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Functions
& Conditions -
Evaluating the Physical Features
Bank
rock content
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physical feature over which an operator or land manager has
little influence, but which strongly affects the way a riparian
area can be used, is the amount of rock in the streambanks.
Streambanks which contain a high percentage of rocky material
(see Figure 2-16) larger than 2.5 inches (gravel-size) are less
likely to be impacted adversely than those which are made up
of mostly sand, silt, and clay particles or those with small
gravel layers interspersed between fine materials, as shown
in Figure 2-17. |
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Figure
2-16
Rocks of cobble size and larger in this channel and
its streambanks provide a high degree of inherent resistance
to disturbance.
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Figure
2-17
In contrast to the previous picture, the fine materials
and interspersed gravel layers in this streambank make
it more susceptible to disturbance. |
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Bank
rock content is extremely important from a management perspective.
Fine-grained soils must be managed more carefully because they
are inherently more susceptible to degradation. They require
more emphasis on the maintenance of healthy vegetation communities,
especially woody species if appropriate, to provide bank stability.
Livestock are more likely to damage fine soils than rocky ones
through such actions as compaction and bank shearing. Therefore,
managers must watch such reaches more carefully. |
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