Swanage Case Study

Location

• - Coastal town
• - South East of Dorset
• - Eastern end of Isle of Purbeck
• - 6.35 miles south of Poole

Why protect the coastline?

• - AONB
• - Jurassic Coast
• - World heritage site
• - Provides services (schools, banks, fire station) not only for itself but also for surrounding areas i.e Corfe Castle
• - European Blue Flag status beach
• - 5300 dwellings

Zone 1 - No active intervention

• - North (Sheps Hollow)
• - Chalk Cliffs - hard rock so more resistant to erosion
• - Land is low value farmland and SSSI land where fossils are found. For fossils to be uncovered, cliff must erode. Value of fossils > value of farmland.

Zone 2 - Active Holding

• - Cliff rock much softer (Wealden rock) and more vulnerable to erosion
• - Without defences, cliff would retreat at 0.6m per year = double the rate of chalk
• - High value land - Pines Hotel, predominant residential and commercial land use
• - Beach Replenishment - sand is dredged from Poole Harbour and added to Southern end of Swanage Bay. Began in 2006 when 90,000m3 of sand was dropped
• - Replenishment makes beach wider and increases distance which waves have to travel to hit the cliff
• - Needs to be recharged with 40,000m3 sand every 20 years
• - Cliff drainage + stabilisation below the Pines Hotel - extending the cliff forwards, making cliff less steep, longer + reducing chances of mass movement
• - Planting trees + vegetation = stabilisation
• - Soil nails and a concrete wall constructed in 2004, '£400,000'
• - Cliff drainage = excess water reduced = cliff less heavy after rainfall + also less vulnerable to freeze - thaw weathering

Groynes

• - Most cost effect + economically sustainable method
• - Several groynes built in 1930s, 18 replaced in 2005
• - Significantly reduce rate of LSD - sediment trapped on south side of groynes, so less transported to North
• - Rate of cliff erosion in south where rock is soft + land value is higher is reduced.
• - Beach builds = waves lose erosive power before reaching cliff = cliff retreat at a slower rate
• - Not very attractive

Zone 3 (No active holding)

• - Hard, Purbeck strata
• - Sea wall built in 1920s - absorbs wave energy and reduces erosion, also provides a promenade
• - Peveril point (headland) provides a natural defence to the area

Sustainability

• Sea Wall
• + social - provides a promenade
• - long term sustainability - produces a strong backwash which undercuts the wall
• Cliff drainage + stabilisation
• - Construction of wall created air pollution and destroyed habitats
• - Political - permission needed from 70 landowners for equipment to be driven along beach - only 68 gave permission = conflict
• - Social - aesthetics of wall
• Beach replenishment
• + Economic - builds beach = increased tourism
• + Social - protects livelihoods of residents, + maintaining natural aesthetics of beach
• Environment + builds beach = cliff top habitats preserved BUT - dredging of sand from Poole Harbour = disrupting eco systems
• Groynes
• + Economic - Build the beach = increase in tourism, protect high value land
• - not very attractive
• Economic sustainability = strongest as strategic zoning = areas most viable to erosion with high land value are given priority in terms of protection