Sea Dikes

Needs Address

Measures against erosion, storm surges, flooding, inundation

Adaptation effects

• Protection of lives and assets from coastal flooding, storm surges and extreme events
• Reduced salinity impacts and productivity losses

Overview and Features

Sea dikes are used to hold back coastal water surges and dissipate wave energy. Small-scale dikes employ sandbags, while large scale dikes are constructed using bulldozers and dredging machines, which haul in sand and soil from different areas to the coastal zone. These large-scale constructions can be ten to hundreds of miles long and aim to separate residential and farm land destructive coastal processes.

Figure: Cross section of a sea dike indicating structural features (Source: Linham and Nicholls, 2010

Cost

• Construction costs
• Material costs – building materials include sand, clay and asphalt
• Maintenance costs
• Dike heightening costs
• Labour costs – variable according to country
• In Vietnam, dike construction costs were shown to vary from US$0.9 to 1.6 million per metre rise in height, per km length, but vary due to varying costs of material, land-use and applied inner/outer protection of the dike’s slope (Danh, V.T and Khai H. V., 2014)
• Maintenance costs per linear km of dikes are estimated at US$0.03 million in Vietnam (Danh, V.T and Khai H. V., 2014)
• Construction and maintenance costs likely to increase in the future due to sea level rise

Energy source

• Fuel etc. for construction equipment
• Human resources for constructions and maintenance

Ease of maintenance

Protection and maintenance of dikes can be achieved through inclusion in an integrated coastal protection plan that employs mangrove and wetland protection 

Technology performance

Dikes are a tried-and-tested method of coastal protection

Considerations

Comprehensive planning processes are critical including measurement of water depths and terrestrial elevations at the location of a sea dike and accounting for potential sea level rise 

Co-benefit, suitability for developing countries

• Enable development of protected land
• The lack of availability of long-term datasets reduces the design quality and therefore ultimate protection level of dikes
• Dikes can provide very high levels of protection against coastal flooding if designed appropriately, which can enable significant development to take place behind them, even if land is low-lying

Information Resources

ClimateTechWiki, n.d. Sea Dikes. Available from: http://www.climatetechwiki.org/content/sea-dikes [27 November 2014]

Danh, V.T and Khai H. V. 2014. Using a Risk Cost-Benefit Analysis for a Sea Dike to Adapt to the Sea Level in the Vietnamese Mekong River Delta. Available at: http://www.mdpi.com/2225-1154/2/2/78 [19 March 2015]

Linham, M. and Nicholls, R.J. 2010. Technologies for Climate Change Adaptation: Coastal erosion and flooding. TNA Guidebook Series. UNEP/GEF. Available from: http://tech-action.org/Guidebooks/TNAhandbook_CoastalErosionFlooding.pdf [27 November 2014]