Hindcast of the Amoco Cadiz event with a coastal zone oil spill model

Abstract

A coastal zone oil spill model (COZOIL) was developed for the US Department of the Interior, Minerals Management Service. The model has been tested against data from the 1978 Amoco Cadiz oil spill off Brittany, France. Tests were conducted at three scales or levels of grid resolution: (1) a relatively detailed, small area (mesoscale, 20 × 40 km) near the wreck site; (2) a large area (macroscale, 100 × 175 km) encompassing virtually the entire shoreline impact area; (3) the same large area with additional detail near the spill site.

The detailed, mesoscale test case overestimated the quantity of oil onshore by as much as a factor of two early in the hindcast, but produced the general variance and distribution of oil. Model and prototype differences appear to be due to the complexity of the shoreline in question and limitations of the hydrodynamic input data at these spatial scales. The macroscale test cases provided less resolution because of grid cell size, but resulted in better measures of the overall distributions of offshore and onshore oil. The dynamic mass balance of onshore oil realistically depicted the actual spill case and compares well with observations. A clear lesson from these tests is that simply increasing resolution of coastal geomorphology will not necessarily produce more realistic simulations, and may result in degraded model performance. With correct matching between hydrodynamic and coastal resolutions, modeled mass balances compared very well with observations in both space and time.