps even towns are going to have to have an understanding of what happens when these types of streams and properties move."
(Lindholm) River Management Director Mike Kline says past flooding records show that in some cases property lines moved with the river boundaries. But in cases where the river took a whole new course, the property lines sometimes stay in place. But, Kline says, it's unclear what will happen in this case.
(Kline) This would be a really good time to get folks in the legal profession to look at this issue carefully because this question needs to be answered very succinctly for people."
(Lindholm) Many questions remain. Should we rebuild homes and businesses-not to mention the state office complex in Waterbury-that lie, or now lie, in floodplains? Should the rivers be manipulated so that they don't flow where our state highways are being rebuilt? Kline says those discussions are already underway in the Agency of Natural Resources and the Agency of Transportation. But we will have to get better at sharing our landscape with what we all now understand are very dynamic rivers.
For VPR news, I'm Jane Lindholm in Colchester.