Komas Bluff, Denman Island
|Photo Credit: Andrew Fyson, Denman Conservancy
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
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.
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
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.
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.