How can sediment be considered a pollutant?
Sediment tends to fall out in spawning areas used by salmonids. This can limit viable spawning areas, as well as smother out existing redds.
Sediment has been known to increase mortalities in juvenile fish. This occurs when abrasive sediment is transported across the gills of juvenile fish causing lesions. This could cause death or produce a secondary fungus across the gills, smothering the fish.
Sediment can kill off many species of aquatic insects, such as stoneflies (plecoptera) and caddisflies (trichoptera). This limits biodiversity.
What causes sediment problems?
Sediment load is a natural part of a watershed. The amount of sediment, however, is what matters. Sediment occurs naturally in a water course from activities such as: natural landslides, seasonal storms, surface erosion, and channel bank erosion.
However, mankind has increased the amount of sediment which results from these natural events due to road construction. Roads, by their very nature, increase surface erosion, cause water diversion problems, decrease slope stability, and place dirt in natural water courses.
What can be done to reduce sediment?
Only changes in land management practices can lead to reduced sediment and an improved ecosystem. Road construction should be subject to more rigid environmental impact standards.
Road management should be approached from an environmental point of view. Fewer roads and better drainages would not only have a positive effect on the environment, but would also reduce maintenance costs on the road network.