Assessing the effect of flood restoration on surface–subsurface interactions in Rohrschollen Island (Upper Rhine river – France) using integrated hydrological modeling and thermal infrared imaging

Abstract

Abstract. Rohrschollen Island is an artificial island of the large Upper Rhine river whose geometry and hydrological dynamics are the result of engineering works during the 19th and 20th centuries. Before its channelization, the Rhine river was characterized by an intense hydromorphological activity which maintained a high level of biodiversity along the fluvial corridor. This functionality considerably decreased during the two last centuries. In 2012, a restoration project was launched to reactivate typical alluvial processes, including bedload transport, lateral channel dynamics, and surface–subsurface water exchanges. An integrated hydrological model has been applied to the area of Rohrschollen Island to assess the efficiency of the restoration regarding surface and subsurface flows. This model is calibrated using measured piezometric heads. Simulated patterns of water exchanges between the surface and subsurface compartments of the island are checked against the information derived from thermal infrared (TIR) imaging. The simulated results are then used to better understand the evolutions of the infiltration–exfiltration zones over time and space and to determine the physical controls of surface–subsurface interactions on the hydrographic network of Rohrschollen Island. The use of integrated hydrological modeling has proven to be an efficient approach to assess the efficiency of restoration actions regarding surface and subsurface flows.

Magnetic resonance sounding measurements as posterior information to condition hydrological model parameters: Application to a hard-rock headwater catchment

“…A full description of the model and of the numerical techniques is available in Jeannot et al (2018). Various comparisons and bench tests (Weill et al, 2017;Jeannot et al, 2018) showed that simplifications brought by NIHM in the flow processes did not jeopardize accurate applications to complex hydrosystems (Jeannot et al, 2019).…”

Variability of Water Transit Time Distributions at the Strengbach Catchment (Vosges Mountains, France) Inferred Through Integrated Hydrological Modeling and Particle Tracking Algorithms

“…The model NIHM used to simulate the response of the Strengbach catchment is a physically based spatially distributed model that describes and couples the flow processes occurring in the surface and subsurface compartments of a watershed [36][37][38][39]. The model can describe flow in the subsurface, in a 1-D stream network, and also over the 2-D land surface.…”

“…This technique drastically reduces the meshing effort and the computational cost while preserving the physics, especially for systems with contrastive topography, as is the case with the Strengbach catchment discussed here. Conversely, the technique also works for flat systems needing a refined mesh to capture small topographic depressions, as exemplified by a riverine island [38,39]. The description of flow in the 1-D stream network is based on a 1-D formulation of the diffusive wave approximation of the St-Venant equations.…”

“…A full description of the model and the numerical techniques used for the resolution is available in [38]. The coupled model was carefully verified using model inter-comparisons and bench tests [37,38], and was proven relevant when applied to actual complex hydrosystems [39].…”

“…In this study, a low-dimensional integrated hydrological model, named the Normally Integrated Hydrological Model (NIHM) [36][37][38][39], is employed to simulate the hydrological response of a mountainous headwater catchment (the Strengbach catchment, in the Vosges Mountains) belonging to the French network of critical-zone observatories. The low-dimensional approach developed in NIHM enables researchers to describe coupled surface-subsurface flow in a physically consistent manner while reducing significantly the computational cost involved.…”