Clients: U.S. Department of the Interior, Bureau of Ocean Energy Management, Regulation, and Enforcement (BOEMRE)

Each spring, snow melt and the break-up of river ice cause fresh water to arrive at the Arctic coast prior to the break-up of the nearshore sea ice. If the sea ice is frozen to the bottom, as typically occurs to depths approaching 2 m, the "bottomfast ice" forms a dam that causes the river discharge to flow on top of the sea ice. The overflow, which can exceed a depth of 1 m, spreads offshore until it drains through holes and cracks in the ice sheet. This brief but energetic phenomenon constitutes a potential hazard to offshore oil and gas development in that it can impede access to facilities, disperse contaminants, and expose buried subsea pipelines through the phenomenon known as "strudel scouring".

In 2007, a study team led by Coastal Frontiers and DF Dickins Associates was selected by the Minerals Management Service (now BOEMRE) to investigate river overflood in the Alaskan Beaufort Sea.

Satellite Image of Beaufort and Chukchi Seas near Barrow, AK

Study Tasks

  • Map the annual river overflood boundaries from 1995 through 2007 using satellite imagery and helicopter-based survey data

  • Assess and compare the utility of imagery from alternative satellite platforms, including those that use the visible spectrum (Landsat 7, SPOT, and MODIS) and those that use SAR (ERS-2 and RADARSAT)

  • Investigate the environmental factors that govern river overflood

  • Assess the hazards associated with overflood (primarily strudel scouring)

  • Compile a database containing approximately 2,000 strudel drainage features and 1,000 strudel scours documented by 19 industry-sponsored studies

  • Incorporate the overflood and strudel data into a GIS database

Based on an assessment of strudel scour frequency and severity, the river overflood areas were segregated into Primary, Secondary, and Tertiary zones according to water depth. The three zones can be used to assess the relative risks associated with prospective pipeline routes.