GROWTH OF THE DEAD CREEK DISTRIBUTARY OF THE MISSISQUOI RIVER, LAKE CHAMPLAIN, VERMONT, BETWEEN 1950 AND 2003

The purpose of this study is to determine expansion of the surface area of the Missisquoi Delta, located in the northeastern portion of Lake Champlain in Franklin County, Vermont. The Dead Creek distributary is fed by the Missisquoi River, one of the northern-most tributaries on the east side of Lake Champlain. The modern development of Dead Creek distributary can be traced to its reactivation by levee breech during the flood of November, 1927. Fillon (1969) found that between 1927 and 1969 Dead Creek lengthened its distributary by 1000 feet (305 meters). This increase represents an elongation rate of approximately 7.9 m/yr. The Missisquoi River has a drainage basin of 2201 km² and has a mean discharge of 46 m³/s. This delta system is controlled by local precipitation, flooding events, upstream erosion, and anthropogenic changes.

Digital aerial photography within a GIS provided the foundation for determining progradation of the Missisquoi distributary. Five sets of aerial photographs from the 1960s to present day depict distinct geomorphic changes to the delta distributaries in Missisquoi Bay. Our study also employs USGS water resource data to evaluate changes in discharge of the Missisquoi River, and precipitation within the drainage basin over the past 50 years .

Currently, sedimentation within the bay has shifted from the pre-existing bird-foot delta north of Hog Island to the Dead Creek distributary. Changes to the distributary in the past fifty years include a greater than fifty percent increase of sedimentation, with an estimated 8,000 m² added to the delta lobe per year. It is hypothesized that this estimated annual progradation is primarily dependent on discharge of Dead Creek in response to climatic changes in precipitation and evapotranspiration, coupled with changes in agricultural practices within the Missisquoi River basin. Additionally, channel length has increased significantly from 1962 to 2003, growing approximately 603 m or at a rate of 14.7 m/yr. This is twice the rate of elongation reported by Fillon in 1969. Furthermore, a well-developed channel system and levee has started to form on the surface of the Dead Creek delta well into Missisquoi Bay. Our data suggest that significant changes have recently impacted the Missisquoi River drainage basin.