Structural barriers are flood protection infrastructure used to control river floodwater flow and protect communities against costly effects of inundation. Structural barriers are typically permanent construction built at a designated point on a waterway’s path to contain water on one side of the barrier. Dams, dikes, locks and levees are common examples of such hard infrastructure. More simple
barriers can also be temporarily implemented in some cases. These barriers are an important adaptation technology for the projected increase in frequency of flood events as a result of climate change. Although often expensive to build and maintain, these structures may be necessary in certain cases to protect communities from loss of private property, public infrastructure and economic livelihoods, as well as risks to health and lives.
Key information to be gathered prior to the project may include soil types, historical flood data, local topographic and meteorological data, predicted future climate conditions and mapping of local utilities/infrastructure to avoid potential interference with structural barriers. Other relevant information includes the potential ecosystem impacts of construction (Environmental Impact
Assessment, or EIA). The planning process should involve all major stakeholders, including engineers, scientists, local decision makers, local volunteer groups, etc. to ensure the structure meets various legislative requirements (construction, environmental), and is built to maximize flood mitigation and reduce negative impacts on local ecosystems. Education on disaster risk and preparedness, including emergency response training, should also be included in the planning phase.
- Mitigates flood damage in high biodiversity value (or other) areas, such as forests, parks, etc.
- Provides flood protection, reducing potential impacts (physical and economic) on health, livelihoods, infrastructure and other economic activities.
- Avoids the need to undertake other complex risk management efforts such as the community resettlement.
- Provides an important source of water during dry periods.
Opportunities and Barriers
- Direct flood protection benefits for the local community
- Effectiveness of structural barriers is increased when implemented together with other flood risk management approaches such as wetland restoration and disaster preparedness education
- Climate change adaptation benefits in areas with increased flood frequency and severity
- Generally an expensive technology with high maintenance costs - High cost structural barriers are best justified by the need to protect high cost infrastructure and properties in densely populated areas. Markets for structural barriers are therefore limited to high development and large population areas, such as coastal cities
- Changes to natural systems can create unintended negative impacts on local ecosystems and water flows. For example, reducing water flow upstream can lead to water shortages downstream, or increase flood severity downstream
- Structural barriers are still at risk of being overtaken or toppled during severe flooding. The resulting force and speed of floodwaters can create even greater damages
Technological maturity: 3-5
Initial investment: 3-5
Operational costs: 3-5
Implementation timeframe: 3-4
* 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
- UNEP-DHI Partnership- Structural barriers to flooding: dams, dikes, locks, and leeves
- ADB (2014). Technologies to Support Climate Change Adaptation in Developing Asia. Asian Development Bank. Available at: ttps://www.adb.org/sites/.../technologies-climate-change-adaptation-execsumm.p…
- Challengeforsustainability.org (n.d.). Permanent Flood Barriers: Levees and Floodwalls Inside the Floodplain. Challenge for Sustainability. Available at: http://challengeforsustainability.org/resiliency-toolkit/levees-floodwa…
- FEMA (2007). Selecting Appropriate Mitigation Measures for Flood prone Structures, Chapter 5: Barriers. Federal Emergency Management Agency. Available at: https://www.fema.gov/media-library-data/20130726-1608-20490-6445/fema55…
- FEMA (2013). Flood proofing Non-Residential Buildings, Chapter 4, Other Flood Protection Measures. Federal Emergency Management Agency. Available at: https://www.fema.gov/media-librarydata/2c435971150193efc6a6ba08f2403863…
- National Research Council (2013). Levees and the National Flood Insurance Program: Improving Policies and Practices, Chapter 6: Implementing Flood Risk Management Strategies. Washington, DC: The National Academies Press. Available at: https://www.nap.edu/read/18309/chapter/8
- UNFCCC (2006). Technologies for Adaptation to Climate Change. United Nations Framework Convention on Climate Change. Available at: http://unfccc.int/resource/docs/publications/tech_for_adaptation_06.pdf
- Water-technology.net (n.d.).Delta Works Flood Protection, Rhine-Meuse-Scheldt Delta, Netherlands. Kable Intelligence Limited. Available at: http://www.water-technology.net/projects/delta-works-flood-netherlands/