Managed Realignment: A Cost Benefit Analysis'

1
Managed Realignment A Cost - Benefit Analysis.
Diane Burgess, Kerry Turner, Emma Coombes, Nina
Jackson.
Session A Climate Change and Coastal Management
Techniques European Conference on Coastal Zone
Research an ELOISE Approach, Portoroz,
Slovenia, November 14 18, 2004
2
Flood and Coastal Protection in the UK

• Traditional approach
• Coastal Defence
• Engineered structures to resist the energy of the
  waves and tides hard defences.
• e.g. breakwaters, seawalls, flood embankments

• English coastline
• 900 KM man-made defences erosion
• 1000 KM man-made defences sea flooding
• 1000 KM natural frontages i.e. cliffs

http//www.stacey.peak-media.co.uk/NNorfolk/northn
orfolk.htm, http//www.ice.org.uk/educationzone/un
dergraduates/rwce_coastal_marine.asp,
http//sites.scran.ac.uk/kestrel3d/flooding/floodi
ng3c.html
3
Current situation

• Defences reaching the end of their design life
• in need of repair and replacing
• Rising sea levels
• Increasing storminess
• Loss of inter-tidal habitat coastal squeeze

Rising maintenance costs
4
A solution for the future Managed realignment?

• Involves removing, breeching, lowering the
  existing defences to allow the coast to retreat
  to a new line of defence inland
• Coastal Mangement - positively managing the
  natural processes to achieve long-term flood and
  erosion security soft defences
• Not a non-intervention approach

• Advantages
• Reduction in wave attack on flood defence
• Lower maintenance costs
• Habitat creation
• Adapts to sea level rise

• Disadvantages
• Loss of reclaimed land
• Residential business properties
• Transport infrastructure
• Freshwater habitat
• Agricultural land
• Heritage culture

5
Assessing managed realignment

• Flood and Coastal Defence legislation in England
  and Wales
• No right to protection from flooding or coastal
  erosion
• No right to any particular standard of protection
  where defences are provided

• Action to manage flood and erosion risk should
  only proceed if the benefits that will flow from
  the action is greater than the costs.
• This principle is maintained in the new Strategy
  currently under consultation
• DEFRA is exploring the use of other methods i.e.
  Multi-criteria Analysis.

• Cost- benefit analysis
• Positive and negative impacts of a scheme are
  compared using a common value base - monetary
  values

http//www.defra.gov.uk/corporate/consult/watersp
ace/consultation.pdf
6
Cost Benefit analysis

• Defining feasible scheme, including do nothing
  option
• Determination spatial and temporal scales of the
  analysis
• Identification of the costs and benefits and
  their monetary values
• Determine economic efficiency do benefits exceed
  costs?
• Sensitivity analysis - assess impact of different
  values of parameters

7
Cost- Benefit Analysis of Managed Realignment in
Humber catchment

• One of largest estuaries in UK.
• Mostly high quality agricultural land.
• The estuarys defences protect
• 90,000 ha of land
• gt 300,000 people.
• 111km2 inter-tidal habitat - (Andrews et al.
  2000)
• 90 mudflats and sandflats,
• 10 saltmarsh (Winn et al., 2003).
• gt 90 of the intertidal area lost over the last
  300 years (Jickells et al., 2000).
• Many defences need improving.
• Rising sea levels.

8
Managed Realignment Scenarios (Based on foresight
scenarios)

• Hold-the-line scenario (HTL)
• Do nothing
• Reference scenario
• Business-as-Usual (BAU)
• Continuation of economic growth
• Accounts for existing managed realignment schemes
• Policy Targets (PT)
• Economic growth AND economic protection
• Policy targets are met i.e. compensatory habitats
  habitat lost
• Deep Green (DG)
• Environmental protection has priority
• Development is NOT assumed to cease
• Compensated habitats gt habitat loss
• Extended Deep Green (EDG)
• Greater emphasis on habitat creation

9
Identification of sites suitable for managed
realignment

• Criterion 1 The Area below the High Spring Tide
  Level
• Criterion 2 The Present Land Use of the Area
• Criterion 3 The infrastructure of the area
• Criterion 4 - The Historical Context of the Area
• Criterion 5 The Spatial Context of the Areas
• SIZE
• SHAPE
• ELEVATION
• PROXIMITY TO EXISTING INTERTIDAL HABITATS

10
Areas suitable for managed realignment for the
Business-As-Usual, Policy Targets, Deep Green and
Extended Deep Green Scenarios in the Humber.
11
Cost Benefit analysis

• Defining feasible scheme, including do nothing
  option
• HTL, BAU, PT, DG, EDG
• Determination spatial and temporal scales of the
  analysis
• Humber Catchment
• 100 years lifespan of defences (government
  guidance)
• Identification of the costs and benefits and
  their monetary values
• Net present values (account for flows of costs
  and benefits by applying a declining discount
  rate (government guidance))
• Refer to a common point in time the base year
• Determine economic efficiency do benefits exceed
  costs?
• Sensitivity analysis - assess impact of different
  values of parameters

12
Value (2001-2)
Study value
Year of study
Costs
811,893/km
2001-2002
Capital costs of realigning defences
811,893/km
Loss of Land
2,110/ha
Grade 1 and 2 land Grade 3 land
2001-2002
2,110/ha
2,382/ha
2001-2002
1,239/km/yr
Maintenance (realigned defences)
1,239/km/yr
1,000/km/yr
1992
Maintenance (non-realigned defences)
5,000/km/yr
2000
5,127/km/yr
Replacement costs
618,000/km
2001
618,000/km
Benefits
General habitat creation benefits
US211/ha/yr US306/acre/y
2003/1990
122-574/ha/yr
Carbon sequestration benefits
7/tonne CO2e
2000
7.18/tonne CO2e
13
Net present Values of Providing Flood Defence
14

• Key findings
• Managed Realignment is economically efficient
  (BgtC)
• As timespan increases, benefits increase
• Most costs relate to capital costs of realignment
• Greater levels of managed realignment greater
  benefits
• Sensitivity analysis showed results to be robust