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In the Iron River, sources of
sediment are abundant and constitute the majority of immediate concerns.
Dirt and sand particles, constantly on the roads in town, are later
introduced into the river through storm drains. This is especially true in
spring, when tons of sand and dirt used on the roads in the winter is washed
into the river during the spring melt. Erosion from gravel pits, urban
development, livestock, and other sources also contribute sediments into the
river annually.
Sediment can affect a stream in a variety of ways. Trout populations are dependent on cold clean water and gravel stream
bottoms. Brook trout, more than other species of trout need this kind of gravel
substrate for their spawning grounds. The gravel protects the eggs and at the
same time allows water flow over the eggs, supplying them with oxygen. When
sedimentation occurs, dirt and sand particles settle over the bottom
of the stream and suffocate the eggs. Similarly, aquatic insects are
deprived of gravel substrate. High concentrations of sediment change the
habitat for these aquatic organisms and in turn, decrease the amount
of food available to trout. Additionally, sedimentation increases turbidity
(clarity of the water). Suspended dirt and sand particles in the water transport pollutants, increase water temperature since darker water absorbs and
retains more heat, and make it harder for fish to find prey.
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| In the Iron River Watershed, sources of sediment are abundant and constitute
the majority of immediate concerns. Numerous storm drains have poor outlets
that either empty directly into the river, or drain at the top of a slope and
result in gullies or washouts. Gravel pit operations near the river have also
contributed tons of sediment from erosion.
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(Click here for next concern: Acid Mine Drainage)
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