Sandwave migration predictor based on shape information

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Abstract

[1] Migration of offshore seabed waves, which endangers the stability of pipelines and communication cables, is hard to measure. The migration rates are small compared to the measurement errors. Here, sandwave migration rates are determined from the change in the crest position deduced from long time series of bathymetric echo-sounding data. The crests are identified as local extremes in a bathymetric profile, after low-pass filtering. This approach is applied to both two-dimensional data and to profiles along pipelines. A consistent migration rate of several meters per year is found. A strong correlation between the sandwave shape and the migration rate is translated in a migration predictor. The predictor assumes that the sandwaves migrate in the direction of the steepest slope, following a quadratic relation with the asymmetry. Furthermore, it is included that longer waves travel faster but higher waves travel slower. The predictor is calibrated against data from nine areas and validated using three additional areas. An error analysis using markers shows that the error of the predictor is small compared to the noise in the individual crest position observations.

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