Slide 69 of 75
Notes:
A simple model to classify and manage urban streams can be constructed based on impervious cover. The model helps determine the impacts of impervious cover based on three stream categories: sensitive, impacted, and non-supporting. When impervious cover is less than 10%, we still can maintain a high quality stream system that maintains stable banks, has high fish diversity and good water quality. Once impervious cover exceeds 10%, the pristine conditions of the sensitive stream cannot be maintained. Impacted streams are characterized by 10% to 25% imperviousness and begin to show the varying degrees of the influence of land development including unstable channels, declining water quality, and diminished biological communities. Non-supporting streams exceed 25 to 30% impervious cover and are characterized as highly unstable, have poor fish and aquatic insect diversity, and very poor water quality.