TY - JOUR
T1 - Measuring Centimeter-Scale Sand Ripples Using Multibeam Echosounder Backscatter Data from the Brown Bank Area of the Dutch Continental Shelf
AU - Koop, L.
AU - van der Reijden, Karin J.
AU - Mestdagh, S.M.F.
AU - Ysebaert, Tom
AU - Govers, Laura L.
AU - Olff, Han
AU - Herman, P.M.J.
AU - Snellen, M.
AU - Simons, D.G.
PY - 2020
Y1 - 2020
N2 - Backscatter data from multibeam echosounders are commonly used to classify seafloor sediment composition. Previously, it was found that the survey azimuth affects backscatter when small organized seafloor structures, such as sand ripples, are present. These sand ripples are too small to be detected in the multibeam bathymetry. Here, we show that such azimuth effects are time dependent and are useful to examine the orientation of sand ripples in relation to the flow direction of the tide. To this end, multibeam echosounder data at four different frequencies were gathered from the area of the Brown Bank in the North Sea. The acoustic results were compared to video and tide-flow data for validation. The sand ripples affected the backscatter at all frequencies, but for the lowest frequencies the effect was spread over more beam angles. Using the acoustic data made it possible to deduce the orientations of the sand ripples over areas of multiple square kilometers. We found that the top centimeter(s) of the seafloor undergoes a complete transformation every six hours, as the orientation of the sand ripples changes with the changing tide. Our methodology allows for morphology change detection at larger scales and higher resolutions than previously achieved.
AB - Backscatter data from multibeam echosounders are commonly used to classify seafloor sediment composition. Previously, it was found that the survey azimuth affects backscatter when small organized seafloor structures, such as sand ripples, are present. These sand ripples are too small to be detected in the multibeam bathymetry. Here, we show that such azimuth effects are time dependent and are useful to examine the orientation of sand ripples in relation to the flow direction of the tide. To this end, multibeam echosounder data at four different frequencies were gathered from the area of the Brown Bank in the North Sea. The acoustic results were compared to video and tide-flow data for validation. The sand ripples affected the backscatter at all frequencies, but for the lowest frequencies the effect was spread over more beam angles. Using the acoustic data made it possible to deduce the orientations of the sand ripples over areas of multiple square kilometers. We found that the top centimeter(s) of the seafloor undergoes a complete transformation every six hours, as the orientation of the sand ripples changes with the changing tide. Our methodology allows for morphology change detection at larger scales and higher resolutions than previously achieved.
KW - angular response curve
KW - survey azimuth
KW - seafloor characterization
KW - underwater video
KW - North Sea
UR - http://www.scopus.com/inward/record.url?scp=85102722030&partnerID=8YFLogxK
U2 - 10.3390/geosciences10120495
DO - 10.3390/geosciences10120495
M3 - Article
SN - 2076-3263
VL - 10
SP - 1
EP - 21
JO - Geosciences (Switzerland)
JF - Geosciences (Switzerland)
IS - 12
M1 - 495
ER -