Hydraulically related hydro‐morphological units: description based on a new conceptual mesohabitat evaluation model (MEM) using LiDAR data as geometric input

Abstract

A new conceptual mesohabitat evaluation model was developed and applied to the Kamp River, Austria. The model uses a functional linkage of three parameters (velocity, depth and bottom shear stress) to distinguish six different mesohabitat types (riffle, fast run, run, pool, backwater and shallow water) based on two-dimensional depth-averaged hydrodynamic-numerical modelling. The results clearly revealed the variety and change of mesohabitat-units under various flow conditions (3.6-89 m 3 s À1 ). In particular for low-energy habitats, a shift from shallow-to backwater habitats was recognized at increasing discharges. Fast runs featured a larger percentage of the total wetted area (9-33%) as discharges increased, whereas pool habitats showed low variability (means of around 15%). A velocity-depth-bottom shear stress relationship (VDSR) was most suitable to differentiate between mesohabitat patterns; this relationship was compared with Froude numbers and with velocity-depth ratios using ANOVA statistical analysis. This study also documented that the accuracy of river geometry plays a decisive role in habitat descriptions. Different height tolerances for the computation mesh (0.2 m, 0.5 m, 1 m accuracy) based on LiDAR significantly reduced important mesohabitats.

Topo-Bathymetric LiDAR for Monitoring River Morphodynamics and Instream Habitats—A Case Study at the Pielach River

“…Finally, based on a two-dimensional depth-averaged numerical model [70] the abiotic characteristics (flow velocity, water depth and bottom shear stress) are simulated and analyzed for different epochs and different discharges (low flow, mean flow and the magnitude of an annual flood event). Considering the variability in discharge dependent changes of flow variables, a mesohabitat evaluation approach (MEM) was selected to determine the impact of morphological changes on the habitat distribution [9]. The MEM approach enables a differentiation of six hydro-morphological units, namely (1) riffle-; (2) fast run-; (3) run-; (4) pool-; (5) backwater-; and (6) shallow water-habitats.…”

“…Habitat modeling was performed using the MEM approach [9] based on hydraulic parameters as input. The applied two-dimensional depth-averaged hydrodynamic-numerical (HN) model Hydro_as-2D [70] calculates hydraulics by applying a finite volume approach based on an unstructured Triangular Irregular Network (TIN).…”

“…The conceptual MEM-model was developed by [9] and allows the differentiation of six different mesohabitats according to their abiotic characteristics. Three abiotic parameters (flow velocity, water depth, and bottom shear stress) are used in the MEM-classification in which the energetic potential of the mesohabitats due to bottom shear stress is one of the criteria for differentiation.…”

Aquatic Habitat Modeling in Running Waters

“…For characterizing mesohabitats, the Froude number, the water surface slope, the range of water depth and velocities, and the bed material size have been used. Based on the importance of mesohabitats for instream studies and river restoration, various parameters have been developed and implemented as different modeling approaches for mesohabitat description and quantification (e.g., Parasiewicz 2001;Le Coarer 2005;Hauer et al 2009). …”

A method for parameterising roughness and topographic sub-grid scale effects in hydraulic modelling from LiDAR data

“…Thus, high resolution laser altimetry data cannot only be extremely useful for the topographic parameterisation of a 2-D hydraulic model but also provide insight into the main set of problems related to scale in its spatial parameterisation (e.g. Hauer et al, 2009). LiDAR data can be used to control the topographic content introduced into a DEM generated for a fixed mesh resolution.…”