However, it is generally recognized that the main stressor in nonpoint source impacts is alteration of the physical habitat structure. In response to these mandates, methods to assess the integrity of our water resources have been developed and tested in a variety of stream types. The quality of the instream and riparian habitat influences the structure and function of fish and macroinvertebrate assemblages in a stream. The effects of water quality on these faunal distributions is sometimes obscured by the presence of a degraded habitat. A comprehensive approach to assessing the quality of stream habitat structure should include an evaluation of habitat complexity, including the variety and quality of the substrate, channel morphology, bank structure, and riparian vegetation.
Biological potential is limited by the quality of the structure of the habitat.
Habitat assessment is becoming a critical tool in evaluating effects to the water resource from nonpoint sources. These metrics relate to various components of the stream and riparian habitat and provide information that, when integrated, allow for the judgment of habitat quality relative to regionally-expected reference conditions. A continuum of conditions for each metric must exist that can be characterized from the optimum for the region of the stream type under study to the poorest situation reflecting substantial alteration due to anthropogenic activities. The judgment criteria for the attributes of each metric should minimize the subjectivity through either quantitative measurements or specific categorical choices. The Investigators are experienced in or adequately trained for stream assessments in the region under study.