Parameterization of the Degree of Burial of Objects in the Coastal Ocean

An issue in coastal management is contamination of coastal sites by anthropogenic waste objects, particularly abandoned underwater munitions, i.e. underwater unexploded ordnance (UXO). Critical to site remediation planning is knowledge of the degree to which these UXO are buried. In coastal environments with sandy bottom sediments burial occurs by scour, which occurs when the presence of an object in a granular bed accelerates the surrounding flow thereby enhancing the local erosion. A scour pit is formed beside and downstream of the object into which it becomes buried. As burial progresses the degree of local acceleration diminishes and an equilibrium depth is reached. Results of laboratory experiments on scour burial designed to encompass the range of objects representative of UXO will be presented. These results are used to improve the modelling of the scour burial for use in site remediation efforts. Improvement in the scour burial parameterization, traditionally based on the sediment Shields parameter, has been obtained by using a new physics-based relationship for equilibrium scour burial that provides a more reasonable scaling of the extant laboratory data. [This study is supported by the Strategic Environmental Research and Development Program.]