Field migration rates of tidal meanders recapitulate fluvial morphodynamics

The majority of tidal channels display marked meandering features. Despite their importance in oil-reservoir formation and tidal landscape morphology, questions remain on whether tidalmeander dynamics could be understood in terms of fluvial processes and theory. Key differences suggest otherwise, like the periodic reversal of landscape-forming tidal flows and the widely accepted empirical notion that tidal meanders are stable landscape features, in stark contrast with their migrating fluvial counterparts. On the contrary, here we show that, once properly normalized, observed migration rates of tidal and fluvial meanders are remarkably similar. Key to normalization is the role of tidal channel width that responds to the strong spatial gradients of landscape-forming flow rates and tidal prisms. We find that migration dynamics of tidal meanders agree with nonlinear theories for river meander evolution. Our results challenge the conventional view of tidal channels as stable landscape features and suggest that meandering tidal channels recapitulate many fluvial counterparts owing to large gradients of tidal prisms across meander wavelengths

Reconstruction of an extreme flood hydrograph and morphodynamics of a meander bend in a high-peak discharge variability river (Powder River, USA)

AbstractUnderstanding of morphodynamic processes associated with large‐scale floods has recently improved following significant advances of modern technologies. Nevertheless, a clear link between flood discharge and in‐channel sedimentation processes remains to be resolved. The hydrological and geomorphological data available for the meandering Powder River (Montana, USA) since 1977 makes it a perfect laboratory to investigate connections between flood discharge and point‐bar sedimentation processes. This study focuses on a point‐bar that accreted laterally ca 70 m during a 50‐year recurrence flood, which lasted about 14 days in May 1978. In September 2018, a trench ca 2 m deep and 70 m long was excavated through the axial point‐bar deposits, and the 1978 flood deposits were delineated based on georeferenced pre‐flood and post‐flood cross‐section surveys. Sedimentological data show that point‐bar deposits accumulated at the early and late flood stages, when the flow was confined to the channel, and have similarities with classical facies models in terms of palaeocurrent patterns and vertical grain‐size trend. However, during high‐stage flood conditions, when the flow overtopped the bar, cross‐cutting of the bar and armouring were typical processes. Integration of sedimentological and palaeo‐hydrological data highlight that the relation between channel cross‐sectional area and flood discharge play a key role in preserving bar deposits. The integrated approach adopted here provides a basis for advancing palaeoflood hydrology beyond the stage of estimating peak discharges to the next stage of estimating palaeoflood hydrographs

Sensation Seeking and Gambling Behavior in Adolescence: Can Externalizing Problems Moderate This Relationship?

Gambling is a widespread phenomenon during adolescence. Among different risk factors involved in the onset of adolescent gambling behaviors, one factor that is studied is the sensation seeking personality trait. However, the literature is heterogeneous and a direct relationship between sensation seeking and gaming behaviors has not always been highlighted. This suggests that the relationship can be influenced by other factors. In particular, we explored the moderating role of externalizing problems in this relationship. A total of 363 adolescents (232 males and 131 females) aged 14 to 20 (M = 16.35, SD = 1.36) completed a battery of questionnaires aimed to assess their gambling behaviors, as well as the levels of externalizing problems and sensation seeking. The results showed that sensation seeking was associated with gambling severity, but this relationship was significant when externalizing problems were high and medium. On the contrary, when externalizing problems were low, the relationship between sensation seeking and gambling severity was not significant. Overall, sensation seeking in adolescence can favor the implementation of risk behaviors, such as gambling, but only in association with the presence of externalizing problems. Limitations, strengths, and social and clinical implications of the present study are discussed