Beach erosion is the long-term process describing the removal of sand, sediment, and rock material from a coastline over time. This process results in the landward retreat of the shoreline, which is a natural adjustment to changing conditions. Chronic erosion occurs when the rate of sediment removal exceeds the rate of supply over an extended period, destabilizing the beach system.
Natural Drivers of Coastal Change
The coast is continuously shaped by powerful forces that drive sediment transport without human intervention. Wave action is the most significant of these forces, as the energy from breaking waves moves vast quantities of sand. Waves that approach the shore at an angle create a current parallel to the coastline, known as longshore current, which constantly shifts sediment along the beach face.
Seasonal changes in wave energy cause a cyclic pattern of erosion and accretion. For example, high-energy winter storms often pull sand offshore to form sandbars, while milder summer waves tend to push that sediment back toward the beach. Major storms, such as hurricanes and cyclones, cause acute erosion events by generating powerful storm surges and extreme wave heights. Beyond wave action, sea level rise plays a significant role by increasing water depth, allowing wave energy to reach further inland and higher up the shore profile. This process causes the entire beach system to migrate landward, resulting in a net loss of beach area.
Human Activity and Accelerated Erosion
While natural processes are responsible for baseline erosion, human activities often interfere with the delicate balance of the coastal system, accelerating the rate of land loss. One major factor is the construction of infrastructure, such as jetties and groynes, which are built perpendicular to the shore to trap sand. These structures create a sand build-up on the up-current side but effectively starve the beaches immediately down-current of their natural sediment supply, leading to severe localized erosion.
Coastal development also plays a part, especially when buildings are constructed too close to the natural dune line. Sand dunes act as a sediment reservoir that supplies the beach during storm events, but construction can destroy or destabilize these natural buffers. Furthermore, upstream river modifications, particularly the construction of large dams, prevent the natural flow of sediment-laden river water from reaching the coast. This interruption cuts off the primary source of new sand for many coastal regions, causing chronic sediment deficit, or “beach starvation.”
Consequences of Beach Loss
The retreat of the shoreline has negative outcomes that affect both the natural environment and human communities. Environmentally, the loss of sandy beaches and adjacent dune systems destroys habitats for coastal wildlife, including nesting sites for sea turtles and various species of shorebirds. The erosion of barrier islands and coastal wetlands also removes natural storm protection for inland areas.
When the beach and its associated dune system are diminished, the interior land becomes vulnerable to storm surge and flooding. The economic effects are immediate, starting with the loss of tourism revenue as recreational beaches shrink or disappear entirely. Additionally, erosion directly threatens private property and public infrastructure, such as roads, utilities, and coastal homes, leading to costly damage and reduced property values.
Managing Erosion and Coastal Protection
Coastal management teams employ various strategies to mitigate or reverse the effects of beach erosion, broadly categorized into hard and soft stabilization methods. Hard stabilization techniques involve building rigid structures designed to stop or alter the natural movement of water and sand. Examples include seawalls and revetments, which are shore-parallel barriers intended to protect upland property.
These hard structures often increase erosion on the seaward side by reflecting wave energy. Because of these drawbacks, there is a growing preference for soft stabilization methods that work more harmoniously with natural coastal processes.
Soft stabilization involves techniques like beach nourishment, which is the process of pumping or trucking in large volumes of sand from an offshore or inland source to widen an eroded beach. Although this method restores the beach for recreation and provides a sacrificial buffer against storms, it is a temporary solution that requires repeated applications and significant expense. Dune restoration and the planting of specialized vegetation are also soft methods, as they help to stabilize the existing sand, capture wind-blown sediment, and rebuild the natural protective reservoir.