Bedform evolution in a tidal inlet inferred from wavelet analysis

Bedforms are common morphological features in subaqueous and aeolian environments and their characterization is commonly the first step to better understand forcing factors acting in the system. The aim of this study was to investigate the spectral characteristics of compound bedforms in a tidal inlet and evaluate how they changed over consecutive years, when morphology was modified and bedforms migrated. High resolution bathymetric data from the Grådyb tidal inlet channel (Danish Wadden Sea) from seven years from 2002 to 2009 (not in 2004) were analyzed. Continuous wavelet transform of bed elevation profiles along a 1600 m long transect across compound bedforms was performed using a Morlet wavelet. The results of this approach showed that the spectrum of compound bedforms in the Grådyb channel is formed by four dominant wavelengths, with mean values of 132, 84, 46 and 6 m respectively, at 95% confidence level. A comparison of annual wavelet power spectra and global wavelet spectra revealed that their occurrence is consistent over the whole analyzed period.