Ice Movement and Shoreline Modification, Lake Champlain, Vermont
Measurements and observations of ice movements and shoreline modifications were made in 1968 on Lake Champlain, with detailed study on Shelburne Bay, near Burlington, Vermont. These investigations showed that distinctive ice movements on Shelburne Bay were caused by lake level rises, ice and snow ablation, and ice temperature fluctuations during the period of complete ice cover, and by wind action during ice breakup. Measured ice expansion and contraction movements can be approximated by theoretically considering the ice cover as a uniformly heated plate. Exact agreement between the observed and calculated values was not found, however, due to the complicating effects of snowfalls during ice contractions and varying lengths of the period of temperature increases during ice expansions. Shoreline modification, in particular ice rampart formation, is very limited on Lake Champlain due to the continuous snow cover, the development of numerous pressure ridges, the relatively short period of partial open water, and the weakened condition of the ice during ice breakup. Factors controlling ice-sediment interactions on Shelburne Bay are particle size, steepness of bottom slope, and shoreline configuration. Fine particle size, gentle bottom slope, and shoreline embayments together are associated with unrestricted ice movements and only minor ice ramparts. Relatively straight shorelines with intermediate particle size and bottom slope are most favorable for ice ramparts. Shoreline convexities with relatively steep bottom slope and coarse particle size favor pressure ridges.