Vliv říčního dřeva na morfologické a sedimentologické parametry koryta na příkladu meandrujícího toku Odry

Abstract

Instream wood is a natural phenomenon that signifi cantly influences a function of the fluvial system in forested river basins and represents a natural part of this system. However, the majority of these relatios between instream wood and fluvial ecosystems were investigated in mountain streams or gravel-bed rivers and we are lacking field data from lowland meandering rivers. This study deals with the complex assessment of instream wood on morphology and sediment parameters including the content of organic material at spatially detailed scale of the selected bend of the Odra River. Within the site of interest (66.5 river km), 12 instream wood pieces were identified (lenght ≥ 1 m, diameter ≥ 10 cm). Their presence significantly affected river morphology, when they were the main initiator of pool formation. In total, 28 samples of surface bed sediments were collected from the thalweg, bars and lateral pool. In laboratory, samples were subjected to grain size analysis (sieving method) and loss on ignition (LOI) to obtain content of organic matter. The majority of bed sediment samples were coarse grained and these samples were located in the thalweg. The main component of these samples is gravel, often supplemented with admixtures of finer fractions. The analysis of data did not show the effect of instream wood on the deposition of organic matter in bed sediments. One of the reasons may be the presence of coarse grained material which generally contains a small amount of organic matter.