Turbulence and turbulent flux events in tidal bores: case study of the undular tidal bore of the Garonne River

The French Middle Gravettian represents an interesting case study for attempting to identify mechanisms behind the typo-technological variability observed in the archaeological record. Associated with the relatively cold and dry environments of GS.5.2 and 5.1, this phase of the Gravettian is characterized by two lithic typo-technical entities (faciès in French): the Noaillian (defined by the presence of Noailles burins) and the Rayssian (identified by the Raysse method of bladelet production).The two faciès have partially overlapping geographic distributions, with the Rayssian having a more northern and restricted geographic extension than the Noaillian. Their chronological relationship, however, is still unclear, and interpretations of their dual presence at many sites within the region of overlap are not yet consensual. Nonetheless, the absence of the Raysse method south of the Garonne River suggests that this valley may have separated two different cultural trajectories for which the Rayssian represents an adaptation to environmental conditions different from those associated with the Noaillian assemblages south of the Garonne River. The aim of this study is to test this hypothesis quantitatively using ecological niche modeling (ENM) methods. We critically evaluate published data to construct inventories of Noaillian and Rayssian archaeological sites. Using ENM methods, we estimate the ecological niches associated with the Middle Gravettian north (Noaillian + Rayssian) and south (Pyrenees Noaillian) of the Garonne River, and these predicted niches are then quantitatively evaluated and compared. Results demonstrate that, despite a relatively large degree of similarity, the niches differ significantly from one another in both geographic and environmental dimensions and that the niche associated with the northern Middle Gravettian is broader than that of the Pyrenees Noaillian. We propose that this pattern reflects different technological, subsistence and mobility strategies linked to the development of the Raysse method in the North, which was likely more advantageous in such environmental contexts than those employed by Pyrenees populations.

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Comparison of high rate GNSS and GNSS-R measurements for detecting tidal bores in the Garonne River

10.5194/egusphere-egu2020-20898 ◽

2020 ◽

Author(s):

Pierre Zeiger ◽

José Darrozes ◽

Frédéric Frappart ◽

Guillaume Ramillien ◽

Laurent Lestarquit ◽

...

Keyword(s):

Sea Level ◽

Sampling Rate ◽

Acoustic Doppler Current Profiler ◽

Satellite System ◽

High Rate ◽

Tidal Bore ◽

Garonne River ◽

Current Profiler ◽

Oceanic Tides ◽

Global Navigation Satellite

The Reflected Global Navigation Satellite System (GNSS-R) is a bi-static radar system in which the receiver collect GNSS signals reflected from the Earth surface and compares them with corresponding direct signals. Measurements can be performed on the waveforms to determine the elevation of the free surface, leading to applications such as ocean altimetry, inland water level variations, soil moisture, snow depth and atmospheric water changes. This study presents the potential of in-situ GNSS-R for tidal bore detection and characterization, and compares it to high rate GNSS observations and other reference datasets.The data we used were acquired on 17th and 18th October 2016 in the Garonne River, at 126 km upstream the mouth of the Gironde estuary. We processed GNSS-based elevations from data acquired on a buoy at a 20 Hz sampling rate using differential GNSS (DGNSS) technique. Acoustic Doppler Current Profiler (ADCP) measurements as well as pressure data were used for validation purposes. These techniques show good results in estimating the amplitude of the first wave, the period of the tidal bore and the oceanic tides. All of these datasets were compared to the retrieval of GNSS-R signals above the river. We have processed the changes in water height throughout the acquisition using Larson et al. (2013) and Roussel et al. (2015) techniques. We finally separate the atmospheric component from the tidal bore and the oceanic tides ones.&#160;Larson, K. M., L&#246;fgren, J. S., and Haas, R. (2013). Coastal sea level measurements using a single geodetic gps receiver. Advances in Space Research, 51(8):1301&#8211;1310.Roussel, N., Ramillien, G., Frappart, F. et al. (2015). Sea level monitoring and sea state estimate using a single geodetic receiver. Remote Sensing of Environment, 171:261 &#8211; 277.

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Perspective on the Tidal Bore: Background and Initiation

Volume 1: Symposia, Parts A and B ◽

10.1115/fedsm2012-72112 ◽

2012 ◽

Cited By ~ 1

Author(s):

S. David Graber

Keyword(s):

Literature Review ◽

Field Data ◽

Historical Context ◽

Companion Paper ◽

Extensive Literature ◽

Scientific Interest ◽

Tidal Bore ◽

Extensive Literature Review ◽

Tidal Bores ◽

The Subject

Tidal bores have been the subject or cause of legend, poetry, recreation, tourism, shipping disasters, and scientific interest for centuries. They pose interesting theoretical questions for the engineer. Introductory details are presented regarding the remarkable tidal bore phenomenon, including discussion of the tidal bore in various locations and a recent photograph taken by the writer of the bore on China’s Qiantang River. A supplemental tabular summary is presented based on an extensive literature review. A simplified theory based on monoclinal rising waves is developed for the initiation of the tidal bore. The theory elucidates the mechanisms of the tidal bore more clearly and completely than more complex theories. Early studies of the tidal bore are cited and discussed in historical context. The intention is to provide greater understanding of the tidal bore for a broad set of readers. The theory is favorably compared to rectangular flume data and to all field data available to the writer. A companion paper builds on the present one by addressing additional features of the tidal bore.

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