Hydraulic biotopes and characterization of streambed habitat diversity in rural and urban streams

The quality of in-stream aquatic habitat can be an indicator of stream health, but its assessment and relationship to biotic diversity has often neglected the incorporation of data on bedform architecture and hydraulics. In this study, the structure and diversity of hydraulic biotopes were determined within reaches of both an urban stream and a rural stream in the Piedmont of North Carolina. Hydraulic descriptors were used to compare biotope characteristics, and differences in hydraulic habitats were compared among the reaches. Habitat diversity and richness were calculated and then compared to species data from the same sites. The diversity of hydraulic habitats was similar in all reaches; the compositions were not. Pools were more abundant in urban reaches, whereas runs and glides were more common in rural reaches. No clear relationships between biotic and hydraulic unit diversity were found. This underscores the need for using multiple stream characteristics in habitat assessment.