Drowning incidents in urban rivers: An underestimated issue with future challenges in need of an interdisciplinary database to characterise its epidemiology

In recent decades, the recreational use of urban rivers has become popular, and public access to riverbanks has improved. However, in the context of global warming, the risk of drowning in urban rivers may increase. The objective of this study is to examine drownings in the Rhone and Saone rivers in Lyon (France) and to identify risk factors, hot spots and high-risk moments using an environmental database. A total of 386 fatal and non-fatal drownings occurred in Lyon on the Rhone and Saone rivers between 2015 and 2021. The analyses identify that, universally, most drowning victims are men (68 %) and young adults (37 %). More drownings occur in the summer period (45 %). There are also hot spots near the city centre and in urban river parks. Three types of drownings are characterised by using principal component analysis (PCA) and hierarchical clustering on principal components (HCPC) methods. These groups are distinguished by hydrological and meteorological conditions, as well as by the seasonality and circumstances of the incident. The first group (G1) corresponds to drownings that occur on cold winter days, with high water flows and turbidity. The second group (G2) corresponds to drownings that resulted from bridge jumping in a festive context or a challenge between friends. These drownings occur on autumn days with interesting hydrological conditions (low flow and clear water). The last group (G3) groups together drownings that occurred while a victim is swimming in an unsupervised area. These drownings occur during the summer on very hot days. Finally, a multiple logistic regression method showed that the average daily outdoor temperature was positively correlated with the occurrence of drowning in Lyon ( p < 0.05) and that daily rainfall was negatively correlated with the occurrence of drowning ( p < 0.05).