Human Actions & Coastal Recession
- Rapid coastal recession is caused by physical factors (geological and marine) but can also be influenced by human actions such as dredging, dams or coastal management
- These actions affect the processes within the coastal system including those in the sediment cell
Dredging
- The removal of sediment from rivers or the sea
- This impacts on the amount of sediment being deposited at the coast
Dams
- The construction of dams, traps river sediment behind the dam wall
- It is estimated 100 billion tonnes of sediment is stored behind the world's dams and this increases by a billion tonnes each year
- Like dredging, this starves the coast of sediment
- It is estimated that dams on the river Ebro in Spain have led to a 93% reduction in sediment downstream
- The reduction of sediment supplied to the coast due to dams and dredging leads to greater coastal erosion because:
- Beaches decrease in size as they are not being supplied with sediment
- Destructive waves have more impact by increasing the rate of coastal erosion
Coastal management
- Coastal management can impact on the rate of recession because it affects the rate of erosion
- In some areas coastal defences such as in places like Hornsea sea walls and rip rap reduce the amount of erosion
- This slows recession of the coast
- In other areas coastal management affects the movement of sediment
- Groynes at Hornsea on the Holderness coast reduce longshore drift
- This starves areas down the coast such as Mappleton of sediment also known as terminal groyne syndrome
- As with dams and dredging the reduced supply of sediment decreases beach size and increases the impact of destructive waves
Exam Tip
The advantages and disadvantages, as well as real life examples of coastal management are covered in detail in section 3.4. You should ensure that you know how coastal management impacts on coastal recession.