The formation of an armouring layer can be observed on the base of morphological changs by direct measurements of granulometry (grain diameter generally grows after flood) or by computer simulation of changes of the grain sieve curve. This procedure is based on the Gessler’s analysis of the probability of grain movement, on the basis of the shear stress of the acting water. The critical shear stress is calculated using the Wang function developed for Carpathian streams. The armouring layer is formed by that part of non-cohesive bed material, which is not washed away during the flow. The increase in critical shear stress is due to the increase of the mean diameter dm as small fractions are washed out from the bed. The thickness of the armouring layer is approximately equal to the size of the largest stones of the layer. This process in rivers with natural flow is different from this one below reservoirs; in the former case it takes place at a significant distance below dams. In this case, the armouring layer formation causes bed scouring, linked with a change in the water slope and depth. This scouring may be assumed to be a stochastic process. According to Gessler, ...
The one of the Polish rivers richest in water with substantial flood hazard and important hydro-energy potential. Two large flood protection and hydroenergy schemes were constructed on the Upper Dunajec: Rożnów-Czchów and Czorsztyn-Sromowce Wyżne. Lower Dunajec extends downstream from the Czchów hydraulic barrage to the outflow to the Vistula and is 67.4 km long. Construction of two large hydraulic schemes resulted in the increase of the low and average discharges, however, simultaneously important disturbance of sediment transport occurred. A large amount of sediment is deposited in the reservoirs. As the result of this process, significant erosion was observed along the Lower Dunajec reaching in some places even 4 m. This process was increased by the sediment exploitation from the river channel. Due to flood problems several training works were executed along the Lower Dunajec. All these resulted in lowering of the river channel, which became a draining river. Stabilization of the river channel is possible by means of the construction of special weirs with inflatable gates. Construction of the weirs gives the possibility of using heads for hydro-energy. It is proposed to construct small hydraulic power plants, which would operate during low and average discharges. ...
Using rivers and mountain streams for economic purposes led to the loss of ecological balance and to the intensification of morphological processes, which in most cases caused erosion as well as the lowering of riverbed. Such changes have made stabilising the river bed and its banks necessary. In our work, on the basis of the analysis of project documentation and the simulations of flood events on several mountain streams, we made an attempt to answer the question: are the river training works enough to let the catastrophic floods pass safely and do they take into account the morphological processes which have a formative influence on the riverbeds? It has been proved that as far as hydraulic structures are concerned, the adjustments that are being planned comply with the requirement of ensuring the required capacity of the river channel. Maintaining the required capacity of the river channel creates the need for constant remedial works. When dimensioning cross-sections with stable bottoms, the width of the river valley is a serious limitation which, in urban environment, does not allow the engineers to design a crosssection of a river channel whose shape would be most efficient one. In case of river channels with moveable ...
A common phenomenon occurring in small river basins is an increase of spatial development in the period of last 20 years. This development is an effect of economic changes in our country, resulting in growing land cover by all sorts of infrastructure as well as in changes in method of development. It may be observed both giving up the intensive agricultural use in large parts of arable areas and even greater intensification of agricultural use in some selected favorable situated locations. Those processes are of increasing character and lead to substantial changes in hydrological conditions of runoff, which imposes the necessity of verification of the functionality of the existing water regulation structures. The authors have presented issues connected with changing basin storage and determined the influence of spatial development on basin surface sealing and rainwater storage. Concepts of land use changes were presented; calculations of water storage reservoir capacity were made, as well as the influence of storage deficit and changes in forest cover magnitude on bedload transport conditions. Critical parameters of bedload movement were calculated. ...
Detailed recommendations formulated by European Commission in 2007 introduce new regulations regarding the continuity of river channels. The existing hydraulic structures should be equipped with fish ladders in order to keep the fish restitution conditions and the new hydro-technical structures should assure tech-nical solutions that do not cause any change in hydro-morphological state. Ac-cording to the Fisheries Institute the following conditions of biological stability should be followed to keep the biological stability conditions for diadromic fishes:- an alluring stream criterion,- a terminal velocity criterion,- a criterion of admissible fish ladder filling,- a criterion of admissible loss Δh for the transom ladder discharge.The paper presents results of numerical modeling of 400-meter sector of a river that includes coated weir, small hydrostation and a fish transom ladder. The action taken concentrated on such formation of the discharge in the ladder and modification of the bed configuration in the hydro mouth that creates the alluring stream. Numerical modeling results were compared to results of calculations by empirical formula.
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Paper concerns the investigations of riverbed sediments in the meandering sector of the Border Odra, In the frame of meander I. As a result of fluvial processes the Odra riverbed is exposed to deformations, leading to often changes of the river itinerary. In the historical time, many meander breaks were registered, the last in 1967 (Meander IV) and in 1997 (Meander I). In the old river bed the discharge is gradually decreasing and the substantial part of the discharge is flowinging through the new channel. It leads to gradual silting of the old river part. The intensive formation of bars and of islands is observed. In the upper part of the old meander, mainly the bed load is deposed, and in the middle and lower part – the suspended load. The superficial part of the layer (cover) is exposed to the formation of pavement. The size of the pavement cover is equal 8,4–9,8 cm, and the granulometry of the lower layer (20–40 cm) equal to d50 = 2,3–2,9 cm. The islands formed by fine sediments were covered in 3-4 years by intensive vegetation (trees and bushes). This process causes an important decreasing of flow velocity in the old channel. The ...
The paper presents results of calibration and verification of one-dimension numerical model of the Wislok River from Besko reservoir to the estuary to the San River. In order to evaluate the quality of this model following coefficient were used: the correlation coefficient, special correlation coefficient, total square error and errors of culmination level, culmination flow, culmination dislocation and flood wave volume. Observations of water levels in the Wislok River are conducted on 5 river gauges. An 5 another gauges are located on the tributaries of the Wisłok River. The ve-rification and calibration process carried out on the waves in 1987 and 1998 al-lowed to confirm the correctness of the hydraulic model in the sector from the river gauge Besko to the Rzeszow river gauge. Between Rzeszow and Tryncza river gauges volumes of waves are not balanced which enforces the admittance in the hydrological model of negative values of a lateral inflow. The volume of 1987 flood wave in the node of the three river gauges in Wislok-San system indicates that the wave is balanced on the Tryncza stream gauge.The performed simulations of the flood wave transformation on the whole Wislok River for different computable scenarios, with usage of hydro-informatic software - ...
1-dimensional models, e.g. HEC-RAS, MIKE 11 are used to calculate water surface elevation concerning probable discharges for flood hazard areas designa-tion. Hydro-informatic software programs HEC-RAS and MIKE 11 are used for modeling of water discharge in the river bed and in the river valley, with engineer-ing objects of complicated structure (bridges, culverts, weirs etc.). The following stages of modeling may be distinguished: schematisation of water network, geodetic measurements of the river bed and engineering buildings, identification of roughness coefficients, hydrological calculations of discharges in selected profiles of the modelled watercourse considering the boundary conditions, numeric calcu-lations with calibration and verification of the model as well as visualisation of the calculations' results. The paper presents the results of modeling of a sector of The Lubcza River in the Wislok basin having length equal 8,7 km (uncontrolled basin), in which 17 bridges and 12 weirs are located. The elevations of the water surface for di-scharges of the defined probability of exceedances and the Digital Model of the Water Surface (DMWS) are the basis for the analyses and comparison of the obta-ined results. Flood hazard areas occur on the intersection of the Digital Terrain Model (DTM) and DMWS. The knowledge of water ...
