Hydro-climatology of the Lower Rhone Valley: historical flood reconstruction (AD 1300-2000) based on documentary and instrumental sources

From the HISTRHONE database we extracted 1483 hydro-meteorological events from AD 1300 to 2000 that occurred in the Lower Rhone Valley, France. Daily heights of the Rhone River at Beaucaire and Arles are also available, from 1816 and 1829, respectively. A total of 517 floods were divided into three categories and a synthetic frequency severity index (FSI) was computed. Running averages of 11 and 31 years show a succession of poor and rich flood fluctuations. Extreme floods tripled in the second half of the period (1650-2000). Singular spectrum analysis isolates a dominant irregular component (main positive anomalies in 1450-1580, around 1700, late 18th century, and most of the 20th century). We focus on the 17th century, with rare flooding events between two secular so-called hyper phases, i.e. frequent and/or severe floods. We also recorded 173 episodes of ice in the river, during the Little Ice Age.