Bioassessment of Biological Criteria and Water Quality to Determine the Effects of Increasing Residential and Commercial Development Around Rock Creek

Abstract

Urbanization is increasing at an alarming rate around the United States, and the city of Frederick, Maryland and the surrounding area are no exception. This increase in urbanization is having a severe, detrimental impact on waterways, and is becoming a leading cause of stream degradation. This study was undertaken to discover if the increase in urbanization around Rock Creek (Frederick County, MD) was causing degradation of the streams' health. Seven sites along Rock Creek were sampled during baseline and storm event conditions each season for one year to determine water quality. Benthic macroinvetebrate sampling occurred twice during the study to determine the effect of urbanization on the biological health of Rock Creek. Field surveys and geographic information systems (CIS) were used to calculate the total urban land cover and impervious surface land cover in the watershed upstream from each site. Rock Creek is surrounded by 51.9% urban land, which translates into 20.36% of impervious surface. Even though Rock Creek is surrounded by a high percentage of imperviousness, it only correlated half the time with water quality, and never correlated with benthic DM scores or Hilsenhoff Biotic Index scores. Sixteen of the 17 water quality parameters showed a statistically significant difference between baseline and storm event conditions. All chemical parameters (baseline and storm event), except four, correlated to some degree with impervious surfaces with 56% of the water quality parameters significantly correlated with impervious surfaces. However, this study failed to show a statistically significant relationship between impervious surfaces with benthic IBI scores and Hilsenhoff biotic index scores. Even though most of the benthic DM scores were low (poor quality) and most of the Hilsenhoff biotic .index scores were high (poor quality), none of the scores correlated with impervious surfaces. Statistically and biologically, urbanization is having an impact on Rock Creek. However, although urbanization is a key factor behind the degradation of Rock Creek it is not the only factor. More needs to be done in order to understand why Rock Creek is in such biologically poor condition, to fully understand the effects of impervious land cover on Rock Creek, and to find the other sources that are causing the degradation of Rock Creek