Colin Beckman

September 29, 2011

As residents of South Royalton, Vermont can attest, the White River still runs opaque with sediment a month after Tropical Storm Irene. Gray when the sky is clear. Brown when it rains. And the water quality is in part a result of how the riverbed has changed. The banks have eroded to shallow slopes and have lost much of their vegetative cover, swathes of sediment still lie over riverside fields, and the old steel truss bridge in the north part of town is missing part of its foundation, rendering it impassible.

Periodic flooding can be necessary to maintaining the health of river ecosystems. So says Frank Magilligan, who studies watershed response to environmental change at Dartmouth College. But Irene was no ordinary flood, and according to Professor Magilligan, an event like Irene happens only once a millennium or half-millennium. Water levels set historic records at eight stream gages: the Saxtons River, Little River, Ayers Brook, Williams River, Walloomsac River, Otter Creek, Dog River, and Mad River all flowed with more volume than ever recorded, according to U.S. Geological Survey stream gages.

The impact on fish has also been serious. The flood swept away food sources in the form of aquatic invertebrates and eggs, and sediment particles can clog gill membranes, making it harder for fish to breathe, and could facilitate the entry of bacteria into the bloodstream. Fishery experts say that native brook trout, which require clear water to spawn, could take as long as five years to recover. Rainbow trout, which spawn in the spring, may be less affected. The fall fly-fishing season is over, according to fly-fishing guide Ron Rhodes. Two of seven fish hatcheries in the state sustained significant losses. The White River National Fish Hatchery, which breeds Atlantic Salmon as a reintroduction effort, lost roughly half its salmon stock, and the Roxbury Fish Hatchery lost more than 70,000 of its 90,000 brook and rainbow trout.

The impact on landscape may be most profound. Professor Magilligan said that stream channels that were altered considerably -- wiping out roads, agricultural land, and bridge foundations -- could take up to ten years to return to pre-Irene dimensions.

If the flooding itself was not enough, the ongoing human response by work crews may also have serious unintended consequences. To cope with destroyed river crossings, threatened homes, and choked channels, many towns have used earthmovers and backhoes to dredge, channelize, and armor streambeds. In at least one Vermont town, the response may have gone too far. Fifty anglers and residents packed the Middlebury Select Board Meeting on September 13th, where people complained that response work in the riverbed was overblown and had damaged fish habitat. People voiced concerns that the reshaping of the Middlebury River could worsen flooding in future years. In an unprecedented emergency like this, mistakes in response work are understandable, but they do not help.

To put Irene in perspective, Hurricane Irene is the tenth weather-related disaster to hit the United States in 2011 where damages amounted to over 1 billion dollars -- the first time there have been ten such disasters since 1980. The disasters include five tornado events (including the Joplin tornado), two other flooding disasters in the upper Midwest and lower Midwest, a wildfire-heat wave combination in the western states, and the blizzard that buried the eastern half of the United States on Groundhog Day. Perhaps, ultimately, the most significant question is whether extreme weather emergencies like Irene have become the new norm, for Vermont and for the country.

Sources

Krista Langlois, Rivers Roll Toward Recovery, Valley News, Sep. 10, 2011, http://www.vnews.com/irene/20110910a.html.

U.S. Geological Survey, River Levels Set Records in 10 States, Released Aug. 31, 2011,

http://www.usgs.gov/newsroom/article.asp?ID=2916.

Lawrence Pyne, Outdoors: Response to Flood Worsens Impact on Rivers, Fish, Burlington Free Press, Sep. 18, 2011, http://www.burlingtonfreepress.com/article/20110918/COLUMNISTS01/110918003/Outdoors-Response-flood-worsens-impact-rivers-fish.

Middlebury Board of Selectmen, Minutes, September 13, 2011 (available at http://www.middlebury.govoffice.com/index.asp?Type=B_BASIC&SEC={9A24CA8E-AB7C-40A3-AD72-09A892EC85B4}).

NOAA Satellite and Information Service, Billion Dollar U.S. Weather/Climate Disasters, http://www.ncdc.noaa.gov/oa/reports/billionz.html (last visited Sep. 29, 2011).