Recent shoreline mapping projects in British Columbia and significance to oil spill countermeasure planning

A number of detailed physical shore-zone mapping studies have been recently completed in British Columbia. Results indicate that over 50% of the shoreline consists of beaches. Detailed mapping in the southern part of the province shows that 55-65% of the coast contains sediment shoreline, while the southern Queen Charlotte Islands have beaches on ca 52% of the shoreline. The results have important implications for oil spill planning, in that sediment or beach shorelines are regarded as having higher oil retention and oil residence periods than rock shorelines. However, ground observations on the coast indicate that the immediate subsurface sediment on many beaches is either fine sand or other impermeable material which would limit oil penetration and retention. Highly permeable pebble/cobble beaches appear to be uncommon. These observations imply that beaches are more common in the region than previously thought and are likely to pose a more complex cleanup problem than would rocky shores. In addition, when estimating potential oil residence times for gravel beaches, oil spill sensitivity models must take into account the observations that indicate that surface sediment texture is not necessarily a good index of permeability. 12 refs., 1 fig., 3 tabs