Coastal management Flashcards
What are the four options for coastal management?
Hold the line- maintain the existing coastal defences.
Advance the line- build new coastal defences further out to sea than the existing line of defence.
Do nothing- Build no coastal defences at all, and deal with erosion and flooding if it happens.
Managed realignment- allow the shoreline to move, but manage retreat so it cause the least damage.
What is a sea wall (hard engineering)?
How it works:
>The wall reflects waves back out at sea, preventing erosion of the coast. It also acts as a barrier to prevent erosion.
Cost:
> It is expensive to build and maintain.
Disadvantage:
> It creates a strong backwash that erodes under the sea wall.
What are gabions (hard engineering)?
How it works:
> Gabions are rock-filled cages. A wall of gabions is usually built at the foot of cliffs. The gabions absorb wave energy and so reduce erosion.
Cost:
> Cheap
Disadvantage:
> ugly
What is a revetment (hard engineering)?
How it works:
> Reveltments are slanted structures at the foot of a cliff. They can be made from concrete, wood or rocks. Waves break against the revetments, which absorb the wave energy and prevent cliff erosion.
Cost:
> Expensive
Disadvantage:
> They create a strong backwash
What is a groyne (hard engineering)?
How it works:
> Groynes are fences built at right angles to the coast. They trap beach material transported through long-shore drift. This creates wider beaches, which slow the waves and so give greater protection against flooding and erosion.
Cost:
> quite cheap
Disadvantage:
> They starve downdrift beaches of sand. Thinner beaches don’t protect the coast as well, resulting in more erosion.
What are breakwaters (hard engineering) ?
How it works:
> Breakwaters are concrete blocks or boulders deposited off the coast. They force waves to break offshore. Therefore reducing the wave energy before it reaches shore.
Cost:
> Expensive
Disadvantage:
> Can be damaged in storms
What is beach nourishment (soft engineering)?
> Beach nourishment is where sand and shingle are added to the beaches from elsewhere. This creates wide beaches, which reduce the erosion of cliffs more than thin beaches.
What is beach stabilization (soft engineering)?
Beach stabilization can be done by reducing the slope angle and planting vegetation, or by sticking old tree trunks in the sand. It also creates wider beaches, which reduces erosion on beaches.
What is dune regeneration (soft engineering)?
Dune regeneration is where sand dunes are created or restored by either nourishment or stabilization of the sand. Dunes provide a barrier between land and sea, absorbing wave energy and preventing flooding and erosion.
Land use management for a dune
Land use management is important for dune regeneration. The vegetation needed to stabilize the dune can easily be trampled or destroyed, leaving the dune vulnerable to erosion.
Wooden walkways or fenced areas for the public all reduce the loss of vegetation.
How does marshlands reduce erosion?
They help protect coastlines from storms, storm surges, and erosion by creating a buffer between dry land and the sea, building up the height of the coast by trapping silt during floods and adding new soil from their decaying vegetation
What is coastal realignment?
Involves breaching an existing defense and allowing the sea to flood the land behind. Over time, vegetation will colonise the land and it’ll become a marshland.
What is hard engineering?
Hard engineering is often expensive, and it disrupts natural processes. They protect land from erosion.
What is soft engineering?
Soft engineering schemes are cheap and require less time and money, soft engineering is normally more sustainable and important compared to hard engineering.
What are shoreline management plans?
1) The coastline is split into stretches by sediment cells. For each cell, a plan is devised for how to manage different areas with the aim of protecting important sites without causing problems elsewhere in the sediment cell.
2) For each area within the cell, authorities can decide to hold, advance, or retreat the line, or to do nothing.
3) The overall plan for each sediment cell is called the shoreline management plan.
