Project File:Overland Flow – Required

From Gsshawiki
Jump to: navigation, search

3.3.1 Required Inputs

Overland roughness coefficients must be assigned to every cell in the active grid. Overland roughness coefficients may be assigned as either a single uniform value, from a GRASS ASCII grid map, or from the Mapping Table. Only one option should be selected. Do not specify either of these cards if roughness values are to be read from the Mapping Table file.

Card Argument Units Description
MANNING_N  ##.##
real none Constant value of Manning’s roughness coefficient to be applied to the entire watershed. Mutually exclusive with ROUGHNESS and Mapping Table file assignment.
ROUGHNESS  "filename.ext"
map name   Name of GRASS ASCII map containing spatially-varied overland flow Manning’s n values. Mutually exclusive with MANNING_N and Mapping Table file assignment.

3.3.2 Optional Inputs

The user can select the overland flow routing scheme. An overland retention depth may also be specified at the discretion of the user. Retention depth can be assigned as a single uniform value, from the Mapping Table, or from a GRASS ASCII grid map. Only one option should be specified.

Card Argument Units Default Value Description
OVERTYPE   [type]
character   ADE Overland routing scheme, one of:

ADE, or

RETEN_DEPTH  ["filename.ext"]
map name
or none
    Specifies distributed retention depth (mm) over the watershed. If followed by a map name, the file will be read in as the retention depth map. If no input is specified, then the retention depth map is generated from the Mapping Table file. Mutually exclusive with RETENTION.
real mm 0.0 Specifies the uniform retention depth to be used for all overland flow cells. Mutually exclusive with RETEN_DEPTH.
READ_OV_HOTSTART  "filename.ext"
map name     Name of map that specifies initial depths, m, of every overland flow cell
WRITE_OV_HOTSTART  "filename.ext"
map name     Name of map that specifies overland depths at the end of the simulation, m, of every overland flow cell
none     Run with overland boundary conditions turned on. The boundary conditions are specified in the mapping table.
real m 0.0 Specifies an initial water surface (meters above sea level.) Used when starting models adjacent to the ocean in conjunction with overland boundary conditions.
real 0.2 Use the momentum formulation from Bates et al. (2010) to compute overland flow. For versions 7.14 and higher specify the time step limitation coefficient (between 0.0 and 1.0) with this card as well. The default time step coefficient is 0.2. Higher values increase speed. Lower values increase stability.
none No Use a strict application of the overland flow time step from Bates et al. (2010).

To include wetlands, which are optional, simply set up a wetlands table. The wetlands are turned on if the table is present and has a valid index map associated with it.

GSSHA User's Manual

3 Project File
3.1     Required Inputs
3.2     Mapping Table – Optional
3.3     Overland Flow – Required
3.4     Interception – Optional
3.5     Rainfall Input and Options – Required
3.6     Infiltration – Optional
3.7     Channel Routing – Optional
3.8     Continuous Simulations – Optional
3.9     Saturated Groundwater Flow – Optional
3.10     Soil Erosion – Optional
3.11     Constituent Transport – Optional
3.12     Subsurface Drainage Network – Optional
3.13     Output Files – Required