North Fork Black Hawk Creek IA 02-CED-551

Assessment Comments

1992 DNR stream use assessment in Grundy county.

Basis for Assessment

Reviewed the field sheet from the June 1992 DNR stream use assessment and field notes from the 1982 ISU collection to continue to assess the support of the Class B(LR) aquatic life uses as FST.   Both surveys were conducted near Dike (i.e., the upstream boundary of the Class B(LR) reach).   The June 1992 DNR stream use assessment noted frequent areas of channel alterations (channel straightening and pasturing of riparian area) and extensive stream bank erosion; only 6 cyprinid species were collected in the evaluation of the fish commnity.   Ten years earlier and approximately 2 miles upstream, an ISU fish survey (JRO-163-1982) was conducted in an area with well-meandered channel form with a fair pool/riffle system.   Although very old data, the ISU assessment was used as the basis for the FST assessment due to (1) presence of a relatively diverse fish community for headwater streams of the Iowan Surface subecoregion (47f) of 16 species from 6 families, (2) presence of all the expected fish taxa (11 of 11) for streams in this subregion, and (3) presence of above average aquatic habitats.   Although results of the 1982 survey suggest full support of the Class B(LR) uses, the habitat evaluation from the 1992 DNR stream use assessment suggest several type alterations to the physical characteristics of this stream that could threaten support of the aquatic communities:  channel straightening, pasturing of the riparian area, and stream bank erosion.   Thus, consider the Class B(LR) uses to be fully supported/threatened.   The data upon which this assessment is based are very old.  Additional monitoring is needed to update this assessment and to better define the status of the aquatic communities and habitats, especially at other locations in the Class B(LR) reach.