Walnut Creek IA 05-NSH-1449

Assessment Comments

Assessment is based on results of 1996 Biocriteria sampling: Fish IBI= 23(poor), 20(poor); BM-IBI= 53(fair), 45(fair).

Basis for Assessment

Used results of the October 1996 DNR biocriteria samplings upstream and downstream from a bridge 4 mi.  WNW of Red Oak, in combination with the 3 DNR stream use assessments conducted in 1991, to upgrade the assessment of support of the Class B(WW) aquatic life uses from PS to FST due to (1) presence of nearly all (7 of 8) of the expected fish taxa for streams in the Loess Hills and Rolling Prairies subecoregion, (2) lack of violations of Class B(WW) WQ criteria in the sample collected during biocriteria samplings, and (3) results of 1991 stream use assessments that showed a good population of adult and juvenile channel catfish (lack of channel catfish in the 1996 biocriteria sampling may have been due to high stream flows that hindered sampling effectiveness or due to sampling late in the season (mid-October)).   Primary threats to continued support of the Class B(WW) uses include excessive pasturing of the riparian corridor of this stream as well as excessive stream bank and gully erosion that contribute sediment to the altered (i.e., channelized) stream channel.