Cliff Stabilization

Climate Change Adaptation Technologies for Water A practitioner’s guide to adaptation technologies for increased water sector resilience WATER ADAPTATION TECHNOLOGY BRIEF

Cliff stabilization

Challenge: Sea level rise Adaptation response: Green infrastructure for shoreline protection

Description Cliff stabilization relates to measures carried out to minimize erosion of sloping soft rock coasts. The coasts are susceptible to erosion due to their relatively loose sediment, which is vulnerable to erosive forces such as waves, wind, tides, near-shore currents, storms and sea level rise. Cliff stabilization measures may take a wide variety of forms, including foot traffic protection, re-grading, smoothing, increasing vegetative cover and improving drainage. It can be implemented alongside various soft and hard coastal management measures.

Cliff stabilization can be a useful option in densely populated areas with high value properties and infrastructure built on sloping soft rock coasts. Cliff stabilization can thus prevent erosion of valuable land and maintain the current coastline.

Implementation Cliff stabilization addresses foot and slope erosion fro, targeting geo-technical instability and subsequent sliding/collapse of the slope. A number of measures may be taken to address these issues, including: Construction of revetments at the cliff foot; artificial smoothing or re-grading of the slope; smoothing the slope by filling it with granular material at the foot of the cliff; establishing vegetative cliff cover to protect against weathering and groundwater seepage; groundwater drainage to prevent the cliff from sliding due to high water pressure; and slope reinforcement through the use of piles to transfer load to an intact geological under layer. Addressing foreshore erosion through hard or soft coastal protection measures is also an integral component of cliff stabilization.

Environmental Benefits - Maintains the amenity value of cliffs, which can be important for recreation and tourism. - Retains the cliff’s natural appearance, if stabilized responsively, and does not adversely affect the local landscape.

Socioeconomic Benefits - Prevents erosion of valuable properties and infrastructure. - Lends itself to, and is well suited for, implementation alongside other adaptation responses.

Opportunities and Barriers Opportunities:

- Can be a useful management option for coastal stabilization in densely populated areas, and can improve public safety in areas where cliffs are in danger of slipping or collapsing - Is a low-tech option that can be implemented by a skilled contractor

Barriers:

- Eroding cliffs are part of the natural coastal landscape and a source of sediment to the coastal system. They should therefore be kept unaltered where possible to allow additional supply to

Download full publication from: http://www.unepdhi.org/publications Climate Change Adaptation Technologies for Water A practitioner’s guide to adaptation technologies for increased water sector resilience WATER ADAPTATION TECHNOLOGY BRIEF

coastal sediment - Smoothing and re-grading of slopes causes land loss, which can be problematic in densely populated areas - If not implemented carefully, artificial smoothing or re-grading can detrimentally affect an environment’s ecosystem or aesthetic value - Can foster the spread of invasive species if their presence is not appropriately addressed

Implementation considerations* Technological maturity: 3-4 Initial investment: 1-3 Operational costs: 1-3 Implementation timeframe: 1-3

* This adaptation technology brief includes a general assessment of four dimensions relating to implementation of the technology. It represents an indicative assessment scale of 1-5 as follows: Technological maturity: 1 - in early stages of research and development, to 5 – fully mature and widely used Initial investment: 1 – very low cost, to 5 – very high cost investment needed to implement technology Operational costs: 1 – very low/no cost, to 5 – very high costs of operation and maintenance Implementation timeframe: 1 – very quick to implement and reach desired capacity, to 5 – significant time investments needed to establish and/or reach full capacity This assessment is to be used as an indication only and is to be seen as relative to the other technologies included in this guide. More specific costs and timelines are to be identified as relevant for the specific technology and geography.

Sources and further information

Clark, A.R. and Fort, S. (2009). Recent UK experience of coastal cliff stabilisation. Proceedings of the Institution of Civil Engineers Geotechnical Engineering, 162 (GE1), pp. 49-58. Available at: http://www.icevirtuallibrary.com/doi/10.1680/geng.2009.162.1.49

Davis Jr, R.A., Fitzgerald D.M. (2004); Beaches and coasts. Blackwell Publishing.

Eurosion (2004). Living with coastal erosion in Europe: Sediment and space for sustainability. Part IV – A guide to coastal erosion management practices in Europe: Lessons learned. The Hague: National Institute for Coastal and Marine Environment / RIKZ. Accessed online 02-12-16 at http://www.eurosion.org/reports-online/part4.pdf. Haslett, S.K. (2009). Coastal systems. Routledge.

Mangor, K. (2004). Shoreline management guidelines. DHI Water & Environment. Available at: https://www.dhigroup.com/marine-water/ebook-shoreline-management-guidelines

Masselink, G., Hughes, M.G. (2003). Introduction to coastal processes and geomorphology. Oxford University Press.

Rosendahl Appelquist, L. et al. (2017). The Coastal Hazard Wheel system, available online at www.coastalhazardwheel.org.

Rosendahl Appelquist, L., Balstrøm, T., Halsnæs, K. (2016). Managing climate change hazards in coastal areas - The Coastal Hazard Wheel decision-support system, UNEP.

Schwartz, M.L. (2005). Encyclopaedia of coastal science, Springer.

Download full publication from: http://www.unepdhi.org/publications