Soil characteristics influence chemical and physical interactions with pollutants. The relatively flat land throughout the Coastal Bend acts to reduce flow velocity in the runoff, reducing the sediment component of NPS pollution. The other major factor determining NPS pollution is land management which is a controllable human influence. Evidence indicates that land modified by human activity is more likely to increase runoff and that the type of activity influences the pollutants found in the runoff. Urban NPS data for the report were compiled from the City of Corpus Christi's National Pollutant Discharge Elimination System permit sampling program.
Storm drains are relatively free of pesticides and organic compounds.
Agricultural data was collected from USGS stream gages at Oso Creek, west of Corpus Christi and Seco Creek, northwest of Hondo, Texas. Dissolved solids at the Oso Creek site were between four and six times those reported for other similar watersheds. Suspended solids recorded from the Seco Creek site were substantially less than that reported for the Galveston Bay area. This figure indicates relative land use in the Coastal Bend. Land use provides a clue to the types of pollution that could potentially be contrained in the runoff.