In natural rivers, bed forms built of sandy and gravel-sandy fractions may be formed on the river bed at some determined hydraulic conditions. Depending on the type of the flow they can be two- or three-dimensional forms (2D, 3D) and they can have straight or curved crestlines (dunes: barkanous, sinusous, lunate, linguoid or catenary). Any bed form can exist individually (for example isolated dunes), but mostly they occur as accumulated single forms. These forms are placed parallel or transverse to the flow. Moreover, they can be arrangement across the flow. The subject the bed forms arising was involving and still is many scientists from abroad and from Poland and the main topic of investigations. Most of the paper covers the issue of sandy bed forms (in the form of ripples and dunes) which one shaping bottom of the lowland rivers [Młynarczyk (1998), Dąbkowski (1989)] and bed forms which observed on the submarine bottom [Pruszak 1998]. So far, there have been only a few publication in the world concerning existing sandy-gravel and typical gravel dunes [Carling at al. 2000, 2005]. This paper presents results of the hydraulic parameters calculations above gravel curved crestline dunes along the estuary part of the Raba ...
At the present time once can easily noticed very lively discussion about introducing modern, ecological friendly hydraulic structures in river training works which are suppose to stay up to the standards given by hydrobiologists, ecologists as well as fluvial geomorphologists. One of the proposals of such structures is a rapid hydraulic structure (RHS) with increased roughness. Along the presented paper such structure is presented. It was constructed within the river channel of the Sanoczek Stream in the Bieszczady Mountains, a part of Polish Carpathians. One of the main problems connected with changes of stability of hydraulic structures (in that case also with RHS) is velocity of running water causing huge turbulence and shear stresses. Thus, the objective of the following paper is to present the distribution of velocities values along the RHS and within the region of its influence. The main aim of the research was to describe conditions upstream and downstream of the structure and compare them in terms of stability of the RHS. Parallel with the main aim, the distribution of shear stresses as well as shear velocities along the RHS apron and the region within its influence are also presented. The work was conducted in Agricultural University ...
