Stormwater Runoff Loadings To Coastal Bayous Under A Gradient Of Watershed Urbanization, North Central Gulf of Mexico

Little information is available on stormwater runoff loadings from urbanized coastal watersheds in the northern Gulf of Mexico. Stormwater discharges from pristine or least (Heron), moderately (Cumbest), and heavily (Chico) urbanized watersheds in Mississippi, were monitored from June 2010 to July 2011 to quantify loadings of nutrients and sediments. There was zero and one discharging pipe available for effective sampling in the Heron and Cumbest watersheds, respectively. The Chico watershed had 83 discharging pipes and was divided into five sections for sampling based on pipe location, size, and accessibility. Annual loads (kg·ha-1·yr-1) of total suspended solids (Chico large = 322.71, medium = 137.72, and small = 1.38; Cumbest = 0.04 x 10-1) were extremely high from both large and medium pipes at the heavily urbanized watershed. Nutrient loads followed the similar trend (e.g., NO3- loading large = 16.04, medium = 4.31, small = 0.05, Cumbest = 0.02 x 10-2). Results of this study suggest that watershed urbanization increased solid and nutrient loads to adjacent surface waters. These results may be helpful for TMDLs development for urbanized coastal watersheds.