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Institut für Wasser- und Umweltsystemmodellierung - IWS



"Application, Validation and Optimization of modelling approaches for the implementation of morphodynamic processes in habitat modelling"

In eco-hydraulic investigations biological, morphological, and hydrological or hydraulic parameters are linked and evaluated with respect to river habitats. Based on the analysis of river habitats for representative ecological indicator-organisms (e.g. fish or macroinvertebrates) the ecological status of rivers can be assessed. Habitat modelling as a suitable tool to bridge the gap between physical and biological parameters has been used successfully in eco-hydraulic projects for several years. Presently, in habitat simulations the basic hydromorphological parameters flow velocity, water depth, and dominant substrate are linked with habitat requirements of chosen indicator-organisms. However, the alteration of morphological and topographical parameters and its effects on hydraulics are usually not considered.

Based on a literature review to emphasize the importance of morphodynamic processes for aquatic organisms, particularly for gravel-spawning fish species; this thesis presents a procedure how morphodynamic aspects are implemented in habitat simulation processes. Thus, habitat dynamics can be simulated by means of temporal and spatial variability of the substrate layer as well as the effects of a changed topography on hydraulic conditions The approach to integrate morphodynamics in habitat modelling was applied to simulate mitigation scenarios to indicate changes in spawning habitat suitability due to improved substrate conditions. Furthermore, investigations were made to consider morphodynamics on meso-scale to indicate typical morphologic characteristics, founded on evaluation of river transects.

Additionally the habitat models, developed in Norway and Germany as well as the two approaches to evaluate habitats on meso-scale were compared.

The case studies illustrated that the investigations on meso-scale are suitable to indicate morphological characteristics of a river. Furthermore it is presented, what impressive influence morphodynamic processes have in terms of simulation of gravel-spawning fish habitats. The essential benefit for the linkage between morphodynamic and habitat modelling was elaborated by simulation of different mitigation scenarios in terms of water management and river engineering in Norway (Sandehølen, Surna) and Austria (Gestütshof, Mur) and should be implemented in the planning process of any mitigation measure.

Keywords: eco-hydraulics, habitat modelling, habitat dynamics, mesohabitats, morphodynamic modelling, morphodynamics, gravel-spawning fish species, CASiMiR, MesoCASiMiR, HABITAT, Meso Scale Classification, MIKE 21C