Ecohydraulic Modelling to Support Fish Habitat Restoration Measures

Abstract

Despite that hydromorphological restoration projects have been implemented since the 1940s, the key to improve the effectiveness of future restoration measures remains a challenge. This is in part related to the lack of adequate aims and objectives together with our limitations in understanding the effects on the physical habitat and ecosystems from interventions. This study shows the potential of using remote sensing techniques combined with hydraulic modelling to evaluate the success of physical restoration measures using habitat suitability as a quantifiable objective. Airborne light detection and ranging (LiDAR) was used to build a high-resolution two-dimensional model for Ljungan River, Sweden, using HEC-RAS 5.0. Two types of instream restoration measures were simulated according to the physical measures carried out in the river to improve salmonid habitat: (a) stones and rocks were moved from the bank sides to the main channel, and (b) a concrete wall was broken to open two channels to connect a side channel with the main river. Results showed that the hydraulic model could potentially be used to simulate the hydraulic conditions before and after instream modifications were implemented. A general improvement was found for the potential suitable habitat based on depth, velocity and shear stress values after the instream measures.

The salmon-peloton: hydraulic habitat shifts of adult Atlantic salmon (Salmo salar) due to behaviour thermoregulation

“…These data provide an unrivaled viewpoint of behaviour and its link to hydraulic conditions, and consequently, open doors for rapid advances in river ecology and provides a blueprint for habitat restoration work. While current habitat restoration is mostly based on coarse scale interpretations of river hydraulics and engineering principles (see recent review by Adeva-Bustos et al, 2019), our findings indicate that the preferred habitat for adult AS during high temperature events is best described by fine-scale, Fr. Adults also endure stress related to habitat restrictions during winter, and it is likely that the hydraulics under and around river ice used by AS will be best described by hydraulic variables such as Fr numbers that are already linked to other habitat choices, e.g., redd sites (Moir et al 2002).…”

Application of a fish habitat model to assess habitat fragmentation using high flow and sediment transport in the Rumei Dam in Lancang River (China)

“…The river regulation by dams is expected to alter river hydrogeomorphology and threatens endemic fish habitats (Hauer et al, 2017; Oliveira et al, 2018). The ecohydraulic model we used in this study quantitatively assess the effects of dam construction and operation, as well as a river restoration strategy where flow velocity, water depth and substrate as three important predictors were considered for evaluating the fish habitats (Adeva‐Bustos et al, 2019; García et al, 2011; Lecours et al, 2015). The major advantage of the study is that the model predicts hydrodynamic conditions, morphodynamic conditions and fish habitats at the same time.…”

Assessing Visual Preferences of the Local Public for Environmental Mitigation Measures of Hydropower Impacts—Does Point-of-View Location Make a Difference?

“…More recently, Tang et al demonstrated improved fish migration and habitat suitability by removing a low-head dam [32]. While hydraulic models can provide flow-related hydrodynamics in river sections affected by environmental measures [33,34], few studies have used hydraulic model outputs to set up visual representations of the consequences of environmental measures such as weir adjustment or removal. One example of the visualization of environmental measures is given by Barton et al in a multicriteria analysis study, where hydraulic simulations were used to set up photo scenarios for weir removal as an input for a reference group survey [10].…”