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Insights into the short-term tidal variability of multibeam backscatter from field experiments on different seafloor types

(2019) GEOSCIENCES. 9(1).
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Abstract
Three experiments were conducted in the Belgian part of the North Sea to investigate short-term variation in seafloor backscatter strength (BS) obtained with multibeam echosounders (MBES). Measurements were acquired on predominantly gravelly (offshore) and sandy and muddy (nearshore) areas. Kongsberg EM3002 and EM2040 dual MBES were used to carry out repeated 300-kHz backscatter measurements over tidal cycles (similar to 13 h). Measurements were analysed in complement to an array of ground-truth variables on sediment and current nature and dynamics. Seafloor and water-column sampling was used, as well as benthic landers equipped with different oceanographic sensors. Both angular response (AR) and mosaicked BS were derived. Results point at the high stability of the seafloor BS in the gravelly area (<0.5 dB variability at 45 degrees incidence) and significant variability in the sandy and muddy areas with envelopes of variability >2 dB and 4 dB at 45 degrees respectively. The high-frequency backscatter sensitivity and short-term variability are interpreted and discussed in the light of the available ground-truth data for the three experiments. The envelopes of variability differed considerably between areas and were driven either by external sources (not related to the seafloor sediment), or by intrinsic seafloor properties (typically for dynamic nearshore areas) or by a combination of both. More specifically, within the gravelly areas with a clear water mass, seafloor BS measurements where unambiguous and related directly to the water-sediment interface. Within the sandy nearshore area, the BS was shown to be strongly affected by roughness polarization processes, particularly due to along- and cross-shore current dynamics, which were responsible for the geometric reorganization of the morpho-sedimentary features. In the muddy nearshore area, the BS fluctuation was jointly driven by high-concentrated mud suspension dynamics, together with surficial substrate changes, as well as by water turbidity, increasing the transmission losses. Altogether, this shows that end-users and surveyors need to consider the complexity of the environment since its dynamics may have severe repercussions on the interpretation of BS maps and change-detection applications. Furthermore, the experimental observations revealed the sensitivity of high-frequency BS values to an array of specific configurations of the natural water-sediment interface which are of interest for monitoring applications elsewhere. This encourages the routine acquisition of different and concurrent environmental data together with MBES survey data. In view of promising advances in MBES absolute calibration allowing more straightforward data comparison, further investigations of the drivers of BS variability and sensitivity are required.
Keywords
multibeam echosounder, seafloor, backscatter, monitoring, short-term variability, sensitivity, high-frequency, BENTHIC MACROFAUNA, SUSPENDED SEDIMENT, OCEAN MEASUREMENTS, GRAIN-SIZE, ENVIRONMENT, INTEGRITY, HABITAT, WATER, SAND, TOOL

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MLA
Montereale Gavazzi, Giacomo Ottaviano Andrea, et al. “Insights into the Short-Term Tidal Variability of Multibeam Backscatter from Field Experiments on Different Seafloor Types.” GEOSCIENCES, vol. 9, no. 1, 2019, doi:10.3390/geosciences9010034.
APA
Montereale Gavazzi, G. O. A., Roche, M., Degrendele, K., Lurton, X., Terseleer, N., Baeye, M., … Van Lancker, V. (2019). Insights into the short-term tidal variability of multibeam backscatter from field experiments on different seafloor types. GEOSCIENCES, 9(1). https://doi.org/10.3390/geosciences9010034
Chicago author-date
Montereale Gavazzi, Giacomo Ottaviano Andrea, Marc Roche, Koen Degrendele, Xavier Lurton, Nathan Terseleer, Matthias Baeye, Frederic Francken, and Vera Van Lancker. 2019. “Insights into the Short-Term Tidal Variability of Multibeam Backscatter from Field Experiments on Different Seafloor Types.” GEOSCIENCES 9 (1). https://doi.org/10.3390/geosciences9010034.
Chicago author-date (all authors)
Montereale Gavazzi, Giacomo Ottaviano Andrea, Marc Roche, Koen Degrendele, Xavier Lurton, Nathan Terseleer, Matthias Baeye, Frederic Francken, and Vera Van Lancker. 2019. “Insights into the Short-Term Tidal Variability of Multibeam Backscatter from Field Experiments on Different Seafloor Types.” GEOSCIENCES 9 (1). doi:10.3390/geosciences9010034.
Vancouver
1.
Montereale Gavazzi GOA, Roche M, Degrendele K, Lurton X, Terseleer N, Baeye M, et al. Insights into the short-term tidal variability of multibeam backscatter from field experiments on different seafloor types. GEOSCIENCES. 2019;9(1).
IEEE
[1]
G. O. A. Montereale Gavazzi et al., “Insights into the short-term tidal variability of multibeam backscatter from field experiments on different seafloor types,” GEOSCIENCES, vol. 9, no. 1, 2019.
@article{8622455,
  abstract     = {{Three experiments were conducted in the Belgian part of the North Sea to investigate short-term variation in seafloor backscatter strength (BS) obtained with multibeam echosounders (MBES). Measurements were acquired on predominantly gravelly (offshore) and sandy and muddy (nearshore) areas. Kongsberg EM3002 and EM2040 dual MBES were used to carry out repeated 300-kHz backscatter measurements over tidal cycles (similar to 13 h). Measurements were analysed in complement to an array of ground-truth variables on sediment and current nature and dynamics. Seafloor and water-column sampling was used, as well as benthic landers equipped with different oceanographic sensors. Both angular response (AR) and mosaicked BS were derived. Results point at the high stability of the seafloor BS in the gravelly area (<0.5 dB variability at 45 degrees incidence) and significant variability in the sandy and muddy areas with envelopes of variability >2 dB and 4 dB at 45 degrees respectively. The high-frequency backscatter sensitivity and short-term variability are interpreted and discussed in the light of the available ground-truth data for the three experiments. The envelopes of variability differed considerably between areas and were driven either by external sources (not related to the seafloor sediment), or by intrinsic seafloor properties (typically for dynamic nearshore areas) or by a combination of both. More specifically, within the gravelly areas with a clear water mass, seafloor BS measurements where unambiguous and related directly to the water-sediment interface. Within the sandy nearshore area, the BS was shown to be strongly affected by roughness polarization processes, particularly due to along- and cross-shore current dynamics, which were responsible for the geometric reorganization of the morpho-sedimentary features. In the muddy nearshore area, the BS fluctuation was jointly driven by high-concentrated mud suspension dynamics, together with surficial substrate changes, as well as by water turbidity, increasing the transmission losses. Altogether, this shows that end-users and surveyors need to consider the complexity of the environment since its dynamics may have severe repercussions on the interpretation of BS maps and change-detection applications. Furthermore, the experimental observations revealed the sensitivity of high-frequency BS values to an array of specific configurations of the natural water-sediment interface which are of interest for monitoring applications elsewhere. This encourages the routine acquisition of different and concurrent environmental data together with MBES survey data. In view of promising advances in MBES absolute calibration allowing more straightforward data comparison, further investigations of the drivers of BS variability and sensitivity are required.}},
  articleno    = {{34}},
  author       = {{Montereale Gavazzi, Giacomo Ottaviano Andrea and Roche, Marc and Degrendele, Koen and Lurton, Xavier and Terseleer, Nathan and Baeye, Matthias and Francken, Frederic and Van Lancker, Vera}},
  issn         = {{2076-3263}},
  journal      = {{GEOSCIENCES}},
  keywords     = {{multibeam echosounder,seafloor,backscatter,monitoring,short-term variability,sensitivity,high-frequency,BENTHIC MACROFAUNA,SUSPENDED SEDIMENT,OCEAN MEASUREMENTS,GRAIN-SIZE,ENVIRONMENT,INTEGRITY,HABITAT,WATER,SAND,TOOL}},
  language     = {{eng}},
  number       = {{1}},
  pages        = {{33}},
  title        = {{Insights into the short-term tidal variability of multibeam backscatter from field experiments on different seafloor types}},
  url          = {{http://dx.doi.org/10.3390/geosciences9010034}},
  volume       = {{9}},
  year         = {{2019}},
}

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