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Institut für Wasser- und Umweltsystemmodellierung - IWS



"Effects of embeddedness on the spawning habitats of fish: an approach "

The ecological integrity of running waters is becoming paramount within integrated watershed management planning. To assess river ecology, habitat models are implemented using hydro-morphological parameters. These models capture the effects of human measures to exploit river resources that are detrimental to natural sediment transport processes. Experience has shown that, in addition to water depth and flow velocity, the embeddedness condition of fluvial substrate greatly influences successful spawning activities. While recognized as important, there is no standard for quantifying embeddedness. With the aim of implementing morphodynamic processes to evaluate habitat dynamics in ecohydraulic examinations, an assessment of embeddedness is crucial.

An impartial methodology was devised for mapping substrate and embeddedness conditions, focusing particularly on aquatic habitats. Its development is based on the application of a number of existing methods. The different techniques were applied across their particular spectrum of embeddedness levels, from negligible to high; and compared based on objectivity, reliability, cost-effectiveness, and applicability.

As a result, the proposed mapping methodology provides modeling parameters in quantifiable terms that are familiar to hydraulic engineers and at the same time provides the necessary qualitative information for fish biologists and ecologists to derive meaning for habitat simulation modeling. This mapping methodology is applicable at both the micro- and meso-scale.

The proposed mapping methodology was successfully implemented in two case studies to evaluate the suitability of salmon and grayling spawning habitat by means of habitat simulation modeling. These case studies illustrate the importance of including embeddedness when modeling gravel spawning habitats.