NUMERICAL MODELING OF OIL SPILLS IN THE INLAND WATERWAYS OF THE LOWER MISSISSIPPI RIVER DELTA

Abstract

ABSTRACT The demand for fossil fuels is driving the rapid expansion of the petroleum industry'S infrastructure. Louisiana'S wetlands are the most industrialized in the world. The oil industry has infiltrated every part of the Lower Mississippi River Delta (LMRD) from the fixed facilities and transport vessels traveling along inland waterways, the pipelines and canals running through the wetlands, and the offshore platforms along the Gulf of Mexico coastline. An oil spill could seriously damage the coastal wetlands that are already rapidly degrading, pollute the water supply, destroy wildlife habitat, and impact other natural economic and social resources. Additionally, proposed coastal restoration initiatives such as freshwater diversions could provide a conduit for spills to travel from the river to open wetland areas. Current inland oil fate and transport models cannot automatically be applied in the deltaic environment because they do not represent the high degree of minerals and fines in suspension, the unique characteristics of the shorelines, or the potential flow into the wetland areas. Thus, a three- dimensional oil fate and transport model was developed to investigate the behavior of oil spilled in the unique environment of the LMRD, assess the vulnerability at specific locations such as freshwater diversions from the river, and provide information for contingency and remediation plans. Simulations of the hydrodynamics of the LMRD were generated using the U.S. Army Corps of Engineers Adaptive Hydraulics (ADH) modeling code. The model simulates the physical and chemical processes affecting the fate of a surface oil spill including slick advection and spreading, the vertical transport of dissolved and emulsified parcels, evaporation, dissolution, adsorption, sedimentation, re-suspension and degradation. The model estimates the distribution of oil in the surface slick, water column, sediments and atmosphere. Almost seventy percent of the Mississippi River'S sediment load is comprised of finer materials. The model is unique in using empirical predictions to describe oil'S interactions with fine suspended material and muddy shorelines. Hypothetical spills representative of the type and location of spills commonly occurring in the region were simulated to investigate the sensitivity of the system to the unique parameters. This model was developed to take advantage of the latest advances in computational fluid dynamics and weathering algorithms, while focusing on the complex hydraulics and sediment characteristics local to the Lower Mississippi River Delta.