Hydrodynamic parameters of floods and related bank erosion events indicated from tree rings and 2D hydrodynamic model for a small ungauged catchment (Sudeten Mts., Poland)

Small mountain catchments usually lack hydrological monitoring and gauges. Therefore, in such areas, data on past flood and bank erosion are often missing, which makes assessing flood and erosion hazards very limited. We attempt to fill in this gap by dating individual flood and erosion events from growth disturbances produced by trees after their stems are tilted, and their roots are exposed and wounded by transported material. We aimed to develop a conceptual approach to integrate dendrochronology and 2D modelling for indicating and assessing past events of floods and bank erosion on a small mountain river Łomniczka, Sudeten mountains, Poland. We dated growth disturbances resulting from tilting of stems of spruce trees which grow on eroded riverbanks, i.e. tree-ring eccentricity and compression wood. We also dated disturbances resulting from the exposure of roots from under the soil cover, i.e. sudden decreases of cell lumen, and root injuries by debris transported by floods, i. e. scars and traumatic resin ducts. Dendrochronology allow to indicate the occurrence of 28 floods since the 1930s, including 11 floods when bank erosion was also recorded at study sites. The approach enables to identify rates of bank erosion during specific floods which ranged at study sites from 20 to 120 cm. The largest discharge was determined for the 1997 flood (106,7 m3 s 1), and the highest flow velocities were obtained for the 1930 floods (4.59 m/s). Results show that the highest shear stress occurred during the floods in 1943 and 1977 (510,3N/m2) and in 1997 flood (469.1 N/m2). We conclude that dendrochronology combined with 2D modelling allowed us to indicate past floods and bank erosion, and to prepare reliable inventories for analyses of flood and erosion hazard. The approach proposed in this paper can also be used as a tool for flood management, spatial management and planning

The Jamuna-Brahmaputra River, Bangladesh

Bangladesh is dominated by three great rivers – the Jamuna–Brahmaputra, Ganga, and Meghna – that combine to feed sediment into one of the World's largest deltas in the Bay of Bengal. The Jamuna River has developed in a region of significant tectonic activity associated with Himalayan uplift and development of the Bengal foredeep. The bedload, although only ~10% of the total sediment load, is critical in generating a wide array of bedforms of different scale that drive channel change and migration. Within the Jamuna River, the ubiquitous occurrence of bifurcations and confluences is a key aspect of the river channel pattern and dynamics, and these features form important nodes in the braidbelt. The nature of floodplain sedimentation and inundation is vital in planning annual crop growth and may adopt great significance in the ongoing debate on the sources, causes, and accumulation of arsenic in the groundwaters of Bangladesh.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Rivers, Ports, Waterways and Dredging Engineerin