EFAS provides different flash flood indicators based on two main concepts: 1) ERIC, generated from high-resolution numerical weather predictions with a lead time of up to 120 hours, and 2) ERICHA, based on radar-based precipitation monitoring and nowcasting for the next 6 hours.

ERIC - Numerical weather prediction based flash flood indicator

The ERIC flash-flood method is described in ERIC flash flood forecasting.

Two ERIC products exist:

• Reporting points  (“ERIC Reporting Points” layers): points in the river network (where the catchment area is <=2000 km2) where flash flooding is possible. Enlarged triangles highlight where the flash flood forecast probability over the next 5 days meets certain criteria:

                    1. probability of exceeding a 5 year return period magnitude of the surface runoff index is forecasted to be greater than or equal to 30%

                    2. lead time of the above criterion being satisfied is <= 48 hours in a region for which an EFAS partner exist

   

• Affected area  (“ERIC Affected Area”): river network which contributes to each ERIC reporting point, i.e. areas at risk from flash flooding (“ERIC Affected Area”)

ERICHA - Radar-based precipitation monitoring and nowcasting flash flood indicators

The ERICHA flash-flood method is described in ERICHA flash flood nowcasting.

Three ERICHA products exist:

• Hourly precipitation maps : Hourly precipitation totals from the  OPERA  radar composite, updated every 15 minutes (“ERICHA hourly accumulation precipitation” layer).
• Flash flood hazard maps : Sections of the river network highlighted because their flash flood forecast probability over the next 4 hours meets certain criteria. The thresholds are based on regional climatic characteristics and river basin upstream area as published by the  MeteoAlarm  consortium (“ERICHA - FF hazard levels forecasts” layer).
• Daily precipitation maps : Daily gauge-adjusted radar rainfall accumulation over the last 24 hours ("ERICHA 24-h accumulations" layer).

For more information

Alfieri, L., Thielen, J., 2015: A European precipitation index for extreme rain-storm and flash flood early warning. Meteorol. Appl., 22(1), 3–13,  doi:10.1002/met.1328

Berenguer, M., Sempere-Torres, D., Pegram, G.G.S, 2011: SBMCast - An ensemble nowcasting technique to assess the uncertainty in rainfall forecasts by Lagrangian extrapolation. Journal of Hydrology 404 (3-4), 226-240,  doi:https://doi.org/10.1016/j.jhydrol.2011.04.033

European Rainfall-InduCed Hazard Assessment system (ERICHA) -  http://ericha.eu/

Fundel, F., Walser, A., Liniger, M.A., Frei, C., Appenzeller, C., 2010: Calibrated precipitation forecasts for a limited-area ensemble forecast system using reforecasts. Monthly Weather Review, 138(1), 176-189,  https://journals.ametsoc.org/doi/10.1175/2009MWR2977.1

Park, S.; M. Berenguer, and D. Sempere-Torres, 2019: Long-term analysis of gauge-adjusted radar rainfall accumulations at European scale. Journal of Hydrology, 573, 768–777,  https://doi.org/10.1016/j.jhydrol.2019.03.093

Raynaud, D., Thielen, J., Salamon, P., Burek, P., Anquetin, S., Alfieri, L., 2015: A dynamic runoff co-efficient to improve flash flood early warning in Europe: Evaluation on the 2013 central European floods in Germany. Meteorological Applications, 22(3), 410–418,  doi:10.1002/met.1469