Hydraulics of Time-Variable Water Surface Slope in Rivers Observed by Satellite Altimetry

The ICESat-2 and SWOT satellite earth observation missions have provided highly accurate water surface slope (WSS) observations in global rivers for the first time. While water surface slope is expected to remain constant in time for approximately uniform flow conditions, we observe time varying wat...

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Bibliographic Details
Published in:Remote sensing (Basel, Switzerland) Switzerland), 2024-11, Vol.16 (21), p.4010
Main Authors: Bauer-Gottwein, Peter, Christoffersen, Linda, Musaeus, Aske, Frías, Monica Coppo, Nielsen, Karina
Format: Article
Language:English
Subjects:
Altimeter
Backwater effect
Data processing
Earth observations (from space)
Flood waves
Flow velocity
Fluid flow
Friction
Gradually-varied flow
Hydraulic models
Hydraulics
ICESat-2
Measurement
Methods
River discharge
River flow
river hydraulics
Rivers
Satellite altimetry
Satellite communications
Satellite observation
Shape effects
Slopes (Physical geography)
Uniform flow
Varied flow
Water
Water discharge
water surface slope
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Summary:The ICESat-2 and SWOT satellite earth observation missions have provided highly accurate water surface slope (WSS) observations in global rivers for the first time. While water surface slope is expected to remain constant in time for approximately uniform flow conditions, we observe time varying water surface slope in many river reaches around the globe in the ICESat-2 record. Here, we investigate the causes of time variability of WSSs using simplified river hydraulic models based on the theory of steady, gradually varied flow. We identify bed slope or cross section shape changes, river confluences, flood waves, and backwater effects from lakes, reservoirs, or the ocean as the main non-uniform hydraulic situations in natural rivers that cause time changes of WSSs. We illustrate these phenomena at selected river sites around the world, using ICESat-2 data and river discharge estimates. The analysis shows that WSS observations from space can provide new insights into river hydraulics and can enable the estimation of river discharge from combined observations of water surface elevation and WSSs at sites with complex hydraulic characteristics.
ISSN:2072-4292
2072-4292
DOI:10.3390/rs16214010