August 23, 2013
Early on August 10th a catastrophic event occurred: during that stormy night, after nearly six inches of rainfall, a beaver dam on Aton Forest could not hold back the increasing water pressure of its twenty-acre impoundment. One person living nearby heard what she thought was the sound of a nearby falling tree during the storm, but turned out to be the sound of a large tear opening in the dam. The breach of this large upper dam led to the breach of a smaller lower dam and the force of more than a million gallons of water swelled behind and then over the stream crossing at South Sandisfield Road. This section of road, not built to allow the passage of this amount of water nor act like a dam, was washed away. By morning a channel was swept clean to a rocky basement and a gap about twelve-feet wide and six-feet deep was exposed. When this catastrophe was discovered by a neighbor, she tried to contact the Town but could only leave a telephone message. She feared that someone might drive into this abyss, as nearly happened when she heard a group of six motorcycles come to a sudden stop at the now missing road. She called the State Police and quickly the Town put up signs and a barricade. By Wednesday afternoon the road was repaired with new concrete and stone retaining walls.
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| Beaver pond at regular level, 2012 |
Also lost were thousands of animals that lived in this beaver pond. Small minnows were found stranded and dead in the newly exposed mud the next day. Imagine being a fishor turtle or beaver suddenly sucked down this drain, carried along with logs and stones, crashing through the streamside forest, finally to settle, dead or alive in Benedict Pond. The full impact of this and sediment plume in Benedict Pond is not yet known (previous washouts of this road have also resulted in gravel deposits in Benedict). What remains of the old beaver pond is knee-deep mud, much of it covered with once floating pond-lilies and watershield.
The loss of this pond makes us realize what diversity beaver have brought to our environment. Beaver were by and large extirpated from Connecticut in the 19th century, due to trapping and loss of habitat. As farmlands were abandoned, the forests returned, so did the beaver. In the past, this particular wetland had been drained and used for agriculture; then, without human clearing or beaver damming, the site was a forested swamp. Finally, the impoundment made by one of our more industrious native creatures created habitat for dozens and dozens of new species, ones dependent upon open water, sunlight, marsh, and large dead trees.
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| Recently drained beaver pond |
Beaver have maintained this pond for over forty years. Past storms have seen over six inches of water top this dam without ill effect. Though there have been a few breaches over the years, but the beaver always managed to repair and maintain their dams and lodges. The road as well has washed out a few times, most recently in 2010. It was at this time that the beaver suddenly disappeared from this pond. They may have been trapped out or all mysteriously died or left. Then in 2012 the beaver returned, though they were not seen as often as before. It is likely this hiatus allowed the dam to rot and leak, eventually a weak spot developed that resulted in the breach on Saturday.
The culvert installed at South Sandisfield Road can carry normal flows, but it strains under flows from the extraordinary precipitation events we have been experiencing lately. The town has installed a grate on the upstream side of the four-foot diameter culvert to keep the beaver and floating deadwood from clogging it. Regular maintenance of this is required, otherwise the clogged grate and the road bed become another dam. This stream crossing is similar to others in town, many of which impedes the movement of wildlife or necessitates hazardous road crossings.
Recently the Norfolk Conservation Commission and Aton Forest co-sponsored two public events to highlight roadside ecology and safe wildlife corridors. The follow up has been discussions regarding what do as a town to improve our roads and roadsides for wildlife. A bridge or wide arched culvert would have been an ideal solution to improving the South Sandisfield Road site, but in this emergency the Town did not have materials or time to do this. The time seems ripe to develop a strategic plan for replacing inadequate culverts and improving these crossings for both people and wildlife. We have been shown that our unnatural impact on natural processes can be prevented or mitigated.
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| Road damage |
In the mean time, the beaver have already begun to rebuild their dam at Aton Forest, though it is likely to be at a lower level. In the past this pond was lower; marsh and swamp covered much of the site. Old dead tussocks and long-drowned tree stumps – still showing beaver cuts – have now been exposed. New open marsh and forested swamp may develop on the margins until the pond reaches its maximum size once again. Such changes are only natural.
