Infrastructure (transects, streets, inlets, LIDs)#

Note

Engine: OpenSWMM 6 — refactored. Documents openswmm.engine.Infrastructure.

The Infrastructure class consolidates the SWMM features that configure complex hydraulic infrastructure:

Transects — irregular channel cross-sections ([TRANSECTS]).
Streets — HEC-22 street geometry for inlet capture ([STREETS]).
Inlets — grate / curb / slot inlets and their capacity curves ([INLETS] / [INLET_USAGE]).
LIDs — Low-Impact Development controls ([LID_CONTROLS] / [LID_USAGE]): bio-retention, infiltration trench, porous pavement, rain gardens, green roofs, swales.

Reference: openswmm_infrastructure.h.

Class signature#

class Infrastructure:
    def __init__(self, solver: Solver) -> None: ...

Key methods#

Transects#

Method	Action
`transect_count()`	Number of registered transects.
`transect_add(transect_id)()`	Create a new transect; returns its index.
`transect_set_roughness(idx, n_left, n_right, n_channel)()`	Manning’s n for left bank / right bank / channel.
`transect_add_station(idx, station, elevation)()`	Append a station-elevation point.

Streets#

Method	Action
`street_count()`	Number of registered street geometries.
`street_add(street_id)()`	Create a new street; returns its index.
`street_set_params(idx, t_crown, h_curb, sx, n_road, gutter_depres, gutter_width, sides, back_width, back_slope, back_n)()`	Crown / curb / cross-slope / Manning’s n, gutter geometry, backing geometry.

Inlets#

Method	Action
`inlet_count()`	Number of registered inlets.
`inlet_add(inlet_id, inlet_type)()`	Create a new inlet; returns its index.
`inlet_set_params(idx, length, width, grate_type, open_area, splash_veloc)()`	Geometric parameters plus the grate-type identifier string (e.g. `"P_BAR-50"`).

LID controls (definitions)#

Method	Action
`lid_count()`	Number of registered LID controls.
`lid_add(lid_id, lid_type)()`	Create a new LID control; returns its index. `lid_type` is a `LidType` code.
`lid_set_surface(idx, storage, roughness, slope)()`	Surface layer.
`lid_set_soil(idx, thick, porosity, fc, wp, ksat, kslope)()`	Soil layer (thickness, porosity, field capacity, wilting point, saturated conductivity, conductivity slope).
`lid_set_storage(idx, thick, void_frac, ksat)()`	Storage layer (thickness, void fraction, saturated conductivity).
`lid_set_drain(idx, coeff, expon, offset)()`	Underdrain (coefficient, exponent, offset height).

LID usage (apply LID to a subcatchment)#

Method	Action
`lid_usage_add(subcatch_idx, lid_idx, number, area, width, init_sat, from_imperv)()`	Attach an LID to a subcatchment: number of units, per-unit area and width, initial saturation (0..1), and the fraction of impervious area treated (0..1).

End-to-end example#

from openswmm.engine import Solver, Infrastructure, Subcatchments

with Solver("urban_streets.inp", "urb.rpt", "urb.out") as s:
    infra = Infrastructure(s)
    sc = Subcatchments(s)

    print(
        f"transects={infra.transect_count()}  "
        f"streets={infra.street_count()}  "
        f"inlets={infra.inlet_count()}  "
        f"lid_controls={infra.lid_count()}"
    )

    # During edit phase: add a bio-retention LID on subcatchment S1
    s.open()
    infra.lid_usage_add(
        subcatch_idx=sc.get_index("S1"),
        lid_idx=0,                       # first LID control
        number=10,
        area=200.0,
        width=20.0,
        init_sat=0.0,                    # 0..1
        from_imperv=0.5,                 # 0..1: treats 50% of impervious area
    )

    from openswmm.engine import EngineState
    s.initialize()
    s.start()
    while s.state == EngineState.RUNNING:
        if s.step() != 0:
            break
    s.end()

Common recipes#

Configure a bio-retention LID control#

# Layer parameters for "BIO_RETENTION_1" (LID control index 0)
infra.lid_set_surface(idx=0, storage=6.0,
                      roughness=0.1, slope=0.0)
infra.lid_set_soil(idx=0, thick=18.0, porosity=0.5,
                   fc=0.2, wp=0.05, ksat=0.5, kslope=10.0)
infra.lid_set_storage(idx=0, thick=12.0, void_frac=0.75, ksat=0.5)
infra.lid_set_drain(idx=0, coeff=1.0, expon=0.5, offset=6.0)

Apply an LID to multiple subcatchments#

for sc_id in ["S1", "S3", "S5"]:
    infra.lid_usage_add(
        subcatch_idx=sc.get_index(sc_id),
        lid_idx=0,
        number=4,
        area=100.0,
        width=10.0,
        init_sat=0.0,
        from_imperv=0.3,                 # treats 30% of impervious area
    )

Add a transect with three stations#

# Trapezoidal channel: deeper in the middle
t = infra.transect_add("TRAPEZOIDAL")
infra.transect_set_roughness(t, n_left=0.05, n_right=0.05, n_channel=0.030)
infra.transect_add_station(t, station=0.0,  elevation=10.0)
infra.transect_add_station(t, station=10.0, elevation=7.0)
infra.transect_add_station(t, station=20.0, elevation=10.0)

Configure a P_BAR-50 grate inlet#

# Create the inlet and configure its geometry + grate type.
idx = infra.inlet_add("INLET_A", "GRATE")
infra.inlet_set_params(
    idx=idx,
    length=3.0,                   # ft
    width=2.0,                    # ft
    grate_type="P_BAR-50",        # named grate from the SWMM library
    open_area=0.9,                # open-area fraction
    splash_veloc=4.0,             # ft/s
)

EngineState requirements & exceptions#

Method group	Required state	Notes
all setters	`OPENED`	Apply before `initialize()` to take effect on the run.
count accessors	`OPENED` or later	n/a

Common EngineError codes:

INVALID_INDEX — out-of-range transect / street / inlet / LID index.
INVALID_TYPE — wrong layer setter for the LID kind, etc.

Infrastructure (transects, streets, inlets, LIDs)#

Class signature#

Key methods#

Transects#

Streets#

Inlets#

LID controls (definitions)#

LID usage (apply LID to a subcatchment)#

End-to-end example#

Common recipes#

Configure a bio-retention LID control#

Apply an LID to multiple subcatchments#

Add a transect with three stations#

Configure a P_BAR-50 grate inlet#

EngineState requirements & exceptions#

See also#