Pollutants in stormwater runoff

Increased Runoff
Increased Runoff Land alterations increases the rate and amount of runoff from the watershed entering the stream.

Carries pollutants, erodes stream channel and banks, and destroys instream habitat
Sediment Dirt and sand on roads, driveways, and parking lots or eroded sediment from disturbed surfaces (e.g. construction sites) enters stream with stormwater runoff; increased flow causes stream bank erosion

Smothers aquatic habitat, depletes oxygen, reduces water clarity, and carries nutrients and toxic contaminants
Nutrients Excess fertilizers on lawns or fields, failing septic systems, and animal waste

Stimulates excessive plant growth, lowers dissolved oxygen levels, degrades aesthetics and destroys native aquatic life

Temperature Warmer water caused by runoff from impervious surfaces, removal of streamside vegetation, and reduction in groundwater flows


Harmful to trout and other cold water species, promotes spread of invasive species and excessive plant growth, reduces dissolved oxygen levels in water
Bacteria Potentially pathogenic microscopic organisms in failing septic systems, sewer overflows, and animal (including pet) waste

Harmful to humans; untreated waste can cause numerous diseases.

Toxic Contaminants/Heavy Metals
Toxic contaminants/Heavy metals Heavy metals such as Mercury, cleaning compounds, pesticides and herbicides, industrial by-products such as dioxin, and vehicle leakage of oil, gas, etc.


Harmful to humans and aquatic life at fairly low levels; many resist breakdown and some accumulate in fish and other animal tissues (including human), and can lead to mutations, disease, or cancer