HYDRAULICALLY RELATED HYDRO-MORPHOLOGICAL UNITS: DESCRIPTION BASED ON A NEW CONCEPTUAL MESOHABITAT EVALUATION MODEL (MEM) USING LIDAR DATA AS GEOMETRIC INPUT

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 (1)). 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, I in accuracy) based on LiDAR significantly reduced important mesohabitats. Copyright (C) 2008 John Wiley & Sons, Ltd.