Abbot Hall Farm (CASE STUDY of soft management scheme)
Managed Realignment along the Essex coastline
1. What is ‘coastal squeeze’?
Coastal squeeze occurs when beaches and salt marshes are trapped between rising sea level and hard defences such as seawalls and flood embankments. On natural coastlines, beaches and salt marshes would simply migrate inland, but the presence of hard defences (e.g. sea walls) make this impossible. Thus instead the sea rises over the salt marshes, gets pinned against the sea wall, leading to deeper water which subsequently causes erosion.
2. Define what is meant by ‘Managed Realignment’?
Managed retreat or managed realignment is a sustainable coastal management solution. It involves setting back the shoreline and allowing the sea to flood areas that were previously protected by embankments and seawalls.
3. How much is the sea level rising along the Essex coastline?
Along the Essex coast the sea level is rising by around 6mm a year.
4. Why is the sea level rising along the Essex coastline?
The 2 reasons for sea level rise along the Essex coastline are; global warming and the settling of the land mass in the south-east due to Isostatic readjustment.
5. When was the sea wall at Abbotts Hall Farm breached?
The sea wall at Abbotts Hall Farm was deliberately breached in October 2002.
6. What is the purpose of allowing the sea wall at Abbotts Hall Farm be breached?
The scheme works by allowing salt water back onto the land originally reclaimed by the construction of the sea wall over 3000 years ago.
7. Why was the breaching of the sea wall timed to precede spring tides?
The breaching of the sea wall was timed to precede spring tides, allowing each tide to float in seeds from the existing marsh outside the breached wall. By midsummer, thousands of new salt marsh seedlings were covering the fields. The development of 81 ha of mudflat, pioneer salt marsh and coastal grassland had begun.
8. What positive changes has this sea wall breaching at Abbott Farm Hall bought about?
· Salt marsh is rare in Europe so this is a positive ecosystem development
· Reduced the pressure on sea walls elsewhere along the Blackwater Estuary
· Saved £500, 000 in sea defences ((reduced the cost of maintaining non-sustainable or expensive sea defences)
· Created a natural defences against flooding and erosion
· Created new wildlife habitats, i.e. inter-tidal mudflats and salt marshes
· restored valuable sediment sinks
9. What disadvantages are associated with managed realignment?
A certain amount of land will be lost in this process while beaches are being built up resulting in settlements, farmland and other property being destroyed. Because of this, managed retreat is often not a socially acceptable plan and may invoke the need for compensation to land-owners. Furthermore managed realignment may interrupt communications and thus there may be the need for new roads and pipelines to be laid.
10. What is a polder?
A polder is a tidal area enclosed by wooden fencing that is designed to regulate tidal flow. This reduces erosion and encourages deposition of sediment. The purpose of polders is to encourage salt marsh creation.
11. How many polder sites are there along the Essex coastline?
There are 26 polder sites in total along the Essex coastline
12.Why are the materials (willow hurdles) used to make polders considered sustainable?
The materials used are willow hurdles. These are low-cost and sustainable as they naturally decompose as the salt marsh becomes established.
13.What are the benefits of using polders to create salt marsh along the Essex coast?
· Sites act as natural flood defence by dissipating wave energy, reducing the effects of sea level rise and storms.
· Reduced environmental impact of sea defence works
· Promoted the wider sustainable use of natural resources in flood risk management.
· Salt marsh vegetation is trapping sediment and stabilising the sites.
· Providing feeding and breeding grounds for important species of birds such as redshank and fish such as herring.
It is Low costing as wood is a renewable and easy to get resources and the creation of the salt marshes are naturally made after the inputing of the wooden fences meaning little reinforcement is needed or care.
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