Behaviour and performance of a dynamic cobble berm revetment during a spring tidal cycle in North Cove, Washington State, USA

In many places, sandy coastlines and their associated assets are at high risk of erosion flooding, with this increasing under climate change sea level rise. context, dynamic cobble berm revetments represent a potentially sustainable protection technique to armour beaches, reduce wave runup protect the hinterland against attack. However, behaviour performance such structures is not well understood. The revetment located in North Cove, WA, USA, was monitored over spring tidal cycle January 2019. A representative 60 m alongshore section 10 days using 2D laser scanner (lidar) measurements, GPS ground elevation surveys, Radio Frequency Identification individual cobbles thickness measurements. These data were used together assess functionality throughout experiment. Over course experiment, surface changed by up ±0.5 m, volume reduced an average 0.67 m3/m. changes found be caused relatively large significant height water levels. demonstrated stability capacity quickly reshape changing hydrodynamic conditions. instrumented transported along cross-shore accumulated toe revetment, but never seaward toe. also managed recover some lost moderate influenced variation cobble-sand matrix. underlying sand dynamics – i.e., accumulation or removal within govern overall important revetment. Seven possible transport regimes identified, model internal developed. During measured here, protected scarp immediately landward prevented flooding hinterland, while armouring sand. time, renourishment will likely required due longshore sediment transport, preliminary guidelines for other aspects design suggested.