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/northnorfolk.htm, http://www.ice.org.uk/educationzone/undergraduates/rwce_coastal_marine.asp, http://sites.scran.ac.uk/kestrel3d/flooding/flooding3c.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/waterspace/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 estuary’s defences protect: • 90,000 ha of land • > 300,000 people. • 111km2 inter-tidal habitat - (Andrews et al. 2000) • 90% mudflats and sandflats, • 10% saltmarsh (Winn et al., 2003). • > 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 > 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. Study value Value £ (2001-2) 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 US$211/ha/yr– US$306/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 (B>C) • 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