Coasts Case Study: Lyme Regis Hard Engineering

South Coast of Dorset

Long fetch – 1000’s of miles across Atlantic = high wave energy = lots of erosion

Cobb stopped LSD = no beach for protection

Blue Lias clay and Shale = lots of landslides

Black Venn – largest area of landslides in Europe – doing nothing

Phase 1 and 2 complete. Stage 3 not happening b/c not worth it

Phase 1 completed in 1995 – sewage pumping station in the new wall = clean water. Protected by 21400 tonnes of rock armour (labradorite) – enviro rewards

Phase 2 completed between 2005 and 2007 – cost £17 million.

Hard and Soft engineering

– New sea wall (250m),

rock armour (36000 tonnes) in front of wall.

Piles (1150) to support slopes,

(2300m) of drainage pipes,

planting (7500m2) to increase soil stability and disguise work,

beach shingle (71000 tonnes) and sand (41000 tonnes) imported

Phase 3: Monmouth beach suffered big landslides – not holding the line as it is not worth protecting

Cost of 1,2 & 5 = £33 million CBA done

52.5 mil x 6 =£315 million    Cost:benefit   1:6