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Recent advances in instruments are transforming our capabilities to better understand, monitor, and model river systems. The present paper illustrates such capabilities by providing new insights into unsteady flows captured with a Horizontal Acoustic Current Profiler (HADCP) integrated at an operational index-velocity gaging station. The illustrations demonstrate that the high-resolution stage and velocity measurements directly acquired during flood wave propagation reveal the intricate interplay among flow variables that are essential for better supporting judicious decision making for river management, flooding, sediment transport, and stream ecology. The paper confirms that the index-velocity method better captures the unsteady flow dynamics in comparison with the stage-discharge monitoring approach. At a time when the intensity and frequency of floods is continuously increasing, a better understanding of the critical features of flood waves during extreme events and the possibility of capturing more accurately their dynamics in real time is of special socio-economic significance.
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Decoding the Hysteretic Behaviour of Hydraulic Variables in Lowland Rivers Using Multivariate Monitoring Approaches
ABSTRACT This paper demonstrates that the multivariate monitoring methods are capable to underpin the systematic investigation of the hysteretic behaviour occurring during gradually‐varied flows. For this purpose, we present simultaneous measurements of stage, index velocity and free‐surface slope acquired continuously with high‐frequency sampling instruments deployed at several river gaging sites exposed to different storm magnitudes. The experimental evidence reveals intrinsic features of unsteady open‐channel flow mechanics that are hinted by pertinent governing equations but rarely substantiated with in situ measurements. The illustrations are intentionally made for fluvial waves propagating in lowland rivers where the relationships among flow variables are most likely displaying hysteretic phasing in the progression of the hydraulic variables and loops in their relationships. The presented measurements highlight that: (a) the hysteretic behaviour is apparent in both time‐independent and time‐dependent graphical representations of any two of the hydraulic variables; (b) the severity of the hysteresis is commensurate with the geomorphic, hydraulic and hydrological characteristics of the measurement site; and (c) there are flow monitoring paradigms that can more accurately track changes of the flow variables during gradually‐varied flows than those currently used in practice. Also discussed are research needs for advancing the understanding of the mechanisms underlying the movement and storage of water in the lowland river environments as well as for increasing the accuracy of streamflow monitoring, modelling and forecasting.
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- Award ID(s):
- 2139649
- PAR ID:
- 10567372
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Hydrological Processes
- Volume:
- 39
- Issue:
- 1
- ISSN:
- 0885-6087
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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