Scale-dependent perspectives on the geomorphology and evolution of beach-dune systems

Abstract

Scale-dependent perspectives on the geomorphology and evolution of beach-dune systems.

Sediment budget controls on foredune height: Comparing simulation model results with field data

“…The study area includes about 5 km of the exposed north‐facing shoreline stretching eastward from the entrance to the St Peters estuary to just beyond the Park boundary (Figures C and D). The shoreline is characterized by a sandy nearshore and beach, which are backed by a continuous foredune ranging in height from 4 to 12 m with the sand deposit extending offshore as a wedge overlying sandstone bedrock (Forbes et al ., ; Walker et al ., ). Bedrock outcrops about 300–500 m offshore and locally is close to the surface near the beach in a few areas.…”

“…Carter, ; Nickling and Davidson‐Arnott, ; Bauer and Davidson‐Arnott, ; Delgado‐Fernandez, ; Hoonhout and de Vries, ). In addition, spatial and temporal variations in the morphology of the inner nearshore and foreshore zones affect the potential sediment supply to the aeolian system and the protection provided by foredune to the secondary backdunes or critical human infrastructure (Aagaard et al ., ; Houser, ; Bochev‐van der Burgh et al ., ; Walker et al ., ). Several researchers have sought to isolate the role of a small number of controls and to investigate the possible limits that they impose on the evolution of the foredune and dune field complexes (e.g.…”

“…A sediment mass balance approach therefore provides the mechanism by which dynamic changes in the height and width of the foredune can be determined. On a decadal scale, these changes are of interest to coastal scientists because they are diagnostic of the coastal nearshore context in which the foredunes evolve (Bauer and Sherman, ; Walker et al ., ), but also because of the role played by foredunes in providing protection to the area landward of the foredune from erosion and flooding from storm events. There is now considerable interest in enhancing understanding of the controls on foredune growth and using these insights to improve morphological models that can be used to test ideas about foredune evolution (Baas and Nield, ; Durán and Moore, ; Hounhout and de Vries, 2016), to predict the vulnerability of natural dunes to scarping and overwash during storms (Claudino‐Sales et al ., ; Brodie et al ., ), to assess the impact of invasive species such as non‐native marram grass (e.g.…”

“…Hilton et al ., ), and to improve the management and restoration of protective dune systems in developed settings (Elko et al ., ). While sediment budget approaches are conceptually simple, it has long been recognized that the actual controls on sediment supply to and from the foredune are numerous and complex (de Vries et al ., ; Walker et al ., ). Conceptual models of foredune evolution have sought to relate morphological response to gradients in specific controls such as sediment supply and littoral drift (Psuty, , ; Davidson‐Arnott and Law, ; Miot da Silva and Hesp, ; Heathfield and Walker, ), beach morphodynamics (Short and Hesp, ; Sherman and Lyons, ; Hesp and Smyth, ), storm frequency and magnitude (Sallenger, ; Houser and Hamilton, ; Splinter and Palmsten, ), vegetation type and cover (Hesp, , ; Hilton et al ., ; Baas and Nield, ; Darke et al ., ), and changes in sea level (Olson, ; Sherman and Bauer, ; Davidson‐Arnott, ).…”

The Role of Large Woody Debris in Beach‐Dune Interaction

“…Foredunes are vegetated shore‐parallel ridges of sand built by aeolian sand delivery across beaches. As such, foredunes are unique aeolian features affected by dynamic interactions between a host of marine, terrestrial, biotic, and atmospheric processes (Bauer & Sherman, ; Hesp & Walker, ; Sherman & Bauer, ; Walker et al, ). Foredunes may be large or small, continuous or discontinuous, and permanent or ephemeral features of the coastline depending on a host of controls such as (1) vegetation type and growth rate (Hacker et al, ; Keijsers et al, ); (2) plant density and distribution (Hesp, ); (3) presence of roughness elements (e.g., woody debris, vegetation wrack, foot prints, and coarse lag deposits) (Bauer et al, ; Eamer & Walker, ; Grilliot et al, ; Nordstrom et al, ; Walker & Barrie, ); (4) nature of sand supply (Aagaard et al, ; Bauer & Davidson‐Arnott, ; R Davidson‐Arnott & Bauer, ; Delgado‐Fernandez & Davidson‐Arnott, ; Hoonhout & de Vries, ; Nickling & Davidson‐Arnott, ; de Vries et al, ; de Vries et al, ); (5) moisture conditions, especially with respect to the sand surface (Anthony et al, ; Bauer et al, ; Davidson‐Arnott et al, ; de Vries et al, ; Ellis & Sherman, ; Namikas et al, ; Smit et al, ); (6) fetch or distance across which the wind blows before reaching the foredune (Bauer et al, ; Bauer & Davidson‐Arnott, ; Delgado‐Fernandez et al, ; Jackson & Cooper, ); and (7) airflow and sand transport interactions with beach‐dune topography (Hesp et al, ; Lynch et al, ; Walker et al, ; Walker et al, ).…”