Shoreline Processes and Features Outline Forces Acting on the Shoreline Wave Impact Abrasion Wave Refraction Longshore Transport Erosional Features Wave-Cut Cliffs and Platforms Sea Arches and Sea Stacks Depositional Features Spits, Bars, and Tombolos Barrier Islands Stabilizing the Shore Protective Structures Beach Nourishment

Forces that act on the Shoreline (1) Wave Impact and (2) Abrasion Caused by Sand/rocks + energy Caused by water + energy

Forces that act on the Shoreline Waves usually approach the shore at a slight angle. Wave refraction causes wave’s path to bend and hit the shore straight on Wave Refraction causes the headlands to receive more energy than beaches. More Energy = More Erosion This shoreline will slowly straighten

Forces that act on the Shoreline Although waves are refracted most still reach the shore at a slight angle. This results in Longshore Transport Longshore Transport A near-shore current that moves fine suspended sand parallel to the coast

Erosional Features These features are produced at areas of the shore that experience high energy impacts from waves

Wave-Cut Cliffs and Platforms Erosional Features Wave-Cut Cliffs and Platforms Platform

Sea Arches and Sea Stacks Erosional Features Sea Arches and Sea Stacks

Depositional Features Features produced by surface currents transporting sediments to areas that receive low impact wave energy LOW ENERGY IMPACTS ALLOW SEDIMENTS TO BE DEPOSITED OUT OF THE LONGSHORE CURRENT

Depositional Features Spits, Bars, and Tombolos

Depositional Features Barrier Islands Narrow sandbars parallel to, but separated from the coast They may start off as sand spits that are later cut off from the mainland by erosion

Stabilizing the Shore Large storms can erode shorelines far greater than average erosion rates. This can effect the natural evolution of the coast, wildlife, and cause property damage This is why large sums of money are spent every year to prevent coastal erosion

Groins, breakwaters, and seawalls protect the coast from erosion They may be doing more harm than good and they need to be maintained Stabilizing the Shore Groins, breakwaters, and seawalls protect the coast from erosion Groins seawall Breakwaters

Stabilizing the Shore Beach Nourishment is the addition of sand to beaches and is an alternative to protective structures Drawbacks: It is expensive to move huge volumes of sand, transported sand “clouds” the water, alters and kills marine habitats, and removes sand from river systems that eventually would eventually make its way to the ocean