Coastal Erosion

Mechanisms of Erosion

• Hydraulic impact - water is driven into the cracks and rock breaks loose
• Abrasion - sand and boulders abrade the cliff
• Solution
• Biological activity - animal borings, people

There are numerous that affect how much erosion occurs. Natural factors are very important in most areas, including the width of the beach, the amount of wave energy present, and the nature of the rock present.

Humans have become very important at changing erosion rates. Cliff tops are loaded with buildings, surface drainage is altered, and roads, seawalls, etc. are constructed. All of these man-made constructs accelerate erosion.

Control of Coastal Erosion

• Riprap - large resistant boulders are placed at the base of a seacliff. Riprap should not be discontinuous as this can hasten erosion.
  
  
• Seawalls - These structures are build to protect clifs. Instead, they will accelerate the erosion of adjacent property.
  



• Groins - are built to block the longshore drift
  
  
  
• Breakwaters - are built to reduce wave action on the coast. Unfortunately, sometimes they cause a build-up of sediment within the harbor. The Santa Monica breakwater (below), for example, required continuous dredging (350,000 m³/yr) when it was in existence.
  

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