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Contenu archivé le 2024-06-18

Morphological Impacts and COastal Risks induced by Extreme storm events

Final Report Summary - MICORE (Morphological impacts and coastal risks induced by extreme storm events)

Executive summary:

Researchers have developed a prototype system to predict the impact of storms on European coastlines. The MICORE Early warning system (EWS) aims to improve civil defence and coastal evacuation plans and could pave the way for an autonomous EWS to save countless lives and protect infrastructure worldwide.

Storms can have a devastating impact on coastal areas, causing extensive beach erosion, destruction of infrastructure and flooding. Using advanced weather circulation models, scientists can forecast storms up to 72 hours in advance. However, different physical characteristics of the coastline will influence how waves and winds behave once they reach the shore, which makes it difficult to predict the correct level of emergency response in each case.

Under the European Union (EU)-funded MICORE project, scientists from across Europe developed a prototype model to combine the warning signs of an upcoming storm with specialist knowledge of a coastal area to predict the precise emergency response actions required. The MICORE scientists identified nine coastal areas throughout Europe and collected data for more than a year on the impact of storms on the living and non-living features of the coastline. This included measuring wave height, flow velocities, beach and dune erosion, inundation (water covered) area and inundation depth.

Based on their case study data and a historical analysis of significant storm events, the scientists developed a generic model linking the extent of the physical impacts on coastlines with indicators of storms detectable offshore, such as increased waves, wind and currents. By combining the model with advanced weather forecasting tools, the scientists developed an EWS to translate the intensity of an upcoming storm into a series of Storm impact indicator (SII)s specific to each of the nine locations, such as the risk of flooding or dyke breaching. These were then interpreted into a risk status (high, medium or low) and practical recommendations to aid local decisionmaking, i.e. the level of evacuation needed.

Part of the MICORE project consisted of a historical analysis of European extreme weather events to investigate whether they were becoming more common or more intense under climate change. For the existing data, they could not establish a link with global climate. However, this is likely to be caused by the different timescales of storms and the historical analysis performed.

A primary objective of the MICORE project was for the model to be easy to use and fully accessible online by all interested parties, thus overcoming issues of data access common in multi-partner projects. The researchers envisage that once an EWS is established for a region, it could run indefinitely without further scientific intervention. Colour coded warnings and visual images of the most at risk areas could be sent automatically to fire departments, civil defence authorities, policymakers and even directly to the public via the internet.

So far, the nine locations have been used to demonstrate the potential value of the MICORE forecasting system, but the researchers intend that the generic concept of combining specialist coastal knowledge and a robust physical model can be applied anywhere. They recommend that EU Member States improve coastal and offshore monitoring to further develop and validate the MICORE model.

Project context and objectives:

Recent extreme hydrometeorological events in coastal areas have highlighted the devastating effects that can occur from hazards of marine origin. The experiences of Hurricane Katrina that struck the city of New Orleans, as well as the two massive tsunamis in the Indian Ocean and Japan tragically demonstrate what can go wrong when engineering design is subjected to forcing beyond its design limits and civil evacuation and management plans fail.

The 1953 storm surge event in the North Sea that resulted in over 2 000 deaths and extensive flooding across the Netherlands, England, Belgium and Scotland is a pertinent reminder that Europe is not immune to coastal threats. With approximately 185 000 km of coastline, Europe encompasses a diverse range of coastal environments, including pristine natural habitats, large coastal cities protected by offshore structures, low-lying sandy dune fields, steep rocky cliffs, exposed oceanic coastlines and enclosed sea basins. Each coastal type presents itself with a unique set of issues for coastal managers to deal with.

Due to economic constraints it is simply not possible to design, fund and build engineering schemes to protect vulnerable coastal areas across Europe from every extreme event foreseeable. Indeed in a rapidly-changing global climate there is a considerable degree of uncertainty as to how extreme events will behave in the future, particularly with regards to the intensity, magnitude and duration of coastal storms. Hence there is a pressing need to develop new coastal management systems; ones that can accommodate this uncertainty and minimise the impacts of extreme conditions that fall outside the design limits of both current and future coastal structures.

In this context, the ability to predict the imminent arrival of coastal threats is a valuable tool for civil protection agencies in order to prepare themselves and, if need be, execute the appropriate hazard-reduction measures. Developments in climate modelling have resulted in coastal storm predictions of a level of sophistication to know quite precisely their timing, intensity and other important storm variables up to approximately three days in advance. Building on from this is a way of knowing and communicating in real-time how these storm forcing predictions translate to morphological impacts and risk scenarios in the coastal zone. The work undertaken throughout the MICORE project has been performed to make significant advancements in this area.

The overall aims of the project were to set up and demonstrate an online EWS for the reliable prediction of morphological impacts due to marine storm events in support of civil protection mitigation strategies. It commenced in June 2008 and had project duration of 40 months.

The project focused on nine case-study sites (corresponding to the nine European countries involved). At all sites a number of individual work phases were conducted in order to reach the end goal of setting up a prototype EWS for coastal storm risk.

These phases included:

- a review of historical coastal storm events;
- field monitoring of storm impacts that occurred throughout the project;
- validating and testing a new as well as existing coastal storm models using the field data results;
- the development of a prototype EWS; and
- linking early warnings to civil protection protocols.

The use of these nine unique and morphologically diverse sites made the approach developed as generic as possible and demonstrated the robustness of the methodology.

Given that coastal storm predictions are typically provided up to a three-day prediction window, the MICORE project specifically related to short-term emergency response rather than on longer-term strategic objectives. As such it is a clear example of a practice-oriented research programme, providing practical outcomes for coastal management that are useful and applicable to end-users.

Project results:

One of the MICORE objectives was to undertake an analysis of changes in storm occurrence and to consider possible future variability in the context of climate change. This analysis included the study of trends in meteorological data (e.g. changes in storminess proxies) and intended to provide guidance for the understanding of the response of coastlines to potential changes in the forcing agents.

To gain an understanding of past coastal storm trends across Europe, a total of 58 long-term (i.e. the past 30+ years) time-series of various storminess indicators were assembled and analysed at 12 unique sites. These indicators included elevated water levels, large waves and strong wind speeds, with their selection depending on data availability, as well as the specific exposure conditions of each site.

Significantly, while some localised trends were observed, no European-wide trend of past coastal storminess was evident. This however is not to say that global climate change consequences (e.g. sea temperature increase, sea level rise) will not have an influence on European storminess and storminess impacts in the future. Rather, for the existing and available datasets, shorter-term (i.e. year-to-year) fluctuations in storminess dominate over any potential longer-term signal.

The inventory of generically applicable thresholds for storm impact showed that each site has its own specific physical features influencing how offshore waves, wind, pressure fields and tides affect the coast. This warrants the setup of a warning system that is based on process models as this is the only way to come up with one generic approach that may be applied to various locations with such variability in physical characteristics like European coastlines.

A common problem for multi-institutional / multi-national research and development (R&D) programmes is that a significant part of the budget is often spent on setting up some basic infrastructure for data and knowledge sharing. Not only is this project-by-project approach inefficient, it also means that data and knowledge developed over the course of a programme can become either difficult to access, indecipherable or, at worst case, lost over time.

To overcome these issues, the MICORE project adopted a new protocol for managing data and knowledge known as OpenEarth. Instead of existing specifically for a single project, OpenEarth (see http://www.openearth.eu online) is a project-transcending database whereby multiple projects can store and actively manage their data, model systems and / or analysis tools. It is built from the best available open source components, in combination with a well-defined workflow, described in open protocols and based as much as possible on widely accepted international standards. By being a common database for many projects OpenEarth promotes project collaboration and skill sharing, for example this generic data-visualisation tool using Google Earth. The many different stakeholders involved in the database also provide a way of guaranteeing its sustainability into the future.

The MICORE project demonstrated that it is advantageous to store and exchange data from various organisations and countries in a multi-project database like OpenEarth. By taking this approach a lot of time and money was saved in the development of such infrastructure. Perhaps its greatest benefit however is that the abundance of quality-controlled data collected throughout the project, such as field measurements of storm impacts and historical storm data will be available for easy use in future R&D programmes, something that is not often the case when projects come to a close.

In MICORE modelling techniques used for morphological modelling are based on an open source approach using the XBeach model, which has undergone extensive testing at a variety of sites. The MICORE project has demonstrated that a community model can indeed be effectively applied within R&D programmes. All field site modellers set up a dedicated version of the model capturing the specifics of each coastline and producing useful and reasonably accurate results. The application of one generic process model to a vast number of field sites proved to be a great advantage to test the model thoroughly. The fact that the open source model could immediately be improved if any bug or problem would emerge, meant that the model was improved significantly throughout the project.

Building a fully operational regional EWS is a very ambitious plan and far beyond the scope of the MICORE project. The set-up of such a system would require at least 5 to 10 years and the support of end-users on a national and European level. It was found that at present end-users are not ready to develop a EWS on a regional scale, although they are indeed interested in applications that demonstrate the capabilities of an operational tool. MICORE therefore focused on providing end-users with a prototype operational chain of models that could demonstrate the capabilities of an EWS for each test site.

A generic structure for an EWS of coastal risk was developed and found to be adaptable to each of the nine prototype systems. This structure is based on five essential modules:

- an observation module, where weather, wave, surge and initial beach profile measurements necessary for numerical modelling are collected;
- a forecast module, consisting of the numerical model forecasts of weather, wave, surge and morphology (i.e. XBeach);
- a decision support module, containing tools (i.e. SIIs and hazard maps) to assist decision making;
- a warning module, where warnings are issued according to various site-specific thresholds a visualisation module, displaying on-line information to assist end-users.

Each prototype EWS was operated in on-line mode, executing this chain of modules daily. Running the EWS in daily mode, instead of only during extreme offshore conditions, was found to be crucial in testing the system's robustness and gaining additional confidence by end-users in its overall performance. It also expanded the applicability of the EWS to more day-to-day functions, such as beach safety.

The fact that, with the selected approach, predictions would be available approximately three days in advance only, limited the kind of decisions for which the information could potentially be used. The frame of reference approach developed by Van Koningsveld and Mulder (2004) was used to help researchers from different field sites to use one method generically applicable to embed their highly specialised model results in a practical decision context. The SIIs are the base for the EWS as the thresholds of these indicators control if, and at what level, a warning should be issued.

The MICORE project intended to prove that based on a predicted storm and sufficient information about the state of the coastal zone and its infrastructures (e.g. bathymetry, topography of beach and dunes, dyke characteristics), accurate predictions of storm impact in support of civil protection mitigation strategies could be made.

Potential impact:

Economic limitations mean it is simply not possible to design, fund and build schemes to protect vulnerable coastal areas from all anticipated events. Indeed, scenarios of climate change impacts from present models are diverse and cannot at present be relied on to give accurate forecast of future extreme event around coastal Europe. Therefore, there is an urgent need to develop new coastal management systems to deal with as yet unforeseen extreme events that fall outside the design limits of existing and future coastal structures. MICORE addressed this by revisiting historical extreme storm events and evaluated closely their impact on the human occupation of the coastal zone.

The work of MICORE has made significant innovations in the area of coastal storm risk management and coastal civil protection schemes. The development of nine fully-operational EWS for coastal storm risk show that such an on-line tool based on real-time data acquisition and using a range of state-of-the-art hydrodynamic and morphological models is feasible for vulnerable areas across Europe.

These prototype EWSs lay the foundation for a greater roll-out across Europe, by adopting the following principles:

- using a generic structure adaptable to a range of different coastal environments;
- using free and open-source software without the need for commercial licenses;
- catering the functionality of the EWS to the needs of end users.

During the work it was found that an obstacle to database building is the freedom of access to meteorological and marine (waves, tide level) datasets.

It is recommended that resources be placed into the development of larger-scale EWS schemes for coastal storm risk, at regional and national levels as well as European wide. These schemes could be merged with existing schemes, such as those already in existence for tsunamis and terrestrial flooding. Furthermore, continued monitoring of future coastal storms using accurate and rapidly-deployable survey methods is crucial to gaining additional understanding as to the changing nature of storm systems across Europe and for further EWS testing.

All stakeholders at regional and national level participated to local meetings that were organised in partner countries. A multi-language report was produced at the end of the project. The dissemination also included workshops for end-users to illustrate the definition of risk for each site and the critical areas. Moreover, the new warning system was presented together with a training session to tell end-users how to use the outputs from modelling, SIIs characteristics and how the information are stored in standardised databases. A web site with web-GIS interface was produced in order to upload on the Internet the project outputs such as risk maps, descriptions of areas at risk and available datasets. SIIs were presented in order to give to end users several parameters, together with their range of variation and thresholds, to estimate the damage and to better understand risk maps.

The dissemination activities carried out in the MICORE project were given high importance because they were considered the most relevant mean to publicise the objectives and the intermediate / final results of the project to the general public and to end users. The theme targeted by MICORE, risk induced on coastal areas by extreme marine storm events, is of vital importance for both integrated coastal zone management strategies and safety of people living and working along European coastlines. The awareness of end users, decision makers, politicians, as well as of the general public on the effects of climate change on the coast can be increased only through a widespread dissemination of the research activities carried out by European Institutions and, consequently, through the delivery of the objectives, when the project starts, and the results, at the end of the project, using every mean available at the present time (television, Internet, printed press, scientific and conference papers, workshops, conferences).

Project website: http://www.micore.eu