Rippled Scour Depressions on Dogger Bank (North Sea): Mapping, Quantification and Geohazard Implications for Offshore Wind Farms

Abstract

Rippled Scour Depressions (RSD) are depressed bedforms containing characteristic ripples. They are a type of sorted bedform that mainly develop in areas with a shallow seafloor, strong waves/currents, and a thin mobile sand cover. This study focuses on RSD developed on Dogger Bank (North Sea) and presents: (1) qualitative descriptions; (2) semi-automated mapping of -12,500 RSD from two bathymetry datasets acquired 8 years apart; and (3) quantitative analysis of > 2,500 features. Most RSD are ephemeral, and they form fields whose location is controlled by seafloor geomorphology. These are abundant in shallow areas (< 24 m water depth) and in zones associated with abrupt topographic variations. Overall, RSD are large and shallow features, often having an area > 100 m2 and a maximum depth < 50 cm. However, RSD > 1 m deep are locally present, and their displacement might be a geohazard for renewable energy projects. This is a companion paper to Dix et al. (2023).