Accidental releases of oil and oil products will cause extensive damage to environment, if timely and effective measures are not available. Predicting the consequences of spilled oil is of significant importance for emergency management. Although software for risk assessment of gas pipelines is very popular, few are available for hazardous liquid pipelines, due to the difference in behaviors of accidental releases of gases and liquids in the same situation. The major differences are that the spread of released oil is mainly affected by the topography of the land and may result in pollution of soil or waterways, while gas pipeline failure may form gas clouds or explosions and merely pose environmental pollution problems. An integrated model was developed in order to analyze the environmental consequences of spills from oil pipelines. The method presented in this paper allowed to predict the flow trajectory of released liquid from a pipeline and other relevant parameters, including the extent of spread of the oil and the proportion of release reaching any important location, such as a river, in any given topography. The methodology has been applied to a release, which occurred in Marshall, Michigan, in 2010. The results obtained are of the correct order of magnitude compared with realistic data. A case-study is presented and discussed to illustrate the features of the methodology. The results confirmed that the proposed model may be considered an important tool within a comprehensive approach to the management of risk related to onshore oil pipelines.