The shorelines and intertidal habitats of our coasts and estuaries provide valuable environmental, social and economic benefits.
However, they are under pressure across the world from human activities (past and present) and climate change. To respond to these pressures, many different shoreline adaptation and habitat creation projects have been carried out.
Such schemes are often designed to make coastlines more sustainable, maintain crucial wetlands and enhance marine biodiversity.
There are many reasons for carrying out shoreline adaptation work. The main two are
- to improve flood protection and address issues related to shoreline change and the effects of sea level rise;
- to restore/protect coastal habitats and offset either past, present or future losses of coastal habitat and biodiversity.
Many of the projects in this database have been pursued with these two central motives in mind. However there are other social and economic objectives associated with shoreline adaptation work. These wider benefits or 'Ecosystem Services' (i.e. the benefits people derive from nature and its restoration) are increasingly being recognised and valued.
A wide variety of techniques have been used, ranging from small schemes to vast landscape restorations.
Explore the database or read on to understand the different techniques.
There are many reasons for carrying out shoreline adaptation work. The main two are
- to improve flood protection and address issues related to shoreline change and the effects of sea level rise;
- to restore/protect coastal habitats and offset either past, present or future losses of coastal habitat and biodiversity.
Many of the projects in the OMReg database have been pursued with these two central motives in mind. However there are other social and economic objectives associated with shoreline adaptation work.
These wider benefits or 'Ecosystem Services' (i.e. the benefits people derive from nature and its restoration) are increasingly being recognised and valued.
Depending upon the scheme in question, these extra benefits can include any of the following:
- Job creation during the project's implementation (short-term) or for the project's ongoing management
- Provision of public space
- Increased visitor numbers leading to economic gains for the region;
- Visual enhancement of the 'seascape';
- Public health and well-being benefits;
- Enhancement of recreational and commercial fisheries;
- Provision of food and raw materials;
- Improvements to water quality;
- Sequestration of carbon (especially in coastal wetlands);
- Creation of resource for community involvement, engagement and education; and
- A location for future research.
One way of restoring vulnerable coastal marine habitats is to ‘feed’ the intertidal areas with introduced sediment. This is especially valuable where habitats are eroding, sinking or subject to coastal squeeze. Such ‘recharge’ schemes may use excavated sediment that is derived from dredging activities in ports and harbours (thus providing a 'beneficial' use for this material). However, they can also use material 'recycled' from areas of accretion along the foreshore or dredged from offshore sand banks.
Intertidal recharge can provide long-term benefits of environmental enhancement and protection. The particle size of the sediment that is used needs to be appropriate to the receiving habitat and the aims of the project. In the past, for example, there have been many large-scale beach nourishment projects have been carried out using sand.
However projects which use silt or shingle to recharge deteriorating coastal habitats are generally fewer in number and often smaller in scale.
View beneficial use projects
A few projects have been carried out that have specifically involved creating island features. Often this has involved using dredge sediment and therefore they also fall under the category of ‘Beneficially Using Dredge Sediment’.
To create islands using dredged sediment requires the use of bunds or other features to keep the bulk of the sediment in place while it settles and consolidates. Only a few projects have been carried out at a large-scale but they may become more common-place in the future as sea levels rise and as existing coastal features become submerged.
The process of ‘Managed Realignment’ involves deliberately breaching an existing sea wall (or removing a section of wall altogether) to allow tidal water from adjacent coasts or estuaries to flow over a defined area of land behind.
For these projects, there is usually a need for a new sea defence ‘counterwall’ to be constructed at the back of the site. However, in situations where the hinterland has rising ground a new defence alignment may not be needed.
Managed Realignment can be used to create a range of habitats including mudflats, saltmarsh, brackish grazing marsh and saline lagoons.
In some cases, the hinterland can also be landscaped (lowered or raised) to manage the newly introduced tidal flows or to create a particular mix of target habitat types.
These projects are also variously referred to as ‘Managed Retreat’, ‘Coastal Realignment’, ‘De-poldering’ or ‘De-Embankment’. They can vary greatly in scale from subtle shifts in sea wall alignments to large changes which create vast new wetland landscapes.
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Modifying manmade structures with ecological enhancements whether at time of building or adding something later is sometimes termed “eco-engineering”.
Measures to enhance the ecological value of manmade structures in the marine environment include inserting features for nesting birds or adding structures that create rock-pools to otherwise solid and flat seawalls.
In addition to this concept of adjusting existing infrastructure, there has also been an increasing drive in recent years to develop and use materials for the construction of marine infrastructure that provide surfaces for the settlement and growth of marine species. These types of marine infrastructure project are therefore included as a distinct example of this type of ‘habitat restoration’.
In many areas of the world reefs (and the species that form them) are in decline. Therefore techniques are being developed to either encourage solecism colonisation or to provide new structures that reef formation species can settle upon. These structures are then placed at appropriate water depths to provide new intertidal or subtidal habitats.
Approaches to reef forming are varied and can often be very creative. They include the deliberate scuttling of ships, the placement of concrete reef balls or other morphologically complex structures (including examples that are created through 3D printing). Reefs that are newly formed or restored in this way can provide associated benefits for such species as refuges or act as wave energy shields to vulnerable coastlines.
Regulated Tidal Exchange adapts established sea defences to allow tidal water to pass through.
This exchange of tidal water through (or over) the seawall can be achieved with different devices such as: sluice gates, spillways, culverts, tide gates, pipes as well as more complex systems of artesian wells.
Unlike Managed or Unmanaged Realignments, the position of the seawall remains unchanged but this process can still be used to create a range of habitats including mudflats, saltmarsh, brackish grazing marsh and saline lagoons.
In the same way as for Managed Realignment, this approach promotes the development of intertidal habitats across hinterland areas. However, it does so in a way that provides greater control over the tidal exchange while also including features that will require ongoing maintenance. In some instances these sites have sea walls that are designed to be overtopped on larger high tides. This can help to divert tidal waters away from other more vulnerable areas in the area during storm surge events.
View regulated tidal exchange projects
In some instances new rocky shore habitats are created using solid surfaces. This might be done when a coastal development causes a loss of this type of habitat and where there is a need to offset this loss to avoid biodiversity impacts. This can be done using rocky substrata from the local area or material that is imported from external sources.
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Shoreline Restoration is a broad term that encompasses a wide variety of different measures undertaken to restore or enhance the overall function and 'naturalness' of processes at the coast
It can include removing or reducing existing sea defences or altering features such as cross-shore groynes to improve sediment transport. Such interventions enable the shoreline profile to relax and so allow natural processes to drive the subsequent evolution of the coastline.
This approach can be seen as distinct from other projects in this database that involve the more active repositioning of coastal defences (e.g. through Managed or Unmanaged Realignment).
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Unmanaged Realignment occurs where existing sea walls or embankments are breached naturally by tidal waters, often following storm events.
In such cases there may be little or no preparation (e.g. no construction of a new counterwall defences and no deliberate opening of the seawalls). However, this does not mean that the risk of flooding was not recognised in advance. Instead, it is often the case that decisions were made to allow this natural site evolution to occur.
Once created in this 'non-deliberate' manner, the site is then left to return to coastal habitat. A decision to not intervene is likely to be taken based on the flood risk to hinterland communities and the role that the site plays in the coastal ecosystem.
View unmanaged realignment projects
Increasingly we are undertaking innovative measures to enhance marine biodiversity such as transplanting seagrass, drilling holes in rocks to create rock pools or restoring oyster beds.
Some of these projects have been undertaken just as research trials. However, as we learn more about these novel techniques and their effectiveness some increasingly large-scale and visionary schemes have been carried out.
