Soutenance de thèse // Célia Maghakian

THESIS

Drownings in the Rhône and Saône rivers in Lyon: making the risk visible to rethink rescue and imagine the future of swimming.

Abstract

 

In the context of climate change, urban densification, and the redevelopment of riverbanks—all of which are leading to increased public use of these areas—the risk of drowning in urban rivers is likely to rise. This thesis proposes an interdisciplinary approach to drowning risk, applied to the Lyon metropolitan area. It combines spatial analyses, in situ experiments, and socio-geographic surveys, with the aim of improving scientific knowledge and operational tools for rescue and prevention.

Three main research questions structure the work.
The first focuses on the epidemiology of drowning. A database of incidents recorded between 2015 and 2022, built from operational archives and environmental data, is used to identify victim profiles, high-risk locations and times, and to understand the social, spatial, and hydrological risk factors associated with these events.

The second question addresses the rescue of drowning victims. It explores the uncertainties related to underwater victim location using two complementary methods: (i) a protocol combining a video-questionnaire survey and geoinformation tools to assess errors and uncertainties in eyewitness reports provided to rescue teams; (ii) a series of drift tests conducted in real conditions with a weighted mannequin to characterize the physical factors influencing a body’s trajectory in a river.

The third question examines the tensions between swimming prevention and prohibition in river environments. A quantitative survey, designed with a prospective outlook toward 2030, explores expectations, needs, and desires related to urban river swimming, as well as the conditions for its implementation.
Using tools from geography, epidemiology, river hydraulics, and cognitive sciences, this research contributes to developing an epidemiology still largely unexplored for this topic at the local scale, improving our understanding of the movement of bodies in water, formalizing uncertainties in rescue operations, and examining local prevention policies. It opens concrete perspectives for the integrated management of swimming and drowning risk in urban environments, at the intersection of scientific analysis and public action.

H₂O'Lyon thesis Directors

Anne Honegger (EVS)