EFFECTS OF BRIDGING ON BIOLOGICAL PRODUCTIVITY AND DIVERSITY

Aquatic communities were studied in rivers at three bridge sites in Florida to determine whether or not bridge design features and construction methods have any adverse impacts on the biota. The sites were I-10 at the Ochlockonee River in Leon Co., U.S. 98 at the Wakulla River in Wakulla Co., and I-75 at the Braden River in Manatee Co. These rivers, respectively, were an alluvial river with a broad floodplain, a clear spring-run with copious rooted macrophytes, and a small tannic river lacking a floodplain. Benthic invertebrates and (at the Wakulla River) rooted macrophytes were collected along transects which extended across the rivers. A transect was placed beneath each bridge span, another well upstream and another well downstream from the spans. At I-10 and I-75 another transect was placed between the spans. The organisms were identified. Densities were determined for each of the taxa of the benthic invertebrates. Biomass was determined for each of the plant species. Mean values were calculated for numbers of individuals, diversity, evenness, and dominance. Statistically significant differences in mean values were used for detecting impacts. No impacts were detected at the Ochlockonee River bridge. Severe impacts were detected beneath the Wakulla River bridge. These were attributable to dredging during construction and to design criteria which caused changes in the current, promoted the scouring of bottom sediments, and caused a deep shadow beneath the bridge. The data for the Braden River site were inconclusive because of the complexity of the natural environment. Oil and grease were allowed to accumulate in the bottom sediments during construction. It was suspected that these petroleum substances were causing a moderately adverse environmental impact on benthic invertebrates. (Author)

• Corporate Authors:

  Florida Department of Transportation

  Bureau of Environment, Haydon Burns Building
  Tallahassee, FL  United States  32301
• Authors:
  • Birkitt, B F
  • Dougherty, B J
  • Thomas, G L
  • Thompson, S S
  • Clewell, A F
• Publication Date: 1979

Media Info

• Features: Appendices; Figures; References; Tables;
• Pagination: 74 p.

Subject/Index Terms

• TRT Terms: Biology; Bridge design; Bridges; Construction management; Dredging; Ecology; Environmental impacts; Living things; Petroleum; Scour; Structural design
• Subject Areas: Bridges and other structures; Construction; Design; Environment; Geotechnology; Highways; Hydraulics and Hydrology; Marine Transportation; Planning and Forecasting; I21: Planning of Transport Infrastructure;

Filing Info

• Accession Number: 00349247
• Record Type: Publication
• Report/Paper Numbers: FL-ER-9-79
• Files: TRIS, STATEDOT
• Created Date: Jun 30 1982 12:00AM