Abstract

Oil spill models are used worldwide to simulate the evolution of an oil slick that occurs after an accidental ship collision or during oil extraction or other oil tanker activities. The simulation of the transport and fate of an oil slick in the sea, by evaluating the physicochemical processes that take place between oil phase and the water column, is the base for the recognition and assessment of its environmental effects. Numerous oil spill dispersion models exist in the bibliography. The contribution of this chapter is the introduction of a 3D oil slick simulation model developed by the Aristotle University of Thessaloniki, which has been recurrently used in different updated forms and applied in operational mode, since 1991 when it was originally created. The model has been tested in various hypothetical scenarios in North Aegean Sea, Greece, and responded with great success. Findings of the present study highlight the existing experience on the subject and denote the applicability of such models in either tracing the source of a spill or in predicting its path and spread, thus proving their value in real-time crisis management.

Keywords: oil spill modeling, simulation of oil slick transport, oil physicochemical processes, operational applications, oil spill monitoring

## 1. Introduction

Pollution that comes from a single source, like an oil or chemical spill, is known as point source. Commonly, this type of pollution has bigger impact on the marine environment, but fortunately, it occurs less often than land runoff [1]. Oil spills occur after a collision and/or the sinking of oil tankers, under bad weather conditions, and are extremely hazardous in ports with dense maritime traffic. The environmental impact of oil accidents is immense on both the water ecosystems and the coastal environment, including the urban and economic growth of the affected coastal zones. Strong winds and significant water currents contribute to the creation of accidents and concurrently to the spreading of the spills. Ship collision or malfunction, or simply cleaning and sailing, can contribute to marine pollution by spreading garbage, black or gray water, sludge, water ballast, coatings or even air emissions, in deep sea or at seashore. The most common nautical accidents occur due to sinking or foundering, grounding, structural failure, scuttling, by contact or collision, explosion or fire, or after disappearance or abandonment [2]. The discharge from oil pipelines, oil platforms, and vessels is also causing significant damage to the marine environment and the coastal areas, including the urban and economic growth of the affected coastal zones. The Exxon Valdez (1989), Atlantic

Empress (1979), Amoco Cadiz (1978), and Torrey Canyon (1967) (Figure 1) are among the most renowned oil spills in history, that alarmed the scientific community and directed all toward the management of anthropogenic environmental disasters in the marine environment.

Spill modeling has a long history [3]. Since 1960s, numerous oil spill models have been developed to simulate weathering processes and forecast the fate of oil

Figure 1. (a) Exxon Valdez (1989); (b) Atlantic Empress (1979); (c) Amoco Cadiz (1978); (d) Torrey Canyon (1967).

#### Oil Spill Dispersion Forecasting Models DOI: http://dx.doi.org/10.5772/intechopen.81764

spilled, in terms of providing valuable support to both contingency planners and pollution response teams. These models, developed by various organizations, companies, and researchers, vary in complexity, applicability to location, and ease of use [4]. There are two categories according to the Industry Technical Advisory Committee (ITAC) for oil spill response. One category, known as oil weathering models, estimates how oil properties change over time, but does not predict potential migration of the slick. The second category includes trajectory or deterministic models, stochastic or probability models, hind cast and three-dimensional models. In addition to predicting weathering profiles, these models estimate the evolution of a slick over time. The first-generation models were limited to tracing the movement of rigid bodies under the influence of current and wind advection. Oil spreading was justified by the balance of forces, and although chemical processes played significant role, most of them were ignored in this modeling [5]. Second-generation models have been summarized in [6, 7], where some of the principal forces and major phenomena, determining the behavior and the fate of the chemicals at sea, were analyzed. The recent generation models are reviewed in many papers [8–12]. Some of the oil spill models that are currently available are: General NOAA Operational Modeling Environment (GNOME), MEDSLIK-II, SeaTrackWeb (STW), Model Oceanique de Transport d' Hydrocarbures (MOTHY), DieCAST-SSBOM (Shirshov-Stony Brook Oil spill transport Model), COastal Zone OIL spill model (COZOIL), etc.

These operational computer models, pondering major physical processes, efficiently simulate the movement, the spreading and the evolution of the floating chemicals. Strong winds and significant water currents, which are contemplated, are major contributors to both the creation of accidents and faster spreading of the oil. Such models can be used either in hind cast mode capable of tracing the source of a spill, or in forecast mode predicting the path, the horizontal dispersion, and the mass balance, assisting in this way the real-time crisis management.
