Coastal floods or storm surges

Channel, Coastal and Floodplain Works

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

Channel, Coastal and Floodplain Works

Hold the line

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

Hold the line

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

Riverine or slow rise floods

EXAMPLE: Early warning system in Sogn og Fjordane (NOR)

nst — Wed, 25 Jan 2017 15:39:06 +0000

EXAMPLE: Early warning system in Sogn og Fjordane (NOR) nst Wed, 01/25/2017 - 16:39

Flash floods

Estuarine floods

Flood Forecasting and Warning

Urban floods

Based on information from the Climate-ADAPT website.

The county of Sogn og Fjordane frequently experiences avalanches and landslides, storm surges and flooding. A demonstration project explored the potential for an effective, reliable and cost-efficient early warning system that has a multi-hazard approach and makes use of location and population-based communication technologies, such as mobile phones, as well as social media such as Facebook and Twitter. The system was tested with a sample warning followed by a survey and data analysis to judge its efficacy.

General description

Sogn og Fjordane is a coastal, mountainous region of Norway that boasts hundreds of thousands of tourist visits annually. Several communities in Sogn og Fjordane are facing numerous hazards such as flooding, avalanches, rock slides and other extreme weather events, that might be exacerbated by climate change. To respond to the challenge an early warning system was developed and tested within a EU research project. The multi-hazard warning system aimed at optimising rescue and other emergency services provided by the county. Due to tourism, it aims to be a cost-effective method reaching all people in the geographic area and not only residents.

A public warning exercise was carried out in 2010 with 2,500 mobile phones receiving the alert as text message and 322 fixed line phones in Aurland received the alert as voice message. The warning exercise was visible on Facebook for 2 hours and received 201,849 viewings. A post-exercise survey was carried out online and a door-to-door survey was conducted in parts of the area to assess the public’s thoughts on the exercise. The population warning exercise was evaluated to measure the efficiency of the warning system by combining an electronic evaluation form and a door-to-door survey.

Key lessons learnt

The project demonstrated how an existing county-encompassing organization could be used to issue the population warning. While the technical aspects of people-centred warning systems are at large readily available, issues concerning confidentiality legislation and system regulations must be solved before successfully implementing efficient location-based warning systems. In order to use social media during crisis situations, the projected concluded that research is needed.

Relevant case studies and examples

Early warning systems

Measure category

Preparedness

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

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: London Mass Evacuation Framework (UK)

nst — Wed, 18 Jan 2017 09:26:41 +0000

EXAMPLE: London Mass Evacuation Framework (UK) nst Wed, 01/18/2017 - 10:26

Emergency Event and Contingency Planning

Urban floods

Public Awareness and Preparedness

In 2014, the London Resilience Partnership developed the second Mass Evacuation Framework for the city of London. The purpose of this Framework is to offer guidance to responders managing a mass evacuation of displaced persons and, where appropriate, other living creatures.

The Framework has been developed by the Multi-Agency London Resilience Partnership Mass Evacuation Group. This group consists for example of the City of London Police, London Fire Brigade Emergency Planning, Environment Agency, Ministry of Defence (London), or Network Rail.

Based on: London Resilience Partnership (2014): Mass Evacuation Framework.

In the city a range of risks could result in a scenario requiring mass evacuation. The current reasonable worst case planning assumption for London is based on a major fluvial flooding incident.

In addition to providing guidance, the framework is intended to support decision-making and expectation management across all multi-agency partners and stakeholders. The content facilitates a flexible, scalable and coordinated approach to managing an evacuation.

The framework is not intended to be prescriptive, as every incident is different; rather, its aim is to capture the core principles for the management of a mass evacuation enabling key organisations to respond consistently and with a clear understanding of their roles and responsibilities.

In more detail, the objectives of this Framework are:

Support the Strategic Coordinating Group to respond effectively to an event that requires the evacuation of part of London;
Provide responding organisations with the necessary strategy to allow them to effectively implement their roles and responsibilities in support of an evacuation; and
Provide the process by which appropriate information is supplied to all responding agencies, the public and businesses, at the start of and throughout the evacuation process.

An incident which causes a mass evacuation may be a ‘sudden impact’ or a ‘rising tide’ type of incident. A ‘sudden impact’ incident will require immediate evacuation of a population to protect life, which may have to be initiated before the full command and control structure is in place. In a ‘rising tide’ incident, agencies will have some warning of a potential incident, enabling command and control structures to be put in place to coordinate the response to the incident and any associated evacuation. Flooding events typically fall under the latter of this incidents.

Evacuation process

The evacuation process is broken down into five principal phases as follows:

Initiate Evacuation

Responding Agencies initiate operating procedures
Transport availability identified
Evacuation assembly point identified
Recovery Cell setup
Alert neighbouring areas

Alert Population

Initiate Warning and Informing methods

Move Population

- Affected Local Authorities (LA) move evacuees requiring help to evacuation assembly point (with assistance from Police)
- LAs to liaise with transport operators and move evacuees to locations where shelter can be provided

Shelter / Assistance

LAs receive evacuees and provide 48hr shelter where needed.

Return / Recovery.

- Handover to Recovery Group
- Inform Population/ Residents
- Assess Situation - Reoccupation (if possible)
- LAs consider longer term shelter options

Training and Exercising

Each organisation is responsible for ensuring that its staff are fully trained in its own emergency response procedures, and in its particular role in support of the operation of the London Mass Evacuation Framework and associated plans and protocols. A standardised approach to training and exercising is described in the framework. It is also stated that agencies have to maintain records of their training programmes as evidence.

Key lessons learnt

Once an evacuation plan has been set, it must be made available to the people who might need to use so they can be trained and the effectiveness of the plan validated. This is usually through an exercise which alows responders to simulate an emergency and their response.

Also a regularly review and update of the plan has to be undertaken. These updates should take into account learnings from exercises, incidents and changes in policy. It has to be ensured that the latest best practise is incorporated.

Relevant case studies and examples

Evacuation planning

Further Readings

City of London

Measure category

Preparedness

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

Spatial Planning and Integrated Coastal Zone Management (ICZM)

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

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

Channel, Coastal and Floodplain Works

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