Publish Date: 03.07.2020

Category: News from the University

Modelling extreme flood events

Under the EU COST programme, researchers from the Faculty of Civil and Geodetic Engineering of the University of Ljubljana (UL FGG) are participating in project DAMOCLES, the aim of which is to further expand the knowledge about composite extreme events.

Composite extreme events such as floods, droughts and fires can result from the simultaneous impact of several different factors; for example, the simultaneous occurrence of high air temperatures and a drought may cause fires, while a high tide coinciding with extreme winds may cause the sea to flood. Researchers study and predict such events with the help of mathematical models, whereby they try to describe or imitate the events taking place in nature.

Obtaining new knowledge about extreme events through the project

Under the EU COST programme, researchers from the Faculty of Civil and Geodetic Engineering of the University of Ljubljana are participating in the DAMOCLES project, the aim of which is to further expand the knowledge about composite extreme events. The fundamental objective of the project is to enable researchers to estimate the frequency, location and impact of such events more reliably, as well as how climate change will affect them. Another aim is to raise the awareness of decision-makers about the possibility of such incidents, and warn them that the simultaneous appearance of two otherwise unrelated events may cause considerable damage to property and endanger lives.

Floods - Slovenia’s greatest threat

In the Slovenian part of the project, researchers from UL FGG are primarily focusing on flood events but they may also get involved in the research on debris flow, which can also cause significant damage within the territory of Slovenia. There are different types of floods. While they are often the result of a more intense precipitation event, floods may also occur due to the simultaneous occurrence of two otherwise unrelated events. An example of this would be the combination of snow cover melting and a precipitation event, most often as winter is moving into spring. This causes higher water levels than if only one of these events took place, i.e. either only the melting of the snow cover, or only the precipitation. This was the case in Slovenia in 2014, when an ice storm damaged over 50% of the forest in some parts of the country. The combination of a precipitation event and higher air temperatures (and thus melting of the ice and snow) then caused the levels of the watercourses to rise. Moreover, since many of the watercourses were also full of flood debris (such as damaged trees), the subsequent floods were even more severe. First, the karst sinkholes became clogged up, causing, among other things, floods on the Planinsko Polje field, with other parts of Slovenia being flooded as well. The flash-flooding which took place a few months later in the Gradaščica river basin, was, to some extent, the result of flood debris which had lodged itself by bridge pylons and similar infrastructure.

Safety climate factors

Researchers from UL FGG have established that the number of such events (with the combination of snow cover melting and floods) might increase in the future in Slovenia, along with the severity of the most extreme events. This means that climate safety factors need to be introduced when considering the designs of facilities on and by the water (e.g. by regulating river channels, setting the appropriate dimensions of bridge openings, etc.). These factors, which take into account the potential increase in flood risk in the future, are already applied in some EU states.

Interdisciplinarity counts the most

In addition to hydrologists, the project involves meteorologists, statisticians, climatologists, decision-makers, risk-modelling researchers, and so on. The basic knowledge necessary for the project is already obtained by students during their interdisciplinary study of Water Science and Environmental Engineering. Within the mandatory teaching process, they gain a foundation which they can subsequently build on in practice, enabling them to successfully implement similar projects by themselves in their future careers.

Modelling extreme flood events