Preventing Beach erosion and Displacement
A beach is generally a narrow, gently sloped strip of sandy land that often lies alongside an inland body of water, such as a river, lake, or ocean. Sand and pebbles cover most beaches. Most coastal beaches are created by the gradual erosion of eroding coastal soil. Water, waves, and rain gradually fill up into the sea or the shoreline, and eventually collapse back into the soil of the beach. Sand layers can vary in thickness from a few millimeters to several feet.
Coastal erosion can occur on different scales. Seawalls and national-park boundaries can cause steep drops in levels of beach and seawall levels for stretches of coastline. These features may also lead to thinning and leveling off of stretches of sand which once contained shells and other materials that have eroded away. Although not always a threat to life, coastal erosion can threaten the property rights of coastal owners.
Coastal erosion can be controlled and prevented through a number of strategies. The most popular of these strategies is “stopping the waves.” Beach surfacing material such as blocks and sandbags are used to create edging, which keeps waves from entering the beach. Another strategy is preventing the rise of seawalls and shorelines. By channeling tide toward the beach and building protective dunes, the rate at which beach waves break against the shore is kept down.
A third method used to slow erosion is offshore levee protection. This system involves installing permanent floor drains to moving water that causes beach level rise. Limestone, gypsum, and quartz are used to prevent beach level rise by serving as an impermeable layer against water, as well as serving as support for the structures that build the shoreline.
If a body of water emptying into an offshore area becomes dam-like, this may also divert beach sand from moving into the sedimentary basin below. As with the edging strategies, structures to channel beach sand may be built to stop coastal erosion. When a body of water emptying into an offshore area is surrounded by sandbars of varying heights, the force of tides may be concentrated in one area. Seawater may flow between these sandbars, forcing the beach sand to move inland.
Although many of these methods are effective, it is difficult to apply them at all times. For example, gradual beach level rise may be less of a concern for someone living on the beach side than someone living at the end of the beach, where the sea level is rising faster. And changing beach temperatures during the winter months can erode beach materials. It is also important to remember that certain beach materials are more expensive to preserve than others. Sand is a beach building material that is easy to preserve over time. Beach materials such as shingles are more expensive to store than concrete or asphalt.