Laurent Pfister / © Marc Hoscheid
Heavy rainfall over the past few weeks has pushed Luxembourg's rivers and streams to their limits
A study on floods by the Luxembourg Institute of Science and Technology( LIST) noted that precipitation is becoming increasingly concentrated across specific time periods, leading to a higher risk of flooding.
In the past, precipitation, especially rain, was more likely to fall evenly throughout the year. However, LIST hydrologist Laurent Pfister explains this is no longer the case: "From mid-October until now, some places have seen over 200 millilitres of rainfall. As far as I am aware, this is also the first time that at least 30 consecutive days of rain have been recorded in France. In southern Luxembourg, we have seen more than 20 percent of average annual rainfall in just three or four weeks."
When asked if climate change is responsible for this development, Pfister says it is difficult to be specific, as weather data records don't go back far enough to provide proof. However, analysis of water samples can provide some details.
"When taking samples from streams and rivers, we have observed that the water in the flood basin is rainfall from weeks, or even months ago. This is down to the fact that water is held in the ground, in the subsoil, so any new precipitation tends to push this water out of the ground and back into the streams and rivers."
In addition to the rain, in some places the ground is also to blame for the flooding, either because it is not permeable, such as clay, or because it has been sealed off by man-made construction. Soil sealing plays an important role in very specific places, at a lower level, says Pfister. The larger the catchment area, the less significant the soil.
According to LIST, there are also local and regional differences in the amount of rainfall experienced across the country. In western Luxembourg, for example, there is 30% more rainfall than in the east.
© Marc Hoscheid