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. 2025 Jul 2;15(1):22776.
doi: 10.1038/s41598-025-99597-2.

Tidal bore revealed by SWOT: a case study from the Severn river

R L Arildsen  1 , O B Andersen  2 , B Nilsson  2 , C B Ludwigsen  2
Affiliations

Tidal bore revealed by SWOT: a case study from the Severn river

R L Arildsen et al. Sci Rep. .

Abstract

We utilize Surface Water and Ocean Topography (SWOT) satellite data to derive a complete longitudinal profile of water surface elevations for tidal waves and capture a tidal bore within the Bristol Channel and Severn River system, marking the first such observation from satellite data. We demonstrate that SWOT high-rate data is highly accurate, even in intertidal zones with significant wetting and drying and extreme tidal amplitude, emphasizing the importance of minimal data smoothing to preserve critical details. By examining the tidal bore and associated tidal waves over three days (April 19-21, 2023), we gain novel insights into tidal bore dynamics and tidal wave interactions with inland waters. SWOT's high-resolution altimetry data bridges the coastal knowledge gap, enabling unprecedented integration of hydrology and physical oceanography. Tidal bores are crucial for ecological processes and hold cultural significance globally. Despite ongoing research, many hydrodynamic aspects of tidal bores remain unresolved, and our findings enhance the understanding of these phenomena.

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Figures

Fig. 1
Fig. 1
Comparative analysis of SSHA between Tide Gauges and SWOT. (a) The area of study with the position of two tide gauges and Newnham show in black stars. (b) SSHA values close to Avonmouth with the 5 points chosen in the comparative analysis shown as stars. (c) Same as (b) but for Sharpness. (d) SSHA values for tide gauge at Avonmouth compared with that of SWOT during the 19-day observational period. (e) Same as (d) but for Sharpness. (f) Same as (d) but for a subperiod from April 19th to April 21st. (g) Same as (f) but for Sharpness. The figure was created using Python v3.10.12, Cartopy v0.23.0 (https://scitools.org.uk/cartopy), and Matplotlib v3.9.2 (https://matplotlib.org).
Fig. 2
Fig. 2
Tidal bore observations in the Bristol Chanel and Severn River. (a) The location of the Severn bore in three consecutive days: April 19th to 21st. (b) The SSHA of the Severn River on April 19th around the tidal bore front which is marked with a red rectangle. (c) The longitudinal SSHA profile of the entire tidal wave from the mouth of the Bristol Channel and 80 km up the Severn River with the position of the tidal bore on April 19th. d-g Same as (b and c) but on April 20th and April 21st and with smaller drops in SSHA associated with large bends shown in red circles. The figure was created using Python v3.10.12, Cartopy v0.23.0 (https://scitools.org.uk/cartopy), and Matplotlib v3.9.2 (https://matplotlib.org).
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References

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