Polish Carpathians

Ramps and Fishway

Numerical 2D Simulation of Morphological Phenomena of a Block Ramp in Poniczanka stream: Polish Carpathians

Description of flow in streams is a very complex problem. Physical analyses of this phenomenon provide a quantitative description of water flow, allowing creating mathematical models having practical meaning. Fast development of programs has improved their practical implementations, so the results of analyses and solutions of flow problems in both open channels and pipes, obtained through numerical modelling, can be applied in practical solutions. Numerical models are often very useful in studies covering a wide range of analyzed parameters. However one must understand that the similarity between a real river and its model could only be partially verified. The main purpose of this paper is to investigate the effect of the selected boulder block ramp hydraulic structure on Poniczanka stream on sediment transport, using the numerical model CCHE2D, assuming several situations, depending on the type of the river bed (erodible, non-erodible, rocky) and kind of rock blocks used for hydraulic structure construction. The obtained results were compared with the Hjulström graph, which is a classic approach for the identification of fluvial processes in the river channel (erosion, sedimentation, transport). In addition to these two methods, field observations were carried out which included the determination of changes in the horizontal and vertical changes of the riverbed morphology of the examined section river reach. The obtained results allowed determining the compatibility of these three methods for evaluation of sediment transport rate of river bed material in the analyzed sections of Poniczanka stream which are engineered with boulder block ramp hydraulic structures (BBR)

A Preliminary Study of Field Scour Morphology Downstream of Block Ramps Located at River Bends

Most of the studies present in the literature deal with block ramps located in straight channels. This is an evident limitation not allowing for a generalization of laboratory model findings. Generally, these structure typologies are located in natural rivers, that are characterized by both quasi-straight branches and bends. In particular, the location of the structure in river bends contributes to deeply modify both the upstream in-flow conditions and the downstream erosive mechanism. Only recently, the scour process downstream of block ramps was analyzed in curved channels and useful relationships were proposed to compute the maximum scour depth. Furthermore, the mentioned analysis was supported by field data validation, resulting in the understanding of the effects of river curvature on downstream scour process in the presence of a protected stilling basin. Despite of the recent study on the topic, there is still a lack of knowledge regarding the equilibrium morphology configuration and the effect of hydraulic parameters on the erosive process. Based on field measurements collected at the Porębianka river (Poland) after flood events, this paper aims to deep the downstream scour hole characteristics and the erosive dynamics. In particular, both the effects of in-flow conditions and river curvature are analysed in terms of resulting equilibrium morphologies, highlighting both similarities and differences with the corresponding configurations occurring in quasi-straight river branches

Using Genetic Programming to Predict Scour Downstream Rapid Hydraulic Structures from Experimental Results

Experimental Studie

Adjustment of the river channel due to block ramps introduction: Porębianka mountain creek, Polish Carpathians

The paper includes a description of 25-five interlocked boulder block ramps with increased roughness located on Porębianka creek and presents an analysis how those low head hydraulic structures fit to a natural river system: riffle-pool. These block ramps with increased roughness structures might be called "close to the nature", and in hydraulics engineering they are replacing traditional drop hydraulic structures. One of the main advantages of block ramps is that they are supposed to be placed in a natural sequence distances which follows pools and riffles pattern along a river, also block ramps allows free movement of fish upstream and downstream without necessity of fish pass constructio