7408604c-1df3-42ce-a50f-11c07d2d0380 urn:uuid eng UTF-8 nonGeographicDataset nonGeographicDataset 2025-06-23T12:50:52 creation ISO 19115 2016 Beach Face and Berm Morphodynamics Fronting a Coastal Lagoon 7408604c-1df3-42ce-a50f-11c07d2d0380 This study documents two different modes of berm development: (1) vertical growth at spring tides or following significant beach cut due to substantial swash overtopping, and (2) horizontal progradation at neap tides through the formation of a proto-berm located lower and further seaward of the principal berm. Concurrent high-frequency measurements of bed elevation and the associated wave runup distribution reveal the details of each of these berm growth modes. In mode 1 sediment is eroded from the inner surf and lower swash zone where swash interactions are prevalent. The net transport of this sediment is landward only, resulting in accretion onto the upper beach face and over the berm crest. The final outcome is a steepening of the beach face gradient, a change in the profile shape towards concave and rapid vertical and horizontal growth of the berm. In mode 2 sediment is eroded from the lower two-thirds of the active swash zone during the rising tide and is transported both landward and seaward. On the falling tide sediment is eroded from the inner surf and transported landward to backfill the zone eroded on the rising tide. The net result is relatively slow steepening of the beach face, a change of the profile shape towards convex, and horizontal progradation through the formation of a neap berm. The primary factor determining which mode of berm growth occurs is the presence or absence of swash overtopping at the time of sediment accumulation on the beach face. This depends on the current phase of the spring-neap tide cycle, the wave runup height (and indirectly offshore wave conditions) and the height of the pre-existing berm. A conceptual model for berm morphodynamics is presented, based on sediment transport shape functions measured during the two modes of berm growth. {"type": "Polygon", "coordinates": [[[151.437, -33.47], [151.441, -33.47], [151.441, -33.457], [151.437, -33.457], [151.437, -33.47]]]} 151.437 151.441 -33.47 -33.457 Oceans | Marine Sediments | Sediment Transport Oceans | Ocean Waves | Wave Types Unnamed resource documentDigital HTML Unnamed resource documentDigital License Graphic PNG Unnamed resource documentDigital HTML