Highly dynamic coastal systems (like sandy beaches, dunes or estuaries) might be best managed by not interfering with the natural processes, but instead accepting that change will occur and adapting backshore management accordingly. Key in this approach is a proper monitoring of the processes to analyze and evaluate the changes (for examples at eroding cliffs or dunes). With a proper planning horizon, these changes can be anticipated and with enough room for the environment to involve this can be a very cost-extensive approach.
Technical feasibility
Adaptive management should be considered at all sites before considering any of the other options of hard engineering coastal defence measures. In some cases this can mean loss of land or other values, so an assessment of these impacts has to be carefully undertaken with the integration of relevant stakeholders.
In contrast to managed realignment, this measure is not a planned retreat (e.g. with opening of dykes or removal of groynes). Instead it is the allowance of natural processes that could lead to relocation of the coastline but does not necessarily have to.
If management of marine erosion is being considered it is assumed that assets of value are being threatened. These assets may be natural, such as a rare habitat or a particularly interesting geomorphological feature. In general erosion of such features would be considered part of their natural evolution and therefore preferable to management interference. More often the assets will have socio-economic importance, ranging from amenity access to a beach up to an industrial complex or power station. The shoreline manager must start by considering the value of the assets that may be at risk, then try to establish an understanding of the likely future evolution of the beach/dune system. Finally the manager must determine whether it is better to lose/move the assets or attempt to prevent or reduce the erosion.
Consideration from Italy: Retreat is expensive - staying too!
Political & social feasibility
Monitoring, consultation and education are at the heart of adaptive management. The shoreline should be continuously assessed using data collected from site, combined with any available historic or published data. The monitoring will allow the management policy to be reviewed from time to time. Impacts of the policy on recreation, land use and habitats should also be monitored.
Consultation is required to assess the values associated with the backshore, and to develop a consensus view on how to deal with the assets. This process is firmly linked with education, requiring the manager to set out the background issues in a language that can be readily appreciated by those who are affected.
Those responsible for the management of eroding dunes and cliffs should be aware of the potential danger to the public of a collapsing dune or cliff face. Dangers exist both from falling down the face and from being buried at the base. Warning signs set up along the crest and at public access points should be the minimum response to these dangers.
Cost of implementation & maintenance
The value of the backshore may be assessed in economic terms, based on the present replacement cost of buildings, infrastructure or land. The assessment should also consider the wider values such as potential loss of jobs, transport routes, rare habitats, recreation or cultural heritage (i.e. archaeological sites). This assessment therefore considers costs and benefits (SET LINK).
Costs associated with adaptive management are site specific and cannot be generalised. Accepting the gradual loss of a site valued as an undeveloped public recreation area may incur no actual cost at all apart from monitoring and minor works to delay erosion or encourage. At the other end of the scale the demolition and replacement of threatened shoreline buildings or recreational facilities may be very cost intensive.
Ecological feasibility
Adaptive management minimises interference with the natural processes and ecosystem of an evolving dune system. The approach allows for the sustainable, long term management of the shore, with no environmentally disruptive engineered schemes.
Adaptive management can result in the controlled loss of backshore assets and the continued evolution of dune habitat and land form. This approach can be highly emotive, with local interest groups protesting vigorously and demanding that more positive actions be taken. However, it must be accepted that both erosion and accretion are natural elements of coastal evolution, and that maintenance of natural evolution is, wherever possible, preferable to costly and environmentally disruptive intervention.