SWMM Urban Drainage Model

The urban drainage model ("urban_drainage") wraps the EPA Storm Water Management Model (SWMM) engine, through pyswmm, to provide an idiomatic Movici interface for simulating storm-water and sewer drainage networks. It models how rainfall becomes runoff, how that runoff (plus any sanitary or externally imposed inflow) is routed through conduits, pumps, orifices, weirs, outlets and storage units, and where the network surcharges, floods or discharges. All data is described in terms of Movici entities and attributes.

This page is written for Movici users who want to set up or run an urban-drainage simulation: it covers the purpose of the model, the physics and terminology behind it, the dataset you must supply (entities and attributes), the results it publishes, the configuration options, and the caveats to be aware of. It is not a substitute for the SWMM5 Reference Manual, which defines the underlying physics in full.

Use cases include:

• Routing storm water and sewage through pipe networks (dynamic-wave hydraulics)

• Rainfall-runoff and infiltration analysis over subcatchments

• Flood and surcharge analysis at manholes and storage basins

• Real-time control studies, driving pumps, orifices and weirs from other models

• Coupling drainage behaviour with other Movici models in a scenario

Goals

• The data model is described, as much as possible, in terms of entities and attributes

• Solver options (routing method, time steps) live in the model config under "options"; data-determined options (unit system, default infiltration model) live in the dataset’s "general" section

• Existing SWMM .inp files can be imported into Movici datasets through the "swmm" dataset-creator source (the runtime model itself reads Movici data, not .inp files)

Model Characteristics

The urban drainage model is a transient, forward-only model. A single live SWMM simulation is opened at initialization and advanced forward to each Movici moment; SWMM cannot rewind, so the model never steps backwards. Like other transient models its output state depends on an initial state and evolves over time even when the input state is unchanged (for example a storage basin draining between updates).

• Time stepping. Movici calls update(moment) at the report_timestep cadence (default 300 s); internally SWMM routes at the finer hydraulic_timestep (default 60 s). At t=0 the model reports the initial conditions without stepping.

• Minimum step. SWMM advances in whole seconds, so the effective minimum step is 1 second; a fractional Movici time_scale is rounded down when stepping (the model logs a warning when the time scale is non-integer).

• Control latency. Control inputs are applied to the live engine before each forward step, so a value supplied at time t governs the step from t onward - a one-step latency, as in real-time control.

• Calendar. SWMM tags every step with an absolute date/time, which it uses for time-of-day-dependent inputs (evaporation, rainfall series) and for the timestamps in its report. The model anchors that calendar to the Movici timeline reference so they line up with the scenario’s world time (falling back to a fixed epoch when no timeline is set).

• One simulation per process. EPA-SWMM permits only a single open simulation per process. Only one urban drainage model can therefore run in a given process; additional instances must run in separate processes (e.g. a distributed simulation). Opening a second simulation raises a clear error.

Hydrology and Routing

A drainage simulation couples two processes:

• Hydrology turns rainfall into runoff. Each subcatchment receives rainfall from its rain gage, loses part of it to infiltration (into pervious soil) and to depression storage, and converts the rest into a runoff flow delivered to the node it drains to.

• Hydraulics moves that water through the network. Routing is the computation of how the flow rate and water depth in each link - and the water level at each node - change over time as water is conveyed downstream, stored, surcharges or floods.

The network is built from nodes (junctions, outfalls and storage units) joined by links (conduits and the regulators: pumps, orifices, weirs and outlets), each link connecting a from node to a to node. Subcatchments sit outside the pipe network and deliver their runoff to a single node; rain gages supply the rainfall that drives the subcatchments. Surface water therefore enters the network as subcatchment runoff (or as an externally imposed generated_inflow at a node) - the model does not separately represent street inlets or grates.

The routing method is chosen with the flow_routing option (see the Innovyze Routing of Flows overview):

• STEADY - each reporting step is treated as an independent steady, uniform flow. Fastest, but it ignores storage, backwater and travel time; suitable only for preliminary or long-term continuity analysis.

• KINWAVE (kinematic wave) - flow and cross-sectional area vary along the conduit and in time, but a conduit cannot convey more than its full-flow capacity and there is no backwater, surcharging or pressurised flow; excess water is ponded or lost.

• DYNWAVE (dynamic wave) - solves the full Saint-Venant equations, so it handles backwater, flow reversal, surcharging, pressurised flow and looped or branched networks. It is the default and is recommended for drainage networks.

How It Works

1. At initialization the model synthesises a transient SWMM .inp file from the Movici entity groups and opens a live Simulation on it.

2. Each update(moment) applies the current control inputs (rainfall, node inflow, regulator settings) to the live SWMM objects.

3. It then advances the simulation forward to the requested moment.

4. Finally it reads the per-element results (depth, head, flooding, flow, runoff, …) back into the published Movici attributes.

Data Model

Each SWMM object type maps to a Movici entity group, listed below with its full attribute set. The Flags column uses INIT (required static input), OPT (optional input or runtime control) and PUB (published result); PUB|OPT marks a published result that, when supplied as input, also seeds the matching initial condition. Geometry and topology come from the underlying Movici entity type. Curves (storage_curve, pump_curve, rating_curve) are inlined per entity as (2,)-csr point arrays - there is no shared curve table. Units assume the default metric flow_units = CMS (metres, m³/s, mm/hr, hectares); selecting US flow_units switches depths and rates to inches.

Junctions

drainage_junction_entities

Junctions are the manholes and pipe-connection nodes of the drainage network. They receive piped flow from connecting links and the runoff of any subcatchment that drains to them; the model does not separately represent street inlets or grates. Junctions derive from PointEntity.

Attribute	Flags	Description
geometry.x	OPT	Map x location ([COORDINATES]); display only (from PointEntity)
geometry.y	OPT	Map y location ([COORDINATES]); display only (from PointEntity)
urban_drainage.invert_elevation	INIT	Node invert (bottom) elevation (m)
urban_drainage.max_depth	OPT	Depth from invert to ground/rim (m); 0 tells SWMM to derive it from the crown of the highest connecting conduit (water is not lost - it floods at that depth)
urban_drainage.surcharge_depth	OPT	Head allowed above max_depth before flooding (m)
urban_drainage.ponded_area	OPT	Ponded surface area when flooded (m²)
urban_drainage.generated_inflow	OPT	Externally imposed point inflow (m³/s)
urban_drainage.water_depth	PUB|OPT	Water depth above the invert (m); if given as input it also seeds the initial depth at t=0
urban_drainage.hydraulic_head	PUB	Hydraulic head = invert + depth (m)
urban_drainage.flooding_rate	PUB	Surface flooding / overflow rate (m³/s)
urban_drainage.total_inflow	PUB	Total inflow to the node (m³/s)
urban_drainage.total_outflow	PUB	Total outflow from the node (m³/s)
urban_drainage.lateral_inflow	PUB	External + runoff inflow to the node (m³/s)
urban_drainage.stored_volume	PUB	Water volume held at the node (m³)

Outfalls

drainage_outfall_entities

Outfalls are terminal nodes that impose a downstream boundary condition on the network. The supported outfall_type values set that boundary: FREE uses the minimum of critical and normal depth (no tailwater), NORMAL uses normal flow depth, and FIXED holds a constant water-surface stage (fixed_stage). TIDAL and TIMESERIES boundaries need external data and are not supported. Outfalls derive from PointEntity.

Attribute	Flags	Description
geometry.x	OPT	Map x location ([COORDINATES]); display only (from PointEntity)
geometry.y	OPT	Map y location ([COORDINATES]); display only (from PointEntity)
urban_drainage.invert_elevation	INIT	Node invert (bottom) elevation (m)
urban_drainage.outfall_type	INIT	Boundary type: FREE / NORMAL / FIXED
urban_drainage.fixed_stage	OPT	Fixed boundary water-surface elevation, used by FIXED (m)
urban_drainage.flap_gate	OPT	Flap gate preventing reverse (back) flow at the boundary (bool)
urban_drainage.generated_inflow	OPT	Externally imposed point inflow (m³/s)
urban_drainage.water_depth	PUB|OPT	Water depth above the invert (m); if given as input it also seeds the initial depth at t=0
urban_drainage.hydraulic_head	PUB	Hydraulic head = invert + depth (m)
urban_drainage.flooding_rate	PUB	Surface flooding / overflow rate (m³/s)
urban_drainage.total_inflow	PUB	Total inflow to the node (m³/s)
urban_drainage.total_outflow	PUB	Total outflow from the node (m³/s)
urban_drainage.lateral_inflow	PUB	External + runoff inflow to the node (m³/s)
urban_drainage.stored_volume	PUB	Water volume held at the node (m³)

generated_inflow is supported on outfalls (verified against pyswmm) - it adds an external inflow at the boundary node, e.g. a modelled discharge.

Storage units

drainage_storage_entities

Storage units are ponds, basins and tanks with a stage-storage relationship. The shape is selected by storage_geometry (or inferred when omitted: a storage_curve means TABULAR, otherwise FUNCTIONAL). Each shape reads a different subset of the parameters below. Storage units derive from PointEntity.

Attribute	Flags	Description
geometry.x	OPT	Map x location ([COORDINATES]); display only (from PointEntity)
geometry.y	OPT	Map y location ([COORDINATES]); display only (from PointEntity)
urban_drainage.invert_elevation	INIT	Node invert (bottom) elevation (m)
urban_drainage.max_depth	INIT	Maximum water depth (m)
urban_drainage.storage_geometry	OPT	Shape enum: FUNCTIONAL / TABULAR / CYLINDRICAL / CONICAL / PARABOLIC / PYRAMIDAL
urban_drainage.storage_constant	OPT	FUNCTIONAL A0: constant surface area (m²)
urban_drainage.storage_coefficient	OPT	FUNCTIONAL A1: area coefficient
urban_drainage.storage_exponent	OPT	FUNCTIONAL A2: area exponent (area = A0 + A1·depth^A2)
urban_drainage.storage_curve	OPT	TABULAR: inline (depth m, area m²) curve; (2,)-csr
urban_drainage.storage_geometry_parameters	OPT	Geometric shapes: (L, W, Z) (m; Z is side slope for CONICAL/PYRAMIDAL, full height for PARABOLIC)
urban_drainage.surcharge_depth	OPT	Head allowed above max_depth before flooding (m)
urban_drainage.ponded_area	OPT	Ponded surface area when flooded (m²)
urban_drainage.generated_inflow	OPT	Externally imposed point inflow (m³/s)
urban_drainage.water_depth	PUB|OPT	Water depth above the invert (m); if given as input it also seeds the initial depth at t=0
urban_drainage.hydraulic_head	PUB	Hydraulic head = invert + depth (m)
urban_drainage.flooding_rate	PUB	Surface flooding / overflow rate (m³/s)
urban_drainage.total_inflow	PUB	Total inflow to the node (m³/s)
urban_drainage.total_outflow	PUB	Total outflow from the node (m³/s)
urban_drainage.lateral_inflow	PUB	External + runoff inflow to the node (m³/s)
urban_drainage.stored_volume	PUB	Water volume held at the node (m³)

Conduits

drainage_conduit_entities

Conduits are the pipes and channels that carry gravity flow between two nodes. Conduits derive from LinkEntity.

Attribute	Flags	Description
topology.from_node_id	INIT	Upstream node id (from LinkEntity)
topology.to_node_id	INIT	Downstream node id (from LinkEntity)
shape.length	INIT	Conduit length (m, > 0)
urban_drainage.roughness	INIT	Manning’s roughness coefficient n
urban_drainage.cross_section_shape	INIT	Cross-section shape enum (CIRCULAR, RECT_CLOSED, RECT_OPEN, TRAPEZOIDAL, …)
urban_drainage.cross_section_geometry	INIT	Geom1-Geom4 (m); meaning per shape - e.g. CIRCULAR: Geom1=diameter; RECT_CLOSED: Geom1=height, Geom2=width; TRAPEZOIDAL: Geom1=height, Geom2=base, Geom3/4=side slopes. Unused slots may be left unset
urban_drainage.barrels	OPT	Number of parallel identical barrels
urban_drainage.from_offset	OPT	Height of the conduit’s upstream end above its from-node invert (m)
urban_drainage.to_offset	OPT	Height of the conduit’s downstream end above its to-node invert (m)
urban_drainage.target_setting	OPT	Control setting 0-1 (1 = fully open)
urban_drainage.flow	PUB|OPT	Flow rate through the link (m³/s); on a conduit, if given as input, also seeds the initial flow at t=0
urban_drainage.flow_depth	PUB	Water depth inside the link (m)
urban_drainage.flow_volume	PUB	Water volume stored in the link (m³)
urban_drainage.froude_number	PUB	Froude number (-)
urban_drainage.current_setting	PUB	Applied control setting 0-1 (-)

Pumps

drainage_pump_entities

Pumps lift water from the inlet node to the outlet node. The pump_curve_type selects how the (inline) pump_curve is interpreted: PUMP1 relates flow to inlet wet-well volume, PUMP2 to inlet depth (step), PUMP3 to the inlet-outlet head difference, PUMP4 to a variable-speed inlet depth; IDEAL (or no curve) simply passes the inlet inflow. Pumps derive from LinkEntity.

Attribute	Flags	Description
topology.from_node_id	INIT	Upstream node id (from LinkEntity)
topology.to_node_id	INIT	Downstream node id (from LinkEntity)
urban_drainage.pump_curve_type	OPT	Pump curve type enum: IDEAL / PUMP1 / PUMP2 / PUMP3 / PUMP4
urban_drainage.pump_curve	OPT	Inline (x, y) curve points; axes depend on the type; (2,)-csr
urban_drainage.startup_depth	OPT	Inlet depth at which the pump switches on (m)
urban_drainage.shutoff_depth	OPT	Inlet depth at which the pump switches off (m)
urban_drainage.target_setting	OPT	Pump relative speed 0-1
urban_drainage.flow	PUB|OPT	Flow rate through the link (m³/s); on a conduit, if given as input, also seeds the initial flow at t=0
urban_drainage.flow_depth	PUB	Water depth inside the link (m)
urban_drainage.flow_volume	PUB	Water volume stored in the link (m³)
urban_drainage.froude_number	PUB	Froude number (-)
urban_drainage.current_setting	PUB	Applied control setting 0-1 (-)

Orifices

drainage_orifice_entities

Orifices are submerged openings regulating flow. orifice_type is SIDE (an opening in a side wall) or BOTTOM (an opening in the invert); orifice_shape is CIRCULAR or RECT_CLOSED. Orifices derive from LinkEntity.

Attribute	Flags	Description
topology.from_node_id	INIT	Upstream node id (from LinkEntity)
topology.to_node_id	INIT	Downstream node id (from LinkEntity)
urban_drainage.orifice_type	INIT	Orientation enum: SIDE / BOTTOM
urban_drainage.orifice_shape	INIT	Opening shape enum: CIRCULAR / RECT_CLOSED
urban_drainage.cross_section_geometry	INIT	Opening dimensions Geom1-Geom4 (m); CIRCULAR: Geom1=diameter; RECT_CLOSED: Geom1=height, Geom2=width
urban_drainage.discharge_coefficient	INIT	Discharge coefficient (-)
urban_drainage.crest_height	OPT	Opening height above the inlet node invert (m)
urban_drainage.flap_gate	OPT	Flap gate preventing reverse flow (bool)
urban_drainage.target_setting	OPT	Opening fraction 0-1
urban_drainage.flow	PUB|OPT	Flow rate through the link (m³/s); on a conduit, if given as input, also seeds the initial flow at t=0
urban_drainage.flow_depth	PUB	Water depth inside the link (m)
urban_drainage.flow_volume	PUB	Water volume stored in the link (m³)
urban_drainage.froude_number	PUB	Froude number (-)
urban_drainage.current_setting	PUB	Applied control setting 0-1 (-)

Weirs

drainage_weir_entities

Weirs are crested structures regulating overflow. weir_type chooses the crest form: TRANSVERSE and SIDEFLOW are rectangular crests (across / along the flow), V-NOTCH is triangular, TRAPEZOIDAL combines both, and ROADWAY models flow over a road embankment. Weirs derive from LinkEntity.

Attribute	Flags	Description
topology.from_node_id	INIT	Upstream node id (from LinkEntity)
topology.to_node_id	INIT	Downstream node id (from LinkEntity)
urban_drainage.weir_type	INIT	Weir type enum: TRANSVERSE / SIDEFLOW / V-NOTCH / TRAPEZOIDAL / ROADWAY
urban_drainage.cross_section_geometry	INIT	Opening Geom1-Geom4 (m): Geom1=height, Geom2=length, Geom3=side slope
urban_drainage.discharge_coefficient	INIT	Weir discharge coefficient (-)
urban_drainage.crest_height	OPT	Crest height above the inlet node invert (m)
urban_drainage.flap_gate	OPT	Flap gate preventing reverse flow (bool)
urban_drainage.target_setting	OPT	Opening fraction 0-1
urban_drainage.flow	PUB|OPT	Flow rate through the link (m³/s); on a conduit, if given as input, also seeds the initial flow at t=0
urban_drainage.flow_depth	PUB	Water depth inside the link (m)
urban_drainage.flow_volume	PUB	Water volume stored in the link (m³)
urban_drainage.froude_number	PUB	Froude number (-)
urban_drainage.current_setting	PUB	Applied control setting 0-1 (-)

Outlets

drainage_outlet_entities

Outlets are flow-control links with a user-defined head/depth-discharge rating. outlet_rating_type picks whether discharge is a FUNCTIONAL power law or a TABULAR curve, and whether it is driven by HEAD (across the outlet) or DEPTH (at the inlet). Outlets derive from LinkEntity.

Attribute	Flags	Description
topology.from_node_id	INIT	Upstream node id (from LinkEntity)
topology.to_node_id	INIT	Downstream node id (from LinkEntity)
urban_drainage.outlet_rating_type	INIT	FUNCTIONAL or TABULAR, rated by DEPTH or HEAD
urban_drainage.crest_height	OPT	Outlet height above the inlet node invert (m)
urban_drainage.rating_coefficient	OPT	FUNCTIONAL coefficient (flow = coeff·x^expon)
urban_drainage.rating_exponent	OPT	FUNCTIONAL exponent
urban_drainage.rating_curve	OPT	TABULAR: inline (head or depth m, flow m³/s) curve; (2,)-csr
urban_drainage.flap_gate	OPT	Flap gate preventing reverse flow (bool)
urban_drainage.target_setting	OPT	Opening fraction 0-1
urban_drainage.flow	PUB|OPT	Flow rate through the link (m³/s); on a conduit, if given as input, also seeds the initial flow at t=0
urban_drainage.flow_depth	PUB	Water depth inside the link (m)
urban_drainage.flow_volume	PUB	Water volume stored in the link (m³)
urban_drainage.froude_number	PUB	Froude number (-)
urban_drainage.current_setting	PUB	Applied control setting 0-1 (-)

Subcatchments

drainage_subcatchment_entities

Subcatchments are surfaces that turn rainfall into runoff. Runoff is routed to one node (outlet_node_id) and driven by the gage referenced through raingage_id. Only a single subarea per subcatchment is modelled (SWMM allows more). Subcatchments derive from PolygonEntity.

Attribute	Flags	Description
geometry.polygon	OPT	Subcatchment outline ([POLYGONS]); display only (from PolygonEntity)
urban_drainage.area	INIT	Subcatchment area (ha)
urban_drainage.width	INIT	Characteristic overland-flow width (m)
urban_drainage.percent_impervious	INIT	Impervious fraction of the area (%)
urban_drainage.slope	INIT	Average surface slope (%)
urban_drainage.outlet_node_id	INIT	Node id the runoff drains to
urban_drainage.raingage_id	INIT	Rain gage id driving the rainfall
urban_drainage.n_imperv	OPT	Manning’s n, impervious area
urban_drainage.n_perv	OPT	Manning’s n, pervious area
urban_drainage.s_imperv	OPT	Depression storage, impervious area (mm)
urban_drainage.s_perv	OPT	Depression storage, pervious area (mm)
urban_drainage.pct_zero	OPT	Impervious area with no depression storage (%)
urban_drainage.max_infiltration_rate	OPT	Horton maximum infiltration rate (mm/hr)
urban_drainage.min_infiltration_rate	OPT	Horton minimum infiltration rate (mm/hr)
urban_drainage.decay_constant	OPT	Horton decay constant (1/hr)
urban_drainage.dry_time	OPT	Time for fully saturated soil to dry (days)
urban_drainage.suction_head	OPT	Green-Ampt soil capillary suction (mm)
urban_drainage.conductivity	OPT	Saturated hydraulic conductivity (mm/hr)
urban_drainage.initial_deficit	OPT	Green-Ampt initial moisture deficit (fraction)
urban_drainage.curve_number	OPT	SCS curve number (-)
urban_drainage.rainfall	PUB	Rainfall reaching the subcatchment (mm/hr)
urban_drainage.runoff	PUB	Surface runoff flow (m³/s)
urban_drainage.infiltration_loss	PUB	Infiltration loss rate (mm/hr)
urban_drainage.evaporation_loss	PUB	Evaporation loss rate (mm/hr)

Infiltration model selection. Each subcatchment’s infiltration model is resolved in this order: an infiltration_model_override in the model config forces one model for every subcatchment; otherwise the model is inferred from which family of attributes is set (Horton: max_infiltration_rate / min_infiltration_rate / decay_constant; Green-Ampt: suction_head / initial_deficit; Curve Number: curve_number); if that is ambiguous (zero or several families set) it falls back to the dataset’s infiltration_model_default (general section), and finally to HORTON. The MODIFIED_* variants cannot be inferred and must be chosen via override/default. Unset parameters use sensible defaults for the active unit system.

Rain gages

drainage_raingage_entities

Rain gages are the rainfall sources for subcatchments. Rainfall is driven at runtime by another model publishing rainfall_intensity - there is no configured time series, so no format or interval is needed. Rain gages derive from PointEntity.

Attribute	Flags	Description
geometry.x	OPT	Map x location ([SYMBOLS]); display only (from PointEntity)
geometry.y	OPT	Map y location ([SYMBOLS]); display only (from PointEntity)
urban_drainage.rainfall_intensity	OPT	Runtime rainfall override (mm/hr)
urban_drainage.rainfall	PUB	Rainfall reported by the gage (mm/hr)

Controls

The model does not implement internal SWMM controls or rules. Operational control is supplied externally, typically by the Rules Model, through these optional inputs:

• urban_drainage.target_setting on a regulator (pump speed, or orifice / weir opening fraction, 0-1)

• urban_drainage.generated_inflow at a node (an imposed point inflow)

• urban_drainage.rainfall_intensity on a rain gage (the runtime rainfall)

These take effect on the forward step following the update in which they change (see Control latency).

Configuration Options

Options fall into three groups, by whether they describe the solver, the data, or the infiltration model (which is data-decided but may be overridden). This keeps a clean separation of concerns: solver options live in the model config under "options" and data options live in the dataset’s "general" section, so a model config cannot silently misrepresent the data (e.g. changing the unit system in the config would not convert the underlying values).

Solver options (model config "options" only)

Option	Type	Description
hydraulic_timestep	number	SWMM routing (hydraulic) step in seconds. Default: 60
report_timestep	number	Movici wake cadence and SWMM report step in seconds. Default: 300
flow_routing	string	Routing method: STEADY / KINWAVE / DYNWAVE. Default: DYNWAVE

Data options (dataset "general" section only)

Option	Type	Description
flow_units	string	SWMM unit system: CMS / LPS / MLD (metric) or CFS / GPM / MGD (US). Default: CMS

Infiltration model (data-decided, config-overridable)

The infiltration model is decided by the data by default but may be overridden at runtime. Per subcatchment it is resolved as: infiltration_model_override (model config, forces all subcatchments) -> inference from which attribute family is set -> infiltration_model_default (dataset general) -> HORTON.

Option	Set in	Description
infiltration_model_default	dataset general	Default infiltration model for subcatchments whose model cannot be inferred. Default: HORTON
infiltration_model_override	model config	Force one infiltration model for ALL subcatchments (overrides inference and the default). Optional

Example Configuration

Model config with solver options:

{
    "name": "drainage_simulation",
    "type": "urban_drainage",
    "dataset": "drainage_network",
    "options": {
        "hydraulic_timestep": 60,
        "report_timestep": 300,
        "flow_routing": "DYNWAVE"
    }
}

Dataset general section with data options:

{
    "general": {
        "flow_units": "CMS",
        "infiltration_model_default": "HORTON"
    }
}

Limitations

• Dividers are not modelled; under dynamic-wave routing SWMM treats them as ordinary junctions

• Link velocity is not published (the live engine exposes no usable per-link velocity); the Froude number is published instead

• Outfalls support FREE / NORMAL / FIXED boundaries only; TIDAL and TIMESERIES (which need referenced boundary data) raise a clear error

• Only a single subarea per subcatchment is modelled

• A subcatchment drains to a single node; run-on between subcatchments is not modelled, so no run-on output is published

• Snow, water quality / pollutants, LID controls and groundwater are out of scope

• Only one SWMM simulation per process (see Model Characteristics)

Other Considerations

Names, IDs and References

SWMM identifies objects by name. The model derives each SWMM name from the Movici entity id (cast to a string) with a per-type prefix, so names are unique across entity groups and link endpoints / subcatchment outlets resolve unambiguously: J junctions, OF outfalls, ST storage, C conduits, PU pumps, OR orifices, W weirs, OU outlets, S subcatchments and RG rain gages (e.g. junction id 12 becomes J12).

Units

Units follow SWMM’s unit system, which is selected by flow_units: the metric CMS / LPS / MLD use metres, m³/s and millimetres; the US CFS / GPM / MGD use feet, ft³/s and inches. The metric CMS default is assumed throughout this page. When importing data, make sure depths, lengths and rates match the configured unit system.

Notes

• Link velocity is not published; the Froude number is published instead.

• SWMM advances in whole seconds, so the smallest meaningful step is 1 second.

• Existing SWMM .inp files can be converted to Movici datasets with the "swmm" dataset-creator source; the runtime model reads Movici data only.

Config Schema Reference

UrbanDrainageConfig

type: object

properties:

dataset: string Name of the urban_drainage_network dataset (required)

options: UrbanDrainageOptions SWMM solver options

UrbanDrainageOptions

type: object

properties:

hydraulic_timestep: number SWMM routing step in seconds (default: 60)

report_timestep: number Report / wake cadence in seconds (default: 300)

flow_routing: string Routing method: STEADY / KINWAVE / DYNWAVE (default: DYNWAVE)

infiltration_model_override: string Force one infiltration model for all subcatchments (optional)