A Struzynski

Bed Stability as a Parameter Describing the Hydromorphological Balance of a Mountain River

The hydromorphological parameters are used as abiotic descriptors for the classification system introduced by the Water Frame Directive. When studying the eco-literature, authors point out that the introduction of vulnerable species into restored river reach is often not effective as long as the ecosystem has been adapted to the changed river parameters. In fact, as being well-explored, hydromorphological parameters can be successfully used as reference factors of rivers. While bedload granulometry changes reflect the variation of many fluvial processes, bed stability is interpreted here as the key parameter. This first attempt of the evaluation is performed for three selected parts of the Carpathian rivers. The bed stability prognosis for different discharges is done by Armour PC program on the basis of the Gessler method which assumes the probabilistic nature of the bedload movement. The threshold of the bed transportation is given by the critical Shields parameter. The discharges causing bed movement are compared to bankfull and dominant ones as well as to Q10 %, Q25 %, Q50 % and Q75 %.

Cross-Section Changes in the Lower Part of a Mountain River After the Flood in Spring 2010, as Presented by Means of CCHE2D Program

The Bialka River flows in the Tatra Mountains region in South Poland. The turn of spring and summer 2010 in Poland was characterized by extremely heavy rainfall which led to two major floods affecting the territory of the whole country. Geodetic measurements of the bankfull channel and measurements of bed material granulation were carried out. Measurements of morphological changes in a mountain river Bialka performed on 12–14 May 2010 turned out to be made immediately before the flood. Inventory measurements conducted afterwards, i.e., on 1–2 July 2010, illustrated the river activity during the flood. The measurements were compared to the results of modeling performed with the use of the two-dimensional CCHE2D computer model. It makes it possible to compute water flows in open channels as well as the transportations. The model of bedload movement for the Bialka River was based on the Wu, Wang, and Jia equation. The amount of transported bedload in the model was compared to the MPM formula, calibrated for mountain rivers.

Flume Experiments on Gravel Bed Load Transport in Unsteady Flow—Preliminary Results

This chapter presents settings and results of laboratory experiments on bed load transport. Experiments were performed for unsteady hydrographs and for steady flow conditions. Continuous measurements of transported mass and flow rate reveal a clockwise hysteresis of bed load rate versus flow rate. A comparison between bed load rate in unsteady and steady flow shows that it depends to a large extent on sediment supply. The results are discussed in the light of variable sediment supply, and suggestions for procedure of further experiments are presented.

The Influence of Large Roughness Elements on Natural Morphological Changes in a Mountain River Bed

The presence of large roughness elements in a river bed influences the existing fluvial processes. Large roughness elements change the flow regime, continuity of river and morphological conditions, such as bed material size, water depth, and bed slope. Large roughness elements (for example boulders) are also often used to improve fish habitat and to change the hydraulic conditions of water flow (velocity magnitude, water flow direction). As long as the riverbed stays under their influence, one can observe that on the border between liquid and solid phases there is an extremely high turbulence. This causes the high erosion potentials in the zone of large roughness area. Determination of influence of large roughness elements on flow conditions is of crucial importance with regard to a proper engineering approach when designing flow channels. In the chapter, the results of investigations carried out in Carpathian mountain rivers: Raba, Porebianka and Czarny Dunajec are presented. Performed measurements included cross-section and longitudinal leveling, bed load sampling and hydrometric measurements. Differentiation of flow velocity in the region of large roughness element and its influence of the bed load size in the stream channel was shown. The aim of the chapter was to find the changes of fluvial processes due to the presence of large roughness elements and to connect it with the fish habitat conditions for different species. This improves the ecological state of water flow which is the requirement of the Water Framework Directive of the European Union.

Wetlands in River Valleys as an Effect of Fluvial Processes and Anthropopression

The aim of the article is to show how the fluvial processes in rivers and their valleys can support wetland restoration activities. The exemplary objects were localized in the Upper Vistula Basin (Poland) and dealt with riverbed stability, channel capacity as well as revitalization of rivers with their valleys regarding wetland restoration. All of the mentioned parameters depend on the intensity of fluvial processes in rivers, especially meandering, anastomozing or braided. Rivers always tend to reach the state of hydrodynamical balance reflecting the actual river dynamics. The nature of channel transformation is quite complex. For example, the curvature of natural river increases proportionally to the transported load alimentation and inversely to the slope of the river. The human-modified rivers also tend to increase the curvature of their channels. Interestingly, all rivers create wetlands in the areas naturally connected to the main channel. Those wetlands are regularly watered by flood events. As a result, the areas with wetlands are a perfect natural environment for fauna and flora. River channels which are situated close to such an environment are also rich in fish and invertebrates. Wetlands in mountainous areas are rare or unique unlike in lowlands where they are more likely to be found. The channel incision reduce a possibility of wetland formation in the river valley, especially after bank enforcement. The presented case studies are the effect of different projects running by the Department of Water Engineering and Geotechnics, the University of Agriculture in Krakow on the rivers and streams: Vistula, Nida, Porebianka, Czarny Dunajec. These rivers differ in many aspects; however, each of the them is located in an area where wetlands or wetted areas are likely to appear. Among the described rivers are lowland and mountain rivers. Some of them are managed according to the European Water Framework Directive, i.e., in a close-to-nature manner.

Numerical Modeling of Flow Dynamics on a Gravel Bar During High Discharge in a Mountain River

Numerical modeling of changing parameters on a gravel bar during different discharges in a small mountain river is presented here. The study bar is one of the best developed bars of the upper Wisloka. Within its reach, the river may erode its banks and transport bed material. Flowing out from the Magurski National Park, the Wisloka may be assumed as being close to a natural river. As fluvial processes are very dynamic there, the bar and channel transformations occur every year. Granulometry measurements demonstrated high variation of bed material composition in different parts of the bar and the channel. The bed material was classified as fine gravel, coarse gravel, cobbles, and coarse sand. This simulation was performed based on a 2015 measurement campaign; however, in situ measurements were started in 2008. From among a wide spectrum of parameters yielded by numerical simulations, the study focused on average vertical velocity and bed shear stresses. They were compared to critical parameters of the bed material movement. The simulations were performed for different flows, from low discharges to bankfull ones, and they indicated potential dynamic changes in the bed activity.

Laboratory studies on bedload transport under unsteady flow conditions

Abstract Two sets of triangular hydrographs were generated in a 12-m-long laboratory flume for two sets of initial bed conditions: intact and water-worked gravel bed. Flowrate ranging from 0.0013 m3 s-1 to 0.0456 m3 s-1, water level ranging from 0.02 m to 0.11 m, and cumulative mass of transported sediment ranging from 4.5 kg to 14.2 kg were measured. Then, bedload transport rate, water surface slope, bed shear stress, and stream power were evaluated. The results indicated the impact of initial bed conditions and flow unsteadiness on bedload transport rate and total sediment yield. Difference in ratio between the amount of supplied sediment and total sediment yield for tests with different initial conditions was observed. Bedload rate, bed shear stress, and stream power demonstrated clock-wise hysteretic relation with flowrate. The study revealed practical aspects of experimental design, performance, and data analysis. Water surface slope evaluation based on spatial water depth data was discussed. It was shown that for certain conditions stream power was more adequate for the analysis of sediment transport dynamics than the bed shear stress. The relations between bedload transport dynamics, and flow and sediment parameters obtained by dimensional and multiple regression analysis were presented.