Shorelines are temporary geologic and topographic features. Explain this statement. (Hint: what are some of the forces affecting both the erosion and deposition of materials? What are some common temporary shoreline features – both erosional and depositional?)
Shorelines change due to the addition and removal of sediment by various forces. Some forces are natural and some are the result of manmade constructions. The most common deposit and removal is done by waves which strike the shore and move down the shore in a kind of sweeping moving action. If this wave ebbing and flowing were the only contributor to the changes to the shore, it would be small and almost predictable in its regularity, however it would change the shape of the shoreline. Tides caused by the moon bring waves directly perpendicular to the shore which in turn brings loose sand and deposits the sand before moving back out to sea with a removal of sediment. This process, move in, drop off sediment, move out taking more sediment continues year to year with both waves and tides.
It is also possible that geological events such as tsunamis or glacial melting would also change the shape of a shoreline. Larger shoreline features may be rearranged with larger forces acting on the shoreline. Major storms with winds and torrential rains have the force to change shorelines as well.
Occasionally it may be deemed necessary to alter a natural shoreline to make it more stable. These methods range from simple replenishment of sand in order to build up the dunes. A second approach to stabilizing shorelines is walls that are built perpendicular to the shoreline called groins and jetties. They are added to the shoreline and are intended to prevent the naturally occurring loss of sand.