Erosion

Hold the line

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)

Hold the line

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

EXAMPLE: Relocation of Clavell Tower, Dorset (UK)

nst — Thu, 26 Jan 2017 15:00:34 +0000

EXAMPLE: Relocation of Clavell Tower, Dorset (UK) nst Thu, 01/26/2017 - 16:00

Combined approach (grey + green)

Removal or relocation

Managed retreat

By 2002, historic Clavell Tower was deemed to be at serious risk of collapsing under the crumbling Dorset coastline at its base. The most technically, socially, and financially feasible solution was to simply dismantle the empty tower and reconstruct it further away from the cliff’s edge on more stable footing. This resulted in a reinvigorated heritage site saved from the dangers of coastal erosion.

Based on information from The Landmark Trust

General description

Located high on a cliff on the Dorset coast of southern England overlooking Kimmeridge Bay, Clavell Tower is a four story circular tower originally built in 1830. The soft and easily erodible shales of the cliff had been steadily crumbling and retreating towards the tower since its construction.

The responsible organisation for managing Clavell Tower, the Landmark Trust, decided that the most feasible solution for this kind of coastal erosion threat was to dismantle the ageing tower and re-erect it on a more stable base further away from the cliffs edge.

The eroding coastline for which Clavell Tower calls home happens to be a UNESCO World Heritage Site known as the Jurassic Coast. It is a popular tourist destination for its natural beauty and geological significance. As such, it is unlikely that more intrusive coastal erosion measures that could be used to stabilize the cliff would be approved. Relocating the tower itself was a more socially acceptable solution.

Innovative & Cost-effectiveness aspects of the measure

Dismantling and re-erecting Clavell Tower was simply the most technically and financially feasible solution for the Landmark Trust to undertake. Four years of fundraising efforts and external funding from the Heritage Lottery Fund allowed the project to commence by 2006. To offset some of the costs and ensure future revenue for maintenance and heritage preservation, the Landmark Trust also currently manages Clavell Tower as a hotel.

This kind of heritage conservation strategy is clearly the most intrusive possible and would not have been undertaken if it was not the most suitable option. Conservation staff carefully recorded and surveyed all the physical aspects of the tower so that the replication was as true to the original as possible. Sightlines from the tower across the bay and landscapes were also replicated as best as possible when orienting the tower in the new location. Lastly, the new tower was built in such a way as to allow additional future relocation should the eroding cliff’s edge make it necessary again.

Key lessons learnt

Even in heritage conservation, where intrusion and alterations are avoided whenever possible, sometimes drastic measures must be taken to combat the threat of coastal erosion. Relocating heritage sites to safer ground is a suitable solution, especially when the eroding coastline is deemed globally significant and has challenging terrain. Dismantling and re-erecting Clavell Tower was not a decision taken lightly, but it has proven to be a successful measure in preserving the tower’s positing as a valued historic landmark on a World Heritage Site.

Relevant case studies and examples

Exposed element relocation and removal

Measure category

EXAMPLE: Vulnerability Assessment for Marin's Ocean Coast, California (USA)

nst — Tue, 24 Jan 2017 13:06:12 +0000

EXAMPLE: Vulnerability Assessment for Marin's Ocean Coast, California (USA) nst Tue, 01/24/2017 - 14:06

Public Awareness and Preparedness

Non-structural measure

In 2015, the Marin County Community Development Agency (CDA) published a Vulnerability Assessment based on information from technical advisors, utility managers, and West Marin residents. The Assessment summarizes the expected timing and extent of impacts, laying a foundation of knowledge to guide adaptation planning.

Based on information from Marin County Community Development Agency (CDA).

General description

Marin County is located in the San Francisco Bay Area of the U.S. state of California. Marin’s coastline is stated to be vulnerable to sea level rise and changing storm patterns that accompany climate change. Over one-quarter of Marin County properties and natural and community assets are threatened by sea level rise along the coast.

The Marin County Community Development Agency together with different partners began in 2014 to develop a Vulnerability Assessment. The assessment presents asset profiles describing the vulnerability of parcels and buildings, transportation networks, utilities, working lands, natural resources, recreational activities, emergency services, and historic and archaeological resources; and community profiles highlighting vulnerable assets in different parts of the county. The findings are based on a combination of different sea level and storm scenarios representing near-term, medium-term, and long-term futures.

The Vulnerability Assessment is “advisory and not a regulatory or legal standard of review for actions that the Marin County government or CA Coastal Commission may take under the Coastal Act.” (CDA 2015: 4)

The Assessment is broken down in five different sections:

Executive Summary and Introduction
Asset Profiles
Community Profiles
Conclusion and Appendices
Vulnerability Assessment Maps

Methodology

The Assessment methodology is based on the California Climate Adaptation Planning Guide (CA Emergency Management Agency, 2012). Based on this planning guide, five phases were undertaken (CDA 2015: 17):

Phase 1| Exposure: Assess potential changes in water level from sea level rise, storm events, and geomorphic change, and the built and natural assets that could be impacted
Phase 2| Sensitivity: Assess the degree of damage or disruption sea level rise and storms could cause on the exposed assets.
Phase 3| Adaptive Capacity: Assess each asset’s adaptive capacity, or ability to respond successfully, to sea level rise and storms.
Phase 4| Potential Impacts: Evaluate the potential consequences to the assets and larger context, assuming no intervention actions.
Phase 5| Risk & Onset: Describe the certainty and timing of impacts.

Key Findings

In the coastal zone of Marin County, over 10 percent of buildings are vulnerable to a scenario with 40 inches of sea level rise and a 100-year storm. In a scenario of 80 inches of sea level rise combined with a 100-year-storm event, even 20 percent of buildings at the coast would be vulnerable. Depending on the scenario between 2.5 and 20 miles of road may be exposed to sea level rise and storm flooding.

Other vulnerable assets of coastal Marin are:

Beaches,
underground on-site wastewater treatment systems
Water distribution pipe
Fire service facilities and tsunami routes
Recreational facilities

More information and the pdf version of the Vulnerability Assessment can be found here: http://www.marincounty.org/depts/cd/divisions/planning/sea-level-rise/draft-vulnerability-assessment

Key lessons learnt

As stated in the document, the assessment is not a regulatory or legal framework but an advisory report. Based on the assessment, adaptation measures can be undertaken. Implementing these measures, new institutional, legal, and financing arrangements might be required. The assessment lays the informational foundation for adaptation planning and implementing the necessary measures.

Relevant case studies and examples

Vulnerability Assessment

Literature sources

CA Emergency Management Agency (2012): California Climate Adaptation Planning Guide, 60 pages.

Marin County Community Development Agency (CDA) (2015): Marin Ocean Coast Sea Level Rise Vulnerability Assessment. Draft Executive Summary and Introduction. 35 pages.

Measure category

Preparedness

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: A participatory adaptation planning approach, Cascais (PT)

nst — Wed, 18 Jan 2017 08:42:04 +0000

EXAMPLE: A participatory adaptation planning approach, Cascais (PT) nst Wed, 01/18/2017 - 09:42

Urban floods

Public Awareness and Preparedness

Non-structural measure

Cascais is a Portuguese city on the Atlantic coast and 30 km west of Lisbon. Within the project BASE, researcher supported the participatory ICZM approach to develop a Climate Adaptation Action Plan.

Based on: Ng, K., Campos, I., & Penha-Lopes, g. (Eds.) (2016): BASE adaptation inspiration book: 23 European cases of climate change adaptation to inspire European decision-makers, practitioners and citizens. Lisbon: Faculty of Sciences, University of Lisbon.

General description

Cascais is a Portuguese city on the Atlantic coast and 30 km west of Lisbon. Flash flooding is of especially high concern due to extensive urbanization in areas with strong economic and touristic activity and concentrated physical capital, namely historical buildings. In the period between 2000 and 2011, there was just over EUR 1 million in private claims to insurance companies, with 40% of that value occurring in a single event in 2008 in two parishes. In the same year, annual private costs due to flooding in Cascais exceeded EUR 400,000.

The Adaptation Response

In 2010 the municipality developed its Strategic Plan for Climate Change Adaptation (PECAC). In 2013-15 under the FP7 BASE project, a comprehensive participatory revision of the Plan was made together with the Agenda 21 of Cascais in order to reassess and reprioritize the implemented adaptation measures, taking into consideration all major stakeholders as well as all key affected sectors. Cascais is moving towards the updated Climate Adaptation Action Plan in 2017. The measures included :

green spaces and corridors in urban areas;
beach and shoreface nourishment;
the rehabilitation and restoration of rivers;
the establishment and restoration of riparian buffers; and
awareness campaigns for behavioural change.

The People and Institutions involved

Participatory methodologies have been extensively used in the Cascais adaptation strategy. BASE research work in Cascais began in October 2012 with preliminary/exploratory meetings with representatives from the municipality. Through nine participatory workshops, one population-wide inquiry (n=1885), one inquiry to the technical body of the municipality (n=99) and several field visits, PECAC 2.0 was completed in 2015. This makes Cascais BASE’s case study icon in the use of participatory methodologies.

Outcome of action

In terms of concrete measures, green corridors, rainwater gardens and rainwater catchments are to be implemented. Green corridors and the re-naturing of Cascais streams is an ongoing adaptation measure that enjoys wide stakeholder consensus and yields positive externalities and socio-political support with relatively low levels of investment needed. Yet its effectiveness in flood risk reduction in this specific case study is still uncertain and a detailed action plan is needed for further analysis.

Key lessons learnt

Climate change adaptation has to do with political choices and is not only a matter of finding the right technical solutions. Participatory experiences such as those developed in, Cascais or Timmendorfer Strand, show that adaptation decisions are political in nature, because they affect different stakeholders and citizens in different ways.

A number of regulatory frameworks and policies can either hinder or promote local action. One important strategy is to involve a wide range of stakeholders and citizens at the early stages of making decisions about measures. Practitioners and decision-makers need to be well informed on local, national and supranational policies, taking stock of potential synergies and addressing potential bottlenecks and constraints posed by public policies.

Relevant case studies and examples

Spatial Planning and Integrated Coastal Zone Management (ICZM)

Further Readings

The BASE project

Case Study report about Cascais

Literature sources

Ng, K., Campos, I., & Penha-Lopes, g. (Eds.) (2016): BASE adaptation inspiration book: 23 European cases of climate change adaptation to inspire European decision-makers, practitioners and citizens. Lisbon: Faculty of Sciences, University of Lisbon. http://base-adaptation.eu/sites/default/files/BASE%20Inspiration%20Book.pdf

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

Managed retreat

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

Managed retreat

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: Wallasea Island Wild Coast project (UK)

nst — Mon, 16 Jan 2017 12:39:10 +0000

EXAMPLE: Wallasea Island Wild Coast project (UK) nst Mon, 01/16/2017 - 13:39

Based on information from the Royal Society for the Protection of Birds (RSPB)

Water flow regulation

Limited intervention

Ecosystem based approach

The aim of the Wallasea Island Wild Coast project is to recreate a natural intertidal coastal marshland to combat the threat of climate-induced coastal flooding. The recreated mudflats, salt and brackish marshes, saline lagoons, and pastures will provide a range of habitats for coastal birds and other wildlife on the Essex coast.

General description

The project uses a technique known as “managed realignment” to recreate an intertidal habitat through the breaching of existing seawalls at strategic locations. These breaches, or holes, allow sea water in, and various kinds of ecosystems can be created depending on the height of the land being flooded. The land of the Wallasea Island will be heightened and extended using the clay, chalk, and gravel excavated from new underground rail line connections in central London. In total, nearly 1500 acres of tidal wildlife habitat will be transformed or created new, including approximately 133ha of mudflat, 276ha of salt marsh, 53ha of saline lagoons, 11ha of brackish marsh, 160ha of grassland, and 15ha of rotational arable fields.

Historically, Wallasea ‘Island’ comprised as many as five individual salt marsh islands. When seawall defences were added to the area to prevent coastal erosion, the landscape eventually evolved into the shape that can be seen today.

Since 2008, the Wallasea Island Wild Coast project has been in partnership with an underground rail line development project called Crossrail. The clay, chalk, and gravel excavated from their tunnelling in central London will be reused to heighten and transform the coastlines of the Wallasea area. The addition of these materials to raise land and extend coastlines is expected to allow approximately 2.1Mm³ of tidal water to enter the area once the sea walls are breached. This would require around 7.5Mm³ of imported fill material. The construction schedule to achieve the objectives of the managed realignment plan is determined by the delivery schedule of the materials from the Crossrail project, and is planned between 2016 and 2019.

The site is located near one of the world’s most important estuaries and one of Europe’s largest economic regeneration zones: the Thames Gateway. The Crouch and Roach Estuaries bordering Wallasea Island have been recognized, under the European Union Directive on the Conservation of Wild Birds, as a Special Protection Area, a Special Area of Conservation, and a Wetland of International Importance through the Ramsar Convention.

In July 2009, the final design of the project received planning approval. Local authorities, yacht clubs, and various organizations were publically consulted and included in developing and designing the project plan.

Innovative Aspects

The Wallasea Island Wild Coast project is a bold initiative to address the alarming amount of coastal change that has happened in this region of Europe. Over the past 400 years, the Essex coast has lost over 91% of its intertidal salt marshes due to accelerating coastal erosion and competition with agriculture for land. The project has set a high standard for 21^st century conservation and engineering efforts, and is at a scale never before attempted in the UK. It jointly considers ecological and economic factors, for the benefit of future visitors, wildlife, and local community members for decades to come.

Perhaps the most innovative aspect of the project is the landmark partnership and collaboration between the project operators, the Royal Society for the Protection of Birds (RSPB), and the underground rail development project Crossrail. By deciding to reuse the excavated materials from London’s new underground connections to achieve the managed realignment objectives of Wallasea Island, the two projects set a global standard for how waste material from large-scale infrastructure projects does not have to be disposed of in a landfill. Instead, excavated soils, clays, and rocks can provide flood protection to coastal communities and refortify coastal ecosystems. Equally, the project cooperation showed that it is possible to transport large amounts of excavation spoil from London to the Essex coast in a safe and reliable way.

Key lessons learnt

The Wallasea Island Wild Coast project showed that despite the challenges, major land realignment can be undertaken in a sustainable way. The use of excavated materials from the London Crossrail project also illustrated a mutually beneficial solution for both stakeholder groups and is an example of cooperation that leads to smart solutions for the benefit of the environment.

Relevant case studies and examples

Marsh vegetation in intertidal and coastal zone

Further Readings

PDF: Documentation about the project

Measure category

Mitigation

Combination of groynes and beach nourishment, Clacton (UK)

nst — Mon, 16 Jan 2017 12:30:37 +0000

Combination of groynes and beach nourishment, Clacton (UK) nst Mon, 01/16/2017 - 13:30

Combined approach (grey + green)

Hold the line

The Clacton to Holland-on-Sea (UK) stretch of coastline has suffered from significant sediment loss, which negatively impacts the local community and economy. Collectively, five kilometres of beach are at risk of washing away including nearby tourism promenades and over 3000 homes and businesses. In response, a major sea defence project is underway to fortify the coast through construction of new rock groynes and beach nourishment activities. It is expected that this project will reduce coastal erosion for the next 100 years.

Based on information from the Tendring Destrict Council.

General description

The beach area at risk is five kilometers long and runs from Clacton Pier to Holland Haven in Essex on the east coast of England. The project involves using 23 fishtail rock groynes, each 90 meters long and 220 meters apart, and adding roughly 950 000 cubic meters of sand and shingle beach material to the coastline

The project is the biggest of its kind to ever be undertaken by the Tendring District Council. It was approved by the UK Environmental Agency in 2013 and costs roughly 36 million pounds, with support from several funding organizations.

The groyne and beach recharge activities were effective, on time, and on budget. The materials for the rock groynes were made up of the crushed materials from the existing structures and new smaller rocks from a quarry, and were covered by a geotextile once in place in the sea. Larger rocks were placed on the geotextile and the groynes were designed in a fishtail style. The fishtail design of the groynes was chosen to allow dual protection, with the bigger arm blocking waves from the North Sea and the little arm blocking waves from Kent. The materials for beach recharge came from a licensed dredge site and was made up of sand and shingle (a mix of sand, gravel and cobbles, mimicking the natural beach material of the area. During high tide, a dredging ship would pump this mix through a pipe onto the beach, forming an 18 metre wide crest about one metre below the promenade walking level.

Key lessons learnt

Pumping the sand and shingle mix early in the project towards the shore created a platform to help construct the many fishtail rock groynes and support the heavy construction machinery used on the beach during construction. Even with all the groynes, periodic beach re-profiling will be necessary in the future due to coastal processes.

Relevant case studies and examples

Groynes

Further Readings

Article about the measure in the East Anglian Daily Times

Scale

Local

Measure category