Lake Mead National Recreation Area
Drought Effects - Erosion
The current
drought has exposed large areas of the what was once desert, then
flooded, and is again desert.
This process has an interesting effect on shoreline areas. The erosion
process in desert reservoirs such as Lake Mead is often considered in
terms of a static shoreline. That would be the shoreline as it existed
when the erosion process at a particular reservoir or area is being
considered.
In fact, Lake Mead and Lake Powell have shorelines which can vary
drastically. The current drought being an extreme example. |
When Lake
Mead is near its 'normal' level, it will have fluctuations in it level
that are much smaller but have more of an effect on the shoreline.
This process is most evident is on the eastern shore of the Overton Arm,
south of Mormon Mesa. In the first photo, we can see at least four
different places where the shoreline had been static long enough to
leave a mark on the surface.
This results in a completely
unpredictable pattern of erosion because the water levels will be
unpredictable.
The erosion pattern which results in some places is different than any
ever seen on this landscape. |
Here
the action of shoreline erosion causes the softer strata to wash away at
different levels causing the caliche layers to collapse on themselves
creating giant piles of flat, exposed caliche.
As this wall of caliche forms, it begins to ward off further erosion.
At some places the soft earth is completely washed or blown away.
This changes how plants can use this area.
It changes a lot of other things in the area and the effects of this
type of erosion might not be fully understood.
Ultimately the erosion process in places along the Lake Mead shoreline
is controlled by the rainfall in the entire Colorado River basin, the
type of soil and rock that is in the area and the requirements of Hoover
Dam.
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