Systematic comparison of 1D and 2D hydrodynamic models for the
assessment of hydropeaking alterations
Abstract
Numerical hydrodynamic models enable the simulation of hydraulic
conditions under various scenarios and are thus suitable tools for
hydropeaking related assessments. However, the choice of the necessary
model complexity and the consequences of modelling choices are not
trivial and only few guidelines exist. In this study we systematically
evaluate numerical one-dimensional (1D) and two-dimensional (2D)
hydrodynamic models with varying spatial resolution regarding their
suitability as input for hydropeaking-sensitive, ecologically relevant
hydraulic parameters (ERHPs), and their computational efficiency. The
considered ERHPs include the vertical dewatering velocity, the wetted
area variation between base and peak flow and the bed shear stress as a
proxy for macroinvertebrate drift. We then also quantified the habitat
suitability of brown trout for different life stages. The evaluation is
conducted for three channel planforms with morphological characteristics
representative for regulated Alpine rivers, ranging from alternating
bars to a braiding river morphology. Our results suggest, that while a
highly resolved 1D model is sufficient for accurate predictions of the
dewatering velocity and wetted area in the less complex alternating bar
morphology, a 2D model is recommended for more complex wandering or
braiding morphologies. For the prediction of habitat suitability and bed
shear stress, a 1D model appears to be always insufficient, and a highly
resolved 2D model is suggested. Reducing the spatial resolution of 2D
models leads to computational efficiency similar to 1D, while providing
more accurate results. This study can serve as guideline for researchers
and practitioners in the selection and setup of hydrodynamic models for
hydropeaking.