lid.h File Reference

Low-impact development controls, usage, and state. More...

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "infil.h"

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Classes
struct	TSurfaceLayer
struct	TPavementLayer
struct	TSoilLayer
struct	TStorageLayer
struct	TDrainLayer
struct	TDrainMatLayer
struct	TLidProc
struct	TWaterBalance
struct	TLidRptFile
struct	TLidUnit

Macros
#define	MAX_LAYERS   4

Enumerations
enum	LidTypes {   BIO_CELL ,   RAIN_GARDEN ,   GREEN_ROOF ,   INFIL_TRENCH ,   POROUS_PAVEMENT ,   RAIN_BARREL ,   VEG_SWALE ,   ROOF_DISCON }
enum	TimePeriod {   PREVIOUS ,   CURRENT }

Functions
void	lid_create (int lidCount, int subcatchCount)
	Allocate LID process definitions and per-subcatchment LID group storage.
void	lid_delete (void)
	Deletes all LID objects.
int	lid_readProcParams (char *tok[], int ntoks)
	Reads LID process information from line of input data file.
int	lid_readGroupParams (char *tok[], int ntoks)
	Reads input data for a LID unit placed in a subcatchment.
int	lid_setDrainParams (int lidIndex, double coeff, double expon, double offset)
	Updates the underdrain flow parameters of a LID process at runtime (API support). The drain parameters are read live each step (lidproc.c), so an edit takes effect on the next step.
void	lid_validate (void)
	Validates LID process and group parameters.
void	lid_initState (void)
	Initializes the internal state of each LID in a subcatchment.
void	lid_setOldGroupState (int subcatch)
	Saves the current drain flow rate for the LIDs in a subcatchment.
double	lid_getPervArea (int subcatch)
	Retrieves amount of pervious LID area in a subcatchment.
double	lid_getFlowToPerv (int subcatch)
	Retrieves flow returned from LID treatment to pervious area of a subcatchment.
double	lid_getDrainFlow (int subcatch, int timePeriod)
	Select the previous or current total LID drain flow of a subcatchment.
double	lid_getStoredVolume (int subcatch)
	Computes stored volume of water for all LIDs grouped within a subcatchment.
void	lid_addDrainLoads (int subcatch, double c[], double tStep)
	Add LID drain pollutant export and BMP removal to mass-balance totals.
void	lid_addDrainRunon (int subcatch)
	Route previous-period LID drain flow and pollutant loads to receiving subcatchments.
void	lid_addDrainInflow (int subcatch, double f)
	Add temporally interpolated LID drain inflows to conveyance nodes.
void	lid_getRunoff (int subcatch, double tStep)
	Advance LID units and compute runoff, drain and return flows.
void	lid_writeSummary (void)
	Writes summary of LID processes used to report file.
void	lid_writeWaterBalance (void)
	Writes a LID performance summary table to the project's report file.
void	lidproc_initWaterBalance (TLidUnit *lidUnit, double initVol)
	Initializes the water balance components of a LID unit.
double	lidproc_getOutflow (TLidUnit *lidUnit, TLidProc *lidProc, double inflow, double evap, double infil, double maxInfil, double tStep, double *lidEvap, double *lidInfil, double *lidDrain)
	Computes runoff outflow from a single LID unit.
void	lidproc_saveResults (TLidUnit *lidUnit, double ucfRainfall, double ucfRainDepth)
	Update LID water balance and optionally emit detailed report results.

Detailed Description

Low-impact development controls, usage, and state.

Author

Caleb Buahin caleb.nosp@m..bua.nosp@m.hin@g.nosp@m.mail.nosp@m..com (OpenSWMM maintenance and extensions)

Copyright

Copyright (c) 2026 Caleb Buahin. OpenSWMM contributions only; original EPA SWMM credits are retained.

License

Apache-2.0 for OpenSWMM contributions; original EPA SWMM provenance is retained.

Macro Definition Documentation

MAX_LAYERS

#define MAX_LAYERS   4

Enumeration Type Documentation

LidTypes

enum LidTypes

Enumerator
BIO_CELL
RAIN_GARDEN
GREEN_ROOF
INFIL_TRENCH
POROUS_PAVEMENT
RAIN_BARREL
VEG_SWALE
ROOF_DISCON

TimePeriod

enum TimePeriod

Enumerator
PREVIOUS
CURRENT

Function Documentation

lid_addDrainInflow()

void lid_addDrainInflow	(	int	j,
		double	f )

Add temporally interpolated LID drain inflows to conveyance nodes.

Parameters

[in]	j	Valid contributing subcatchment index.
[in]	f	Current-period interpolation weight, normally in [0, 1]; old values use weight 1 - f and the function does not clamp extrapolation.

Postcondition

Updates receiving Node.newLatFlow and newQual loading rates and wet-weather mass-balance totals, after applying drain pollutant removal.

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lid_addDrainLoads()

void lid_addDrainLoads	(	int	j,
		double	c[],
		double	tStep )

Add LID drain pollutant export and BMP removal to mass-balance totals.

Parameters

[in]	j	Valid contributing subcatchment index.
[in]	c	Borrowed Nobjects[POLLUT] concentration array, in pollutant mass per liter.
[in]	tStep	Runoff interval in seconds.

Postcondition

Updates loading totals for BMP_REMOVAL_LOAD and eligible RUNOFF_LOAD. Drain-to-pervious units are excluded; absent LID groups perform no action.

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lid_addDrainRunon()

void lid_addDrainRunon

(

int

j

)

Route previous-period LID drain flow and pollutant loads to receiving subcatchments.

Parameters

[in]

j

Valid contributing subcatchment index.

Postcondition

Adds drain runon and pollutant loading rates to configured receiving subcatchments. Uses oldDrainFlow and the source oldQual, adjusted by drain removal. No action is taken when the source has no LID group.

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lid_create()

void lid_create	(	int	lidCount,
		int	subcatchCount )

Allocate LID process definitions and per-subcatchment LID group storage.

Parameters

[in]	lidCount	Nonnegative number of LID process definitions.
[in]	subcatchCount	Nonnegative number of subcatchment group slots.

Postcondition

Initializes module pointers/counts and default layer properties. Each process receives a pollutant-removal array. Allocation failure sets ErrorCode to ERR_MEMORY and leaves partial allocations for lid_delete().

Precondition

Previous project LID storage has already been released.

lid_delete()

void lid_delete

(

void

)

Deletes all LID objects.

lid_getDrainFlow()

double lid_getDrainFlow	(	int	j,
		int	timePeriod )

Select the previous or current total LID drain flow of a subcatchment.

Parameters

[in]	j	Valid subcatchment/LidGroups index.
[in]	timePeriod	PREVIOUS selects oldDrainFlow; any other value selects newDrainFlow.

Returns

Drain flow in cubic feet per second, or zero when no LID group exists.

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lid_getFlowToPerv()

double lid_getFlowToPerv

(

int

j

)

Retrieves flow returned from LID treatment to pervious area of a subcatchment.

Parameters

[in]

j

Subcatchment index.

Returns

Flow returned to pervious area (cfs).

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lid_getPervArea()

double lid_getPervArea

(

int

j

)

Retrieves amount of pervious LID area in a subcatchment.

Parameters

[in]

j

Subcatchment index.

Returns

Amount of pervious LID area (ft2).

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lid_getRunoff()

void lid_getRunoff	(	int	j,
		double	tStep )

Advance LID units and compute runoff, drain and return flows.

Parameters

[in]	j	Valid subcatchment index with initialized runoff state.
[in]	tStep	Positive runoff interval in seconds.

Postcondition

Updates LID states, group newDrainFlow/flowToPerv, and shared evaporation, infiltration, inflow, runoff, drain and return volumes. Flow rates use cfs and interval volumes use cubic feet. Missing groups or lists return unchanged.

Note

Operates on shared current-subcatchment flux state and is not reentrant.

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lid_getStoredVolume()

double lid_getStoredVolume

(

int

j

)

Computes stored volume of water for all LIDs grouped within a subcatchment.

Parameters

[in]

j

Subcatchment index.

Returns

Stored volume of water (ft3).

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lid_initState()

void lid_initState

(

void

)

Initializes the internal state of each LID in a subcatchment.

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lid_readGroupParams()

int lid_readGroupParams	(	char *	toks[],
		int	ntoks )

Reads input data for a LID unit placed in a subcatchment.

Parameters

	toks	Array of string tokens.
[in]	ntoks	Number of tokens.

Returns

Error code Format of input data line is: Subcatch_ID LID_ID Number Area Width InitSat FromImp ToPerv (RptFile DrainTo FromPerv) where: Subcatch_ID = name of subcatchment LID_ID = name of LID process Number (n) = number of replicate units Area (x[0]) = area of each unit Width (x[1]) = outflow width of each unit InitSat (x[2]) = % that LID is initially saturated FromImp (x[3]) = % of impervious runoff sent to LID ToPerv (x[4]) = 1 if outflow goes to pervious sub-area; 0 if not RptFile = name of detailed results file (optional) DrainTo = name of subcatch/node for drain flow (optional) FromPerv (x[5]) = % of pervious runoff sent to LID.

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lid_readProcParams()

int lid_readProcParams	(	char *	toks[],
		int	ntoks )

Reads LID process information from line of input data file.

Parameters

	toks	Array of string tokens.
[in]	ntoks	Number of tokens.

Returns

Error code Format for first line that defines a LID process is: LID_ID LID_Type Followed by some combination of lines below depending on LID_Type: LID_ID SURFACE parameters LID_ID PAVEMENT parameters LID_ID SOIL parameters LID_ID STORAGE parameters LID_ID DRAIN parameters LID_ID DRAINMAT parameters LID_ID REMOVALS parameters.

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lid_setDrainParams()

int lid_setDrainParams	(	int	lidIndex,
		double	coeff,
		double	expon,
		double	offset )

Updates the underdrain flow parameters of a LID process at runtime (API support). The drain parameters are read live each step (lidproc.c), so an edit takes effect on the next step.

Parameters

[in]	lidIndex	LID process index.
[in]	coeff	Underdrain flow coeff. (in/hr or mm/hr).
[in]	expon	Underdrain head exponent.
[in]	offset	Offset height of underdrain (in or mm).

Returns

0 if successful, 1 for a bad index, 2 for a bad value (units match readDrainData; the API wrapper maps the codes).

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lid_setOldGroupState()

void lid_setOldGroupState

(

int

j

)

Saves the current drain flow rate for the LIDs in a subcatchment.

Parameters

[in]

j

Subcatchment index.

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lid_validate()

void lid_validate

(

void

)

Validates LID process and group parameters.

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lid_writeSummary()

void lid_writeSummary

(

void

)

Writes summary of LID processes used to report file.

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lid_writeWaterBalance()

void lid_writeWaterBalance

(

void

)

Writes a LID performance summary table to the project's report file.

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lidproc_getOutflow()

double lidproc_getOutflow	(	TLidUnit *	lidUnit,
		TLidProc *	lidProc,
		double	inflow,
		double	evap,
		double	infil,
		double	maxInfil,
		double	tStep,
		double *	lidEvap,
		double *	lidInfil,
		double *	lidDrain )

Computes runoff outflow from a single LID unit.

Parameters

	lidUnit	Ptr. to specific LID unit being analyzed.
	lidProc	Ptr. to generic LID process of the LID unit.
[in]	inflow	Runoff rate captured by LID unit (ft/s).
[in]	evap	Potential evaporation rate (ft/s).
[in]	infil	Infiltration rate to native soil (ft/s).
[in]	maxInfil	Max. infiltration rate to native soil (ft/s).
[in]	tStep	Time step (sec).
[out]	lidEvap	Evaporation rate for LID unit (ft/s).
[out]	lidInfil	Infiltration rate for LID unit (ft/s).
[out]	lidDrain	Drain flow for LID unit (ft/s).

Returns

Surface runoff rate from the LID unit (ft/s).

For debugging only ******************************************** if (i == 0) { fprintf(Frpt.file, "\n WARNING 09: integration failed to converge at %s %s", theDate, theTime); fprintf(Frpt.file, "\n for LID %s placed in subcatchment %s.", theLidProc->ID, theSubcatch->ID); }

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lidproc_initWaterBalance()

void lidproc_initWaterBalance	(	TLidUnit *	lidUnit,
		double	initVol )

Initializes the water balance components of a LID unit.

Parameters

	lidUnit	A particular LID unit.
[in]	initVol	Initial water volume stored in the unit (ft).

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lidproc_saveResults()

void lidproc_saveResults	(	TLidUnit *	lidUnit,
		double	ucfRainfall,
		double	ucfRainDepth )

Update LID water balance and optionally emit detailed report results.

Parameters

[in,out]	lidUnit	Non-null borrowed current LID unit; its report-file state and saved result string may be updated.
[in]	ucfRainfall	Rate conversion from ft/s to authored in/hr or mm/hr.
[in]	ucfRainDepth	Depth conversion from feet to authored inches or millimeters.

Precondition

theLidUnit identifies the same active unit as lidUnit, and shared current fluxes/volumes were set by the immediately preceding evaluation.

Postcondition

Updates its water balance, HasWetLids and dry-period report tracking. Does not close report streams or check fprintf failures.

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