Shoreline Types

  • Sand and Gravel

    Sand and Gravel Shores are formed where a great deal of smaller particle sediment is available from sources such as sandstone bluffs.

  • Rocky Shore

    Rocky shores typically consist of a solid rock bench across the intertidal zone, which may or may not extend up to the high water mark.

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  • Boulder and Cobble Shores

    Boulder and Cobble Shores occur where cobble or heavy gravel sediment is available from eroding rock benches or cliffs.

  • Coastal Bluffs

    Coastal Bluffs are steep slopes where soil and vegetation cover the underlying rock formations.

  • Estuaries and Mud Flats

    Estuaries and mud flats can include large flat deltas such as the Fraser River Estuary, and steep river mouths such as those found at the head of many coastal fjords.

What are the different shoreline types?

There are five main types of shorelines. The case studies on this site are categorized by shoreline type and by city or location. Please review the sections below to learn more about each shoreline.

Sand and Gravel Shores

Sand and Gravel Shores are formed where a great deal of smaller particle sediment is available from sources such as sandstone bluffs.

Often these shores are very sensitive to disturbance and can change very quickly. Sand and gravel shores are found on both steeply sloped shores, and coastal plains that have a significant supply of loose sand, gravel or small cobbles. These materials erode easily and are readily transported by wave and current action. Coastal cliffs (bluffs) are often a major source of beach sediment.

Features such as spits and coastal lagoons can be created when the sediment associated with longshore drift accumulates. Finer sediments, including gravel and sand, are often moved down the coast by wave action and accumulate as pocket beaches in sheltered bays between headlands, or as gravel beaches near high water in small indentations along the coast.

Sand and gravel shores are highly sensitive to human interference and interruption of longshore transport processes. Breakwaters, groynes and modifications to the onshore/offshore movement of sediment transport can have serious effects. Coastal plain shores are also susceptible to flooding during high tides, surges and storm waves.

Rocky Shores

Rocky Shores are usually very stable and cover much of the BC coast. They are quite resistant to change and provide habitat for a variety of intertidal organisms.

A rocky shore typically consists of a solid rock bench across the intertidal zone, which may or may not extend up to the high tide line. Thin gravel and boulder veneer deposits are often found on these benches, but usually cover less than 10 percent of the intertidal area.

This type of shore can also be a near vertical rock cliff that may extend above and below the intertidal zone. Sand, gravel and cobble sediment deposits often form small beaches near the high tide line. Rocky shores are resistant to erosion and do not provide a significant supply of unconsolidated sediment to the coast.

Boulder and Cobble Shores

Boulder and Cobble Shores occur where cobble or heavy gravel sediment is available from eroding rock benches or cliffs. If the sediment includes some finer material, a dense cover of stable shore vegetation will grow.

Rock and large sediment shores are usually found on rocky coasts where loose sediments overlay 10 to 40 percent of the intertidal shore area. These sediments usually form thin layers of cobbles or heavy gravel.

The main source of these sediment deposits is wave erosion of the adjacent rock bench or cliffs. Large sediments such as boulders or cobbles do not usually move along the shore but form what is called a “lag deposit” on top of the solid bedrock.

Coastal Bluffs

Coastal Bluffs are steep slopes where soil and vegetation cover the underlying rock formations. Many of today’s coastal bluffs were formed at the end of the last ice age.

Coastal bluffs are an important source of sediment to beaches and coastal spits. Arresting erosion by hardening the toe of bluffs can lead to starving downstream beaches of these sediments.

Low Banks are formed of sediment less than 5 meters in height. They can be considered small coastal bluffs, as many of the physical processes (wave erosion, sediment transport) are similar, with the exception that upland slope processes (surface and groundwater runoff) affect higher coastal bluffs more than low bank areas.

Estuaries and Mud Flats

Estuaries and Mud Flats are very sensitive to change. Estuaries are formed where a river enters the ocean.

Rich nutrients and fine sediments carried by the rivers, the variety of habitat created by the formation of deltas, and the mixing of fresh and salt water make estuaries highly productive. They are important nursery habitats for many kinds of fish and invertebrates.

Estuaries come in many forms. They include large flat deltas such as the Fraser River Estuary, and steep river mouths such as those found at the head of many coastal fjords.

The form of the estuary depends on a number of factors: the river’s flow and volume, the topography and water depths near the river mouth, and the type, size and availability of sediment in the catchment area. Typically, large rivers with a relatively flat mouth, such as the Fraser, form extensive deltas made up of fine sand and silt sediments. Steep rivers may also form small deltas if there is an upland source of erodible material. In these situations, the sediment on the delta is usually much coarser gravel and cobbles.