- Lake level
The level of Lake Michigan rises and falls as amounts of precipitation
and evaporation change within the lake basin and drainage area.
The historic record for Lake Michigan shows approximately 1.5 m
(5 ft) variation over time. Currently, lake levels are low.
Changes in lake level
affect the width of the subaerial beach (the above-water part of
the beach which in turn affects dune processes.
US Army Corps of Engineers (2005). More information on Great Lakes
water levels is available at their website.
refer to the International Great Lakes Datum of 1985 (IGLD 1985)
which is a reference zero point for the Great Lakes established
near the mouth of the St. Lawrence River in 1985.
|A wide beach (at low lake
levels) represents a larger supply of sand that can be moved by the
wind to inland dunes. During low lake levels, coastal foredunes grow.
As a beach narrows (when lake levels rise), the supply of sand decreases
and foredune growth slows down.
Approximately 10 m (33 feet) of subaerial beach is visible.
(Hoffmaster State Park in September 2005.)
|When waves come right
up to the foredune (there is no subaerial beach), vegetation and sand
are eroded from the dune. The waves move dune sand to the underwater
part of the beach. Wind can also move sand inland from areas of the
dune no longer protected by vegetation.
No subaerial beach and waves come right up to foredune.
(Hoffmaster State Park in August 2004.)