Grey infrastructure

Based on kindly provided information by the Scottish Natural Heritage

Groynes are cross-shore structures designed to reduce longshore transport on open beaches or to deflect nearshore currents within an estuary. On an open beach they are normally built as a series to influence a long section of shoreline that has been nourished or is managed by recycling. In an estuary they may be single structures.

Groynes reduce longshore transport by trapping beach material and causing the beach orientation to change relative to the dominant wave directions. They mainly influence bedload transport and are most effective on shingle or gravel beaches. Sand is carried in temporary suspension during higher energy wave or current conditions and will therefore tend to be carried over or around any cross-shore structures. Groynes can also be used successfully in estuaries to alter nearshore tidal flow patterns.

Technical feasibility

Groynes can be made from different material. Rock is often favoured as the construction material, but timber or gabions can be used for temporary structures of varying life expectancies (timber: 10-25 years, gabions: 1-5 years). Rock groynes have the advantages of simple construction, long-term durability and ability to absorb some wave energy due to their semi-permeable nature. Wooden groynes are less durable and tend to reflect, rather than absorb energy.

Groynes along a duned beach must have at least a short “T” section of revetment at their landward end to prevent outflanking during storm events. The revetment will be less obtrusive if it is normally buried by the foredunes. Beach recycling or nourishment is normally required to maximise the effectiveness of groynes. On their own, they will cause downdrift erosion as beach material is held within the groyne bays.

Groynes can have a significant impact on the shoreline, and schemes should always be undertaken under the supervision of a competent coastal consultant. As with all rock structures on the shoreline the rock size, face slopes, crest elevation and crest width must be designed with care. Rock size is dependent on incident wave height, period and direction, structure slope, acceptance of risk, cross-sectional design, and the availability/cost of armour rock from quarries. In general 1-3 tonne rock will suffice for the landward parts of the groynes, provided that it is placed as at least a double layer, with a 1:1.5 to 1:2.5 face slope, and there is an acceptance of some risk of failure. Larger rock, probably 3-6 tonne, may be needed for the more exposed body and seaward head of each structure.

The groyne berm should be built to the anticipated crest level of the beach. The groyne berm length should equal the intended crest width of the updrift beach. The groyne should extend down the beach at a level of about 1m above the anticipated updrift shingle beach, normally at a slope of about 1:5 to 1:10. The groyne head should extend down into the sand beach, allowing for some future erosion.

As a general rule, groynes should not be built on an open beach unless construction is accompanied by a commitment to regular recycling or nourishment. Without this commitment the groynes are likely to cause downdrift erosion as the upper beach becomes starved of sediment. Where there is a plentiful sediment supply, or where downdrift erosion is not considered to be a significant issue, then recycling may not be required.

Timber groynes must be built from hardwood to endure the harsh shoreline environment. Much hardwood comes from tropical sources, making it both costly and potentially environmentally unacceptable. Timber groynes tend to reflect, rather than absorb, wave energy making them significantly less effective than rock on exposed coasts. They are also more likely to structural failure due to formation of scour channels around their seaward ends.

Political & social feasibility

Rock structures on recreational beaches should be built with a view to minimising the potential for accidents involving beach users slipping between rocks

Cost of implementation & maintenance

The costs of groynes are considered as moderate

Ecological feasibility

Implementing groynes disrupts natural processes. The effects must be properly monitored and if possible compensated.

Key lessons learnt

Provided that groynes are used in appropriate locations, they reduce dependency on regular recycling or nourishment, and therefore reduce future disturbance of the shoreline environment. Localised accumulations of beach material will encourage new dune growth. Recycling, fencing and transplanting will help to keep the revetment sections buried, thereby enhancing habitat regeneration.

Measure category

Mitigation

Breakwaters

nst — Wed, 22 Mar 2017 08:49:13 +0000

Breakwaters nst Wed, 03/22/2017 - 09:49

Riverine or slow rise floods

Estuarine floods

Combined approach (grey + green)

Based on the information available on the ClimateAdapt Platform

A breakwater is a coastal structure (usually a rock and rubble mound structure) projecting into the sea that shelters vessels from waves and currents, prevents siltation of a navigation channel, protects a shore area or prevents thermal mixing (e.g. cooling water intakes). A breakwater typically comprises various stone layers and is typically armoured with large armour stone or concrete armour units (an exception are e.g. vertical (caisson) breakwaters). A breakwater can be built at the shoreline or offshore (detached or reef breakwater). This measure is not directly addressed to protect the coast in flood events, but can indirectly stabilize the coast by preventing erosion.

To build breakwaters, rock size, face slopes, crest elevation and crest width and toe protections and aprons should be designed according to the natural characteristics of the sites as these factors have an important impact on the shoreline. Sand may build up behind breakwaters to form salients. Sand can accumulate enough to connect with the breakwater and form a tombolo (a stretch of sand developed by wave refraction, diffraction and longshore drift forming a ‘neck’ connecting the structure to the shore). Considering the significant impact these structures have on the coastal environment, they should only be considered as part of a global adaptive management policy, taking into account the characteristics of the specific site and the potential effects on the whole coast. The construction of breakwaters could also be linked to a beach nourishment programme, and breakwaters can be used in a protected beach nourishment approach.

Stakeholder participation

If an EIA is undertaken, the EU Directive provides for the right to access information and to participate in the environmental decision-making procedures to the public concerned by the project. If a project creates a significant impact on a Natura 2000 site, the ‘appropriate assessment’ of the infrastructure project could include a public participation process, but this is not mandatory. Similarly, the Floods Directive, the Water Framework Directive and the Maritime Spatial Planning Directive establish public participation processes that may include these projects.

A range of stakeholders could be affected by the construction of breakwaters: for local communities and landowners, hard defences could negatively impact their property. Hard defences can visually disrupt the landscape, affecting tourism interests, recreational users and other sectors. Waterborne activities can also be adversely affected if the installation of hard structures goes wrong.

Success and Limiting Factors

Artificial structures such as breakwaters tend to modify longshore drift, and have adverse effects on adjacent beaches by causing downdrift erosion. In general, to avoid these effects on the coastline, artificial nourishments and/or dune development are often preferable over hard structures unless there are other needs, such as the safe berthing of ships. However, the extent of the blocking of longshore drift, disturbance of adjacent beaches and degradation of landscape values depends very much on the design, orientation of the structure and the main wave/sediment transport direction at the specific site.

Breakwaters provide safe mooring and berthing procedures for vessels in ports. They enhance workability and provide thus higher efficiency in loading and unloading vessels.

Costs and Benefits

Construction costs depend significantly on structure dimensions. Costs can be highly influenced by availability of suitable rocks, transport costs to the construction sites and associated costs of beach nourishment.

In the Netherlands, breakwaters are estimated to cost about EUR 10,000 to 50,000 per running meter (Deltares, 2014).

According to Scottish Natural Heritage, in 2000 construction costs of breakwaters are high – GBP 40,000 to 100000 (50,000-125,000€) – but they require low maintenance; for these structures in particular, beach nourishment costs should be added.

Legal Aspects

The construction of coastal works to mitigate erosion and hard sea defences ‘capable of altering the coast’ fall into Annex II of the EIA Directive (codified as Directive 2011/92/EU): Member States decide whether projects in Annex II should undergo an EIA procedure, either on a case-by-case basis or in terms of thresholds and criteria. However, this requirement does not affect the maintenance and reconstruction of these works.

Any infrastructure project likely to have a significant impact on a Natura 2000 site must be subjected to an ‘appropriate assessment of its implications for the site’ to determine whether the project will adversely affect the integrity of the site.

The Water Framework Directive calls for the Good Environmental Status of Europe’s water bodies, including coastal waters. Coastal defences could alter the hydromorphological characteristics of coastal waters, for example in terms of water flow, sediment composition and movement, and thus to a deterioration of ecological status. Any projects that do so would need to meet criteria set out in Art. 4 of the Directive. The EU Floods Directive (2007/60/EC) provides a legal framework for flood actions and defence. The construction and restoration of dikes could be part of measures under flood risk management plans. The 2014 Maritime Spatial Planning Directive requires the consideration of the interactions between land and sea, along with maritime activities and adaptation to climate change. Breakwaters could affect these land/sea interactions.

Life Time

Breakwaters have a typical design lifetime of 30-50 years. This is the case for most rock structures.

Further Readings

Scottish Natural Heritage: A guide to managing coastal erosion in beach/dune sy…

VLAAMS INSTITUUT VOOR DE ZEE: Detached Breakwaters

Measure category

Mitigation

Land claim

nst — Tue, 07 Feb 2017 13:09:59 +0000

Land claim nst Tue, 02/07/2017 - 14:09

Combined approach (grey + green)

Move seaward

EXAMPLE: Artificial Island - Amager Beach, Copenhagen (DK)

The main objective of land claim is neither erosion nor storm reduction. The aim of land claim is to create new land from areas that were previously below high tide. These measures can be taken to reduce the exposure of these areas to coastal flooding. For example, in Singapore and Hong Kong, there are enforced minimum reclamation levels to account for future sea level rise

Based on information from ClimateTechWiki.

General Description

Land claim is likely to be accomplished by enclosing or filling shore or nearshore areas (Bird, 2005). Several alternative terms may be used when referring to land claim; these may include land reclamation, reclamation fill and advance the line. Typically this measure is undertaken to gain land (French, 1997), today especially around coastal cities (like Singapore and Hong Kong), where very high land values are justifying the costs.

In order to enclose areas for land claim, hard coastal defences must be constructed seaward of the existing shoreline. Dike and seawalls are typically constructed to protect the claimed land from flooding by the sea (Burgess et al., 2007). Two main methods of land claim are: (1) enclosing and defending shore or nearshore areas; and (2) filling shore or nearshore areas, often using the same techniques used in beach nourishment. When considering adaptation to climate change, land claim using fill methods is perhaps more appropriate as it does not carry such a great flood risk.

Advantages and disadvantages of the technology

The key advantage of land claim is the gain of additional coastal land for uses such as agriculture or development. Apart from the valuable land, this additional coastal land can function as a buffer and reducing the risks of flooding.

Land claim can also generate a number of negative impacts. The process of land claim requires either the enclosure of intertidal habitats by hard defences, or the raising of their elevation above that of sea level to prevent inundation. This causes the direct loss of intertidal habitats such as saltmarshes, intertidal flats and sand dunes (French, 1997). Another disadvantage is dewatering. By draining reclaimed land which has a high water content, land is caused to dry out, compact and shrink (French, 1997), thus reducing its elevation in relation to sea level. This causes a difference between land elevations inside the flood defences, where compaction and shrinkage has occurred and outside, where natural intertidal environments continue to naturally accrete sediments. This difference in elevation is also exacerbated by SLR and results in an ever increasing requirement for flood defences (Burgess et al., 2007). It also requires an ongoing commitment to defend these areas (French, 1997).

Any type of land claim will cause the displacement of water during a natural tidal cycle. Because of this displacement, incoming tides have a smaller area to inundate. This will cause water depths to increase and will mean intertidal areas are submerged for longer – this has the potential to cause negative biological consequences and can also increase the tidal range upstream (French, 1997).

Financial requirements and costs

The financial costs of land reclamation are dependent on a number of factors:

Chosen method of reclaim (enclosing previously intertidal areas using hard defences or raising the elevation of previously submerged land)
Availability and proximity of fill material from onshore or offshore sites
Number, type, size and availability of dredgers
Requirement for hard protection measures to defend reclaimed land from coastal flooding and erosion
Project size and resulting economies of scale
Estimated material losses

If land claim is conducted by enclosing previously intertidal areas, the additional costs of providing hard protective measures, such as seawalls or dikes, to prevent flooding and erosion of these areas is important. Ongoing maintenance costs for these structures must also be considered.

If land claim is achieved by raising the elevation of previously submerged land, the cost of fill material is likely to be the main determinant of project cost. In turn, this cost will be influenced by the availability of appropriate materials, their proximity to the construction site and the characteristics of the reclaim site – this influences the type of dredging equipment which can be used. Changes in the cost of fill material are likely to occur in future due to increased demand and greater restrictions on dredging.

Institutional and organisational aspects

The institutional and organisational requirements of land claim projects are likely to depend on the scale and ambition of the project. Small-scale land claim for agricultural uses is more likely to be achievable at the community level than large-scale island enlargement and creation as seen in Singapore or Dubai. These large-scale projects will require the involvement of large organisations and large amounts of funding.

Key lessons learnt

One barrier to the use of land claim is potential long-term costs. Land claim creates land which will require protection from coastal flooding and/or erosion. This requires construction of defences such as seawalls or dikes with associated construction and ongoing maintenance costs. Land claim through elevation raising may also be a cost-effective method of disposing of dredged material from ports, harbours and navigation channels. This could reduce the overall cost and eliminate the need to identify offshore disposal sites for dredge material. As with beach nourishment, pollutant levels in the dredge material should be carefully monitored.

Environmental concerns may provide another barrier to implementation. By reclaiming land in these areas, environmentally important intertidal habitats are lost, and knock-on impacts such as alterations to ebb/flood dominance may also occur. As a result, environmental opposition to land claim may mount. In the EU, compensation for lost habitats is required

Relevant case studies and examples

Further Readings

Wang et al (2014): Development and management of land reclamation in China

Literature sources

Bird, E. (2005) Appendix 5: Glossary of Coastal Geomorphology in Schwartz, M.L. (ed.). Encyclopedia of Coastal Science. The Netherlands: Springer, 1155-1192.

Burgess, K., Jay, H. and Nicholls, R.J. (2007) Drivers of coastal erosion in Thorne, C.R., Evans, E.P. and Penning-Rowsell, E.C. (eds.). Future Flooding and Coastal Erosion Risks. London: Thomas Telford, 267-279.

French, P.W. (1997) Coastal and Estuarine Management. London: Routledge.

Measure category

EXAMPLE: MOSE system of mobile flood barriers, Venice (IT)

nst — Tue, 07 Feb 2017 08:35:19 +0000

EXAMPLE: MOSE system of mobile flood barriers, Venice (IT) nst Tue, 02/07/2017 - 09:35

Flash floods

Reduction

Water flow regulation

Flood and storm surge barrier

Venice, Italy, is a city famous around the world for not only its stunning canals and historic buildings, but also for its high vulnerability to flooding. The MOSE system of mobile flood barriers is a bold initiative intended reduce risk, preserve the cherished cityscape, and protect the entire Venice Lagoon from flooding.

Based on information from the project website

General description

The MOSE (short for “Modulo Sperimentale Elettromeccanico” in Italian) system consists of four mobile barriers closing off three inlets in the Venice Lagoon. The barriers themselves are made up of 78 flap gates that are installed at the bottom of the inlets to separate the lagoon from the sea when raised. The system takes approximately 30 minutes to open and can be closed in 15 minutes, but takes on average five hours to close. Once raised, the barriers are able to withstand three meters of high tide. The barrier at the Malamocco inlet even has a lock system installed to allow merchant and industrial ships to cross while the MOSE system is in operation to reduce interference on port activities.

Seasonal high water is a constant threat to Venice, and the city has adapted with raised walkways, waterproofed buildings, and power outlets installed halfway up the wall in businesses and homes. Flooded scenes of a usually picturesque St Mark’s Square can be explained due to the fact that it is the city’s lowest point. However, more extreme high tides that occur roughly every three years and can raise water levels by over a meter present a much greater risk to Venice’s cultural heritage and justify a system such as MOSE.

Governance aspects

Venice and its Lagoon is a UNESCO World Heritage Site, which makes its protection even more important. The MOSE project was implemented by the Italian Ministry of Infrastructure and Transport and managed by the Consorzio Venezia Nuova for the purposes safeguarding Venice and the lagoon. The decision to construct the mobile flood barriers was made after collaboration between all levels of government and consideration of various other coastal defence measures.

Innovative aspects

The MOSE system in its entirety is an impressive and innovation response to the threat of coastal flooding and erosion, both from a construction and coordination standpoint. The hydrological and geophysical profile of the Venice Lagoon needed to be fully considered when designing the barriers and their final locations.

While the MOSE Control Centre uses advanced technology to predict flooding, model the effects of gate manoeuvres, predict port traffic, determine warning levels, and so on, the MOSE project also employs other smaller scale measures to optimise the overall goal of flood risk reduction in the lagoon. These local defences consist of raising quaysides, roads, walkways, and installing smaller gates in the urban canals in the lagoon settlements, known as the “Baby MOSE” gates. This holistic and comprehensive approach to encouraging protection for the entire lagoon, aside from that which is provided by MOSE, is also innovative.

Key lessons learnt

It is not easy to construct such large-scale defences in fragile environments, but, as the MOSE system illustrates, sometimes this approach is necessary to provide significant long-term protection. Venice represents an especially vulnerable coastal city with globally significant heritage sites and a very active tourism industry. With so much at risk, the MOSE system will ensure businesses, residents, and visitors will be able to enjoy the fabled canals, palaces, and plazas without the threat of flooding and building damage. The implementation of local defences diversifies the resilience of the settlements in the lagoon and increases the rate of success for the MOSE project.

Relevant case studies and examples

Further Readings

CityLab: Venice's Vast New Flood Barrier Is Almost Here

Measure category

EXAMPLE: Seawall at Skara Brae, Scotland (UK)

nst — Tue, 24 Jan 2017 08:37:41 +0000

EXAMPLE: Seawall at Skara Brae, Scotland (UK) nst Tue, 01/24/2017 - 09:37

Skara Brae is one of Scotland’s most significant and famous UNESCO World Heritage Sites and it has been under constant threat of damage due to coastal erosion for decades. Fortunately, a seawall protects the base of this archaeological site from the erosive power of waves and storm events.

Based on information from Historic Environment Scotland and UNESCO World Heritage Centre.

General description

The 5000 year old settlement of Skara Brae is one of the four monuments that make up the Heart of Neolithic Orkney, a UNESCO World Heritage Site. It is also quite possibly one of Scotland’s most at-risk historic sites due to coastal erosion. Ironically, Skara Brae was only discovered as a result of coastal erosion from major storm events since the 1800’s.

The risk of coastal erosion to Skara Brae was addressed in the early days of its heritage management. The first seawall was constructed in the late 1920’s, and has been refortified several times since then. Like all seawalls, this 4-meter high wall serves as a protective barrier that is able to absorb the brunt of wave action and thereby shield vulnerable infrastructure, or in this case archaeological structures, from eroding.

Historic Environment Scotland, the public body responsible for managing Scotland’s heritage sites, has been over the years maintaining the integrity of the wall, with the support of other organizations. There has also been extensive monitoring of the entire bay area to determine the rate and location of erosion so that additional fortification can be made. Skara Brae is a cherished piece of Scotland’s history and therefore has much public support for protection from coastal erosion.

Innovative aspects

Considering the early adoption of a seawall protection measure for Skara Brae, Scottish authorities have been quite proactive in ensuring the long term reduction of coastal erosion at this heritage site. With the first wall erected in the late 1920’s, this measure was a relatively pioneering tactic for heritage conservation. Today, Historic Environment Scotland has also employed the latest technologies of 3D and 4D digital surveying to monitor the state of erosion along the coast and measure the ongoing effectiveness of the sea wall.

Key lessons learnt

When it comes to vulnerable heritages sites along eroding coastlines, time is of the essence. While powerful storms throughout history revealed the existence of Skara Brae to the world, these same storm events and constant wave action threaten the longevity of the site as a place for future generations to enjoy. The prompt action of Scottish authorities to construct a seawall to protect the archaeological site decades ago has since been proven to have been a wise decision. Knowing what we know about the possibility of more hidden archaeological sites in the area, it is important to continue the monitoring efforts to not only assess the stability of Skara Brae, but also the impacts of the seawall as an element of the natural environment. The Bay of Skaill is a dynamic and ever changing system, and it is possible that the seawall might increase erosion from intensified wave action on the unprotected sand dunes on either side of Skara Brea.

Relevant case studies and examples

Seawall or Revetment

Further Readings

BBC report on Skara Brae

Measure category

EXAMPLE: Coastal setbacks on the island of Kauai (USA)

nst — Mon, 16 Jan 2017 13:34:18 +0000

EXAMPLE: Coastal setbacks on the island of Kauai (USA) nst Mon, 01/16/2017 - 14:34

Avoidance

Coastal and river setbacks

On the island of Kauai, Hawaii in the USA, the local governing county has implemented flexible and protective coastal setbacks that protect communities from coastal erosion and avoid shoreline armouring in the long term.

Based on J.F. O’Connell et al. (2010): "The island of Kauai, Hawaii's progressive shoreline setback and coastal protection ordinance" In: Shifting Shorelines: Adapting to the Future,The 22nd International Conference of The Coastal Society , June 13-16, 2010 ,Wilmington, North Carolina.

General description

In this particular case, there is a disconnect between state regulations on coastal zone management and local or County regulations. In Hawaii, there are state laws that require setbacks along shorelines that are no less than 20 and not more than 40 feet inland from the shoreline and armouring the shoreline is permitted. The regulations at the state level, have however, led to inappropriate constructions in areas that jeopardize the island’s valuable sandy beaches. Thus in spite of an innovative and flexible Ordinance developed in 2008 called the ‘Shoreline Setback and Coastal Protection Ordinance’, the state still allows armouring.

The Ordinance puts into place procedures establishing minimum construction setbacks based on average lot depth and long-term shoreline erosion rates that are generated by the University of Hawaii.

The objectives of the Ordinance are manifold:

To provide a buffer zone to protect shorefront development from loss due to coastal erosion for a period of time;
To provide protection from storm waves;
To allow the natural dynamic cycles of erosion and accretion of beaches and dunes to occur;
To maintain beach and dune habitat;
And to maintain lateral beach access and open space for the enjoyment of the natural shoreline environment.
To avoid armouring or hardening the shore which along eroding coasts has been documented to ultimately eliminate the fronting beach.
The Island of Kauai is a county within Hawaii and is also the fourth largest of the Hawaiian islands. It is vulnerable to a variety of coastal hazards including inundation, erosion, hurricanes, and tsunamis.

Local Setting

On the island of Kauai the coasts and sandy beaches are important to the economy and the community. Shoreline armoring as a measure for dealing with climate change can benefit coastal infrastructure but it can also threaten coastal marine habitats and beaches. The potential loss of sandy beaches due to coastal hardening is particularly important in a state like Hawaii and specifically on Kauai where the local economy depends on tourism and beach activities.

In Kauai, the county takes the state wide implemented setback of 40 feet as a minimum standard and finds flexible and specific setback lines based on average lot depth and long-term coastal erosion rates that are developed and provided by the University of Kauai. The county, therefore, has taken steps to avoid shoreline armoring and establish safe and environmentally effective setback distances for construction of structures with a 2008 Ordinance. However, the regulations developed at the County level do not match those set by the state.

Political setting

The Kauai case study provides an example of when different levels of government set different regulations that are in conflict with one another. In Kauai, a local level Ordinance has set environmentally protective standards in place that go further than State coastal zone management laws to ensure the integrity of Kauai’s sandy beaches. While the State sets general measures for coastal setbacks and infrastructure development, the County appears to be setting up legislation that is more accurately informed by local circumstances and data and that prioritizes environmental considerations.

The Ordinance puts into place procedures establishing setbacks that go beyond the state-wide laws. The County setbacks also consider lot depth and long-term shoreline erosion rates. In order to determine the erosion rates of different areas around the island, the County has partnered with the University of Hawaii Sea Grant College Program to conduct an assessment on Climate Change and Coastal Hazards in Kauai and to provide data regularly.

Innovative aspect

In Kauai, the county takes the state wide implemented setback of 40 feet as a minimum standard and finds flexible and specific setback lines based on average lot depth and long-term coastal erosion rates that are developed and provided by the University of Kauai. For existing structures 20 feet is the minimum setback area. It also requires lot depths of greater than 160 feet with a proposed building footprint less than or greater than 5000 square feet to calculate the setback by multiplying the erosion rate by 70 or 100, respectfully on top of a forty food safety buffer.

The purpose of the Ordinance is to ensure that structures are not built in areas that are vulnerable to hazards and that shoreline hardening is avoided and not depended on to protect property during its lifetime. There are also specific rules regarding activities and structures that are allowed within the setback are, however, no structure approved within the setback area by variance will be eligible for protection by shoreline hardening.

Key lessons learnt

There are several interesting elements of the Kauai case study. Firstly, there is an inter-change between local levels of the island County and established state laws on zoning and management. The Ordinance that determines county rules for setback measures is more protective and exact in determining the rules for building and at the same time was designed in a way that is flexible to specific projects and also informed by local data and research. The partnership between the County and the University of Kauai to establish appropriate setback measurements based on erosion rates on the island illustrates the importance of partnerships between governing entities and institutions with relevant scientific data and knowledge. Finally, the Ordinance is designed to be somewhat flexible but is ultimately environmentally focused in protecting the integrity of sandy beaches and avoiding the hardening of the coast in the future to protect any existing structures.

Relevant case studies and examples

Further Readings

More information from NOAA

Literature sources

O'Connell, James and Aiu, Imaikalani and Milnes, Leslie and Smith, Lisa Ellen (2010) The island of Kauai, Hawaii's progressive shoreline setback and coastal protection ordinance. In: Shifting Shorelines: Adapting to the Future,The 22nd International Conference of The Coastal Society , June 13-16, 2010 ,Wilmington, North Carolina

O'Connell, James et al. (2009): A PROGRESSIVE, BALANCED COASTAL CONSTRUCTION SETBACK ORDINANCE ON THE ISLAND OF KAUAI, HAWAII: IMPLEMENTATION AND LESSONS LEARNED. Proceedings of Coastal Zone 09, Boston, Massachusetts, July 19 to 23, 2009

Measure category

EXAMPLE: Relocation in Criel sur Mer, Normandy (FR)

nst — Mon, 16 Jan 2017 12:49:39 +0000

EXAMPLE: Relocation in Criel sur Mer, Normandy (FR) nst Mon, 01/16/2017 - 13:49

Exposed element relocation and removal

Criel sur Mer is a small town in Normandy in the region of Northern France, known for its stunning coastline of steep chalk cliffs. Erosion of the cliffs in Criel sur Mer is occurring rapidly as a result of climate change but also due to man-made construction works further up the coast. In Criel sur Mer a short piece of land on the coast that is eroding rapidly and several homes built near the sea are threatened by the predicted collapse of the cliff. In particular, a street of homes were faced with immediate danger from erosion. Between 1995 and 2003, the local administration organized the abandonment and demolishment of 14 homes due to imminent risk from natural disaster under the Barnier Law. The adoptive policy was to do nothing against cliff erosion and to demolish and relocate those in immediate threat and compensate them fairly for their lost property.

General description

Coastal erosion is a common challenge along many stretches of the coast in Normandy. The cliffs are extremely steep and the rock material is chalk which is soft and easily erodible. The verticality of the cliffs mean that erosion is especially intense at the base of the cliff leading to significant fractures and collapse of cliff and loss of pebble beaches that would otherwise help mitigate erosion from the sea. Moreover, in Criel sur Mer considerable engineering works carried out along the coast have exacerbated erosion. Specifically, the construction of the ports Le Havre, Fécamp, Saint-Valery-en-Caux, Dieppe, and Le Tréport as well as structures for water and nuclear stations in Paluel and Penly; and the creation of coastal defence structures (sea fronts, groynes etc) at the mouths of all the valleys. These manmade constructions have created disturbances to the transport of sediment (mainly course pebbles) to the shore and resulted in a faster rate of erosion due to lack of protection. Pebbles have also been extracted for gravel purposes. Loss of pebbles leads to a retraction of the beach which protect the mouths of the rivers and the cliffs.

One of the immediate challenges for the community of Criel sur Mer was the actual loss of cliffs where houses existed.Responding to this emergency, the local administration considered both hard and soft measures with for instance the consideration of the implementation of defence works at the base of the cliff. The high cost of defence measures and the low cost of the real estate threatened by erosion led the local administration to evacuate the families faced and to implement a coastal setback plan whereby any new developments must take place 100 m from the cliff top.

The innovative aspect of this relocation measure was the fact that the compensation rate to those individuals that lost their property was calculated against the real market value. It is common that properties known to be at imminent risk lose real market value quickly, however, in the case of Criel sur Mer the French Government ensured that those families losing property were provided for financially based on the ‘riskless’ market value of the homes.

Key lessons learnt

The lesson of the Criel sur Mer illustrates is the inevitability of managed retreat in the face of climate change and the fact that multiple variables affect the situation and decision taken. For example, the cause of erosion was not only climate change but also a result of manmade constructions and attempts to mitigate against erosion. Moreover, the possibility of implementing a hard defense was considered but was economically disadvantageous. Thus, the Criel sur Mer provides an example of an extreme case of communities being threatened by climate change and provides an example of how governments and administration can more fairly compensate them economically.

Relevant case studies and examples

Further Readings

PDF: Geotechnical study

Scale

Local

Measure category

EXAMPLE: Managed Retreat at Surfer’s Point, California (USA)

nst — Mon, 16 Jan 2017 10:38:51 +0000

EXAMPLE: Managed Retreat at Surfer’s Point, California (USA) nst Mon, 01/16/2017 - 11:38

Based on a case study from the Climate Adaptation Knowledge Exchange (CAKE)

The Ventura County Chapter of the Surfrider Foundation in California, USA decided against traditional coastal defence measures to reduce beach erosion at a popular beach spot called Surfer’s Point. Along with other stakeholders, the County instead designed a two-phase plan to strategically relocate a parking lot, pedestrian path, and bike path away from erosion zones.

General description

Surfer’s Point is a popular beach and surfing location in the City of Ventura, USA which has suffered from coastal erosion for decades. Since the 1980’s, concern has grown amongst tourists and local residents over the eroding shoreline which has threatened a main bike path and parking lot.

The project involved the relocation of the bike path and parking lot approximately 60 feet inland, completely removing rip-rap (shoreline rock amour), undertaking natural beach restoration and beach nourishment, and potentially later inland waterway work to restore natural sediment supply. The project cost is estimated at approximately $3.8 million (USD).

The City of Ventura had taken the traditional approach to coastal protection in the 1980’s and 1990’s. This “shoreline hardening” had the effect of causing increased erosion both onsite and elsewhere along the coast. By 1995, the California Coastal Commission stepped in to prevent further shoreline hardening, and plans were in place by 2001 to address erosion risk through managed retreat.

The project is a partnership of the City of Ventura, the Ventura County Fairgrounds, the California Coastal Conservancy, California State Parks, the California Coastal Commission and the Surfrider Foundation. Project leaders have identified the importance of good communication and participation of all players in the planning process to ensure successful project execution.

Ecosystem-based aspects

During the first phase of the project, in addition to the relocation and removal of grey infrastructure, volunteers planted native vegetation on sand dunes and around bioswales. Increased vegetation cover provides slope stability so the dunes and bioswales can in turn protect the beach and ocean from intense storm water runoff while protecting the new grey infrastructure from wave action.

The project was specifically intended to address all natural and human factors that exist at Surfer’s Point, including the sand, stones, wind, vegetation, and human activities and infrastructure. By doing so, the functionality of the beach can be improved for those communities and people who use it while strengthening the resilience of the natural environment to erosion and threats such as storms and sea level rise.

Key lessons learnt

Surfer’s Point has remained stable, functional, and aesthetically pleasing since the implementation of the first phase of the project and as a result of ongoing efforts. While much of the City of Ventura Promenade suffered damage from erosion during the winter of 2015, the beach at Surfer’s Point did not experience the same level of damage.

While managed retreat, involving relocation and removal of exposed elements, is not the most popular shoreline management technique, it can sometimes be the most economically and environmentally appropriate. In the case of Surfer’s Point, the failure of historical strategies and the notable effectiveness of relocating and removing at-risk infrastructure both illustrate this clearly.

Relevant case studies and examples

Exposed element relocation and removal

Further Readings

More information on the project website

Measure category

EXAMPLE: Beach drainage in Quend-Plage (FR)

nst — Fri, 13 Jan 2017 08:44:16 +0000

EXAMPLE: Beach drainage in Quend-Plage (FR) nst Fri, 01/13/2017 - 09:44

In the face of increasing beach and dune erosion, the community of Quend-Plage, located on the Picardy coast of northern France, installed a beach drainage system in 2008. As a result of this, the macrotidal beach of Quend-Plage has been stabilized, preserving both natural habitats and recreational spaces.

Based on: Bain, Olivier, Renaud Toulec, Anne Combaud, Guillaume Villemagne, and Pascal Barrier. "Five Years of Beach Drainage Survey on a Macrotidal Beach (Quend-Plage, Northern France)." Comptes Rendus Geoscience 348.6 (2016): 411-21. Web.

General description

The Quend-Plage beach is characterized by a mix of transverse bars and troughs along the tidal flat. The wider coastal region is subject to the influence of both waves and tides, and by contrasting temperate and oceanic climates.

The implementation of a beach drainage system had never been used in the north of France, despite being tested elsewhere in Europe and overseas. The system was placed in the upper tidal flat of the beach, and consists of a drainage pathway 5 m wide, 900 m long, and 1.5 m deep. The system is susceptible to damage from storms and can malfunction over time, requiring maintenance.

Tourism plays a large role in the local economy of the Picardy coast. With hundreds of thousands of visitors per year, much of the coast is dominated by the tourism industry including Quend-Plage beach. Mussel farming and sea animal harvesting are also important to the local fishing economy.

After several years of beach erosion, and degradation of the existing sea wall, Quend-Plage beach lost much of its dry sand and recreational activities moved inland toward the dunes, which increased erosion of the dune foot and reduced tourism income. In response, the community of Quend-Plage invested in researching various coastal protection strategies, and the implementation of a beach drainage system was chosen.

Funding was received by European and national funds. The French government authority “Direction départementale des territories et de la mer” later requested a five-year long monitoring survey be undertaken to determine the effectiveness of the largely experimental technique for that region of France.

Exploring a new technique

One of the reasons why a beach drainage system solution to coastal erosion was selected by the Quend-Plage authorities was because it had never been done before in northern France and on the Picardy coastline. This was an opportunity to explore a new technique that, if successful, could be replicated along the coastline where deemed appropriate. The initiation of an extensive 5-year monitoring program, considering topographic, geomorphic, and granulometric factors, by the French “Direction départementale des territories et de la mer” indicates the experimental focus of the project and the commitment for long-term solutions.

Key lessons learnt

The use of a beach drainage system to combat coastal erosion along the Picardy coastline is a feasible and effective solution. In the case Quend-Plage, the beach morphology was significantly altered in the first five years after the system was installed. The upper beach and foot of the dunes recovered and increased in size. However, there was some erosion of the middle and lower beach and a small directional change of the bars and troughs. Overall, the drainage system facilitated a complete re-establishment of the Quend-Plage beach features, which ultimately brought more stability and usability to the community

Relevant case studies and examples

Beach drainage

Measure category

Riverine or slow rise floods

Managed realignment

giacomo.cazzola — Sun, 11 Sep 2016 21:33:51 +0000

Managed realignment giacomo.cazzola Sun, 09/11/2016 - 23:33

Estuarine floods

Combined approach (grey + green)

EXAMPLE: Titchwell Marsh (UK) seawalls and managed realignment

Managed realignment is a measure that usually results in the creation of a salt marsh by removing costal protection an allowing for an area previously protected from flooding to become flooded. Managed realignment is a measure dealing with sea level rise and coastal erosion. It is also often a method that replaces hard coastal defense measures with soft coastal landforms. Rather than relying on hard structures for defense, managed realignment depends on natural defenses to absorb or dissipate the force of waves.

Based on kindly provided information by the ClimateTechWiki and the TNA Guidebook on 'Technologies for Climate Change Adaptation' by Matthew M. Linham & Robert J. Nicholls

Managed realignment effectively forms intertidal habitats. Intertidal habitats are effective in absorbing wave energy and reducing offshore sediment transport or erosion. Extensive root networks created by saltmarshes also help to prevent erosion.

Managed realignment sometimes requires the complete removal of existing coastal defense structures. In some cases managed realignment is an introduced alternative measure when existing coastal defenses can no longer be maintained and are abandoned.

Conditions to consider in undertaking managed realignment according to Gardiner et al., 2007 are:

1) presence of coastal defences

2) availability of low-lying land

3) desire or need to improve flood or coastal defence systems

4) presence of a sustainability-oriented coastal management attitude

5) desire or need to create intertidal habitats

6) societal awareness about the benefits of managed realignment

Advantages of the technology

Realignment is considered a soft measure and can significantly reduce the cost of protection against coastal flooding and erosion. Intertidal habitats such as saltmarshes, or mangroves, are effective in reducing the energy and inertia of incoming waves and thus the damage that they do. With intertidal habitats the need for intrusive hard defenses is reduced and often avoided. In addition to protecting against floods and buffering storms, rich intertidal zones can improve the resilience of the local ecosystem and provide environmental benefits such as absorbing carbon dioxide and methane emissions which are stored in the sediment deposits.

Increasingly intertidal habitats are implemented in areas that have been surrendered or abandoned. In these cases, degraded land or land that would otherwise be used for development is used to create an intertidal habitat. Intertidal habitats are important ecosystems for a variety of flora and fauna. Realignment in the UK for instance has created new opportunities for ecotourism with activities such as walking and bird watching.

Intertidal habitats can also improve water quality in nearby urban areas. In situations where drinking water is threatened by sea level rise, intertidal habitats can help avoid saltwater intrusion from inappropriate land use and reduce the effects of eutrophication.

Disadvantages of the technology

When managed realignment is implemented, land is effectively relinquished to the sea. One of the greatest disadvantages or barriers is the loss of the land itself and the potential necessity of relocating important coastal infrastructure which can be expensive.

Although experience in the application of managed realignment is increasing, the approach is still relatively new and uncertainties still exist. For example, it is not fully understood how long it will take to create typical intertidal habitats that deliver the full benefits of naturally occurring systems. Moreover, managed realignment is not well monitored which has not built up an evidence base for future projects.

The approach is also not appropriate for all environments as wetlands and saltmarshes tend to occur in locations where wave energy is low and where high volumes of sediment are available. It is therefore important to carefully evaluate the feasibility and effects of this approach in specific locations.

Barriers to implementation

Relinquishment of land by the coastline is also often met by a lack of public acceptance and conflicts among those that own the land. In densely populated coastal areas this may be very difficult. Conflicts between users and landowners bring about legal and financial difficulties. For example the creation of intertidal habitats is often at sectoral odds with social and economic factors when the proposed land area is used for agriculture production. One way to navigate conflicts of interest is to ensure a participatory process in decision making and planning.

The potentially high cost of managed realignment also poses a barrier. The relocation of infrastructure and/or compensation to landowners in the managed realignment zone is potentially costly.

Managed realignment can only take place in certain areas and contexts. It is especially beneficial to have low-lying land that is sheltered by existing coastal defences as well as societal willingness.

Opportunities for implementation

Managed realignment is an extremely effective soft measure that replaces or reduces the need for constructing hard measures. When implemented managed realignment creates space for new habitats that are beneficial for flora and fauna and that preserve land. They are an effective soft measure to the coastline dealing with sea level rise and extreme weather events and also reduce the need for additional climate change measures to be implemented behind them.

Managed realignment usually requires significant amounts of coastal land. The beneficial environmental impacts of this are complimented also open up new opportunities for the creation of a new nature reserve and ecostourism.

Relevant case studies and examples

Literature sources

Main source: Matthew M. Linham & Robert J. Nicholls (2010): TNA Guidebook on 'Technologies for Climate Change Adaptation' UNEP , 166p.

Gardiner, S., Hanson, S., Nicholls, R., Zhang, Z., Jude, S., Jones, A., Richards, J., Williams, A., Spencer, T., Cope, S., Gorczynska, M., Bradbury, A., McInnes, R., Ingleby, A. and Dalton, H. (2007) The Habitats Directive, coastal habitats and climate change - case studies from the south coast of the U.K. Norwich: The Tyndall Centre for Climate Change Research. (http://www.tyndall.ac.uk/sites/default/files/wp108.pdf)

Measure category