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Bedload transport analysis using image processing techniques

Ermilov Alexander A, Fleit Gábor, Conevski Slaven, Guerrero Massimo, Baranya Sándor, Rüther Nils

Acta Geophysica

2022

Vol. 70, no 5

2341--2360

Bedload transport is an important factor to describe the hydromorphological processes of fluvial systems. However, conventional bedload sampling methods have large uncertainty, making it harder to understand this notoriously complex phenomenon. In this study, a novel, image-based approach, the Video-based Bedload Tracker (VBT), is implemented to quantify gravel bedload transport by combining two different techniques: Statistical Background Model and Large-Scale Particle Image Velocimetry. For testing purposes, we use underwater videos, captured in a laboratory fume, with future field adaptation as an overall goal. VBT offers a full statistics of the individual velocity and grainsize data for the moving particles. The paper introduces the testing of the method which requires minimal preprocessing (a simple and quick 2D Gaussian filter) to retrieve and calculate bedload transport rate. A detailed sensitivity analysis is also carried out to introduce the parameters of the method, during which it was found that by simply relying on literature and the visual evaluation of the resulting segmented videos, it is simple to set them to the correct values. Practical aspects of the applicability of VBT in the field are also discussed and a statistical filter, accounting for the suspended sediment and air bubbles, is provided.

Bedload transport in the Vistula River mouth derived from dune migration rates, southern Baltic Sea

Lisimenka Aliaksandr, Kubicki Adam

Oceanologia

2019

No. 61 (3)

384--394

In this paper, bedload sediment transport to the Baltic Sea in the main Vistula River mouth (Przekop Wisły) is estimated. For the first time in this area, investigations were performed based on the non-invasive measurement techniques with the using of hydroacoustic tools. Repeated bathymetric surveys were carried out using a multibeam echosounder for the period with hydrological conditions close to that of the long-term mean annual water discharge. Quantification of the bedload transport, as a main factor for the subaqueous Vistula delta development, involved applying the bedform tracking technique, and estimating the dune celerity by analysing the cross-correlation functions of bed elevation profiles (BEPs). The BEPs were obtained along two transects of 500 m in length situated in two different morphological parts of the river mouth — in the “shallow” and in the “deep” sites located upstream and downstream of the submerged sandbar, respectively. Contrarily to previous observations, the bedload transport was found to take place constantly. Moreover, a significant difference in a character of dune migration between the two sites of the investigated area was determined. The “shallow” dunes migrate 7 times faster (0.022 m/h) than the “deep” ones (0.003 m/h). Estima-tion of the daily bedload transport towards the Baltic Sea revealed values about 40.9 t/day and 8.4 t/day for “shallow” and “deep” sites, respectively. This result can probably indicate that a significant portion of sediments (ca. 80%) transported by the river during average hydrological conditions is deposited temporarily on the submerged sandbar, causing its growth.