SMS:ADCIRC Spatial Attributes 11.1

ADCIRC Spatial Attributes

Spatial attributes (or nodal attributes) are parameters that can be applied to the entire domain of the simulation in the form of a dataset with values assigned to the nodes of the mesh. ADCIRC supports several such spatially varying input parameters and SMS (starting with version 11.0) includes functionality to assist the user in defining, managing and editing these parameters. With each release of ADCIRC, the list of supported nodal attributes changes. There are several such attributes that are under development and are used by individuals in the ADCIRC community, but are not available in the release version. Therefore, the interface in SMS is a combination of specifically defined attributes to correspond with the standard parameters in ADCIRC and custom attributes to allow for customization and support of attributes not yet included in either the ADCIRC release or the standard list in the SMS interface.

In version 50 of ADCIRC, the following predefined nodal attributes are supported:

• primitive_weighting_in_continuity_equation – Tau0
• surface_submergence_state – StartDry
• quadratic_friction_coefficient_at_sea_floor – Fric
• surface_directional_effective_roughness_length – z0Land
• surface_canopy_coefficient – VCanopy
• bridge_pilings_friction_parameters – BK, BAlpha, BDelX, POAN
• mannings_n_at_sea_floor – ManningsN
• chezy_friction_coefficient_at_sea_floor – ChezyFric
• sea_surface_height_above_geoid – GeoidOffset
• wave_refraction_in_swan ‐ SwanWaveRefrac (Supported in list of predefined attributes in SMS 11.2)
• bottom_roughness_length ‐ Z0b_var (Supported in list of predefined attributes in SMS 11.2)
• average horizontal eddy viscosity in sea water wrt depth – ESLM
• elemental_slope_limiter ‐ elemental_slope_limiter_grad_max (Supported in list of predefined attributes in SMS 11.2)
• advection_state ‐ AdvectionState (Supported in list of predefined attributes in SMS 11.2)

Please visit the ADCIRC web site to learn more about the meaning of each of the spatial attributes listed above.

The user can define these attributes in the Spatial Attributes command/dialog through the ADCIRC menu.

How to Use Spatial Nodal Attributes in a Simulation

Spatial nodal attributes are managed in the SMS using editable datasets. The creation and management of attributes is managed through the Spatial Attributes dialog. You can access the Spatial Attributes dialog by selecting ADCIRC | Spatial Attributes from the menu.

You can create a new spatial attribute by selecting the attribute name in the New Attribute combo-box. This will bring up the Spatial Attributes Initial Values dialog (discussed below).

The top left of the dialog has a list of the currently defined spatial attributes. The currently selected spatial attribute can be modified by the controls on the right side of the dialog or by editing specific dataset values by selecting the specific node(s) and entering a value. Each attribute has an associate comment. The comment is ignored by the model and is generally used for units information. The value below the comment is intended to represent the default value, or the value used the most in the dataset. Values at nodes that do not use the default value are written by the SMS to the fort.13 file as exceptions. The reset button will bring up the Spatial Attributes Initial Values dialog (discussed below).

You can delete the current attribute by clicking on the Delete button. For each spatial attribute, SMS creates one or more datasets in the project explorer. However, these datasets cannot be deleted through the project explorer. They must be managed through the Spatial Attributes dialog.

Initial Values Dialog

The initial values dialog is used to setup the initial values for the dataset(s) used for the spatial attribute. Every spatial attribute has the option of starting from a constant value or use the values from an existing dataset. In addition, some spatial attributes have an option to populate the spatial attribute based upon other data inside of SMS, using a rule, or using a utility similar to those provided on the ADCIRC websit to generate.

Populate Options

A spatial attribute consists of one or more datasets that can include unique values at each of the nodes in the mesh. This is potentially a lot of data and will generally not be specified manually. Two options exist for general population of the dataset. These include:

• Constant – the user specifies a single value for all nodes. The user can later select one or more regions of nodes and assign a different value to these nodes using the scalar edit box at the top of the SMS interface.
• Dataset – the user selects an existing data set that is copied to the spatial attribute. The user may use any of the standard methods for defining the souce dataset including interpolation and the data calculator. Individual edits can still be made to nodes or regions of nodes by manually selecting them.

In addition to these two default methods of populating data sets, SMS supports some custom population approaches for specific attributes. These are described below.

Primitive weighting

The SMS includes a tool for populating the primitive weighting coefficient for each node based on the node spacing and the node depth. The user specifies a threshold for node spacing (Critical average node spacing) and depth (Critical depth). The defaults for these are 1750 m and 10 m respectively. The user also specifies a values for tau for three conditions including default (0.03), deep (0.005) and shallow (0.02).

If the average distance between a node and its neighbors is less than the critical value then tau0 for that node is set at the tau default. If the average distance between a node and its neighbors is greater than or equal to a critical value then tau0 for that node is reduced to Tau Deep (default is 0.005) for depths greater than critical depth (default 10m) and Tau Shallow (default is 0.02) for depths less than the critical depth.

Quadratic, Manning N, and Chezy friction coefficients

The spatial attributes which reflect bottom friction "Chezy_friction_coefficient_at_sea_floor," "Mannings_n_at_sea_floor," and "quadratic_friction_coefficient_at_sea_floor" can be populated from NLCD land use data. You can obtain NLCD geo-tiffs from the Multi-Resolution Land Characteristics Consortium website (www.mrlc.gov). Use the seamless server to download the data in the area you are interested in.

When populating any of these spatial attributes, you provide a value for each land-use type and a default value that will be used in areas of the rasters that are NULL or outside the bounds of the rasters.

The values are extracted from all of the visible rasters. For each node in the mesh, the "area of influence" is computed for the node. The area of influence is a polygon that represents the area of the mesh around a node. This is computed as the area encompassing the node and half the distance to each of his neighboring nodes. All of the raster values within the area of influence are extracted from all the visible rasters. A composite n value is computed taking a weighted average of all the raster values. If the area of the extracted values is less then the area of influence around the node (because we passed the extent of the rasters or encountered null values), the default value is used to compute the composite n using the area not represented in the values.

Surface canopy coefficient

Allows canopy coefficient values for each vegetation type. Composes the contributing vegetation types associated with each node in a mesh and assigns canopy coefficient value to the datasets for the node.

Surface directional effective roughness

Composes the contributing vegetation types associated with each of the 12 directions (30 degrees each) around each node in a mesh and assigns the 12 characteristic or composite reduction values to the datasets for the node.

Related Links

• ADCIRC
• Boundary Conditions
• Coverage
• Linear Truncation Error Analysis (LTEA)
• Meshes
• Model Control
• Steering