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Subcatchment LID Controls Grid (SWMM)

This grid contains a series of records defining the LID control structure parameters for the subcatchment, and is displayed by clicking on the button located to the right of the LID controls field in the Subcatchment properties.

The fields which comprise the grid are described in the following table.

Database Table Name: sw_sub_suds

Field Name

Help Text

Database Field

Data Type

Size

Units

Precision

Default

Error Lower Limit

Error Upper Limit

Warning Lower Limit

Warning Upper Limit

LIDS structure ID

A name which identifies this particular LIDS structure. id Text 254

LIDS control ID

The name of the LID control object, which applies to this structure, can be selected from the dropdown list.

suds_structure Text 254

Control type

A read-only field which displays the type of LID control object. control_type Text 254

Area

The footprint of the LID structure. area Double NA 3 0

Number of units

The number of LID structures of the selected type within this subcatchment. num_units Long integer 1 0 0

Area of subcatchment

A read-only field which displays the area of the subcatchment affected by the number of units. This field is automatically updated when the Area or Number of units fields are edited. area_subcatchment_pct Double 3

Unit surface width

The width of the outflow face of each LID structure. This parameter applies to Green roof, Infiltration trench, Permeable pavement, Rooftop disconnection and Vegetative swale that use overland flow to convey surface runoff off from the unit. It is disabled for Bio-retention cell, Rain garden and Rain barrel types of SUDS controls. unit_surface_width Double L 3 0 0

Initial saturation

For Bio-retention cells, Rain gardens, and Green roofs this is the degree to which the unit's soil is initially filled with water (0 % saturation corresponds to the wilting point moisture content, 100 % saturation has the moisture content equal to the porosity). The storage zone beneath the soil zone of the cell is assumed to be completely dry.

For other types of SUDS controls, it corresponds to the degree to which their storage zone is initially filled with water.

initial_saturation_pct Double 3 0 0 100

Impervious area treated

The percent of the impervious portion of the subcatchment's non-LID structure's area whose runoff is treated by the LID practice. (E.g., if rain barrels are used to capture roof runoff and roofs represent 60% of the impervious area, then the impervious area treated is 60%). If the LID unit treats only direct rainfall, such as with a green roof or roof disconnection, then this value should be 0. If the LID structure takes up the entire subcatchment then this field is ignored. impervious_area_treated_pct Double 3 0 0 100

Pervious area treated

The percent of the pervious portion of the subcatchment's non-LID structure's area whose runoff is treated by the LID practice. pervious_area_treated_pct Double 3 0 0 100

Outflow to

The outflow from the LID structure can be set to either Outlet, Pervious or Impervious by selecting the appropriate option from the drop-down list. outflow_to Text 15 Outlet

Drain to subcatchment

The subcatchment to which the selected LID structure is to drain can be selected from a drop-down list. drain_to_subcatchment Text 254

Drain to node The node to which the selected LID structure is to drain can be selected from a drop-down list. drain_to_node Text 254

Note: If both the Drain to Subcatchment and Drain to node fields are blank, then the drain flow goes to the outflow specified in the Outflow to field.

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