Thursday, 16 October 2014

A complex approach for evaluation of sediment (un)balance in a steep headwater channel

A new paper was published in Catena, where a dendrogeomorphic approach was combined with ERT sounding and bedload transport simulations to estimate sediment budget during high-magnitude flood in a steep channel. It has been resulted from the cooperation with the dendrogeomorphic section of the Department of physical geography and geoecology, University of Ostrava. The methodology and results of this research were also presented on the Conference of Association of Slovac geomorphologists in Snina in October 2014. 

Sediment (un)balance budget in a high-gradient stream on flysch bedrock: A case study using dendrogeomorphic methods and bedload transport simulation
Detailed quantification of material supply into stream channels is crucial for determining sediment (un)balance budget during flood events. Unfortunately, existing quantification methods require long-term field monitoring; otherwise, there is an insufficient amount of usable data. In this study, we introduce a new approach, based on dendrogeomorphic methods, to determine the volume of material supply generated from flysch high-gradient stream bank failures. This approach was supplemented by 1D sediment transport modelling, using a TOMSED model.
We analysed 138 cross-sections from the roots of predominantly broad-leaved trees, which were exposed in bank failures from different floods. Using the spatial position of the roots and dating the exposure time, we determined the volume of material supply into the channel during the last flood, in 2010. In-channel sediment transport was analysed on 14 cross-sections, and the channel sediment thickness was estimated using the geophysically based ERT (Electrical Resistivity Tomography) method.
The total volume of material loss during the 2010 flood within the study area, according to the TOMSED model, was found to be at least 300 m3. This means that the calculated total volume of sediment supply resulting frombank failures during the flood (63.9 m3 based on dendrogeomorphic methods) was significantly lower than the calculated bedload transport for the entire study area. This finding implies that contemporary sediment sourcescannot adequately cover the transport capacity during high-magnitude flood events, and in general, in-channel erosion processes prevail.