CMS-Flow:Structures
Representation of Structures in CMS
Rubble mound structures are a common coastal engineering structure used for shoreline protection and flow and sediment transport control. They are typically used as seawalls, groins, breakwaters and jetties. The design of rubble mound structures often consists of a core of small to medium size rock or riprap covered with larger rock or riprap to armor against wave energy. In coastal modeling, it is usually reasonable to assume that the flow through these structures is negligible, and they are represented as solid structures, impermeable to both flow and sediment transport. However, some rubble mounds such as that of Dana Point, CA are designed with a sufficiently large diameter core material to allow for flow and fine sediments to pass through and coarser sediment to be trapped within.
Since permeable rubble mounds are a significant control of the hydrodynamic and sediment transport in the coastal zone, it is important to include them in the CMS. An algorithm is developed based on the Forchheimer equation (1901), which represents the introduction of a non-linear term in the Darcy equation for porous media. Both the linear and non-linear coefficients in the equation are evaluated using data from studies by Gent (1995) and Sidiropoulou et al. (2007). The structures are implemented within the CMS framework by extending the steady flow equation of Forchheimer to the unsteady shallow water equations. The CMS is verified by comparing the model output to results of analytical solutions for steady flow cases. A sensitivity analysis was also conducted to determine the sensitivity of the rubble mound simulations to uncertainty in the input parameter values.