BROWNFIELD DEVELOPMENT AND IMPLICATIONS TO WATERSHED: A CASE STUDY

An 84 acre shopping center has been proposed to the city of Rome, Georgia to be built along Burwell Creek, a tributary of the Oostanaula River. The building site is located within the 100 year flood plain of the Oostanaula River and is a brownfield. The goals of this research are to provide the city of Rome with base-line hydrologic data for the area, to predict the impacts on the watershed as a result of the development, and to suggest innovative strategies the developers can incorporate into the project that would negate some of the adverse effects of building.

The research combines fieldwork and watershed modeling based on empirical parameters defined for Burwell Creek. Fieldwork included creating cross-sections of the creek and collecting water samples for chemical analysis. Site visits helped to identify landscape variables needed to accurately estimate infiltration and runoff amounts based on the Curve Number and rational runoff methods. An empirically derived unit hydrograph was constructed for Burwell Creek's drainage basin to characterize time-to-peak during flood events.

The measured cross-sections and site visits indicate a previously altered stream channel with steep banks and reduced meandering. The water chemistry indicates that the stream has between 12 – 15 ppm dissolved oxygen and zero phosphates or nitrates; iron was found in all of the samples and the concentration increases from site A (100 ppb) located above the landfill to site C (220 ppb) located below the landfill indicating leeching from the landfill. The saturation point for the current condition of the site based on a 100 mm rainfall event, with a four year recurrence interval, is estimated to be 84 mm compared to 13 mm with the introduction of impermeable surfaces over 97% of the area. The empirically derived unit hydrograph for Burwell Creek shows peak flow for the same rain event ranging from 8.5 to 33 m3/second. The amount of runoff calculated from the rational runoff method ranges from 20 to 80 m3/second for the same rainfall event.

Recommendations to the builders include the use of porous pavement and vegetated swales. Installing porous pavement would reduce storm water runoff by allowing the water to infiltrate the pavement and the soils beneath the parking lot. Runoff can also be diverted into vegetated swales where plants filter it before infiltrating the soils beneath the parking lot.