OCEANOGRAPHIC OBSERVATIONS AND THEORETICAL ANALYSIS OF OIL SLICKS DURING THE CHEVRON SPILL, MARCH 1970

Oceanographic observations near the Chevron spilling well off the Mississippi Delta in March 1970 revealed relative roles of various physical factors of the regional estuarine system in the behavior of oil slicks. Surface stress from the wind was most important, at speeds above 15 mph the slick orientation was generally determined by the wind direction. The wind also indirectly affected oil which was sunk by dispersant in the wind waves promoted mixing, which in turn affected the vertical stability, hence eventually the velocity profile. Wind setups and setdowns were correlated with downward and upward isopycnal movements, respectively. Both calculations and observations showed that tidal currents produced and L-shaped slick geometry when winds were below about 15 mph. The diurnal rotation of the tidal currents served to limit the excursion length of oil from the source, keeping it short of the nearest shore. The presence of fresh water from the Mississippi River in the surface layer and the consequent development of convergence lines often formed a natural barrier, preventing oil from encroaching upon the shore. Theoretical analysis using turbulent diffusion theory disclosed that the area and length of a steady-state oil slick increased with oil discharge but decreased with current speed and the lateral diffusion coefficient. Slick width increased with the rate of discharge and decreased with current speed but was independent of the diffusion coefficient. The width/length ratio of an oil slick, which was notably independent of current speed, was controlled only by the diffusion coefficient and the oil discharge. In order to be able to predict oil slick behavior, understanding of the interaction between these multiple factors is essential and, for that end, the use of a multiple-sensor array with automatic data transfer and processing capability is recommended.

  • Corporate Authors:

    Louisiana State University, Baton Rouge

    Coastal Studies Institute
    Baton Rouge, LA  USA 
  • Authors:
    • Murray, S P
    • Smith, W G
    • Sonu, C J
  • Publication Date: 1970-7

Media Info

  • Features: References;
  • Pagination: 110 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00019674
  • Record Type: Publication
  • Source Agency: United States Coast Guard
  • Report/Paper Numbers: 714104/A/006-2
  • Contract Numbers: DOT-CG-03592-A
  • Files: TRIS
  • Created Date: Nov 25 1973 12:00AM