Surge barriers and closure dams are protective measures designed to prevent a storm or high tide from flooding an area. A surge barrier is often a movable structure that is signaled to close prior to a storm and reopen to facilitate transport of goods and boats or if protecting an estuary, to allow natural movement of tides. A closure dam on the other hand is a permanent structure. Both are significant physical barriers that require advanced civil engineering and substantial construction. They provide a physical barrier and are used to protect coastal communities, tidal inlets, rivers and estuaries from extreme weather events.
An additional potential benefit of barriers is the opportunity to generate significant quantities of sustainable electric power through a flood barrier. This is starting to look more feasible than previously, now that existing sources of non-renewable power are rising in cost.
Advantages of the technology
Storm surge barriers provide protection from flooding during extreme weather events and by using a movable barrier can still allow a flow of either maritime traffic or even natural movements of water to and fro. In particular, movable barriers are useful when an estuary is also acting as a trading port with an ecosystem that requires a specific balance of salt and fresh water.
Storm surge barriers are often accompanied by other coastal defense measures as they exist in areas that are susceptible to extreme weather events. Building a storm surge barrier can reduce the need to strengthen defences behind the barrier and thus reduce the need for maintenance and construction costs on the landward side of the barrier. (Hillen et al., 2010).
Disadvantages of the technology
Since storm surge barriers are considerable hard defence structures the costs of implementing and maintaining them are considerably high. Moreover, the costs of implementing a weather forecasting and information service must also be considered since these measures are required movable barrier to be effective.
Another issue with storm surge barriers and closure dams is that they can sometimes cause flooding behind the barrier when water levels are high or when a movable barrier remains closed for a long period of time.
Surge barriers and closure dams also affect the natural ecosystem of the water body in which they are implemented. They may alter the water salinity, temperature, suspended matter, nutrients which all have the potential to affect local communities of organisms. This is particularly true in cases where a permanent barrier is built (IOC, 2009).
Institutional and organisational requirements
Due to the complexity of the engineering and the significant costs of construction, storm surge barriers must have considerable political and public support. The construction requires considerable consultancy with civil engineers, local populations, NGOs, and government.
Barriers to implementation
The high cost associated with building surge barriers or closure dams is one of the most obvious setbacks. The physicality and imposition of a solid structure puts storm and surge barriers into a hard measure category during a time when alternative soft measures are being assessed as sometimes less expensive and more environmentally friendly.
Opportunities for implementation
Surge barriers and closure dams can have on knock-on positive effects. For example in Venice the implementation of the movable defence barrier called MOSE offers environmental benefits to water quality by dispersing pollutants from the repeated opening and closing of the structure.
Storm surge barriers can also be designed to serve several purposes simultaneously. For example, in Singapore the Marina Barrage is surge barrier that also provides a large reservoir, the latter of which is used to meet water needs of the local urban community (Moh & Su 2009). Moreover, the barrier itself was designed to contain art galleries and shops, thereby creating a touristic attraction within the defense itself.