Signs of Abundance Tour – The information on this page compliments that which appears on the sign that has recently been erected on Goose Spit. To go to the map of all the signs in this series click here.

A Dynamic Landscape

Spit Formation

A spit or sandspit is a deposition landform in the formation of a bar or beach which forms when longshore drift reaches a point where the direction of the shore inland re-enters or changes direction more than 30 degrees, such as at the mouth of the K`ómoks Estuary. At this point the longshore current dissipates and can no longer carry the full load. Thus the sediment is dropped or deposited. As longshore drift continues the amount of sediment deposited increases and a sandspit is formed. This process will continue until the water pressure (such as a river) becomes too strong and does not allow sand to deposit. The length and height of the spit is dependent on the strength of wave driven current, the wave angle, and the height of incoming waves. A spit has two important features: (1) the proximal end (or head) is attached to the land and may form a barrier between the sea and estuary, and (2) the distal end (down-drift end or tail) may become long and curved due to the influence of varying wave direction.

Goose spit was formed and is maintained with sand coming from the Willemar Bluffs. It comes to an end where the water pressure from the Courtenay River carries the sand away from the area. Goose Spit protects Comox Harbour and much of the K’ómoks Estuary.

Information from www.geocaching.com.

Longshore Drift

Longshore drift, also known as longshore transport or littoral drift, is the movement of sediments (clay, silt, sand and shingle) when waves meet a coastline at an angle and then backwash perpendicular to the shore, thus moving sediment in a zigzag pattern through the water alongside the beach.  Therefore, longshore drift is dependent on the strength and direction of prevailing winds, which drive the force and direction of the waves, and the degree of backwash, which erodes the shoreline and moves sediment down the beach due to gravity.

Sometimes people build walls such as groyns to try and slow down longshore drift. The sand and gravel just ends up piled along the groyn and the beach or landform on the other side of the groyns are deprived of the sand they used to receive. These beaches and landforms, such as spits, will shrink and could disappear over time degrading and reducing important habitat for marine life.