CASE STUDY - Christchurch bay

Question 1

management strategies implemented (intentional)

Answer 1

• timber groynes at Hengistbury Head and Milford-on Sea –> interrupts LSD
• sea walls and Friars Cliff and Milford-on-Sea –> reduce erosion and protect high-value infrastructure
• cliff drainage and vegetation –> reduce mass movement and cliff erosion
• beach nourishment at Hurst Spit —> maintain its role as floor barrier

Question 2

reasons for the management strategies implemented

Answer 2

• Economic: £50m+ real estate, e.g., holiday homes at Naish and golf course.
• Environmental: Protect SSSI (Naish), prevent erosion of natural defences.
• Social: Tourism value (e.g., Christchurch) and coastal access.

Question 3

Impacts of management strategies on PROCESSES & FLOWS BUDGET

Answer 3

• groynes interrupt LSD - starving Hurst Spit of sediment
• cliff stabilisation (drainage and rip rap at Barton-on-Sea and Highcliffe) - reduces natural cliff erosion - leading to lower sediment input into sediment budget
• sediment stored at groyned beaches (eg Milford-on-Sea) but downdrift areas are depleted of sediment
• beach nourishment at Hurst Spit artificially maintains sediment levels but requires regular replenishment - ££ and not sustainable in the long term

Question 4

Impacts of management strategies on ENERGY BUDGET

Answer 4

• sea walls at Friars Cliff and Milford-on-Sea reflect wave energy
• rip rap (Naish Beach) allows percolation of swash energy - reducing reflected wave power and slows erosion
• groynes interrupt wave-driven longshore transport, trapping sediment but reducing downstream movement and energy redistribution

Question 5

Impacts of management strategies on CHANGING LANDFORMS

Answer 5

HURST SPIT
- would normally grow but starved of sediment due to groynes
- maintained by artificial nourishment
- not retreating - holding the line

HIGHCLIFFE CLIFFS
- stabilised with rip rap + veg
- reduced slumping but blocks sediment supply from cliff
- less upper beach formation - natural dynamic processes disrupted

NAISH BEACH
- more natural with embryo dunes and less hard engineering
- cliff is steeper due to rapid erosion of clay

FRIARS CLIFF
- sea wall reflected wave energy, steepening the beach profile and increasing basal erosion

Question 6

Consequences of these changing landscapes

Answer 6

• terminal groyne syndrome - east of Barton-on-Sea –> bc upstream groynes rap sediment so more erosion downstream –> stepped coastline (defended sections contrast with defended ones)
• more embayment in unmanaged areas –> where clay cliffs erode rapidly no protection = high erosion = recessed coastline
• fragmented coastline –> some are heavily managed like Friays Cliff and Milford, others are ‘do nothing’ zones. –> loss of sediment cell balance