Soft Engineering Flashcards
How does beach nourishment work?
Replaces beach sediments eroded/transported by longshore drift. A large beach will absorb wave energy and protect the backshore from erosion.
What are the benefits of beach nourishment?
-Uses natural sediments = beach looks natural.
-Provides an amenity for recreation and so supports the local tourist industry.
What are the disadvantages of beach nourishment?
-Cost £10 per metre cubed.
-May have to be replaced frequently after winter storms.
-If sediments are dredged from offshore, it alters the sediment cell = removes habitats.
How does cliff-regrading work?
Regrading an unstable cliff, prone to sudden collapses, creates a new slope angle that is stable for the characteristics of the rock type.
What are the benefits of cliff regrading?
-Creates a natural looking slope.
-Will remain stable as long as the base of the slope is protected from erosion.
What are the disadvantages of cliff re-grading?
-Cost = about £1 million.
-Other defences needed to protect the cliff base.
-Cliff drainage may also be required.
How does cliff drainage work?
The cliff lithology has permeable above impermeable rock, drains with gravel are inserted to drain the cliff quickly.
What are the benefits are cliff drainage?
-Reduces the risk of mass movement after heavy rainfall.
-Looks natural once revegetated as engineering is not visible.
What are the disadvantages of cliff drainage?
-Only reduces the risk of mass movement, does not prevent it.
-Implementing across a whole cliff disturbs the cohesion of the rock layers.
How does dune stabilisation work?
Dunes can provide a natural barrier to sea level rise and storm waves, but are fragile. Monitoring their condition and repairing them with a geofabric/replanting the marram grass helps to keep them in place.
What are the benefits of dune stabilisation?
-Looks natural and is an effective barrier to higher sea levels/tides.
-Provides a natural ecosystem and recreational area.
-Can be used to restore dunes lost to storm surges/blown out by trampling.
What are the disadvantages of dune stabilisation?
-Costs £1000 per 100m for replanting dunes.
-May need to be fenced off while plant grow.
-Powerful storms can undo this.
