Sedimentation Rate Change
Winooski River Delta
Chris Ricker and Brian Connelly
Looking at the edge of the delta,
breaking waves offshore.
Delta extends well into Lake Champlain, while the
surrounding country side is deforested for agriculture
GPS Coordinates
Location
Burlington
Bridge
Burlington
Delta
Colchester
Bridge
Colchester
Delta
Looking at the bridge upstream
Abstract
Historical air photographs, from 1937 show the
Winooski River Delta extended much farther into Lake
Champlain that modern photos and surveying show
the delta today. Two major changes took place to the
river since 1937. The River narrowed significantly
since 1974 (old woman) and more significantly to
deltaic processes, reforestation has reduced the
amount of sediment flux in to the lake. When river
water reaches Lake Champlain it slows significantly,
loosing energy and depositing river sediment in the
delta. The change in erosion rate was determined by
comparing the 1937 delta to the modern delta. A
change in volume was calculated by using basic
trigonometric and geometric functions (old air photo,
new air photo, cross-sectional area). The change in
volume was calculated to be 1.0*10^8 cubic meters.
Calculations can then show the change in
sedimentation rate.
Reduced deltaic margin.
River Data Used and Calculated
Calculating sediment lost to wave action
Easting Northing
637214 4932241
637191 4932155
637192 4932318
636985 4932366
Glacial History of the Winooski Delta
Calculating the difference in sedimentation rate
During the height of the Laurentide Ice sheet, the
Winooski Delta area was completely covered by ice.
As the ice retreated Glacial Lake Vermont formed, with
its shores at high elevations. Later, the retreat caused
sea water to enter into the Champlain basin forming the
Champlain Sea. Soon the ground rebounded and
caused the formation of Lake Champlain where the
Winooski began building the delta.
Conclusion
Sedimentation rates, and therefore erosion, were 39x
higher than today, averaged over the Winooski Drainage
Basin. Although hill slope instability along the river, it is in
the uplands where hillslope stability affects the Winooski
Delta the most. While deforested, the uplands faced more
erosion and landslides, increasing the sediment load in the
Winooski. When reforested, the hillslopes became more
stable and decreased the sediment flux into the lake.