Abstract. Floods have strong impacts in the Mediterranean region and there are concerns about a possible increase in their intensity due to climate
change. In this study, a large database of 171 basins located in southern
France with daily discharge data with a median record length of 45 years is
considered to analyze flood trends and their drivers. In addition to
discharge data, outputs of precipitation, temperature, evapotranspiration
from the SAFRAN reanalysis and soil moisture computed with the ISBA land
surface model are also analyzed. The evolution of land cover in these basins
is analyzed using the CORINE database. The trends in floods above the
95th and 99th percentiles are detected by the Mann–Kendall test
and quantile regression techniques. The results show that despite the
increase in extreme precipitation reported by previous studies, there is no
general tendency towards more severe floods. Only for a few basins is the
intensity of the most extreme floods showing significant upward trends.
On the contrary, most trends are towards fewer annual flood occurrences
above both the 95th and 99th percentiles for the majority of
basins. The decrease in soil moisture seems to be an important driver for
these trends, since in most basins increased temperature and
evapotranspiration associated with a precipitation decrease are leading to
a reduction in soil moisture. These results imply that the observed
increase in the vulnerability to these flood events in recent decades is
mostly caused by human factors such as increased urbanization and population
growth rather than climatic factors.