Publications

2018

• Equilibrium modeling of the beach profile on a macrotidal embayed low tide terrace beach
  
  • Lemos Clara
  • Floc'H France
  • Yates Marissa L.
  • Le Dantec Nicolas A
  • Marieu Vincent
  • Hamon Klervi
  • Madec Cuq Véronique
  • Suanez Serge S.
  • Delacourt Christophe
  Ocean Dynamics, Springer Verlag, 2018, 68 (9), pp.1207-1220. Eleven-year long time series of monthly beach profile surveys and hourly incident wave conditions are analyzed for a macrotidal Low Tide Terrace beach. The lower intertidal zone of the beach has a pluriannual cycle, whereas the upper beach profile has a predominantly seasonal cycle. An equilibrium model is applied to study the variation of the contour elevation positions in the intertidal zone as a function of the wave energy, wave power, and water level. When forcing the model with wave energy, the predictive ability of the equilibrium model is around 60% in the upper intertidal zone but decreases to 40% in the lower intertidal zone. Using wave power increases the predictive ability up to 70% in both the upper and lower intertidal zones. However, changes around the inflection point are not well predicted. The equilibrium model is then extended to take into account the effects of the tide level. The initial results do not show an increase in the predictive capacity of the model, but do allow the model free parameters to represent more accurately the values expected in a macrotidal environment. This allows comparing the empirical model calibration in different tidal environment. The interpretation of the model free parameter variation across the intertidal zone highlights the behavior of the different zones along the intertidal beach profile. This contributes to a global interpretation of the four model parameters for beaches with different tidal ranges, and therefore to a global model applicable at a wide variety sites. (10.1007/s10236-018-1185-1)
  DOI : 10.1007/s10236-018-1185-1
• Transport of moderately sorted gravel at low bed shear stresses: The role of fine sediment infiltration
  
  • Perret E.
  • Berni Céline
  • Camenen B.
  • Herrero A.
  • El Kadi Abderrezzak K.
  Earth Surface Processes and Landforms, Wiley, 2018, 43 (7), pp.1416-1430. A reliable estimation of sediment transport in gravel-bed streams is important for various practical engineering and biological studies (e.g., channel stability design, bed degradation/aggradation, restoration of spawning habitat). In the present work, we report original laboratory experiments investigating the transport of gravel particles at low bed shear stresses. The laboratory tests were conducted under unsteady flow conditions inducing low bed shear stresses, with detailed monitoring of the bed topography using a laser scanner. Effects of bed surface arrangements were documented by testing loose and packed bed configurations. Effects of fine sediments were examined by testing beds with sand, artificial fine sand or cohesive silt infiltrated in the gravel matrix. Analysis of the experimental data revealed that the transport of gravel particles depends upon the bed arrangement, the bed material properties (e.g., size and shape, consolidation index, permeability) and the concentration of fine sediments within the surface layer of moving grains. This concentration is directly related to the distribution of fine particles within the gravel matrix (i.e., bottom-up infiltration or bridging) and their transport mode (i.e., bedload or suspended load). Compared to loose beds, the mobility of gravel is reduced for packed beds and for beds clogged from the bottom up with cohesive fine sediments; in both cases, the bed shear stress for gravel entrainment increases by about 12%. On the other hand, the mobility of gravel increases significantly (bed shear stress for particle motion decreasing up to 40%) for beds clogged at the surface by non-cohesive sand particles. (10.1002/esp.4322)
  DOI : 10.1002/esp.4322