To facilitate the assessment of seabottom ice scours on pipelines,' a computerized ice scour data base has been established for the Canadian Beaufort Sea. Side scan sonar, bathymetric and sub-bottom profile data are digitized, computer processed, and incorporated into a location-referenced data file. The digitization process includes outlining the discrete scour events on sonographs and tracing the seabed profiles on echographs. Individual scours are defined in a 27 column data file and characterized by 1ocation, orientation, length, width, form, smoothness, sediment infilling, associated sediment type and other features. Scour depths are derived' by automatic measurement from computer-normalized echo sounder profiles.
Scour parameter distributions and inter-relationships can be statistically analyzed and graphically illustrated. In addition, the relationships between scour parameters and environmental conditions such as bathymetry can be examined for the entire data set or selected subsets. This scour analysis technique allows for a full range of conditions to be tested for potential impact on Arctic marine pipeline design.
Ice scour marks identified by side scan sonar on the continental shelf of the Canadian Beaufort Sea are evidence of historic and recent ice/seafloor interactions. (4) The grounding of sea ice (generally in the form of pressure ridges) represents a geologic hazard to the safe installation of subsea petroleum facilities. Adequate design for the protection of such structures requires an understanding of ice scour processes and an accurate data base' of the scour parameters critical to risk assessment.
Analysis of the ice scour record for engineering purposes is problematic as it represents a cumulative geologic history of scouring events including the effects of sea level changes, geologic processes of scour degradation (sedimentation, erosion) and temporal variations in sea-ice conditions. A number of statistical and interpretive studies have been undertaken in the Beaufort Sea, (e.g. 1, 2, 3, 4, 5, 6, and 7) and more recently in numerous proprietary industry studies.
The most critical phase preceding the statistical analysis of ice scour data involves an accurate interpretative transfer of each scour parameter from the analogue acoustic data to a computerized data base. Traditionally, data analysis has been done manually using measuring scales for lengths, widths, orientations, etc. However this is a tedious, subjective and costly process, particularly for large data sets which exist for the Beaufort Sea
A computer analysis technique has recently been developed by Geoterrex Ltd. whereby ice scour data is first digitized by an experienced interpreter, subsequently processed by specialized software to generate scour parameters and finally listed in a comprehensive location referenced data base. To date, in excess of 5,000 km of industry/government acoustic data from the Beaufort Sea have been incorporated into the data base. This technique has been found to be both highly accurate and time efficient.
The object of this paper is to present an overview of the various data processing methods and to illustrate some of the interpretative capabilities of this ice scour analysis system.