INVESTIGATING THE EFFECTS OF URBANIZATION ON THE TROUT BROOK SUB-BASIN OF THE PARK RIVER WATERSHED IN GREATER HARTFORD, CONNECTICUT: ANALYSIS OF STREAMFLOW AND SUBMERSIBLE DATA LOGGER CONDUCTIVITY MEASUREMENTS

We investigate the impacts of urbanization on a fluvial system by measuring instantaneous discharge and long-term conductivity, parameters that can be used as criteria to assess ‘urban stream syndrome’. The Trout Brook sub-basin, which is a tributary of the south branch of the Park River Watershed in West Hartford, CT flows through suburban to urban neighborhoods. The stream is channelized in downstream reaches, receives significant storm water from a major sanitary sewer overflow (SSO) and lacks any permanent gauging station on the south branch which makes quantifying discharge a challenge.

The stage-discharge method was used to build a baseline rating curve for the Trout Brook. Stage height was established at an easily accessible and repeatable location and discharge was measured four different times during the fall of 2012. We selected a stretch of river that is completely contained within a concrete rectangular channel to simplify the geometry of the cross-sectional area of the stream. Submersible pressure data loggers were employed to estimate real-time stage height at the same site. Using the resulting hydrograph, it was determined that the rating curve represented times of low and medium flows. Several rain events resulted in a flashy hydrograph response suggesting a symptom for urban stream syndrome. We also compared our results with the real time USGS gauging station data from the less developed north branch of the Park River to contrast the hydrograph response.

Submersible conductivity data loggers were used to assess the contribution of the SSO to the Trout Brook. Baseline conductivity levels at and upstream of the SSO were established, as well as conductivity patterns in both locations during significant storm events. Using the hydrograph produced from pressure data loggers, diurnal effects in conductivity, independent of stage height variations were also observed. Storm event patterns at the SSO record an initial “super-spike” of conductivity during the first flush of the storm water system followed by dilution during the majority of the storm event. The conductivity recorded upstream of the SSO did not record this initial super spike. The rapid conductivity variations observed in the Trout Brook at the SSO are potentially harmful to aquatic life in the river and likely contributes to urban stream syndrome.