Location of Roads
The location and pitch of roads can be obstacles to migratory fish and affect the character of the stream.
Parking lots, highways, buildings, and any man-made infrastructure constructed close to a stream or river have effects on the stream. Runoff from these sources goes directly into the stream. Rip rap, for example, used on road construction projects interrupts natural water flow as well as fish habitat. Contaminants like road salt, sand, and engine oil on large surface areas such as parking lots and highways can run into streams after rainstorms seriously affecting water quality.
Culverts
Culverts can be barriers to fish passage. Many culverts cause problems due to poor engineering design or installation. They restrict migrations and reduce natural stream flow.
River flow and turbulence are increased to such an extent that weaker fish are excluded
Many culverts are undersized for high flow periods
Some culverts are suspended above the stream bed presenting a physical waterfall that acts as a barrier to non-leaping migratory fish
Debris accumulates during storms or through lack of maintenance preventing flows or creating flooding conditions, neither of which are conducive to passage
With the proper placement and design, culverts can be beneficial in fish passage
Runoff from roads can cause the following:
Erosion - Results from increased runoff on the stream bank and this often leads to loss of vegetation
Sedimentation - Results from runoff, when sand and salt from roads accumulate in the river. Sediment fills in the nooks and crannies between the cobble that fish use as spawning habitat. This smothers the eggs.
Contamination - Results when runoff carries waste oil from vehicles, pesticides and nutrients from fields, salt from roads, etc.
Heating - On hot days, runoff from roads increases the temperature of nearby streams. This unnatural temperature increase can be lethal to fish and aquatic insects.
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