ABSTRACT
Unstructured block ramps are river engineering structures to stabilize a river bed, using the dissipative behavior of large macro-roughness elements randomly placed on the river bed and to enhance fish migration in upstream direction. Physical model tests were conducted to determine design rules regarding stability aspects on the one hand and to analyze flow and turbulence conditions with respect to fish migration on the other hand. Both aspects are strongly linked to each other. The dissipated specific power density is an important bulk parameter to rate fish migration corridors. With an adapted flow resistance equation we determined the specific power density for different flow conditions and bed slopes. Using 2D-LDV (Laser-Doppler-Velocimetry) measurements, contour maps along the ramp were generated to distinguish regions of suitable and non-suitable conditions for different fish species. These maps can finally be used to theoretically show migration corridors along the ramp and to estimate the overall functionality of a planned block ramp in terms of fish migration. The measurements show that for example in the barbel region with a critical velocity of https://www.w3.org/1998/Math/MathML"> 1.7 m / s https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429069246/b59e18fc-9e1d-4389-b000-a1069c1cd27e/content/eq15237.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> only https://www.w3.org/1998/Math/MathML"> 10 - 20 % https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429069246/b59e18fc-9e1d-4389-b000-a1069c1cd27e/content/eq15238.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> of the cross section offer suitable conditions.
