Theme 5 State of the Art/ Introduction article

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This article presents a state of the art review of the ENCORA project Theme 5: Long-term geomorphological change and climate impacts. This theme is concerned with promoting the development, demonstration & dissemination of new and emerging models & methodologies for prediction of long term changes to coastal systems, including the effects of climate change.


Theme rationale

Effective management of coastal systems is crucial to the protection and preservation of all coastal communities. All coastal authorities are faced with the need to make predictions concerning the behaviour of the coastline over a timescale of the order of 50 to 100 years in order to fulfil Integrated Coastal Zone Management (ICZM) planning requirements. This timescale holds in particular for sedimentary or soft rock coasts. The main challenge addressed by this theme, therefore, is to promote the development and demonstration of emerging and new methodologies for the prediction of long-term geomorphological changes to coastal and estuarine behaviour systems including the effects of climate change and to disseminate this new knowledge across Europe.

Important criteria are to both develop calibrated modelling tools and the framework in which they are used, and also to demonstrate the implementation of this methodology using a standard of data quality and coverage that can be reasonably achieved by European coastal authorities.

It is envisaged that this pioneering work will inform further developments at the European level. Considerable progress can be made at the European level by networking activities to spread existing examples of good practice and research amongst European partners.

Within the ENCORA project it was decided to develop the Coastal Wiki to provide the most effective tool for networking and dissemination of the state of the art. Within Theme 5 the following topics were identified as being of particular relevance:

Coastal processes

Coastal classification

Models

Policy

Practices

Issues

Case studies

Data sets


The rest of this article provides an overview of these topics, setting them in context and providing some generic conclusions.

Coastal processes

This section provides a comprehensive description of waves, currents, coastal hydrodynamics, sediment transport processes and causes of coastal erosion. An appreciation of these matters is fundamental to the subsequent sections.


Coastal classification

This section discusses both the classification of coastal profiles and the classification of coastlines. The type of coastal profile, in itself, is not sufficient to characterise the coastal morphology or to evaluate the stability of the coastlines. The interaction between the given coastal geology and sediment sources and pathways, results in the formation of different types of coastlines and coastal features. Therefore, in order to be able to make an overall evaluation of a certain site in relation to shoreline management activities, it is also relevant to study the coastline features.


Models

This section provides a comprehensive overview of both existing modelling techniques and the latest developments in new and emerging modelling systems. Different tools are needed to predict the response of the coastline at different time and space scales, but they can all be ascribed to a limited number of model types. These methods come with different levels of reliability, accuracy, skill and required expertise and may be allocated to one of the following basic types: 1. Process-based numerical models; 2. Behaviour-based numerical models 3. Statistical analysis; 4. Geomorphological analysis; 5. Parametric equilibrium models; and 6. Emerging techniques

The traditional approach has been to use a model to make a deterministic prediction of future morphology. However, an increasing awareness of the importance of probability and risk has led to an increase in the use of models for making stochastic predictions. Hybrid models are also under development. In this context, hybrid models are models in which limited coastal area process modelling is combined with empirical knowledge of morphological behaviour.


How to apply models

Numerical models have reached a level of accuracy and detail over the past 25 years that allow most of the dominant processes in the coastal environment can be quantified, though still subject to wide confidence limits. However, the numerical models are tools only for the coastal engineers and planners. This article discusses the optimal use of the modelling tools at various stages of a coastal development project. Further, examples are given of projects where proper analysis and modelling have formed the basis for successful coastal projects.

Process-based Morphological Models – Applications to longer Time Frame The so-called coastal area models, which combine waves, currents and sediment transport models and include updating of the model bathymetries, have proven to be very strong tools in the short to medium term (days to weeks) for the study of morphological impacts from significant changes to the coastal system. This article discusses how such models can be applied for longer time frames, which is an ongoing research area.

Long-term modelling using 1-line models - GENESIS and new extensions One-line beach models are the classic type of a behaviour-based numerical model. They calculate sediment transport due to a longshore component of wave energy (process based, though abstract) and also assume an unchanging long term averaged surface slope (behavioural). They thus provide a deterministic prediction of the evolution of the shoreline (e.g. the one-line). These models are highly schematic representations and require tuning with field data, and therefore are only reliable for prediction purposes if present and future situations are not too different. The GENESIS model is one of is the best known and used models of this type. The article provides a full description of the model concepts and recent developments.


Stability Models: Linear and nonlinear

Coastal systems may self-organize at various length and time scales. Sand banks, sand waves both in the shelf and at the coastline, sand bars, tidal inlets, cuspate forelands, spits (among others) are morphologic features that are frequently dominated by self-organized processes. Stability models are a recently developed, powerful tool to understand these processes and make predictions on the dynamics of those features. Stability models are generally limited to the stage of initial development of coastal features: studying the further development (finite-amplitude behaviour) is possible only in certaincases and for highly schematized situations. Such models are presented here in some depth.


Policies

This section is intended to provide examples of relevant policies across Europe. Currently, this section provides examples from Poland and the UK, with further contributions expected as the Coastal Wiki grows.

The UK Foresight Flood and Coastal Defence Project (2004) provides an example whereby the aim of the project was to use the best available science to provide a challenging vision for flood and coastal defence in the UK between 2030 and 2100 and so inform long-term policy. The work covers all of the UK and looks at flooding from rivers and the sea, as well as internal flooding in towns and cities. It also considers the risks of coastal erosion. Sustainability analysis was at the heart of the analysis, considering economic, social and environmental consequences of flooding and erosion. The report contained key messages with regard to the consequencies of climate change and made recommendations for future policy, practice and research in the UK, much of which could be relevant across Europe.


Practices

This section begins with a generic description of shore protection, coast protection and sea defence methods, which may be applied Europe-wide. Some examples of good practice are then given from the UK and from a previous European project Eurosion.

Shoreline Management Plans (SMPs) were introduced in the UK in the 1990’s. The new criteria for the preparation of the next generation of SMPs now require each local coastal authority to consider coastal management strategies that must address a time-scale of 70 years into the future. Emphasis is placed on the need to make predictions of coastal changes and quantitative risk assessments over this timeframe. To address this need the UK Futurecoast project provided a major step forward in conceptualising the factors affecting coastal change. A ‘behavioural systems’ approach was adopted, which involves the identification of the different elements that make up the coastal structure and developing an understanding of how these elements interact on a range of both temporal and spatial scales.

Eurosion was a European study into coastal erosion at a European scale. Its outputs were: • A map-based assessment of European coasts exposure to coastal erosion; • A review of existing practices and experience of coastal erosion management; • Guidelines to incorporate coastal erosion into environmental assessment, spatial planning and hazard prevention; and • Policy recommendations to improve coastal erosion management.

Eurosion concluded that a more strategic and proactive approach to coastal erosion is needed for the sustained development of vulnerable coastal zones. Eurosion considered that coastal sediment cells constitute the most appropriate units for achieving the objective of favourable sediment status and hence coastal resilience.


Issues

There are two main issues of particular relevance to long term geomorphological change, climate change and reliability and risk assessment. The principal drivers of climate change on coastal evolution include sea level rise, increased storminess and changes in wave direction. There is currently much scientific study of climate change and policy and practice responses, which are summarised in this section. The concepts of reliability and risk assessments are currently becoming central to the analysis of coastal flooding and erosion studies and in the design process for new coastal engineering schemes. These issues are briefly addressed in this section.


Case studies

Case studies can provide a valuable source of information to guide future studies across Europe. Such information has traditionally not been easily accessible. In this section a wealth of such studies, drawn from across Europe have been collated.


Data sets of coastal hydrodynmics and morphodynamics

This section provides links to a set of website addresses to databases/ data sets. The intention here is to increase awareness of available data sources, which readers may not otherwise be aware of.


Conclusions

The current state of the art with regard to our understanding of coastal processes, coastal classifications and the causes of coastal erosion are well established and applied throughout Europe. However quantification of sediment dynamics remains subject to large uncertainties and the prediction of the evolution of coastal features is still sbject to conjecture.

Existing modeling systems designed specifically to make a useful contribution to long term coastal management planning are still under active development. Process based models are being developed alongside a variety of behaviour based modeling systems, together with statistical and geomorphological analyses.

Concepts of reliability and risk are beginning to be applied in some countries, to provide resilient and sustainable solutions to coastal erosion and coastal flooding, but this is by no means widely applied across Europe.

The UK Foresight study of flood and coastal defence provides an excellent model for the formulation of policy, which could be more widely adopted across Europe.

The use of shoreline management plans and the futurecoast study, pioneered in the UK, are examples of good practice which could be more widely adopted across Europe. The European Eurosion project contains many excellent recommendations for policy and practice that could be adopted across Europe, many of which have not yet been implemented.

The issue of climate change impacts is an area of rapidly developing research. Policy and practice is still evolving, dependent not only on the science but on the political will to effect the necessary changes.

The main author of this article is Prof. Chadwick, Andrew John
Please note that others may also have edited the contents of this article.