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  • Author: Artur Radecki-Pawlik x
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Bankfull discharge determination using the new Invertebrate Bankfull Assessment Method

Bankfull discharge determination using the new Invertebrate Bankfull Assessment Method

Along the paper the new method called Invertebrate Bankfull Assessment method (IBA method) of determination of bankfull discharge is presented. The investigation of bankfull discharge using IBA were performed within one Polish Carpathian stream in the mountain region: the Ochotnica Stream. As an index of bankfull the existence of certain species of invertebrates was used which are present and resistant to specific water discharge conditions. The borders within a cross section of the mountain stream with a gravel bed were defined where characteristic invertebrates are present which are recognized as bankfull borders. Finally three invertebrates benches (IB-ms) were recognized which are characterized by very specific invertebrate species. Bankfull discharge was calculated up to this IB-ms and corelated using Canonical Correspondence Analysis with other values of bankfull calculated for a cross section using different bankfull.

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On bankfull methods determination again – why we care?

Abstract

One more time we would like to pay attention of especially of the hydraulic engineer audience to bankfull stage and discharge. Along the paper we show commonly accepted definitions of it and ways of calculations. It is difficult to determine the size of the bankfull flow level, that is why the authors are presenting many selected methods. Some of the methods allow the determination of biotic bankfull flow through the occurrence of zones of vegetation characteristic and based on the observation of the occurrence of ground beetles (e.g. the Woodyer and the Radecki-Pawlik and Skalski methods). Some of the methods – most popular- are using morphometric parameters (e.g. the Williams, the Hey and Thorne, the Gauckler-Manning and finally the Lambor methods).

We believe that the value of bankfull discharge would be accepted as a supporting tool for designers, hydraulics engineers and managers, especially those who care about river channel environment and cooperate with fluvial geomorphologists- and biologists as well as environmental agencies.

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Runoff formation in terms of changes in land use – Mściwojów water reservoir area/ Odpływ powierzchniowy w rejonie zbiornika wodnego Mściwojów w świetle planowanych zmian urbanistycznych

Abstract

Along the paper the size of peak runoff was assessed affected by the influence of changes in water catchment area by land use due to future planned agricultural changes. The investigations were conducted in the Winna Góra catchment area located in Mściwojów, Lower Silesian voivodship at the Mściwojów water reservoir. At present, the catchment is used as arable land, forest and meadows. In the future the area of sealed surfaces such as: roofs, roads and car parks will increase. This can contribute in the change of water balance components. Analyses has shown, that changes in the use of a catchment area lead to reduction of surface flow time from the catchment (less resistance to motion) - in effect it causes increase of the runoff volume at about 28%. The increase of the water runoff volume may have significant influence on the Winna Góra development and functions as well as volume of water run into the Mściwojów water reservoir. To counteract the results of adverse changes caused by the catchment sealing - it is recommended for the investigated area to apply a balanced approach. This would consist of retaining precipitation water in its place of origin.

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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.

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