Comparison of dynamic cobble berm revetments with differing gravel characteristics

Pressure on the coastline is escalating due to impacts of climate change, this leading a rise in sea-levels and intensifying storminess. Consequently, many regions coast are at increased risk erosion flooding. Therefore coastal protection schemes will increase cost scale. In response there growing use nature-based which aim be sustainable, effective adaptable. An example solution dynamic cobble berm revetment: constructed from other gravel sediments high tide wave runup limit. These structures limit excursion protecting hinterland inundation, stabilise upper beach adapt changes water level. Recent experiments field applications have shown suitability these for protection, however processes design considerations poorly understood. This study directly compares two prototype scale laboratory tested revetments with approximately same geometry but differing characteristics; well-sorted rounded (DynaRev1) poorly-sorted angular (DynaRev2). both cases were using identical forcing including incrementally increasing level erosive conditions. The results presented paper demonstrate that designs responded changing conditions by approaching dynamically stable state, where individual mobilised under action remains constant. Further, acted reduce swash excursions compared pure sand beach. However, their morphological behaviour varied considerably. Once overtopping designed crest occurred, revetment developed peaked grew elevation as or height increased, further limited overtopping. By comparison, was characterised larger volume submerged lower flat less well occurred processes: (1) case, sorting moved small medium material (D50<70mm) (2) nature promoted interlocking. Both led matrix more resistant gravitational effects. experienced some sinking beneath front slope. rate case continued throughout large pore spaces within matrix. For sorted DynaRev2, ceased after 28 h development filter layer sand-gravel interface reducing porosity location, hence preserved structure. present low-cost sandy coastlines an engineering viewpoint it appears better avoid greater angularity has been seen stability.