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Bluff Shoreline

Komas Bluff, Denman Island

Bluff, James Island
Bluff1 Bluff .Jamesisland WEB
Photo Credit:  Andrew Fyson, Denman Conservancy Association


Description

Bluffs are formed of steeply-sloped compacted sediments, not rock, and for that reason are often eroding. Bluffs occur on the eastern shore of Denman Island and the south ends of Sidney and James Islands.

The bluff shore type is less than 1% of the total shoreline in the Islands Trust area based on the twelve major islands that had shoreline mapping completed.  Only Denman Island at 9% and Galiano Island at 0.4% have bluffs, all other islands have no bluff shore type including South Pender Island.  

Physical Features

Bluffs are often a major source of beach sediment and can provide a significant supply of easily-erodible materials that can be transported primarily in longshore drift cells but in places sediments can also be transported offshore by wave and current action. 

Spits and coastal lagoons may form where the transported sediments accumulate, and interruption of the sediment supply feeding the longshore transport, as might be caused by construction of seawalls or jetties, can change sediment deposition features downstream from the structures.  

Bluffs are very dynamic on a human time scale.

Biological Features

On moderate to high energy mobile beaches at the base of eroding bluffs, the intertidal zone may be bare of attached algae and invertebrates. Burrowing animals such as clams and various species of worms can be common, as are mobile invertebrates such as sea stars and crabs.  

Eelgrass, a shallow water flowering plant, often found seaward of coastal bluffs in areas of finer substrates of sand or mud with protected wave exposures. A highly productive community, eelgrass beds provide important nursery areas for many species of fish, including herring and juvenile rockfish.  

Shallow nearshore water can be important feeding areas for diving sea ducks and other waterfowl. 

Page last updated: 01/10/15
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