Abstract

This doctoral research in geography explores the restoration of hydrological processes in heavily modified agricultural streams of the St. Lawrence Lowlands, Québec. Over the past century, these streams have been straightened, incised, and backfilled, reducing their ecological integrity and connectivity. Chapter 2 (published article) examined residual hydrological connectivity in two straightened streams (Pot-au-Beurre and Martin) through high-resolution piezometric monitoring. Maximum correlations analysis between stream stage and groundwater levels revealed that, despite anthropogenic alterations, lateral and vertical exchanges persist, especially near abandoned meanders, indicating a potential for natural recovery where subsurface floodplain processes remain active. Chapter 3 developed on a steady-state hydrogeological model (MODFLOW) for a degraded 300 m reach of the Pot-au-Beurre. Results showed that residual floodplain features, such as fine and coarse alluvial deposits act as key nodes for groundwater–surface water exchanges. The study emphasizes the central role of geomorphological context in sustaining subsurface connectivity, even within simplified channel systems. Chapter 4 documented the co-design and implementation of the pilot project Un Méandre à la fois (“One Meander at a Time”), conducted with a local farming family. This semi-passive restoration initiative combined crop withdrawal from the historical floodplain, culvert replacement, and the delineation of a functional freedom space. Ecological and hydrological monitoring (vegetation, fauna, groundwater) assessed outcomes, while governance and social acceptability were analyzed to inform broader replication. Together, these components show that degraded agricultural stream restoration can build upon residual hydrological processes, provided that geomorphic conditions are respected and local stakeholders are engaged through flexible and adaptive strategies.