Rollnic, M. and Medeiros, C., 2013. Application of a Probabilistic Sediment Transport Model to Guide Beach Nourishment Efforts

This study focused on establishing the probability of different sediment grain size be transported by coastal currents, as a prognostic tool to guide nourishment efforts at a coastal section near Recife, NE-Brazil (UTM 9105000-9089969N; 0297000-0289227E). The SisBahia hydrodynamic module FIST3D was applied linked to the Lagrangian-Probabilistic Transport Module over a 27km-long coastal band from 0 to 17m isobaths. The bathymetry and sedimentary coverage was characterized in a 200m grid. Input and calibration data were originated from a 3-years field work comprising 40 stations and considering seasonal variability. Data base included instantaneous current measurements, current, tide and wave time-series and CTD profiles. A finite-element grid (876 quadratic elements; 3703 nodes) was generated and twenty one depth levels defined through the water column. Simulations were performed with a 50s time-integration intervals, resulting an average 4.57 Courant number. Dry and rainy season scenarios under neap and spring tides were simulated with good agreement between simulated and in situ data. Simulation for each scenario was conducted over a 10-days period, and the probability of the different currents intensity near the bottom relative to its ability to move the various sediments fractions were mapped. Simulation indicated a high potential for sediment transport in the area under more severe erosion. Here current intensification was verified at both seasons and during neap and spring tides. Fine sand have a 90% probability of being transported by local currents, medium and coarse sands a probability of 80% and very coarse sands a probability of 60%.