A deformation analysis of a dynamic estuary using two-weekly MBES surveying

Pluymaekers, S.J.A.; Lindenbergh, R.C.; Simons, Dick G.; Ronde, J. de

doi:10.1109/oceanse.2007.4302305

Cited by 8 publications

(13 citation statements)

References 7 publications

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“…From a managing point of view, sand waves in shallow areas may form a danger to navigation, for example, in the shipping lane approaching the harbor of Rotterdam, the Netherlands. Empirical knowledge on the regional dynamics of sand waves and megaripples leads to more efficient survey planning and dredging strategies for those authorities that are either charting the seafloor areas or maintaining critical navigation depths [ Cullen , 2005; Dorst , 2004; Pluymaekers et al , 2007; Wüst , 2004].…”

Section: Introductionmentioning

confidence: 99%

Separating bathymetric data representing multiscale rhythmic bed forms: A geostatistical and spectral method compared

Dijk

Lindenbergh

Egberts³

2008

J. Geophys. Res.

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[1] The superimposition of rhythmic bed forms of different spatial scales is a common and natural phenomenon on sandy seabeds. The dynamics of such seabeds may interfere with different offshore activities and are therefore of interest to both scientists and offshore developers. State-of-the-art echo sounding accuracy allows for the analysis of bed form dynamics on unprecedented spatial and temporal scales. However, the superimposition of bed forms complicates the automated determination of morphodynamic parameters of individual bed form components. In this research we present the extension and comparison of two well-known, automated signal-processing methods for the 1-D and 2-D separation of bathymetric data derived from multibeam echo soundings into different components that each represents a bed form of a particular length scale. One method uses geostatistical filtering, and the other uses a Fourier decomposition of the bathymetric data. The application of both methods in two case studies of the North Sea shows that both methods are successful and that results correspond well. For example, megaripples up to 0.83 m height could be separated from 1.49-2.28 m high sand waves, and regionally averaged lengths and heights of sand waves, as calculated in either method, differ only 0.42-8.2% between methods. The obtained sand wave migration rates differ 7-11% between methods. The resulting morphometric and morphodynamic bed form quantification contributes to studies of empirical behavior and morphodynamic model validation and is valuable in risk assessments of offshore human activities.Citation: van Dijk, T. A. G. P., R. C. Lindenbergh, and P. J. P. Egberts (2008), Separating bathymetric data representing multiscale rhythmic bed forms: A geostatistical and spectral method compared,

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Section: Introductionmentioning

confidence: 99%

Separating bathymetric data representing multiscale rhythmic bed forms: A geostatistical and spectral method compared

Dijk

Lindenbergh

Egberts³

2008

J. Geophys. Res.

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“…2) Determine the orientation of the bedforms using either a 2D fast Fourier transform or variability analysis (Van Dijk and Lindenbergh 2017; Pluymaekers et al 2007). 3) Take transects of the backscatter intensity perpendicular to the bedform crest.…”

Section: April 2018 J O N E S a N D T R A Y K O V S K Imentioning

confidence: 99%

A Method to Quantify Bedform Height and Asymmetry from a Low-Mounted Sidescan Sonar

Jones

Traykovski

2018

Journal of Atmospheric and Oceanic Technology

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Rotary sidescan sonars are widely used to image the seabed given their high temporal and spatial resolution. This high resolution is necessary to resolve bedform dynamics and evolution; however, sidescan sonars do not directly measure bathymetry, limiting their utility. When sidescan sonars are mounted close to the seabed, bedforms may create acoustical ''shadows'' that render previous methods that invert the backscatter intensity to estimate bathymetry and are based on the assumption of a fully insonified seabed ineffective. This is especially true in coastal regions, where bedforms are common features whose large height relative to the water depth may significantly influence the surrounding flow. A method is described that utilizes sonar shadows to estimate bedform height and asymmetry. The method accounts for the periodic structure of bedform fields and the projection of the shadows onto adjacent bedforms. It is validated with bathymetric observations of wave-orbital ripples, with wavelengths ranging from 0.3 to 0.8 m, and tidally reversing megaripples, with wavelengths from 5 to 8 m. In both cases, bathymetric-measuring sonars were deployed in addition to a rotary sidescan sonar to provide a ground truth; however, the bathymetric sonars typically measure different and smaller areas than the rotary sidescan sonar. The shadow-based method and bathymetric-measuring sonar data produce estimates of bedform height that agree by 34.0% 6 27.2% for wave-orbital ripples and 16.6% 6 14.7% for megaripples. Errors for estimates of asymmetry are 1.9% 6 2.1% for wave-orbital ripples and 11.2% 6 9.6% for megaripples.

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“…2.19 (Ashley, 1990;Nielsen, 1992 2. Determine the orientation of the bedforms using either a 2D fast Fourier transform or variability analysis (Van Dijk and Lindenbergh, 2017;Pluymaekers et al, 2007).…”

Section: Bedform Parameter Distributionsmentioning

confidence: 99%

Measurements and dynamics of multiple scale bedforms in tidally energetic environments

Jones¹

2018

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The presence of superimposed bedforms, where smaller bedforms exist on larger bedforms, is ubiquitous to energetic tidal environments. Due to their wide range in scale, it is difficult to simultaneously observe these features over tidal timescales. This thesis examines the morphological response of superimposed bedforms to a tidally reversing flow using novel instrumentation and platform systems. A method is outlined in chapter 2 to expand the functionality of low-mounted sidescan sonars by utilizing sonar shadows to estimate bedform height and asymmetry. Empirical models are generated to account for realistic variability in the seabed and the method is validated with bathymetric observations of wave-orbital ripples and tidally reversing megaripples. Given the high temporal and spatial resolution of seafloor frame mounted rotary sidescan sonars, the dynamics and evolution of the bedforms over an approximately 40 m x 40 m area can be resolved. In chapter 3 the method is applied to data of superimposed bedforms at Wasque Shoals, an ebb delta off the southeast corner of Martha's Vineyard, MA. These data reveal the small, superimposed bedforms reversing their asymmetry with the flow while the larger bedforms on which they reside remain oriented in the direction of the dominant flow. Similar bedform dynamics are observed at Nauset Inlet, a dynamic inlet system, on Cape Cod, MA using an autonomous jet-powered kayak, the

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A deformation analysis of a dynamic estuary using two-weekly MBES surveying

Cited by 8 publications

References 7 publications

Separating bathymetric data representing multiscale rhythmic bed forms: A geostatistical and spectral method compared

Separating bathymetric data representing multiscale rhythmic bed forms: A geostatistical and spectral method compared

A Method to Quantify Bedform Height and Asymmetry from a Low-Mounted Sidescan Sonar

Measurements and dynamics of multiple scale bedforms in tidally energetic environments

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