Abstract
Downstream of the confluence of rivers, complex hydrological and morphological processes control the flow and sediment transport. This study aimed to analyze the spatio-temporal dynamics of suspended sediment in the confluence area of the Tisza and its main tributary Maros River using Sentinel-2 images and to reveal the correlation between the hydrological parameters and the mixing process through a relatively long period (2015–2021). The surficial suspended sediment dynamism was analyzed by applying K-means unsupervised classification algorithm on 143 images. The percentages of the Tisza (TW) and Maros (MW) waters and their mixture (MIX) were calculated and compared with the hydrological parameters in both rivers. The main results revealed that the areal, lateral, and longitudinal extensions of TW and MIX have a better correlation with the hydrological parameters than the MW. The Pearson correlation matrix revealed that the discharge ratio between the rivers controls the mixing process significantly. Altogether, 11 mixing patterns were identified in the confluence area throughout the studied period. The TW usually dominates the confluence in November and January, MW in June and July, and MIX in August and September. Predictive equations for the areal distribution of the three classes were derived to support future water sampling in the confluence area.
Highlights
Published: 7 November 2021River confluences are one of the most essential geomorphological spots along rivers, as they control the flow and sediment transport conditions downstream [1]
Five small overbank floods (Algyő: ≥610 cm; Szeged: ≥500 cm) were recorded in the Tisza River at Szeged (Figure 2), whereas just two floods developed on the Maros (Makó: ≥310 cm)
The mixing process in the confluence area of the Tisza and its tributary and its correlation with the hydrological parameters of both rivers were analyzed in detail based on 143 Sentinel-2 satellite images taken between July 2015 and May 2021
Summary
River confluences are one of the most essential geomorphological spots along rivers, as they control the flow and sediment transport conditions downstream [1]. The hydrodynamics in the confluence area is complex, and it has a spatio-temporal variability. This complexity arises from the various parameters (e.g., water slope, velocity, discharge, momentum, and geomorphological characteristics) of the joining rivers, controlling the water and sediment transport process [3,4]. The transferred momentum from the tributary and the water circulation in the confluence area increases the probability of scour hole formation, which could alter river morphology [5]. The sampling process of any water constituents in a confluence should be performed only if the actual mixing situation is identified, as various mixing can highly influence the results
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