6 Human activity - Sandbanks

Question 1

Background

Answer 1

Dorset, England’s south coast
Sediment cell 5
Sandbanks peninsula is a spit that separates Poole Harbour (estuary) from Poole Bay

Question 2

Background: Who manages the Sandbanks peninsula?

Answer 2

Joint responsibility of Poole Borough Council, Poole Harbour Commission and the Environment Agency
Two Bays Shoreline Management Plan (Poole Bay and Christchurch Bay sediment sub-cell)

Question 3

Processes: What processes are occurring?

Answer 3

• LSD from east to west (sandbanks/poole bay)
• Tidal currents flowing into and out of Poole Harbour, transporting fine sediments
• Refraction of prevailing SW waves around the Isle of Purbeck
• Onshore and offshore transport of sediment by constructive and destructive waves
• Undefended cliffs at Hengistbury Head provides sediment input
• LSD from west to east

Question 4

Need for management: What is the economic need (properties) for management?

Answer 4

Residential properties - high demand and premium prices (4th highest/m2 in world)
Large houses >£10mil, luxury flats >£2mil
£18mil damage to residential properties over next 20 years with no intervention

Question 5

Need for management: What is the tourism need for management?

Answer 5

Beach major tourist attraction
Blue Flag for water quality and a gently shelving profile that makes it safe for swimming

Question 6

Need for management: What is the commercial need for management?

Answer 6

High value commercial properties (eg Sandbanks Hotel and Haven Hotel)
Both provide significant employment opportunities and generate spending in the local economy

Question 7

Need for management: Why is Poole Harbour an area which needs to be protected?

Answer 7

Sheltered waters of Poole Harbour make it a suitable port for cross channel ferris and cargo ships
Without sandbanks, LSD would transport sediment into the Harbour –> deposition in navigation channels

Question 8

Need for management: Why is Poole Harbour good for water sports and other marine clubs?

Answer 8

Shelters Poole Harbour from high energy –> good for water sports
Harbour home to yacht clubs and marinas
Internationally important wetlands and salt marshes

Question 9

Need for management: What effect would climate change have?

Answer 9

0.6m of sea level rise is predicted here by 2100
Cause flooding of many properties and could breach the peninsula at its lowest and narrowest point at junction of Shore Road and Banks Road
Cut off peninsula off from mainland

Question 10

Management techniques: How have rock groins been used?

Answer 10

To maintain a deep, wide beach by minimising the movement of sediment from NE to SW by LSD
Restricts sediment from entering the Harbour, protecting shipping lanes, also absorbs wave energy and reduces erosion - without groins, retreat rates estimated to be 1.6m/year

Question 11

Management techniques: How has beach recharge been used?

Answer 11

Conserve beaches
Sand dredged from offshore and sprayed onto the beach (£20/m3)
Recent trial of dumping sediment dredged from the Harbour just offshore, and using natural currents to transport it onto the spit, costs just £3/m3
Total, over 3.5m m3 of sediment has been added to Poole Bay beaches

If all sediment recharge used natural currents instead approx £60million would have been saved

Question 12

Management techniques: What is the overall management approach for Sanbacks?

Answer 12

Aim of the SMP is ‘Hold the Line’
Combined rock groin/each recharge strategy is so effective that the width of the beach at Sandbanks is increasing slightly - line is actually advancing