openswmm_infrastructure.h File Reference

OpenSWMM Engine — Infrastructure (Transects, Streets, Inlets, LIDs) C API. More...

#include "openswmm_engine.h"

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Functions
SWMM_ENGINE_API int	swmm_transect_add (SWMM_Engine engine, const char *id)
	Add a new transect for irregular cross-sections.
SWMM_ENGINE_API int	swmm_transect_set_roughness (SWMM_Engine engine, int idx, double n_left, double n_right, double n_channel)
	Set Manning's roughness for left overbank, right overbank, and channel.
SWMM_ENGINE_API int	swmm_transect_add_station (SWMM_Engine engine, int idx, double station, double elevation)
	Add a station–elevation data point to a transect.
SWMM_ENGINE_API int	swmm_transect_count (SWMM_Engine engine)
	Get the total number of transects in the model.
SWMM_ENGINE_API int	swmm_street_add (SWMM_Engine engine, const char *id)
	Add a new street cross-section definition.
SWMM_ENGINE_API int	swmm_street_set_params (SWMM_Engine engine, int idx, double t_crown, double h_curb, double sx, double n_road, double gutter_depres, double gutter_width, int sides, double back_width, double back_slope, double back_n)
	Set the geometric parameters for a street cross-section.
SWMM_ENGINE_API int	swmm_street_count (SWMM_Engine engine)
	Get the total number of street definitions in the model.
SWMM_ENGINE_API int	swmm_inlet_add (SWMM_Engine engine, const char *id, const char *type)
	Add a new inlet definition.
SWMM_ENGINE_API int	swmm_inlet_set_params (SWMM_Engine engine, int idx, double length, double width, const char *grate_type, double open_area, double splash_veloc)
	Set the geometric parameters for an inlet.
SWMM_ENGINE_API int	swmm_inlet_count (SWMM_Engine engine)
	Get the total number of inlet definitions in the model.
SWMM_ENGINE_API int	swmm_lid_add (SWMM_Engine engine, const char *id, int type)
	Add a new LID (Low Impact Development) control.
SWMM_ENGINE_API int	swmm_lid_set_surface (SWMM_Engine engine, int idx, double storage, double roughness, double slope)
	Set the surface layer properties for a LID control.
SWMM_ENGINE_API int	swmm_lid_set_soil (SWMM_Engine engine, int idx, double thick, double porosity, double fc, double wp, double ksat, double kslope)
	Set the soil layer properties for a LID control.
SWMM_ENGINE_API int	swmm_lid_set_storage (SWMM_Engine engine, int idx, double thick, double void_frac, double ksat)
	Set the storage layer properties for a LID control.
SWMM_ENGINE_API int	swmm_lid_set_drain (SWMM_Engine engine, int idx, double coeff, double expon, double offset)
	Set the underdrain properties for a LID control.
SWMM_ENGINE_API int	swmm_lid_count (SWMM_Engine engine)
	Get the total number of LID controls in the model.
SWMM_ENGINE_API int	swmm_lid_usage_add (SWMM_Engine engine, int subcatch_idx, int lid_idx, int number, double area, double width, double init_sat, double from_imperv)
	Assign a LID control to a subcatchment.

Detailed Description

OpenSWMM Engine — Infrastructure (Transects, Streets, Inlets, LIDs) C API.

Transect creation and station data, street parameters, inlet definitions, LID control layers, and LID usage assignment.

See also

openswmm_engine.h

Author

Caleb Buahin caleb.nosp@m..bua.nosp@m.hin@g.nosp@m.mail.nosp@m..com

Copyright

Copyright (c) 2026 HydroCouple. All rights reserved.

License\n MIT License

Function Documentation

swmm_inlet_add()

SWMM_ENGINE_API int swmm_inlet_add	(	SWMM_Engine	engine,
		const char *	id,
		const char *	type
	)

Add a new inlet definition.

Parameters

engine	Engine handle (SWMM_STATE_BUILDING).
id	Unique null-terminated identifier.
type	Inlet type string (e.g., "GRATE", "CURB", "SLOTTED", "CUSTOM").

Returns

SWMM_OK on success, or an error code.

swmm_inlet_count()

SWMM_ENGINE_API int swmm_inlet_count

(

SWMM_Engine

engine

)

Get the total number of inlet definitions in the model.

Parameters

engine

Engine handle.

Returns

Number of inlets, or -1 on error.

swmm_inlet_set_params()

SWMM_ENGINE_API int swmm_inlet_set_params	(	SWMM_Engine	engine,
		int	idx,
		double	length,
		double	width,
		const char *	grate_type,
		double	open_area,
		double	splash_veloc
	)

Set the geometric parameters for an inlet.

Parameters

engine	Engine handle.
idx	Zero-based inlet index.
length	Inlet length.
width	Inlet width.
grate_type	Grate type string (e.g., "P-50", "GENERIC").
open_area	Open area fraction (0–1).
splash_veloc	Splash-over velocity threshold.

Returns

SWMM_OK on success, or an error code.

swmm_lid_add()

SWMM_ENGINE_API int swmm_lid_add	(	SWMM_Engine	engine,
		const char *	id,
		int	type
	)

Add a new LID (Low Impact Development) control.

LID types: 0=BIO_CELL, 1=RAIN_GARDEN, 2=GREEN_ROOF, 3=INFIL_TRENCH, 4=PERM_PAVEMENT, 5=RAIN_BARREL, 6=ROOFTOP_DISCONN, 7=VEGETATIVE_SWALE.

Parameters

engine	Engine handle (SWMM_STATE_BUILDING).
id	Unique null-terminated identifier.
type	LID type code.

Returns

SWMM_OK on success, or an error code.

swmm_lid_count()

SWMM_ENGINE_API int swmm_lid_count

(

SWMM_Engine

engine

)

Get the total number of LID controls in the model.

Parameters

engine

Engine handle.

Returns

Number of LID controls, or -1 on error.

swmm_lid_set_drain()

SWMM_ENGINE_API int swmm_lid_set_drain	(	SWMM_Engine	engine,
		int	idx,
		double	coeff,
		double	expon,
		double	offset
	)

Set the underdrain properties for a LID control.

Parameters

engine	Engine handle.
idx	Zero-based LID index.
coeff	Drain coefficient.
expon	Drain exponent.
offset	Drain offset height above the storage layer bottom.

Returns

SWMM_OK on success, or an error code.

swmm_lid_set_soil()

SWMM_ENGINE_API int swmm_lid_set_soil	(	SWMM_Engine	engine,
		int	idx,
		double	thick,
		double	porosity,
		double	fc,
		double	wp,
		double	ksat,
		double	kslope
	)

Set the soil layer properties for a LID control.

Parameters

engine	Engine handle.
idx	Zero-based LID index.
thick	Soil thickness.
porosity	Soil porosity (fraction).
fc	Field capacity (fraction).
wp	Wilting point (fraction).
ksat	Saturated hydraulic conductivity.
kslope	Slope of the conductivity–moisture curve.

Returns

SWMM_OK on success, or an error code.

swmm_lid_set_storage()

SWMM_ENGINE_API int swmm_lid_set_storage	(	SWMM_Engine	engine,
		int	idx,
		double	thick,
		double	void_frac,
		double	ksat
	)

Set the storage layer properties for a LID control.

Parameters

engine	Engine handle.
idx	Zero-based LID index.
thick	Storage layer thickness.
void_frac	Void fraction (porosity of gravel/aggregate).
ksat	Seepage rate through the storage layer bottom.

Returns

SWMM_OK on success, or an error code.

swmm_lid_set_surface()

SWMM_ENGINE_API int swmm_lid_set_surface	(	SWMM_Engine	engine,
		int	idx,
		double	storage,
		double	roughness,
		double	slope
	)

Set the surface layer properties for a LID control.

Parameters

engine	Engine handle.
idx	Zero-based LID index.
storage	Surface storage depth.
roughness	Surface Manning's n.
slope	Surface slope (fraction).

Returns

SWMM_OK on success, or an error code.

swmm_lid_usage_add()

SWMM_ENGINE_API int swmm_lid_usage_add	(	SWMM_Engine	engine,
		int	subcatch_idx,
		int	lid_idx,
		int	number,
		double	area,
		double	width,
		double	init_sat,
		double	from_imperv
	)

Assign a LID control to a subcatchment.

Multiple LID units of the same or different types can be assigned to a single subcatchment.

Parameters

engine	Engine handle.
subcatch_idx	Zero-based subcatchment index.
lid_idx	Zero-based LID control index.
number	Number of replicate LID units.
area	Area of each LID unit in project area units.
width	Top width of the overland flow surface per unit.
init_sat	Initial saturation of the soil layer (0–1).
from_imperv	Fraction of impervious area runoff treated by this LID (0–1).

Returns

SWMM_OK on success, or an error code.

swmm_street_add()

SWMM_ENGINE_API int swmm_street_add	(	SWMM_Engine	engine,
		const char *	id
	)

Add a new street cross-section definition.

Parameters

engine	Engine handle (SWMM_STATE_BUILDING).
id	Unique null-terminated identifier.

Returns

SWMM_OK on success, or an error code.

swmm_street_count()

SWMM_ENGINE_API int swmm_street_count

(

SWMM_Engine

engine

)

Get the total number of street definitions in the model.

Parameters

engine

Engine handle.

Returns

Number of streets, or -1 on error.

swmm_street_set_params()

SWMM_ENGINE_API int swmm_street_set_params	(	SWMM_Engine	engine,
		int	idx,
		double	t_crown,
		double	h_curb,
		double	sx,
		double	n_road,
		double	gutter_depres,
		double	gutter_width,
		int	sides,
		double	back_width,
		double	back_slope,
		double	back_n
	)

Set the geometric parameters for a street cross-section.

Parameters

engine	Engine handle.
idx	Zero-based street index.
t_crown	Crown thickness (rise of the crown above the gutter).
h_curb	Curb height.
sx	Cross slope of the roadway.
n_road	Manning's n for the road surface.
gutter_depres	Gutter depression depth.
gutter_width	Gutter width.
sides	Number of sides (1 or 2).
back_width	Backing (sidewalk) width.
back_slope	Backing slope.
back_n	Manning's n for the backing area.

Returns

SWMM_OK on success, or an error code.

swmm_transect_add()

SWMM_ENGINE_API int swmm_transect_add	(	SWMM_Engine	engine,
		const char *	id
	)

Add a new transect for irregular cross-sections.

Parameters

engine	Engine handle (SWMM_STATE_BUILDING).
id	Unique null-terminated identifier.

Returns

SWMM_OK on success, or an error code.

swmm_transect_add_station()

SWMM_ENGINE_API int swmm_transect_add_station	(	SWMM_Engine	engine,
		int	idx,
		double	station,
		double	elevation
	)

Add a station–elevation data point to a transect.

Stations must be added in order from left to right across the cross-section.

Parameters

engine	Engine handle.
idx	Zero-based transect index.
station	Horizontal distance (station) from a reference.
elevation	Elevation at this station.

Returns

SWMM_OK on success, or an error code.

swmm_transect_count()

SWMM_ENGINE_API int swmm_transect_count

(

SWMM_Engine

engine

)

Get the total number of transects in the model.

Parameters

engine

Engine handle.

Returns

Number of transects, or -1 on error.

swmm_transect_set_roughness()

SWMM_ENGINE_API int swmm_transect_set_roughness	(	SWMM_Engine	engine,
		int	idx,
		double	n_left,
		double	n_right,
		double	n_channel
	)

Set Manning's roughness for left overbank, right overbank, and channel.

Parameters

engine	Engine handle.
idx	Zero-based transect index.
n_left	Manning's n for the left overbank.
n_right	Manning's n for the right overbank.
n_channel	Manning's n for the main channel.

Returns

SWMM_OK on success, or an error code.