Climate information for flood management

A major consequence of climate change is an altered water cycle, which, in Norway and neighbouring countries, results in an increased precipitation intensity and heavy precipitation frequency. This leads to higher flood risk and increased pressure on flood management, especially in urban areas. The demand from society for robust, accessible and practical climate information is growing and the need for adaptation is obvious. Design precipitation values are an example of statistics that are widely used in long term planning and infrastructure design.

In this presentation we will provide an overview of the latest developments in such statistical analyses and products from the Norwegian Meteorological Institute. These developments are partly results from a Nordic-Baltic collaboration within the ECCO (Enhancing resilience in a Changing Climate through comprehensive urban flOod design) project that addresses the growing need for improved local adaptation strategies to water-related climate change impacts, focusing on urban flooding in the Nordic-Baltic region. 

A large majority of flood events in this region occur from a combination of factors, either happening simultaneously or in sequence. These are referred to as compound events, and are associated with increased damage potential which can lead to high societal costs. Examples of compound events that may result in flooding are heavy precipitation combined with high water levels, river flooding or high antecedent soil moisture. 

According to the IPCC, human-caused climate change has likely made compound events more common in the past, and they are expected to become even more frequent as global temperatures rise (Seneviratne et al., 2021). Nevertheless, traditional flood management deals with each hazard separately, for instance through design values for heavy precipitation, river flooding or storm surge. Design values are often based on current climate conditions, and do not consider the impact of climate change on compound water events. Additionally, the lack of observations is a challenge for estimating design values.

We will present work within the ECCO project that deals with the aforementioned challenges, as well as some preliminary analyses of water compound events in Norway and how their estimated design values deviate from current recommendations.