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Morphological effects of large woody debris in meandering rivers: case from the Svratka, Lužnice and Morava Rivers
Roštínský, Pavel ; Máčka, Zdeněk ; Krejčí, L.
The contribution presents the results of a complex large woody debris (LWD) research (distribution and quantity, decay status, recruitment processes) in four meandering river reaches in Moravia and south Bohemia, focused on its morphological effects (e.g. bank erosion, bed scour and aggradation, bed-forms creation – bars, pool, log-steps). Wood pieces with and without such effects are compared, and presence of the morphological effects is interpreted in relation to selected LWD characteristics (length, diameter, orientation, rootwad and treetop preservation, position within a channel). The variability of morphological effects between rivers is discussed regarding the differences in stream vegetation, and floodplain management. Examples of varied morphological effects are illustrated.
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New suspect in the investigation into the cause of flash floods
Bíl, M. ; Fürst, T. ; Vodák, R. ; Pražák, Josef ; Šír, Miloslav ; Tesař, Miroslav
The aim of this contribution is to introduce a new possibility of the description of unsaturated porous media flow. The approach presented here is entirely different from the traditional ways (e.g. the Richards‘ Equation). It will be explained why the traditional models often fail to describe various observed phenomena. The new approach provides certain interesting forecasts, among others a possible mechanism for flash-flood formation. The authors explain why they think that, under specific conditions, porous medium discharge may substantially exceed the infiltration due to rainfall.
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