Although water levels have finally dropped below flood stage on Lake Champlain this week, a Flood Warning remains in effect and facilities and businesses near low-lying shorelines continue to be heavily impacted by high waters.

The Ausable Point Campground remains closed, as is the campground access road. Many Valcour Island campsites and access points are still flooded and due to the high waters, floating docks have not been installed and bathrooms are closed at Peru Dock, Port Douglas, Willsboro Bay and other boat launches. Vermont closed all access to Lake Champlain except for Tabor Point, malletts Bay, Lamoille River, Converse Bay, and Larabee’s Point. Quebec closed all access and shut down boating to prevent further shoreline erosion due to wakes.

The Lake Champlain Basin Program has posts a summary of the Lake Champlain flooding impacts on-line [pdf], but here are some of the details:

During the height of flooding, the area of Lake Champlain increased by 15%; the volume increased by about 12.7% (867 billion gallons). The increased volume will mean that lake temperatures will remain cooler as summer warming is slowed. With wetlands at maximum, the potential for more destructive flooding is higher.

Hundreds of homes were flooded in New York, Vermont, and Quebec as the lake reached the highest level ever recorded. Winds brought some very destructive waves to shore in flooded areas which carried trees and other debris. Much of the damage will not be able to be assessed until the waters finally recede.

Water supply facilities at Rouse’s Point was nearly flooded, but continued to function well. Port Henry, Essex, and Willsboro were forced to issue boil water notices that affected about 3,500 people. Most wastewater treatment facilities were forced to operate at or above capacity (including at Montpelier on the Winooski and Plattsburgh); two plants in the Missisiquoi overflowed sewage (small communities, mostly storm water).

The Lamoille, Winnooski, and Ausable Rivers experienced 100 year floods. The phosphorus load from these and many other tributaries was very high. In the last week of April alone, for example, the Winooski River phosphorous load was equal to about half the typical annual amount. Tributaries with the highest phosphorus load included the Little Otter, Lewis, Bouquet, La Platte, Winooski, Ausable, Lamoille, Great Chazy, Mill, Jewett, Stevens, Missisquoi, Rock and Pike. In addition to the nutrient load, lake tributaries also discharged an enormous amount of sediments and shoreline erosion was dramatic.

It’s expected that the risk of blue-green algea blooms has risen dramatically do to the increase in nutrients, however other factors are required for blooms to develop, including: warm temperatures, sunshine, and windless days.

With the expanded lake size, shallow-spawning fish have more habitat, but cooler temperatures may delay spawning and inshore movement (lake trout and whitefish fry emergence has been delayed at least two weeks). Eggs and larval fish, along with other species such as amphibians may be stranded when waters recede. Fish, birds, and mammals that rely in seeing their prey underwater will be disadvantaged because of the cloudiness of the lake. Some sea lamprey traps were buried or destroyed (Lake George Asian clam control is expected to be helped by high waters).

With wetland areas expanded, inundated, and eroded habitat for dabbling ducks and other water birds, beaver, and muskrat has increased, but other terrestrial animals have been displaced or drowned; mussels (native and invasive) have been buried. Wetlands have been contaminated with sediments and nutrients, and possibly invasive species such as purple loosetrife, phragmites, and Japanese knotweed. Some waterborne invasive species are also likely to spread, including Eurasian watermilfoil, and water chestnut.

Photos: Above, sediment plume from the Ausable River and Dead Creek; Below, headland erosion and suspended sediment north of Mooney Bay. Photos courtesy the Lake Champlain Basin Program.