EFAS notifications are classified into three categories: Formal, Informal, Flash floods. EFAS Formal and Informal notifications are computed by comparing EFAS medium-range discharge forecasts to pre-computed return period discharge thresholds (T=1.5yrs / 2yrs / 5yrs / 20yrs). Similarly, EFAS flash flood notifications are based on the comparison of the forecasted surface runoff accumulated over the upstream catchment with a reference threshold.  The discharge and runoff return period thresholds are established through a simulation with a time span of approximately 30 years, utilizing observed meteorological data from the past ~30 years to drive the hydrological model and simulate the historical discharge and runoff series (model climatology). The return period discharge thresholds are then derived by the statistical analysis of the historical discharge and runoff time series. By comparing forecasts with model-derived threshold exceedances, EFAS can provide an early assessment of potential flood situations. Find the criteria for the different types of notification below. For previous criteria, read more in the Wiki under EFAS versioning system.

EFAS Formal Flood Notification

An EFAS Formal Flood Notification is issued when the probability of exceeding critical flood thresholds are forecasted more than 2 days ahead in a river basin with a minimum upstream area of 2000 km2 where there is an EFAS partner. The forecast also must be persistent (see below under criteria) and at least one deterministic forecast must exceed the EFAS 5-year return period. Formal flood notifications are automatically added to the ERCC overview (restricted information) and disseminated to the respective EFAS partner(s), the ERCC and the Civil Protection.


Criteria:

  • Catchment part of CoA (Condition of Access)
  • Catchment area >= 2000 km2
  • Event >= 48 h ahead
  • 3 consecutive forecasts with >= 30% exceeding EFAS 5 year return period according to ECMWF ENS or to COSMO-LEPS forecasts
  • At least one of the deterministic ECMWF or DWD forecasts exceeds EFAS the 5 year return period.

EFAS Informal Flood Notification

The EFAS Informal Flood Notification is issued when a probability of exceeding critical flood thresholds are forecasted in a river basin where there is an EFAS partner but the forecasted event does not satisfy the rules of an EFAS Formal Flood Notification, e.g. warning lead time, size of river basin, or location of event. An EFAS Informal Flood Notification can also be issued if EFAS results are not conclusive but one of the multiple forecasts indicates risk of severe flooding. Informal flood notifications are sent to the respective EFAS partner(s) and the ERCC.

Criteria:

  • Any of the criteria for a formal flood notification is not met
  • Catchment part of CoA (Condition of Access)
  • Catchment >= 1000 km2
  • Any other doubt

EFAS Flash Flood Notification

An EFAS Flash Flood Notification is issued when the probability of exceeding a 5 year return period magnitude of the surface runoff index is forecasted to be equal or greater than 30% and the earliest lead time to the occurrence of the threshold probability exceedance is <= 48 hours, in a region where there is an EFAS partner. Flash flood notifications are sent to the respective EFAS partner(s) and the ERCC.
 

EFAS Flash flood notifications are issued for administrative regions not for basins.

Criteria:

  • Catchment part of CoA (Condition of Access)
  • Probability of 5 year ERIC return period is >= 30%
  • Lead time to the event is <= 48 hours ahead

EFAS ERCC Overview

A daily overview is sent to the Emergency Response Coordination Centre (ERCC) of the European Commission which contains information on ongoing and forecasted floods in Europe as reported by the national services and forecasted by EFAS.

Giving feedback and reporting missed events 

EFAS notifications are sent by the Officers on Duty of DISS to the EFAS partner or third party partner of the area affected by the event, and to the ERCC. The partners are encouraged to provide a feedback on each received EFAS notification (after the event has terminated). This feedback allows to evaluate the accuracy of EFAS notifications with regard to the detection of the event, of its magnitude, of its timing. Instructions on how to provide feedback are available from this EFAS wiki page. The feedbacks are analysed with yearly frequency and all the reports are published in the EFAS home page; the most recent report can be found on EFAS homepage (type “Feedback” in the search field). The collection of information on missed flood events is complementary to the collection of feedback on issued notifications.  A missed flood event is an event that was observed by an EFAS (third  party) partner, but for which no notification was issued. The EFAS (third party) partners are encouraged to report missed events via the EFAS-IS. Instructions on how to report a missed event are available from the dedicated EFAS wiki page and the webinar on missed events provides detailed step-by-step instructions. The analysis of the feedback on issued notifications and of the missed events is crucial to identify weaknesses in the service and outline strategies for improvement.