Subcatchment Data Fields (InfoWorks)

Subcatchment data can be edited on either the Subcatchment Grid Window of the Subcatchments Grid or the Subcatchment Property Sheet.

Most data can be edited on the grid, but some fields cannot be displayed in the grid format.

To view and edit all subcatchment data, use the Property Sheet.

The following describes all the data which can be used to define a subcatchment. For details of results fields, see the Subcatchment Results Data Fields (InfoWorks) topic.

Common Data Fields

Fields that are common to the majority of objects can be found in the Common Fields topic.

Subcatchment Data

Database Table Name: hw_subcatchment

Show Columns	Database Names
	Size, Type and Units
	Defaults and Error Limits

Field Name

Help Text

Database Field

Data Type

Size

Units

Precision

Default

Error Lower Limit

Error Upper Limit

Warning Lower Limit

Warning Upper Limit

Subcatchment ID

A unique name for the subcatchment.

subcatchment_id

Text

System type

Choose the System type from the drop-down list. See System Type for more information.

Database Value	Description	Help Text
STORM	Storm	Rainfall collection system
FOUL	Foul	Wastewater collection system (UK terminology)
SANITARY	Sanitary	Wastewater collection system (US terminology)
COMBINED	Combined	Rainfall and wastewater collection system
OVERLAND	Overland	Overland floodwater collection system
OTHER	Other	Other system type

system_type

Text

Other

Drains to

The type of object to which this subcatchment drains. Choose an object type from the drop-down list:

Option	Help Text
Node	The Node ID field is enabled, allowing you to specify to which node the subcatchment drains.
Link	The Node ID and Link Suffix fields are enabled, allowing you to specify to which link the subcatchment drains.
Subcatchment	The To subcatchment ID field is enabled, allowing you to specify another subcatchment to which this one drains.
Multiple links	The Lateral links and Lateral weights fields are enabled, allowing you to specify to which links the subcatchment drains.
2D point source	The 2D point source ID field is enabled, allowing you to specify to which 2D point source the subcatchment drains.

drains_to

Text

Node ID

Enabled when Drains to is set to Node or Link.

The name of the node to which this subcatchment drains. The name can be either be typed in or selected from a drop-down list of all nodes in the current network.

node_id

Text

Link suffix

Enabled when Drains to is set to Link.

The link suffix of a single link that the subcatchment drains to. In order for a subcatchment to drain to a single link, both the Node ID and Link suffix fields must be filled-in.

When running a simulation, the simulation engine applies runoff from the subcatchment laterally along the link identified by the Node ID and Link suffix fields.

link_suffix

Text

To Subcatchment ID

Enabled when Drains to is set to Subcatchment.

The name of another subcatchment to which this subcatchment drains. This name can be either be typed in or chosen from the drop-down list.

to_subcatchment_id

Text

2D point ID

Enabled when Drains to is set to 2D point source.

The name of the 2D point source to which this subcatchment drains. The name can be either be typed in or selected from a drop-down list of all 2D point sources in the current network.

2d_pt_id

Text

Lateral links

Enabled when Drains to is set to Multiple links.

A series of records defining all the lateral links which a subcatchment can drain.

The records are entered on the Lateral links grid which is displayed by clicking on the button.

Field Name

Help Text

Node ID

The node to which this lateral link drains. The name of the node can either be typed in or selected from a list of all nodes in the current network.

Link suffix

The link suffix to which this lateral link drains.

Weight

If the Lateral weights field is set to User, then this field is enabled and is used to specify the proportion of the total weight that is to be assigned to this lateral link. The total of all links included in the grid must add up to 1.

If the Lateral weights field is set to Length, then this field is read-only and displays the calculated weight values. These values are calculated to be proportional to the length of the associated links and normalised so that the sum of all weights adds up to 1.

If no link exists in the network with an ID corresponding to the Node ID and Link suffix specified in a grid row, then the weight is zero for that row.

If a change is made to the network (after the grid values have been saved by clicking OK), and the grid editor is re-opened, the Length-based weights will be updated, if the change affects the weighting. For example, if an entry in the grid row is saved but it does not have a corresponding link (therefore Weight=0), and a corresponding link is subsequently created in the network and the grid editor is re-opened, then a non-zero weight, determined by the new link’s length, will be displayed.

The Length-based weights are also updated during the validation process. Therefore, it is not necessary to re-open the grid editor in order to update the weights before performing a simulation.

For lateral links, the flow from a subcatchment is connected laterally. However, if any link is a control, then the flow into that link will be connected at the upstream node unless that node is an outfall, in which case it will be connected at the downstream node. If the nodes at both ends of a link are outfalls, then the flow will be lost.

lateral _links

Structure

Lateral weights

Enabled when Drains to is set to Multiple links.

The method by which the weighting for the Lateral links is to be set can be chosen from the drop-down list. Set to either User, to indicate that the user is to specify the proportion of the subcatchment drainage that is assigned to each link, or to Length (default), to indicate that weightings are to be calculated by the system.

lateral_weights

Text

Length

Limit drain to capacity

A check in the box indicates that the runoff, from a subcatchment to its Drains to object, is to be limited to a value which is specified in the Capacity limit field.

If unchecked, no limit is applied.

limit_drain_capacity

Boolean

Capacity limit

Displayed when the Limit drain to capacity box is checked.

The maximum runoff that goes to this subcatchment's Drains to object.

Note: If the Capacity limit is set to 0 (default), no limit is applied, and all runoff goes to this subcatchment's Drains to object.

How the runoff above the limit is modelled is determined in the Exceedance flow type field.

capacity_limit

Double

Exceedance flow type

Displayed when the Limit drain to capacity box is checked.

Determines how the flow above the Capacity limit is modelled. The choices are:

Lost - the exceedance flow is lost from the system.

2D mesh - the exceedance flow is included in the 2D simulation.

Note: If the Exceedance flow type is set to 2D mesh, the subcatchment must Drain to a node within a 2D mesh element. It can be any type of node except Outfall or Outfall 2D.

exceed_flow_type

Text

Total area

The full area of the subcatchment, including those parts that do not drain into the system you are modelling. This item is for your information, and is not essential.

total_area

Double

Contributing area

The area that drains into the system you are modelling. You must enter a value here, even if it is just zero.

contributing_area

Double

The X co-ordinate for the centre of the subcatchment boundary region.

Double

The Y co-ordinate for the centre of the subcatchment boundary region.

Double

Slope

The average gradient at which the subcatchment drains to the node.

If the 1 link for the node the subcatchment drains to is a conduit then default ground slope = (u/s ground level - d/s ground level) / length, otherwise default is zero.

Note that for the RAFTS model, the minimum value for the average gradient that will be used in the calculation of RAFTS B is 0.002 even if a lower value is specified in this field.

catchment_slope

Double

Standard percentage runoff

Standard percentage runoff used to calculate runoff from pervious surfaces when using the UKWIR Model.

A value may be entered manually or populated from selected WRAP soil type or HOST soil class.

To populate from soil class, set the flag to #D select which data source to use to provide SPR values from the SPR calculation field and set a WRAP soil type or HOST soil class as appropriate.

ukwir_soil_runorr

Double

0.1

0.6

SPR calculation

Source of soil class SPR values, which can be used to determine Standard percentage runoff for use with the UKWIR Model.

Database Value	Description	Help Text
WRAP	WRAP	Select WRAP soil class to provide SPR value
HOST_Soils	HOST predominant soils	Select HOST soil class to provide SPR value
HOST_FEH	HOST FEH 1999	Select HOST soil class to provide SPR value

soil_class_type

Text

WRAP soil type

Choose the WRAP soil class number from the dropdown.

Essential for the Wallingford Procedure UK runoff model.

May be used to provide Standard percentage runoff values for the UKWIR Model.

soil_class

Long Integer

HOST soil class

HOST soil class used to provide Standard percentage runoff values for the UKWIR Model.

soil_class_host

Long Integer

Maximum soil moisture capacity

Maximum soil moisture capacity.

Calculated via the Calculate ReFH Parameters dialog when the Unit Hydrograph Definition is set to ReFH.

max_soil_moisture_capacity

Double

Curve number

SCS Runoff Curve Number

A list of curve number values that can be used can found here.

curve_number

Double

100

Drying time

Used in the CNSWMM runoff volume model.

Time in days for a fully saturated soil to dry completely. Typical values range from 2 to 14 days.

drying_time

Double

0.001

Rainfall profile

The source of the rainfall data to be applied to the subcatchment during a simulation. The interpretation of this field depends on whether you are using a Rainfall Event or TSDB data for simulation.

Note

For model networks created using Version 8 onwards, or updated pre-version 8 ones or ones copied from another database:

The same Rainfall profile must be specified for all subcatchments that use the same RTK hydrograph.

Rainfall Event

This specifies the name of the rainfall profile applied to this subcatchment. Each profile within a Rainfall Event has a unique name. You must set a value in this field, or set the field flag to #D to use the User Defined Default.

If the field does not contain a valid rainfall profile ID, the following action is taken when you run a simulation:

if the Rainfall Event contains a single profile, this profile is applied in the simulation. This makes the assumption that if there is only one profile, you will want to apply it to the whole model
if the Rainfall Event contains more than one profile, InfoWorks ICM uses the first profile in the event. A warning is included in the simulation log file

When using a Rainfall Event containing rain-gauge boundary data, the Rainfall Profile is over-ridden and depends on which rain-gauge boundary contains the point defined by the subcatchment’s X and Y fields (if these are set) or the Drainage node (if they are not set). See Spatially Varying Rainfall.

TSDB Data

This specifies the name of the TVD connector that will apply rainfall to this subcatchment.

If the field does not contain a valid TVD connector ID, the following action is taken when you run a simulation:

If the network contains exactly one TVD connector that has rainfall as its output, that rainfall is applied in the simulation. This makes the assumption that if there is only one such TVD connector, you will want to apply it to the whole model.
If the network contains more than one TVD connector that has rainfall as its output, rainfall from the TVD connector with the alphabetically-first ID is applied in the simulation. A warning is included in the simulation log file.

When using TSDB spatial rainfall data, the above rules are overridden and rainfall is allocated to each subcatchment based on its location (given by its X,Y fields or by the location of drainage node if these are not set) or on the area covered by the subcatchment (if you use the option for area-averaged rainfall )

rainfall_profile

Text

Evaporation profile

The source of the evaporation data to be applied to the subcatchment during a simulation. The interpretation of this field depends on whether you are using a Rainfall Event or TSDB data for simulation.

Rainfall Event

This specifies the name of the evaporation profile which is applied to this subcatchment during a simulation.

Each profile within a Rainfall Event has a unique name.

If no evaporation profile is specified, it is assumed that the evaporation profile is the same as the Rainfall profile.

If an evaporation profile is defined but does not match any profile IDs in the evaporation data in the event, then evaporation will be set from the first profile.

Note

If the routing model is PDM, then SIM calculates the current evaporation rate for a subcatchment regardless of the time delay of the PDM descriptor if a valid evaporation profile is specified.

ReFH routing does not support independent evaporation.

If the Rainfall has an absolute start time, then so must evaporation data.

TSDB Data

This field specifies the name of the TVD connector that applies evaporation to this subcatchment.

evaporation_profile

Text

Use area-averaged rain

Applicable when using spatial rainfall from Events or TSDB.

Check this option to calculate rainfall for the subcatchment as the area-average of the rainfall of all rainfall polygons or radar cells that overlap the subcatchment. Any areal reduction/calibration factors set for the rainfall polygons are incorporated in the calculation of the area-averaged rainfall.

A rainfall profile is created for each subcatchment which is then passed to the simulation engine.

If this option is not checked, the rainfall polygon or radar cell that contains the centroid of the subcatchment will be used to provide rainfall data for the entire subcatchment. The rainfall rate for every radar cell is sent to the simulation engine as a separate rainfall profile, and the engine checks the centroids to determine which profile to use.

See Spatially Varying Rainfall and Using Spatial Rainfall in Simulations for further details.

Note

The simulation engine can process up to 2,147,483,647 TSDB generated rainfall profiles in a single simulation. Therefore if radar images with more cells than this are imported, spatial rain zones must be used to crop them to less than 2,147,483,647 cells for any given simulation (and similarly for subcatchment-averaged rainfall, where per-subcatchment profiles also need to be taken into account).

area_average_rain

Boolean

Dimension

This field is required by the Large Catchment runoff model and the Desbordes runoff model (representing catchment length) and the SWMM runoff model (representing catchment width). It is not used by the standard Wallingford Procedure runoff model or the SPRINT runoff model.

Calculated as the radius of a circle with area = Contributing Area.

catchment_dimension

Double

ReFH/ReFH2 Parameters

A series of records that define the ReFH parameters for the subcatchment. The records are entered on the Calculate ReFH/ReFH2 Parameters Dialog.

Catchment descriptors can be loaded from the FEH CD-ROM or downloaded from the web. See Importing Catchment Parameters from the FEH CD or Web Service for further information.

Database Table Name: hw_sub_refh_desc

Show Columns	Database Names
	Size, Type and Units
	Defaults and Error Limits

Position in Data Structure	Field Name	Help Text	Database Field	Data Type	Error Upper Limit
1	BFIHOST	Catchment descriptor Baseflow index	bfihost	Double	1
2	PROPWET	Catchment descriptor Proportion of time the catchment soil moisture deficit (SMD) was below 6mm during the period 1961-1990.	propwet	Double	1
3	DPLBAR	Catchment descriptor Mean drainage path length	dplbar	Double
4	DPSBAR	Catchment desciptor Mean drainage path slope	dpsbar	Double
5	URBEXT1990	Extent of urban and suburban land cover. Value derived from Land cover data based on satellite imagery taken around 1990	urbext1990	Double	1
6	URBEXT2000	Extent of urban and suburban land cover. Value derived from CEH LAnd Cover Map 2000	urbext2000	Double	1
7	Urban extent choice	Select URBEXT1990 or URBEXT2000	urbext_choice	Long Integer	1
8	Cmax method	Cmax calculation option: Design - Cmax is calculated using catchment descriptors. Cmax Value is calculated Cmax multiplied by Cmax factor User - user entered value specified in Cmax Value field is used Cmax Value field corresponds to subcatchment Maximum Soil Moisture Capacity field.	cmax_method	Long Integer	1
9	Cmax factor	Multiplying factor applied to calculated Cmax design value	cmax_factor	Double
10	Tp method	Tp calculation option: Design - Tp is calculated using catchment descriptors. Tp Value is calculated Tp multiplied by Tp factor User - user entered value specified in Tp Value field is used Tp Value field corresponds to subcatchment Time to Peak field.	tp_method	Long Integer	1
11	Tp factor	Multiplying factor applied to calculated Tp design value	tp_factor	Double
12	Up method	Up calculation option: Design - standard value of 0.65 is used. Up Value is 0.65 multiplied by Up factor User - user entered value specified in Up Value field is used Up Value field corresponds to subcatchment Unit Hydrograph Peak field.	up_method	Long Integer	1
13	Up factor	Multiplying factor applied to calculated Up design value	up_factor	Double
14	Uk method	Uk calculation option: Design - standard factor of 0.8 is used. Uk Value is 0.8 multiplied by Uk factor User - user entered value specified in Uk Value field is used Uk Value field corresponds to subcatchment Degree of Kink field.	uk_method	Long Integer	1
15	Uk factor	Multiplying factor applied to calculated Uk design value	uk_factor	Double
16	Bl method	Bl calculation option: Design - Bl is calculated using catchment descriptors. Bl Value is calculated Bl multiplied by Bl factor User - user entered value specified in Bl Value field is used Bl Value field corresponds to subcatchment Baseflow Lag field.	bl_method	Long Integer	1
17	Bl factor	Multiplying factor applied to calculated Bl design value	bl_factor	Double
18	Br method	Br calculation option: Design - Br is calculated using catchment descriptors. Br Value is calculated Br multiplied by Br factor User - user entered value specified in Br Value field is used Br Value field corresponds to subcatchment Baseflow Recharge field.	br_method	Long Integer	1
19	Br factor	Multiplying factor applied to calculated Br design value	br_factor	Double

refh_descriptors

Array

RTK hydrograph

The name of the RTK Hydrograph associated with the subcatchment.

Any RTK Hydrographs already defined can be selected from the dropdown list. Alternatively, a new one can be added or an existing one modified using the button located to the left of the field. This displays the non-visual object menu, from which you can select the appropriate option.

For model networks created using Version 8 onwards, or updated pre-version 8 ones, or ones copied from another database:

As SWMM5 associates RDII (Rainfall Derived Infiltration and Inflow) with nodes, ensure that the Drains to field is set to Node.
Only one RTK hydrograph can be specified for any subcatchment that drains to the same node.
All subcatchments which use the same RTK hydrograph must also use the same Rainfall profile.

unit_hydrograph_id

Text

Snow pack

The name of the Snow Pack associated with the subcatchment.

Any Snow Pack already defined can be selected from the dropdown list. Alternatively, a new one can be added or an existing one modified using the button located to the left of the field. This displays the non-visual object menu, from which you can select the appropriate option.

snow_pack_id

Text

Baseflow calculation

Baseflow calculation method.

Used when runoff volume type of runoff surfaces referenced by associated land use is set to SRM.

Database Value	Description	Help Text
PDM	PDM	Calculate baseflow using PDM model.
None	None	Do not carry out baseflow calculation.

baseflow_calc

Text

PDM

Soil moisture deficit

Source of soil moisture deficit values.

Used when runoff volume type of runoff surfaces referenced by associated land use is set to SRM.

Database Value	Description	Help Text
PDM	PDM	Obtain soil moisture deficit values from output from a PDM model.
Event	Event	Obtain soil moisture deficit values from Soil Moisture Deficit Data profiles in the Rainfall Event Editor

soil_moist_def

Text

PDM

SRM runoff coefficient

Surface runoff coefficient used in the calculation of effective rainfall.

Used when runoff volume type of runoff surfaces referenced by associated land use is set to SRM.

srm_runoff_coeff

Double

SRM linear time constant 1

Time constant of cascade of two linear reservoirs.

Used when runoff volume type of runoff surfaces referenced by associated land use is set to SRM.

srm_k1

Double

HOURS

15.0

SRM linear time constant 2

Time constant of cascade of two linear reservoirs.

Used when runoff volume type of runoff surfaces referenced by associated land use is set to SRM.

srm_k2

Double

HOURS

3.0

SRM time delay

Delay applied to rainfall start time.

Used when runoff volume type of runoff surfaces referenced by associated land use is set to SRM.

srm_tdly

Double

HOURS

0.0

ARMA ID

The name of the ARMA error prediction model associated with the subcatchment.

An existing ARMA ID can be selected from the dropdown list. Alternatively, a new one can be added or an existing one modified using the button located to the left of the field. This displays the non-visual object menu, from which you can select the appropriate option.

arma_id

Text

Output lag

The fixed amount of time to delay the outflow from a subcatchment to its Drains to destination.

output_lag

Double

Min

Bypass runoff

Enabled when the Drains to field is set to Subcatchment.

A check in the box indicates that the outflow from a subcatchment that drains to another subcatchment is added to the total outflow of the Drains to destination subcatchment. If unchecked, the outflow will be applied as an additional input to the runoff surfaces of the destination subcatchment.

bypass_runoff

Boolean

Degree urbanisation

Enabled when the Routing model is set to RAFTS and the Per-surface RAFTS box is unchecked.

A fraction between 0.0 and 2.0, which describes the degree of urbanisation for the subcatchment. See the RAFTS Routing Model for further information.

degree_urbanisation

Double

RAFTS adapt factor

Enabled when the Routing model is set to RAFTS and the Per-surface RAFTS box is unchecked.

A calibration factor used to calculate the storage factor that is output for each subcatchment. See the RAFTS Routing Model for further information.

rafts_adapt_factor

Double

RAFTS B

Enabled when the Routing model is set to RAFTS and the Per-surface RAFTS box is unchecked.

The storage delay time coefficient. See the RAFTS Routing Model for further information.

rafts_b

Double

RAFTS n

Enabled when the Routing model is set to RAFTS.

A storage non-linear exponent. See the RAFTS Routing Model for further information.

rafts_n

Double

-0.285

Unit hydrograph definition

Method of calculation of Unit Hydrograph:

Database Value	Description	Help Text
Clark	Clark	For use with Clark Unit Hydrograph Routing Model
Desbordes-Tc	Desbordes-Tc	For use with Unit Hydrograph Routing Model
Giandotti-Tc	Giandotti-Tc	For use with Unit Hydrograph Routing Model
Kirpich-Tc	Kirpich-Tc	For use with Unit Hydrograph Routing Model
Passini-Tc	Passini-Tc	For use with Unit Hydrograph Routing Model
Rational	Rational	For use with Unit Hydrograph Routing Model
ReFH	ReFH	For use with ReFH Routing Model
SCS-Forest-Tc	SCS-Forest-Tc	For use with Unit Hydrograph Routing Model
SCS-Rural-Tc	SCS-Rural-Tc	For use with Unit Hydrograph Routing Model
SCS-User-Tc	SCS-User-Tc	For use with SCS Unit Hydrograph Routing Model
Snyder	Snyder	For use with Snyder Unit Hydrograph Routing Model
User-Tc	User-Tc	For use with Unit Hydrograph Routing Model
User-Tp-Tb	User-Tp-Tb	For use with Unit Hydrograph Routing Model or SCS Unit Hydrograph Routing Model

uh_definition

Text

User-Tp-Tb

Time of concentration method

Enabled when Unit hydrograph definition is set to Rational.

Method for calculating Time of concentration, tc (see Unit Hydrograph Model for details).

Database Value	Description	Help Text
User	User	Set value for Time of concentration, tc manually
Kraven	Kraven	Calculate Time of concentration, tc using the Kraven method
Uniform	Uniform flow velocity	Calculate Time of concentration, tc using the Uniform velocity method
PWRI	PWRI	Calculate Time of concentration, tc by specifying a PWRI coefficient

tc_method

Text

Overland flow time

Enabled when Unit hydrograph definition is set to Rational and Time of concentration method is set to Kraven or Uniform.

Travel time of overland flow.

See Unit Hydrograph Model for details.

overland_flow_time

Double

MIN

0.01

Flood wave celerity

Enabled when Unit Hydrograph Definition is set to Rational and Time of concentration method is set to Kraven.

Velocity of flood wave.

See Unit Hydrograph Model for details.

flood_wave_celerity

Double

PWRI coefficient

Enabled when Unit Hydrograph Definition is set to Rational and Time of concentration method is set to PWRI.

Coefficient for calculating Time of concentration, tc.

See Unit Hydrograph Model for details.

pwri_coefficient

Double

RS_HOURS

0.00001

Time of concentration, tc

Subcatchment response time. Used to define Unit Hydrograph.

time_of_concentration

Double

Timestep factor

Timestep factor. Used to define Unit Hydrograph.

tc_timestep_factor

Double

1.0

Time to peak factor

Time to peak factor. Used to define Unit Hydrograph.

tc_time_to_peak_factor

Double

1.0

Unit hydrograph peak

The dimensionless instantaneous unit hydrograph ordinate at time to peak.

If the Unit Hydrograph Definition is set to ReFH, then the Unit hydrograph peak is calculated via the Calculate ReFH Parameters Dialog.

See ReFH Unit Hydrograph Model for details about the model.

uh_peak

Double

Degree of kink

The dimensionless instantaneous unit hydrograph 'kink' factor.

If the Unit Hydrograph Definition is set to ReFH, then the Degree of kink is calculated via the Calculate ReFH Parameters Dialog.

See ReFH Unit Hydrograph Model for details about the model.

uh_kink

Double

Time to peak, tp

Time of peak flow. Used to define Unit Hydrograph.

If the Unit Hydrograph Definition is set to ReFH, then the Time to peak, tp is calculated via the Calculate ReFH Parameters Dialog.

time_to_peak

Double

99999999

Base time, tb

Total runoff time for unit hydrograph.

base_time

Double

99999999

Peaking coefficient

Enabled when Unit Hydrograph Definiton is set to Snyder.

Coefficient that represents the variation of unit hydrograph peak with subcatchment characteristics.

See Snyder Unit Hydrograph Model for details.

peaking_coeff

Double

0.4

0.94

Equivalent Manning's n

Enabled when:

The associated runoff surface Routing model is set to Non-linear.
May be used to calculate Storage factor K and Lag time tl.
See Non-Linear Routing Model for details.
The Unit hydrograph definition is set to Rational and Time of concentration method is set to Uniform.
Used in the calculation of Time of concentration, tc.
See Unit Hydrograph Model for details.
The associated runoff surface Routing model is set to RAFTS and the Per-surface RAFTS box is unchecked.
May be used in the calculation of RAFTS B on a subcatchment basis. The specified value must be within the range of 0.01 to 0.1. A default value of 0.025 is used if no other value is specified when the Routing model is set to RAFTS and the Per-surface RAFTS box is unchecked.

equivalent_roughness

Double

Hydraulic radius

Enabled when:

The associated runoff surface Routing model is set to Non-linear and Lag time method is set to Flood velocity.
Used to calculate Lag time, tl.
See Non-Linear Routing Model for details.
The Unit Hydrograph Definition is set to Rational and Time of concentration method is set to Uniform.
Used in the calculation of Time of concentration, tc.
See Unit Hydrograph Model for details.

hydraulic_radius

Double

Lag time, tl

Time from the centroid of the excess rainfall to the hydrograph peak.

Enabled when Unit Hydrograph Definiton is set to Snyder or Clark. See Snyder Unit Hydrograph Model or Clark Model for details.

Also enabled when Unit Hydrograph Definiton is set to Non-linear and Lag time method is set to User. See Non-Linear Routing Model for details.

lag_time

Double

99999999

Lag time method

Enabled when associated runoff surface Routing model is set to Non-linear.

Method used to calculate lag time:

Database Value

Description

Help Text

User

Value specified in Lag time, tl field is used.

Kimura

Kimura method is used to calculate lag time.

See Non-Linear Routing Model for details.

Flood velocity

Flood velocity method is used to calculate lag time.

See Non-Linear Routing Model for details.

lag_time_method

Text

Kimura

Non-linear routing method

Enabled when associated runoff surface Routing model is set to Non-linear.

Method used to calculate K, p coefficients:

Database Value

Description

Help Text

User

Value specified in Storage factor K and Exponent e fields are used.

Izzard

Izzard method is used to calculate K, p coefficients.

See Non-Linear Routing Model for details.

Equivalent roughness

Equivalent roughness method is used to calculate K, p coefficients.

See Non-Linear Routing Model for details.

non-linear_routing_method

Text

Izzard

Storage factor K

Enabled when associated runoff surface Routing model is set to Cascade or Non-linear and the Non-linear routing method set to User.

Characteristic coefficient of catchment. See the Non-Linear Routing Model and the Cascade Routing Model for further information.

storage_factor

Double

0.000001

Internal routing

Choose the method by which the surface of the subcatchment is to drain. Set to:

Direct to drain directly to the outlet of the subcatchment

To previous to drain the impervious surfaces of the subcatchment to the previous surfaces of the same subcatchment

To impervious to drain the pervious surfaces of the subcatchment to the imprevious surfaces of the same subcatchment

internal_routing

Text

Direct

Runoff routed internally (%)

Enabled when Internal routing is set to To pervious or To impervious, and determines what percentage of the runoff is routed to the selected surface. The remaining runoff is routed directly to the outlet.

percent_routed

Double

100

Exponent p

Enabled when associated runoff surface Routing model is set to Non-linear.

Characteristic coefficient of catchment.

See Non-Linear Routing Model for details.

storage_exponent

Double

0.000001

Per-surface RAFTS B

Enabled when Routing model is set to RAFTS.

Indicates if RAFTS B routing is applied on a runoff surface or a subcatchment basis. A check (x) indicates that RAFTS B routing is applied on a per surface basis. See the RAFTS Routing Model for details.

rafts_per_surface

Boolean

Connectivity (%)

The percentage of foul flow for this subcatchment that drains into the system. Foul flow is derived from population, per capita flow and profile. If you leave this field blank, the software uses the default from the land use definition

connectivity

Long Integer

100

Wastewater profile

The reference for the wastewater profile that applies to this subcatchment. This refers to the profile number in the Wastewater event. You associate a Wastewater Event with the network when setting up a simulation. See Editing Trade and Waste Water Events and scheduling a Run.

The wastewater profile contains dimensionless values that the software multiplies by the base wastewater flow to give a time varying aspect. If you leave this field blank, the software uses the default from the land use definition. If you enter a zero in this field, the software does not apply foul flow to this subcatchment

wastewater_profile

Long Integer

999

Population

The number of people in the subcatchment. The software uses this, together with the average flow per person and diurnal variation in the wastewater profile, to determine the amount of foul flow.

Population can be defined to a precision of two decimal places. This supports the use of much more detailed models. You could even define individual properties as subcatchments.

If you leave this field blank the software calculates the population from the contributing area and the population density in the land use definition

population

Double

SUDS controls

A series of records defining the SUDS controls structure parameters for the subcatchment. The records are entered on the Subcatchment SUDS Controls grid which is displayed by clicking on the button. See the Subcatchment SUDS Controls Grid topic for further information.

Each SUDS structure may have one or more SUDS control objects associated with it. The SUDS control objects are defined on the SUDS control tab of the Subcatchment Grid. However, a new SUDS control can also be added using the button located to the left of the field. This displays the Insert New SUDS control Object option that allows you to add the new object.

Trade flow

The nominal trade flow for the subcatchment. Throughout a simulation, the software multiplies this by the time varying factors from the trade profile, and the trade profile factor.

trade_flow

Double

Additional foul flow

An additional flow that is added to the nominal wastewater flow (NWF) draining into the system (NWF= per capita flow X population X connectivity). The time varying multiplier from the wastewater profile applies to the total wastewater flow, (total wastewater flow = NWF plus additional foul flow).

additional_foul_flow

Double

Base flow

The base infiltration flow into the system from this subcatchment. This is a constant inflow into the system.

base_flow

Double

Trade profile

The reference for the trade profile that applies to this subcatchment. This refers to the profile number in the Trade event. You associate a Trade Event with the network when setting up a simulation. See Editing Trade and Waste Water Events and Scheduling a Run.

A trade profile represents the flow from an industrial source. It contains dimensionless values that the software multiplies by the trade flow to give a time varying aspect.

trade_profile

Long Integer

999

Ground infiltration ID

The name of the ground infiltration type for the subcatchment.

Any ground infiltation objects already defined can be selected from the dropdown list. Alternatively, a new one can be added or an existing one modified using the button located to the left of the field. This displays the non-visual object menu, from which you can select the appropriate option.

ground_id

Text

Ground infiltration node

The name of the node which receives the ground water inflow within this subcatchment. This field is only enabled when a Ground infiltration ID has been specified. Choose a Ground infiltration node from the drop-down list. If no Ground infiltration node is specified, then any groundwater inflow goes to the same destination as the runoff.

Note

The ground water cannot flow to an outfall type of node.

ground_node

Text

Baseflow lag

Baseflow Lag

If the Unit Hydrograph Definition is set to ReFH, then the Baseflow Lag is calculated via the Calculate ReFH Parameters Dialog.

baseflow_lag

Double

RS_HOURS

Baseflow recharge

Baseflow recharge donor correction (multiplying factor)

If the Unit Hydrograph Definition is set to ReFH, then the Baseflow recharge is calculated via the Calculate ReFH Parameters Dialog.

baseflow_recharge

Double

Surfaces management

The Surfaces Management Editor displays the subcatchment runoff areas in a graphical format.

Runoff area, Area measurement type and Land use ID values can be viewed and edited in the Surfaces Management Editor.

surface_management

Array

Land use ID

The name of the land use that applies to this subcatchment. The land use definition contains default values for various subcatchment parameters and a list of Runoff Surfaces available in the subcatchment.

Any Land use objects already defined can be selected from the dropdown list. Alternatively, a new one can be added or an existing one modified using the button located to the left of the field. This displays the non-visual object menu, from which you can select the appropriate option.

New land use and runoff surfaces can also be defined from the grid editor using the Land use and Runoff surface tabs.

land_use_id

Text

PDM Descriptor

The name of the PDM descriptor that applies to this subcatchment.

The PDM descriptor contains all the PDM model parameters required when runoff volume type of the runoff surface referenced by the associated land use is set to PDM, or when Baseflow calculation is set to PDM.

Any PDM Descriptors already defined can be selected from the dropdown list. Alternatively, a new one can be added or an existing one modified using the button located to the left of the field. This displays the non-visual object menu, from which you can select the appropriate option.

pdm_descriptor_id

Text

Build-up/washoff land uses

A series of records that define the SWMM build-up/washoff land uses which apply to this subcatchment. These are entered on a grid which is displayed by clicking on the button.

Database Table Name: hw_swmm_coverage

Show Columns	Database Names
	Size, Type and Units
	Defaults and Error Limits

Field Name	Help Text	Database Field	Data Type	Size	Units	Precision	Default	Error Lower Limit	Error Upper Limit	Warning Lower Limit	Warning Upper Limit
Build-up/washoff land use	The SWMM Build-up/Washoff Land Use model can be selected from a list.	land_use	Text	64
Area	The percentage of this subcatchment that the SWMM build-up/washoff land use applies to.	sediment_fraction	Text	4			0	0	100

swmm_coverage

Structure

Area measurement type

Database Value	Description
Absolute	Absolute	area for each surface type is specified as an absolute value
Percent	Percent	area for each surface type is specified as a percentage of the contributing area

area_measurement_type

Text

Absolute

Runoff area 1 (%)

The Runoff Area fields define how much of the subcatchment belongs to the particular runoff surface type. The Runoff Area (%) fields are only populated if the Area Measurement Type is Percent. The value is a percentage of the contributing area.

Runoff Surface IDs defined in the Land Use associated with the subcatchment are displayed read-only on the property sheet next to the appropriate area value. To change the runoff surfaces edit the current Land Use or attach a different Land Use.

Define the runoff characteristics of the Runoff Surface on the Runoff Surface Grid Window in the Subcatchments Grid.

area_percent_1

Double

Runoff area 2 (%)

see Runoff area 1

area_percent_2

Double

Runoff area 3 (%)

see Runoff area 1

area_percent_3

Double

Runoff area 4 (%)

see Runoff area 1

area_percent_4

Double

Runoff area 5 (%)

see Runoff area 1

area_percent_5

Double

Runoff area 6 (%)

see Runoff area 1

area_percent_6

Double

Runoff area 7 (%)

see Runoff area 1

area_percent_7

Double

Runoff area 8 (%)

see Runoff area 1

area_percent_8

Double

Runoff area 9 (%)

see Runoff area 1

area_percent_9

Double

Runoff area 10 (%)

see Runoff area 1

area_percent_10

Double

Runoff area 11 (%)

see Runoff area 1

area_percent_11

Double

Runoff area 12 (%)

see Runoff area 1

area_percent_12

Double

Runoff area 1 absolute

The Runoff Area fields define how much of the subcatchment belongs to the particular runoff surface type. The Runoff Area (Absolute) fields are only populated if the Area Measurement Type is Absolute.

The InfoWorks ICM Native unit for these fields is Hectares.

Define the runoff characteristics of the Runoff Surface on the Runoff Surface Grid Window in the Subcatchments Grid.

area_absolute_1

Double

Runoff area 2 absolute

see Runoff area 1 absolute

area_absolute_2

Double

Runoff area 3 absolute

see Runoff area 1 absolute

area_absolute_3

Double

Runoff area 4 absolute

see Runoff area 1 absolute

area_absolute_4

Double

Runoff area 5 absolute

see Runoff area 1 absolute

area_absolute_5

Double

Runoff area 6 absolute

see Runoff area 1 absolute

area_absolute_6

Double

Runoff area 7 absolute

see Runoff area 1 absolute

area_absolute_7

Double

Runoff area 8 absolute

see Runoff area 1 absolute

area_absolute_8

Double

Runoff area 9 absolute

see Runoff area 1 absolute

area_absolute_9

Double

Runoff area 10 absolute

see Runoff area 1 absolute

area_absolute_10

Double

Runoff area 11 absolute

see Runoff area 1 absolute

area_absolute_11

Double

Runoff area 12 absolute

see Runoff area 1 absolute

area_absolute_12

Double

Points

An array of X/Y values defining the geometry of the subcatchment

boundary_array

Array

Wallingford Procedure Model

Subcatchments Grid

Property Sheets

Spatially Varying Rainfall

Editing Trade and Waste Water Events