Roberts Creek IA 01-TRK-187
confluence with Howard Cr. (S25 T94N R5W Clayton Co.) to confluence with Silver Cr. in S16 T94N R5W Clayton Co.
The Class BWW2 use was assessed as "not supported" based on biological and habitat sampling data. The primary cause of impairment is believed to be habitat alterations; impairments due to this type of non-pollutant stressor are appropriate for Category 4c (impaired but TMDL not required) of the Integrated Report. All other designated uses were "not assessed."
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site Name Site Description Iowa DNR 6 BIO See Below 178 Roberts Creek Farmersburg BioNet Site ID Date Drainage Area (mi2) Ecoregion Major Drainage/Thermal BM Sample Gear BMIBI score BMIBI Class 52b BMIBI BIT BMIBI Pass/Fail 178 7/31/00 67 52b MS/WW Hess 67 Good 61 Pass BioNet Site ID Date Drainage Area (mi2) Ecoregion Major Drainage/Thermal Riffle Stream? FIBI score FIBI Class 52b FIBI BIT FIBI Pass/Fail 178 7/31/00 67 52b MS/WW NA 39 Fair 52 Fail Community Assessment Type Assessment Result Support Level IR Category Reason Benthic Macroinvertebrates Evaluated Pass (1/1) Full Fish Evaluated Fail (0/1) Not Overall Evaluated Fail Not 4c Assessment was evaluated because it was based on a single sample. BioNet Site ID Sample Date FIBI Score 52b FIBI BIT EFHI Score FIBI-BIT Difference FIBI-EFHI Difference EFHI-BIT Difference 178 7/31/00 39 52 47 -13 -8 -5
Presumptive Class A1 - No Data
Class BWW2 - Biological Sampling:
Benthic Macroinvertebrates:
Fish:
Overall Assessment:
Class BWW2 – Habitat
Index Evaluation:
For Roberts Creek, the observed FIBI score was moderately less than the
EFHI-predicted FIBI score. When theobserved FIBI score-EFHI-predicted FIBI score difference is +8 to -5 points, water quality and/or other factors besides
physical habitat do not limit the stream’s ability to meet the FIBI BIT. The
FIBI-EFHI difference at Roberts Creek was slightly larger than the acceptable limit
(-8 vs -5); however, DNR still believes category 4c is the appropriate category
for this segment. The 2001 BMIBI score passed indicating there was not a water
quality problem at this site in 2001. The fact that the EFHI score is below the 52b FIBI BIT is an indication that Roberts Creek will have difficulty meeting the
FIBI BIT because of habitat conditions at the site. The 2002 IR indicated that
habitat alterations caused by agriculture, bank or shoreline
modification/destabilization, and habitat modification was the cause of the
lower FIBI score.