sand gravel 1  220x136 hhWhat are sand/gravel shorelines?

Sand and gravel shorelines have steep or shallow slopes and are composed of sediment that ranges from pebbles to fine quartz sand or muddy sand. They are dynamic environments characterized by constant movement of the sediment with the waves and currents. Most of the life supported by these types of shorelines resides within the sediment.

Where are sand/gravel shorelines found around the CRD?

Some of the more well-known sandy beaches in the region include Sidney Spit, Island View Beach and Witty’s Lagoon. In the main urban harbours of the Capital Region, smaller sand/gravel areas and pocket beaches can be found in Esquimalt Harbour and Portage Inlet and the Gorge Waterway. Coburg Peninsula in Esquimalt Lagoon is a unique example of a coastal sand dune system, on a barrier spit formation.

How are sand/gravel shorelines formed?

The sediment that forms these shorelines often comes from glacial till deposits. Glacial till is ground-up rock that was pushed in front of a glacial ice sheet as it advanced, or sediment that was deposited by rivers formed from the retreating ice sheet. Rivers or streams may also deposit fine sediments. The forces of waves, currents and tides control the formation and shape of these shorelines. Waves erode bluffs in one location and deposit the sediment in other locations (see coastal sediment processes).

What lives on sand/gravel shorelines?

Sand and gravel shorelines support fewer types of organisms than do rocky shorelines or boulder/cobble shorelines. However, large numbers of individuals may be present, despite the fact that most aren’t immediately visible. Many animals burrow in the sediment to cope with varying temperature and salinity and constantly shifting sediment. Some of the species found on sand/gravel shorelines are described below.

Backshore zone (above the high tide line)

  • Vegetation such as sea asparagus, sandwort, dune grass, wild rose
  • Insects, spiders, small mammals such as mice

Intertidal zone (between high and low tide lines)

  • Microorganisms such as bacteria, diatoms, blue-green algae and protozoa
  • Shellfish such as sand dollars, clams, sand crabs
  • Worms such as lugworms and bristleworms
  • Amphipods such as “beach hoppers”
  • Birds such as sand pipers, plovers, killdeers, Great Blue Herons, crows and gulls forage on sand/gravel shores

Subtidal zone (below the low tide line)

  • Vegetation such as eelgrass and green algae; kelp in larger gravel
  • Anemones, jellyfish, clam worms, bat stars, sea cucumbers
  • Dungeness crabs, geoduck clams, native oysters, hermit crabs, mud shrimp, moon snails
  • Fish such as herring, sole and juvenile salmon (in shallow, protected areas)
  • Birds such as surf scoters, cormorants, loons and geese

Why are sand/gravel shorelines important?

These shorelines provide habitat for wildlife, and recreation opportunities for people. Sandy beaches may contain back shore dunes, which support some rare species and are very sensitive to disturbance.

What threatens sand/gravel shorelines?

Due to their enormous popularity among sunbathers, beachcombers and surfers, sand and gravel shorelines are highly prized real estate. Unfortunately, development too close to the beach can severely alter natural sediment processes.
  • Seawalls and other shoreline reinforcement, designed to prevent property damage by waves, can paradoxically result in greater erosion and loss of habitat (see coastal sediment processes and altered shorelines).
  • Removing protective vegetation can destroy fragile dune ecosystems and cause sand to be removed by the wind.
  • Trampling can damage sensitive plants among sand dunes and driftwood.
  • Sediment and pollution can enter the marine environment from runoff in the watershed, causing damage to marine plants and animals. Types of pollution include: pesticides and fertilizers from farms and gardens; oils and heavy metals washed off roads by rainwater; soaps and hazardous chemicals disposed of in storm drains or household sinks/toilets.

How can I help protect sand / gravel shorelines?

For information on protecting shorelines, please visit our How Can I Help section.

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© Image courtesy of Mary Sanseverino

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