GenCade 2.0 Structures Dialog

The GenCade Structures/Events coverage allows the user to define the structures and planned events for a GenCade simulation. Only one of this type coverage can be added to the simulation, so it should contain arcs for all structures and events needed. However, there can be multiple arcs of the same types within this coverage unless it is mentioned in the sections below.

This coverage uses Feature Arcs within the SMS to define the positioning for each type and to assign a variety of attributes including:

• Geometric object – shoreline and contours.
• Structure – jetty, inlet, seawall, or breakwater and their associated parameters.
• Event – bypass or beach nourishment events and their time ranges and parameters.

This coverage is combined with the Gencade Grid and Points coverages to define all necessary pieces for the Gencade simulation.

The Structures and Events coverage contains many different types as shown and described below.

Generic

A Generic arc is the default for this dialog. Generic arcs are not yet assigned to be of any type and no information for these arcs is written to the input files.

Initial Shoreline

Only one Initial Shoreline is allowed per GenCade simulation. This is the definition of where the water meets the land. The points for the shoreline can be loaded into SMS in several ways including from ArcGIS Shapefiles. As mentioned in the USACE Technical Report,

Rigorous quality control is required to make sure the initial shoreline accurately represents the shoreline of interest. This process requires a detailed inspection of the shoreline. It is recommended to smooth out sudden changes in shoreline orientation especially near an inlet. The smoothing algorithm [in SMS] can be used for this purpose.

Regional Contour

In some cases, a regional contour may be added to the simulation. This arc can be defined in a similar manner, however it should be declared as the "Regional Contour" type under Arc Options on this dialog. Once the regional contour is specified, GenCade will maintain a desired overall shoreline curvature, e.g., preserving a bay shape without the presence of structures, even if the model is run for very long time periods.

Adding a regional contour represents a simplified method to describe the effects on the shoreline evolution of processes acting at longer time scales than what is simulated in GenCade. Thus, the regional contour should incorporate large-scale trends in shoreline shape, and not small-scale features that are expected to change at time scales modeled by GenCade.