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Top 5 Weather Events of 2011 across the North Country
Main 5 4 3 2 1

#2 Weather Event: Lake Champlain Record Flooding
The National Weather Service Burlington, Vermont #2 event is the record flooding which occurred on Lake Champlain from April 13th through June 19th. The combination of record amounts of snowfall during the winter months and a record amount of rainfall in the spring of 2011 resulted in the highest lake level ever at 103.27 feet on 6 May 2011. This broke the previous record of 101.86 feet on 27 April 1993 by 1.41 feet and was an astounding 3.27 feet above flood stage. This record breaking lake level caused significant damage to lake side houses, impacted numerous roads near the lake, including Route 2 and Route 78 through the islands, and closed many marinas and beaches for the start of the summer season.
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Figure 7 shows a graph of Lake Champlain lake level from 12 March through 18 June 2011, along with flood stage (red dotted line), and a plot of maximum know elevation (red line), and maximum observed stage (green line).

From the graph you can see the peak stage of 103.27 feet on 6 May 2011 was much higher than the previous record flood stage of 101.86 feet on 27 April 1993.
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In this section we will examine the causes, which resulted in the record Lake Champlain flooding during the spring of 2011. Figure 8 shows the North Country seasonal snowfall totals for 2010 to 2011. During the winter of 2010-11, Burlington received its 3rd snowiest winter ever with 128.4 inches, which would eventually melt and have significant impacts on Lake Champlain. Meanwhile, seasonal snowfall totals observed atop Mount Mansfield were 252.7 inches with 223 inches falling at North Underhill, Vermont. This much above normal snowfall created snow depths in the mountains between 4 and 8 feet, with total water equivalent values between 10 and 20 inches. Figure 8 shows the 2010 to 2011 snowfall across the North County, with over 200 inches falling in the central and northern Green Mountains of Vermont.
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The next image (figure 9) shows the snow water equivalent on 15 March 2011 from the National Operational Hydrologic Remote Sensing Center. This image shows the snow pack on 15 March 2011 held between 15 and 25 inches of water in northern Adirondack Mountains in New York and between 20 and 30 inches in the central and northern Green Mountains in Vermont. Meanwhile, the snow pack held between 4 and 8 inches of water across the Champlain Valley. This large amount of water in the snow pack, combined with record amount of spring rainfall, resulted in the worst Lake Champlain flooding in history.
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Figure 10 shows the record amount of rainfall which occurred across northern New York and most of central and northern Vermont between March and May of 2011. This map shows over 24 inches of rain fell across the mountains of central and northern Vermont, with 28.29 inches falling atop Mount Mansfield, Vermont during this 3 month period. In addition, in the Champlain Valley, Burlington, Vermont received a record 19.84 inches. All these factors from record amount of snowfall during the winter months, followed by record amount of rainfall during the springtime had significant impacts on Lake Champlain, and ultimately caused historic and long duration flood even on Lake Champlain.
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Furthermore, several strong southerly wind events on 23 April and 5 May 2011 produced significant wave action, and additional storm surge flooding along the south facing shorelines. Meanwhile, several northerly wind events occurred, causing additional surge flooding on the north facing shorelines on 9 May and 1 June of 2011. Lake Champlain was above flood stage for 67 days straight, reaching a peak stage of 103.27 feet on 6 May 2011. This long duration event damaged hundreds of houses along the shoreline (Fig. 11), nearly made the U.S. Route 2 Causeway to the Champlain Islands impassable (Fig. 12), and caused significant erosion along the causeway and bike path (Fig. 13).
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Figure 7: Lake Champlain lake level (blue line) at Burlington, VT from 12 March through 18 June 2011, along with flood stage (red dotted line), plotted maximum know elevation (red line), and maximum observed stage (green line).
Figure 8: North Country Seasonal Snowfall Totals 2010-11.
Figure 9: Snow Water Equivalent Map on 15 March 2011 from the National Operational Hydrologic Remote Sensing Center.
Figure 10: North Country Precipitation Totals from March through May 2011
Figure 11: Lake Champlain flooding during the spring of 2011
Figure 12: Lake Champlain flooding on Route 2 Spring 2011
Figure 13: Lake Champlain flooding on the causeway portion of the bike path spring 2011.


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Burlington
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