The COST 731 Action : a review on uncertainty propagation in advanced hydro-meteorological forecast systems

Quantifying uncertainty in flood forecasting is a difficult task, given the multiple and strongly nonlinear
model components involved in such a system. Much effort has been and is being invested in
the quest of dealing with uncertain precipitation observations and forecasts and the propagation of
such uncertainties through hydrological and hydraulic models predicting river discharges and risk
for inundation. The COST 731 Action is one of these and constitutes a European initiative which
deals with the quantification of forecast uncertainty in hydro-meteorological forecast systems.
COST 731 addresses three major lines of development: (1) combining meteorological and
hydrological models to form a forecast chain, (2) propagating uncertainty information through this
chain and make it available to end users in a suitable form, (3) advancing high-resolution numerical
weather prediction precipitation forecasts by using non-conventional observations from, for
instance, radar to determine details in the initial conditions on scales smaller than what can be
resolved by conventional observing systems. Recognizing the interdisciplinarity of the challenge
COST 731 has organized its work forming Working Groups at the interfaces between the different
scientific disciplines involved, i.e. between observation and atmospheric (and hydrological)
modeling (WG-1), between atmospheric and hydrologic modelling (WG-2) and between hydrologic
modelling and end-users (WG-3).
This paper summarizes the COST 731 activities and its context, provides a review of the recent
progress made in dealing with uncertainties in flood forecasting, and sets the scene for the papers of
this Thematic Issue. In particular, a bibliometric analysis highlights the strong recent increase in
addressing the uncertainty analysis in flood forecasting from an integrated perspective. Such a
perspective necessarily involves the area of meteorology, hydrology, and decision making in order
to take operational advantage of the scientific progress, an aspect in which COST 731 is
successfully contributing to furthering the flood damage mitigation capabilities in Europe.