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Caspian Sea Scour

During winter, wind stresses on sea ice in the northeast Caspian Sea result in the formation and movement of ice ridges and grounded ice piles called stamukhi. These grounded ice ridges and stamukhi cause scours and pits in the seabed beneath. The potential loads exerted on pipes by these scouring events is an important factor in pipeline design and routing.

(Right: Stamukha illustration courtesy of Lusilier)

C-CORE conducted a project to determine the frequency and distribution of pit and scour features (such as depth, width, area, etc.) from multi-beam survey data in the area of interest and extrapolate findings to infrastructure reliability targets for input into the design process.

A key aspect of the work was the statistical treatment of uncertainty in the data. Methods were developed to account for uncertainty due to the limited number of years of data available and the  uncertainty in the distribution type. Additional variations in scour and pit parameters relate to water depth; soil type; annual variation in metocean conditions; distance to existing structures; and distance to shoreline – all of which must be taken into account.

A stochastic scour model was implemented that considers soil type and was calibrated to match observed distributions of scour widths and depths given the general distribution of soil properties, ice feature sizes and shapes, and water depths. The model accounted for changes in ice thickness during the year, the occurrence of wind-induced ice movements, and changes in water depth due to surge and seabed slope.  The model provided a distribution of scour depth parameters for different soil types.

This project is more fully described in the technical papers linked here:

(Above: Field researcher atop an ice ridge in the Caspian Sea)

Parr, G., Fuglem, M., Jordaan, I., Verlaan, P., 2013, Stamukha pits – input characteristics for design of pipelines in the Caspian sea, POAC.

Fuglem, M., Parr, G., Jordaan, I., Verlaan, P., Peek, R., 2013, Sea ice scour depth and width parameters for design of pipelines in the Caspian sea, POAC.