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Driftwood and other debris collects along the shoreline in Colchester, VT. Photo by Lake Champlain Basin Program

Lake Flooding - What's it Mean?

Lake Champlain reached new heights this spring, cresting at 103.2' on Friday, May 6th, shattering the previous record high level in May of 1869 (~102.1’).  High water has inundated homes, displaced people, closed roads, triggered mudslides, and washed sewage, litter and debris into the lake. As of this writing, tons of sediment are flowing into Lake Champlain as wind, waves and high water erode stream banks and lakeshore. The Lake Champlain Ferry from Essex to Charlotte is closed because the landing is under water.  The ferry at Crown Point is still running but Vermont roads to the ferry are closed on the south and are restricted to one lane from the north. Amtrak service from Montreal to Schenectady, NY has been interrupted. Traffic along the Route 2 causeway between Grand Isle and Colchester is reduced to one lane as work crews repair damage. Damages are expected to be in the millions. Both Governors Cuomo and Shumlin have declared states of emergency for portions of the lake shore.  The Canadian Forces have been called out to assist in flooded areas north of the border.

Are Lake levels managed?
Discharge from Lake Champlain is controlled by a bedrock sill near St. Jean Quebec. Fryers Dam, the first dam one encounters after leaving Lake Champlain, is downstream of this sill. Changes in the Chambly canal system in the early 1970’s increase lake levels up to 0.5’ during high water events. Tests by Parks Canada suggest that opening the Canal by-pass during high water could reduce lake levels.

Flooding has also been severe along the Richelieu River, downstream of Lake Champlain. In 1973 the International Joint Commission (IJC) debated whether to regulate the level of the Richelieu River and Lake Champlain to address shoreline flooding in Quebec. An IJC-appointed engineering board agreed that regulating water levels could reduce flood damage, but they disagreed on the environmental affects that would occur. The IJC continued their investigation until January of 1981. The Lake Champlain Committee, with the support of Dr. Stockton Barnett of PSUNY and other scientists compiled extensive evidence that artificially manipulating lake levels would have costly economic and environmental impacts. Ultimately the IJC opted against regulating water levels, and instead recommended improved flood forecasting and a variety of non-structural measures to lessen flood damage. In the current flooding we see damage both upstream and downstream of Lake Champlain’s grade control, suggesting lake level regulation will not alleviate the impacts of high water events.

Is this related to climate change?
While you can’t attribute any one single weather event to climate change, the high precipitation levels this winter and spring that led to flooding continue a pattern that has been seen over the last few decades. Total annual precipitation between 1976 and 2005 was approximately three inches greater on average than it had been in the preceding eight decades according to a report on climate change impacts from The Nature Conservancy. It certainly has not gotten drier since 2005. The TNC report concludes “The basin could receive as much as 10-15% (ca. 4-6 inches) more precipitation in an average year, with heavy storms events becoming more frequent.”

When will the Lake recede?
Though it appears that waters are now starting to recede, it is impossible to predict when lake levels will return to normal. Snow pack in the mountains accounts for the greater part of increased flows and, while much of that has melted, some snow pack remains in the High Peaks and at high elevations. Continued wet weather will delay a return to more typical lake levels. Discharge rates recorded at gauges on the Richelieu River in Quebec have set records too; water is flowing out as fast as it can. As spring progresses, plants will take up water from the ground as they grow and transpire. Warming temperatures will promote evaporation from the lake. Bottom line: it will be weeks before the lake returns to normal levels. The last two times the lake exceeded 100’ (2007 and 2008), it took over a month for it to drop three feet. The National Weather Service estimates it takes about twenty days for the lake to drop one foot when at flood stage.

Will the flooding cause higher nutrient and sediment loading?
Yes. We expect phosphorus loading for the year to be higher than normal due to the flooding. High waters, particularly in tributaries, increase erosion and transport of phosphorus pollution to Lake Champlain. Most phosphorus now entering the lake is attached to soil particles that move with high flows. Wind and wave action erode shorelines that are normally above the high water mark, resulting in extensive soil erosion, transport and lake deposition. Flooded tributaries running over farm fields that have not yet been planted are causing even more erosion. Sediment loading to the lake from this event could be unprecedented in recorded history. You can see examples of sediment load from shoreline erosion and river discharges in the slide show. (Aerial photos courtesy of the Lake Champlain Basin Program.)

Will there be more algae blooms because of the flooding?
It’s not clear how or if the high lake levels will affect blooms. Although phosphorus brought into the lake with high water flows is known to promote algae blooms, the exact trigger for blooms is unknown. The form and timing of phosphorus inputs may be as important as the quantity. Phosphorus takes many different forms and it is possible that the sediment-bound form will be less available to feed blooms.

Has more sewage entered the lake?
Yes. In addition to erosion, pollution has entered the lake from wastewater treatment facility overflows caused by high waters. Between April 26 and May 5 there were eight reported facility overflows in Vermont: Enosburg Falls, Vergennes, South Burlington, Williston, Fair Haven, and three in Essex Junction. Additional overflows were reported in a DEC press release from Johnson, St. Albans and Woodstock (outside the Champlain Basin). The New York DEC website does not provide up-to-date information on sewer overflows. While wastewater overflows contribute to phosphorus loading, the biggest problem they present is the introduction of potential pathogens to waterways.

One thing people can do to reduce the stress on waste water treatment systems is to conserve water. Wasted water from homes and businesses increases the quantities going to treatment plants and thus increases the chances of a combined sewer overflow.

Are there health effects from flooding?
Flooding presents other potential human health effects besides those from untreated wastewater discharges. Pathogens also enter the water when flooding causes septic tank failures, and when pet waste in the vicinity of rivers and shorelines is washed away. The extra turbidity caused by flooding also impairs public drinking water supplies. The communities of Willsboro and Essex have been under ‘boil-water’ orders as a result. Flooded homes and camps will harbor potential mold problems once the waters recede. All porous materials such as sheetrock should be replaced after flooding to prevent mold from growing.

Will the lake stay colder, longer?
While intuitively one would expect the extra water to mean the lake is colder, since more water should take longer to warm up, the lake temperature at this time is within its normal range. The added rainwater actually warms the lake compared to snowmelt. Still, the most important variable in the lake’s temperature is the amount of sunlight and heat the lake receives. So how fast the lake warms up depends on how much sunny weather we see in the coming weeks.

How will plant life be affected?
High water levels may delay the growth of aquatic vegetation. Aquatic plants need light to penetrate to the bottom for them to germinate and grow through the water column. High waters refract the light before it hits the bottom. Turbid sediment laden waters refract even more light. Plants that rely upon early growth to outcompete neighbors may find themselves at a disadvantage this year. One example is variable-leafed milfoil, an invasive exotic found just last year in Missisquoi Bay.

Future implications
The increased intensity of storms in the Champlain Valley and rising lake levels, as experienced and predicted, mean that we need to reconsider how we adapt and respond to a changing environment. At a very basic level, we need to re-evaluate sizing criteria for stormwater and wastewater management structures. Currently, the size of many facilities, including road culverts and retention ponds, is based upon increasingly outdated storm event data. Clearly storms are getting bigger – and more frequent. We will need larger stormwater structures. Likewise, floodplain management along the lakeshore, and flood hazard mitigation plans will need to be adjusted to higher lake levels – suggesting the need for elevated roadways and buildings, increased shoreline setbacks and buffers, and environmentally sound shoreline stabilization practices.

Yuck! What can you do?
Once the water goes down, the litter that has been washed into the lake and onto shore will still be a hazard and an eyesore. Clean-up efforts this year will also have to cope with an abundance of dead alewives from a recent die-off caused by cold winter waters. Flooding has impeded efforts to remove alewives from Port Henry beaches; high waters, wind and waves are expected to move dead fish into other bay and shoreline areas. Many Paddlers’ Trail sites, boat launches, and fishing access areas that are currently underwater will also need attention. Check in with municipal and state managers and LCC to see what is needed. Consider coordinating a clean-up effort at your favorite local spot.

People whose homes and businesses have been damaged by flood waters should check for sheens and odors from gasoline, oil and other substances that may have leaked from fuel-oil tanks, furnaces and equipment before pumping out water. Contact the spill hotline (800-457-7362 in New York and 800-641-5005 in Vermont) for further guidance. Flooded septic systems should be inspected to ensure they function properly. Property owners looking to repair eroded and damaged shoreline should contact the state environmental permit offices before undertaking any work.

The high lake levels and extensive flooding that ensued reinforce the need for each of us to do our part to protect our waterways – conserve water, pick up after pets, plant buffer strips of native vegetation, contain stormwater through retention ponds, rain gardens, rain barrels, and plantings. Many small and ongoing efforts make a big difference.

May 10, 2011