European Flood Alert System

The European Flood Alert System project is a European Commission initiative to increase preparedness for riverine floods across Europe.

Content Table

History

Over the last decades severe fluvial floods of trans-national dimensions have taken place in Europe. There is evidence that in particular transboundary floods can be more severe in their magnitude, affect larger areas, result in higher death tolls, and cause more financial damage than non-shared river floods do [1]. The European Environmental Agency estimated that floods in Europe between 1998 and 2002 caused about 700 deaths, the displacement of about half a million people and at least 25 billion Euros in insured economic losses (EEA, 2003). Some river basins suffered repeated flooding within a time span of a few years only - for example the Rhine and Meuse floods in 1993 and 1995 or the Po floods in 1994 and 2000.

The disastrous floods in the Elbe and Danube basin in summer 2002, acted as a wake-up call for the National Authorities as well as the European Commission to investigate new strategies for flood prevention and protection, with focus on coordinated actions among countries sharing the same river basin.Shortly after the 2002 floods, the European Commission announced in the communication COM(2002)-481 the development of a European Flood Alert System (EFAS).

EFAS is part of a strategy for improved disaster management in Europe to reduce the impact of transnational floods through early warning. First of all, the aim of the system is to provide, useful, complementary and shared information on upcoming flood events to the national hydrological services. Furthermore, EFAS provides for the first time a coherent overview on ongoing and forecasted floods across Europe, which is needed for improved coordination of international civil protection actions on European scale during severe flood events.

Project

Following the encouraging results of a research study[2][3], the European Flood Alert System (EFAS) was launched in 2003 at the DG Joint Research Centre of the European Commission[4], [5].

It is being developed by the FLOODS action of the Institute for Environment and Sustainability, located in Ispra, Italy. Since 2005, EFAS provides national water authorities and the European Commission with early flood warning information up to 10 days in advance. Since 2007, when the EFAS-Information System (EFAS-IS was launched, hydrological partner organisations can access the real-time flood forecasts any time and interact with the EFAS development and monitoring team. Real-time forecasts are password protected and only distributed to those organisations that have signed a specific agreement. This is to avoid that real-time flood warning information is distributed to non-experts who are not trained on the specific EFAS products. Currently the EFAS network holds 27 partner organisations. An archive of EFAS results with information older than 1 month is publicly available on the floods portal of the action.

Closely associated with EFAS are two major data collection systems. One is the European Terrestrian Network for River discharge (ETN-R) which has been launched by the European Commission to collect realtime waterlevels and discharges across Europe's transnational river basins. ETN-R is being executed by the Global Runoff Data Centre (GRDC), which operates under the auspices of the World Meteorological Organisation. The second project is the EU-FLOOD-GIS, a comprehensive data integration system to support the flood forecasting activity on floods in Europe. It collects meteorological and hydrological data in real-time data, including ETN-R, across Europe and also holds historic time series needed for calibration and validation of the system. Furthermore, information on cross sections, reservoirs, flood extent information, collected for specific case studies, are held in this data base. Because of the restricted data policy in Europe, EU-FLOOD-GIS data cannot be distributed. Only the associated catalogue will be made available in the future, after all data providers have agreed to this.

EFAS has been declared a testbed of the Hydrological Ensemble Prediction Experiment (HEPEX)

EFAS system components and methodologies

Ensemble Prediction Systems – key to longer flood warning times

Most hydrological services rely either on observations only or on short-term deterministic rainfall forecasts of up to two days or less because the high degree of uncertainty in weather forecasts at longer lead times. Since these uncertainties are also unpredictable, they render the results unreliable and therefore not useful for decision making. Since the last 10 years, however, the hydrological community is looking increasingly at the use of ensemble prediction systems (EPS) instead of single (deterministic) forecasts for flood warning times beyond 48 hours. EPS have already become an integral part of operational weather forecasts over the past years[6]. They are designed to give a measure of the predictability of the weather and uncertainty in the model solution for lead times up to two weeks which would be considered well outside the range of predictability for deterministic models. The trend for implementing hydrological ensemble prediction systems in operational flood forecasting centres can clearly be seen in Europe[7], [8].

EFAS uses multiple weather forecasts and EPS as input. Its forecasts are based on two deterministic, medium-range forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the German Weather Service (DWD), (and thus different models) and on two sets of EPS: One from ECMWF which covers the medium-range up to 15 days globally (with a spatial resolution of ~~~~~~~~30 km and 51 members, and one from the Consortium for Small-scale Modeling (COSMO), a limited area model EPS covering most of Europe with a shorter range up to 5 days (with a spatial resolution of 7 km and 16 members). The reason for using the shorter term EPS is to enhance the spread of EPS within the first few days and to have a finer grid information in particular for mountainous areas. This allows to better identify the location of the floods within the river basin [9]. In a case study it has been demonstrated that using the eight global medium-range EPS available worldwide can provide a higher reliability for the results[10], but is computationally intensive.

LISFLOOD - the hydrological model for EFAS

The hydrological model used for EFAS is LISFLOOD. The model is a hybrid between a conceptual and a physical rainfall-runoff model combined with a routing module in the river channel. LISFLOOD has been specifically designed for large river catchments[11][12]. A particular feature of LISFLOOD is its strong use of advanced Geographical Information System (GIS), in particular as a dynamic modelling framework.[13]

Reducing false alarms - threshold exceedance and persistence

EFAS is providing information to the national hydrological services only when there is a danger that critical flood levels might be exceeded. In EFAS, the critical thresholds are needed at every grid point and therefore cannot be derived from observations. Instead, based on observed meteorological data, long term discharge time series are calculated at each grid with the same LISFLOOD model parameterization that is setup in the forecasting system. From these long-term simulations return periods are estimated – currently the 1, 2, 5 and 20 year return periods. All flood forecasts are compared against these thresholds – at every pixel – and the threshold exceedance calculated. Only when critical thresholds are exceeded persistently over several forecasts, information at these locations is produced, e.g. in the form of colour coded overview maps or time series information at control points. The persistence criteria has been introduced to reduce the number of false alarms and focus on large fluvial floods caused mainly by widespread severe precipitation, combined rainfall with snow-melting or prolonged rainfalls of medium intensity.

Related Articles

References

This article was taken from Wikipedia. To read the article in full, CLICK HERE. 

  1. ^ Bakker M. H. N.: Transboundary river floods: vulnerability of continents, international river basins and countries. Ph.D Dissertation, Oregon State University, 276p. URL: http://hdl.handle.net/1957/3821, 2007.
  2. ^ Kwadijk, J.: EFFS - European Flood Forecasting System. Final report of Contract EVG1-CT-1999-00011 (http://effs.wldelft.nl), 2003.
  3. ^ Gouweleeuw, B., Thielen, J., Franchello, G., De Roo, A., Buizza, R.: Flood forecasting using medium-range probabilistic weather prediction. Hydrological and Earth System Sciences, 9(4), 365-380, 2005.
  4. ^ Thielen, J., Bartholmes, J., Ramos, M.H., de Roo, A. (2009) The European Flood Alert System – Part 1: Concept and development. Hydrology and Earth System Sciences, 13 (2): 125–14
  5. ^ Bartholmes, J., J. Thielen, M. Ramos & S. Gentilini, 2009: The European flood alert system EFAS – Part 2: statistical skill assessment of probabilistic and deterministic operational forecasts. Hydrol. Earth System Sci., 13, 141–153.
  6. ^ Buizza R, Hollingsworth, A, Lalaurette F, Ghelli, A. 1999. Probabilistic Predictions of Precipitation Using the ECMWF Ensemble Prediction System. Weather and Forecasting. 14, 168-189
  7. ^ Cloke H., Thielen J., Pappenberger F., Nobert S., Balint G., Edlund C., Koistinen A., de Saint-Aubin C., Sprokkereef E., Viel C., Salamon P., and Buizza R. (2009) Progress in the implementation of Hydrological Ensemble Prediction Systems (HEPS) in Europe for operational flood forecasting ; ECMWF Newsletter, Autumn 2009, 121, 20-24
  8. ^ Cloke, H.L. and Pappenberger, F., 2009. Ensemble Flood Forecasting: A Review. Journal of Hydrology, 375(1-4): 613-626,
  9. ^ Thielen J., K. Bogner, F. Pappenberger, M. Kalas, M. del Medico, and de Roo, A., 2009b: Monthly-, medium-, and short-range flood warning: testing the limits of predictability; Meteorol. Appl., 16, 77-90.
  10. ^ Pappenberger F, Bartholmes J, Thielen J, Cloke, H.L., Buizza R. and de Roo A, 2008: New dimensions in early flood warning across the globe using grand-ensemble weather predictions. Geophysical Research Letters. 35, L10404, doi:10.1029/2008GL033837.
  11. ^ De Roo, A.P.J., Wesseling, C.G. and Van Deursen, W.P.A., 2000, Physically based river basin modelling within a GIS: The LISFLOOD model. Hydrological Processes, 14, pp. 1981–1992.
  12. ^ Van Der Knijff, J. M., Younis, J. and De Roo, A. P. J.(2008) LISFLOOD: a GIS-based distributed model for river basin scale water balance and flood simulation, International Journal of Geographical Information Science, 99999:1, DOI: 10.1080/13658810802549154
  13. ^ Thielen Del Pozo J, Salamon P, De Roo A. Geographical Information Systems - An Integral Part of the European Flood Alert System (EFAS). Geo-Focus (8); 2008. p. 12-16.
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