The United Nations Office for Disaster Risk Reduction UNISDR [2009] defines Early Warning Systems as the set of capacities needed to generate and disseminate timely and meaningful warning information to enable individuals, communities and organizations threatened by a hazard to prepare and to act appropriately and in sufficient time to reduce the possibility of harm or loss. This definition encompasses much more than the scientific and technical tools for forecasting and warning issuing [Maskrey, 1997] and transcends to the political and social context. The concept of people-centred early warning systems [Basher, 2006, ISDR, 2006, Maskrey, 1997, Molinari et al., 2013, NOAA and COMET, 2010, UNISDR, 2009] considers four operational components of effective early warning systems, namely: (i) risk knowledge, (ii) monitoring and warning system, (iii) dissemination and communication and (iv) response capability (see Figure 1.1). These components are closely interconnected and a failure in any one of the four key components leads to the failure of the whole system [ISDR, 2006]. As stated by Maskrey [1997] early warning systems are only as good as their weakest link. Flood early warning system components https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780138745011/4fb24d6a-9066-47bb-9de4-4671bef5bb47/content/fig1_1.tif"/>