Understand and restrict the impact of extreme meteorological and hydrological events

Published on 27/07/2018

In July 2016 and June 2018, Luxembourg was hit by torrential rain, in particular, in the east of the country. Hundreds of Luxembourgish citizens found themselves under surges of water and mud that resulted in, depending on the circumstances, the collapse of roads and even the flooding of cellars and ground floors in some houses. At certain moments and in certain places, the equivalent of a month’s worth of rain, or even more, fell in one hour. This phenomenon, the occurrence and localization of which prove very difficult to predict at this time, has been scrutinized by hydroclimatology researchers at the Luxembourg Institute of Science and Technology (LIST) as part of their research into extreme precipitation and rising water levels.

Hydroclimatology observatory at the forefront

LIST researchers have looked into these extreme episodes at the Luxembourgish hydroclimatological observatory, one of the best equipped in the world. Thanks to observations dating back 150 years for certain measurement sites, LIST hydrologists are today able to work on the values of statistical distributions. They were able to put the exceptional precipitation and flows observed over the last few years in Luxembourg into a larger historical context and came to two conclusions:

  • The quantities and intensities of rain, just like the related peak flows that characterized recent events, largely exceed the scale of hydrometeorological episodes specific to the 30-year reference periods, which are incidentally considered as ‘normal’.
  • The high frequency of catastrophic hydrometeorological events, as observed over the last few years, goes hand-in-hand with a change in paradigm towards the non-stationarity of environmental systems as a result of global change. In other terms, rain events still considered exceptional 15 years ago see their return period decrease due to the occurrence of repeated flash floods.

This evolution has a direct consequence on conventional tools for observing, forecasting and predicting hydrometeorological events. These tools, all developed based on the supposition that environmental systems are stationary, prove to be not well- or not at all adapted to extreme events.

Anticipate in order to react better

In view of the scientific and technological challenges inherent to the impact of global change on environmental systems, LIST researchers are constantly endeavouring to better understand and restrict the impact of extreme meteorological and hydrological events. LIST researchers have been working on this long-term undertaking since 1995.

At present, there are several projects underway in this area, both in the laboratories and in the field. LIST currently hosts around 15 doctoral researchers, specialized in hydrology, remote sensing, soil erosion and hydrological modelling, in a hydrological sciences doctoral training unit. LIST was able to set up this unit, managed in collaboration with four partner institutes, (University of Luxembourg, TU Vienna, KIT Karlsruhe and the University of Wageningen), thanks to the “Doctoral training unit in in hydrological sciences” project (Hydro-CSI), financed by the Luxembourg National Research Fund (FNR). Together, doctoral researchers and experienced researchers will work on exploring new interdisciplinary approaches in view of stretching the limits of our current understanding of how catchment basins work. Thanks to its extensive work, LIST not only intends to anticipate the rise and movement of water over several hours, but also more broadly to forecast its evolution over several decades. Moreover, LIST is training future generations of experts who will be able to face problems of an unequalled complexity related to global change.

Apart from understanding the functioning of hydrosystems, LIST devotes particular attention to developing new technologies for the observation of extreme hydrometeorological events. Thus the “Low-Power Wide-Area Networks enabled flash-flood monitoring and forecasting” project (Flash-flood), also financed by the FNR via the Public-Private-Partnerships programme, focuses particularly on episodes of flash flooding for which monitoring and forecasting remain difficult. Thanks to this project, carried out in partnership with POST Telecom and the Environment Agency (Administration de la Gestion de l’Eau), by 2021, LIST wants to improve not only the spatial representativeness of the precipitation measuring protocols but also the quality of hydrological forecasts.

Further activities that will contribute to LIST being at the cutting-edge of research in the domain of extreme precipitation and flooding are: long-term observation programmes of environmental systems, development of new technologies for the observation and modelling of extreme hydrometeorological events, and the training of experts with interdisciplinary profiles.

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Dr habil. Laurent PFISTER
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