#LID Defaults from the EPA SWC

The following defaults are from the EPA Stormwater Calculator

https://www.epa.gov/water-research/national-stormwater-calculator

A few of these parameters such as the capture ratio are not parameters in InfoSWMM Sustain

There are some additional points to keep in mind when applying LID controls to a site:

1.      The area devoted to Disconnection, Rain Gardens, and Infiltration Basins is assumed to come from the site’s collective amount of pervious land cover while the area occupied by Green Roofs, Street Planters and Porous Pavement comes from the site’s store of impervious area.

2.      Underdrains (slotted pipes placed in the gravel beds of Street Planter and Porous Pavement areas to prevent the unit from flooding) are not provided for. However since underdrains are typically oversized and placed at the top of the unit’s gravel bed, the effect on the amount of excess runoff flow bypassed by the unit is the same whether it flows out of the underdrain or simply runs off of a flooded surface.

3.      The amount of void space in the soil, gravel, and pavement used in the LID controls are listed in Table 4 below. They typically have a narrow range of acceptable values and results are not terribly sensitive to variations within this range.

Table 3. Editable LID parameters.

LID Type	Parameter	Default Value
Disconnection	Capture Ratio	100 %
Rain Harvesting	Cistern Size	100 gal
	Cistern Emptying Rate	50 gal/day
	Number of Cisterns	4 per 1,000 sq ft
Rain Gardens	Capture Ratio	5 %
	Ponding Depth	6 inches
	Soil Media Thickness	12 inches
	Soil Media Conductivity	10 inches/hour
Green Roofs	Soil Media Thickness	4 inches
	Soil Media Conductivity	10 inches/hour
Street Planters	Capture Ratio	6 %
	Ponding Depth	6 inches
	Soil Media Thickness	18 inches
	Soil Media Conductivity	10 inches/hour
	Gravel Bed Thickness	12 inches
Infiltration Basins	Capture Ratio	5 %
	Basin Depth	6 inches
Porous Pavement	Capture Ratio	100 %
	Pavement Thickness	4 inches
	Gravel Bed Thickness	18 inches

Table 4. Void space values of LID media.

Property	LID Controls	Default Value
Soil Media Porosity	Rain Gardens, Green Roofs and Street Planters	45 %
Gravel Bed Void Ratio	Street Planters and Porous Pavement	75 %
Pavement Void Ratio	Porous Pavement	12 %

Flow Routing in InfoSWMM and Innovyze SWMM Products

Flow Routing

Flow routing within a conduit link in InfoSWMM H₂OMap SWMM InfoSWMM SA  is governed by the conservation of mass and momentum equations for gradually varied, unsteady flow (i.e., the Saint Venant flow equations). The  InfoSWMM H₂OMap SWMM InfoSWMM SA  user has a choice on the level of sophistication used to solve these equations:

1. Steady Flow Routing
2. Kinematic Wave Routing 
3. Dynamic Wave Routing

Steady Flow Routing

Steady Flow routing represents the simplest type of routing possible (actually no routing) by assuming that within each computational time step flow is uniform and steady. Thus it simply translates inflow hydrographs at the upstream end of the conduit to the downstream end, with no delay or change in shape. The Manning equation is used to relate flow rate to flow area (or depth).

This type of routing cannot account for channel storage, backwater effects, entrance/exit losses, flow reversal or pressurized flow. It can only be used with dendritic conveyance networks, where each node has only a single outflow link (unless the node is a divider in which case two outflow links are required). This form of routing is insensitive to the time step employed and is really only appropriate for preliminary analysis using long-term continuous simulations.

Kinematic Wave Routing

This routing method solves the continuity equation along with a simplified form of the momentum equation in each conduit. The latter requires that the slope of the water surface equal the slope of the conduit.

The maximum flow that can be conveyed through a conduit is the full-flow Manning equation value. Any flow in excess of this entering the inlet node is either lost from the system or can pond atop the inlet node and be re-introduced into the conduit as capacity becomes available.

Kinematic wave routing allows flow and area to vary both spatially and temporally within a conduit. This can result in attenuated and delayed outflow hydrographs as inflow is routed through the channel. However this form of routing cannot account for backwater effects, entrance/exit losses, flow reversal, or pressurized flow, and is also restricted to dendritic network layouts. It can usually maintain numerical stability with moderately large time steps, on the order of 5 to 15 minutes. If the aforementioned effects are not expected to be significant then this alternative can be an accurate and efficient routing method, especially for long-term simulations.

Dynamic Wave Routing

Dynamic Wave routing solves the complete one-dimensional Saint Venant flow equations and therefore produces the most theoretically accurate results. These equations consist of the continuity and momentum equations for conduits and a volume continuity equation at nodes.

With this form of routing it is possible to represent pressurized flow when a closed conduit becomes full, such that flows can exceed the full-flow Manning equation value. Flooding occurs when the water depth at a node exceeds the maximum available depth, and the excess flow is either lost from the system or can pond atop the node and re-enter the drainage system.

Dynamic wave routing can account for channel storage, backwater, entrance/exit losses, flow reversal, and pressurized flow. Because it couples together the solution for both water levels at nodes and flow in conduits it can be applied to any general network layout, even those containing multiple downstream diversions and loops. It is the method of choice for systems subjected to significant backwater effects due to downstream flow restrictions and with flow regulation via weirs and orifices. This generality comes at a price of having to use much smaller time steps, on the order of a minute or less (InfoSWMM will automatically reduce the user-defined maximum time step as needed to maintain numerical stability).

Surface Ponding

Normally in flow routing, when the flow into a junction exceeds the capacity of the system to transport it further downstream, the excess volume overflows the system and is lost. An option exists to have instead the excess volume be stored atop the junction, in a ponded fashion, and be reintroduced into the system as capacity permits. Under Steady and Kinematic Wave flow routing, the ponded water is stored simply as an excess volume. For Dynamic Wave routing, which is influenced by the water depths maintained at nodes, the excess volume is assumed to pond over the node with a constant surface area. This amount of surface area is an input parameter supplied for the junction.

Alternatively, the user may wish to represent the surface overflow system explicitly. In open channel systems this can include road overflows at bridges or culvert crossings as well as additional floodplain storage areas. In closed conduit systems, surface overflows may be conveyed down streets, alleys, or other surface routes to the next available stormwater inlet or open channel. Overflows may also be impounded in surface depressions such as parking lots, back yards or other areas.

SWMMLive Manager in Innovyze #SWMM5 Products

SWMMLive Manager

The InfoSWMM SA SWMMLive Manager is the single utility in InfoSWMM SA to manage all interactions between InfoSWMM SA models and SWMMLive model data exchange.  It exports the active InfoSWMM SA scenario as the baseline model to SWMMLive.  It allows extension of selected InfoSWMM SA scenarios as additional supporting model data to SWMMLive for scenario switching.  It also accepts an exported SWMMLive model for detailed diagnosis run in InfoSWMM SA, supported with all the familiar InfoSWMM SA utilities.

InfoSWMM SA SWMMLive Manager is accessed from the AddOn Extension Manager via its toolbar button or from the Tools menu (Tools -> AddOn Extension Manager).

The InfoSWMM SA SWMMLive Manager User Interface is shown below.

The InfoSWMM SA SWMMLive Manager main dialog box has three tabs: Export Model to SWMMLive, Extend Scenario Data to SWMMLive, and Diagnose SWMMLive Model.  All model exchanges between InfoSWMM SA and SWMMLive are made through model definition files with extension inp.

<![if !supportLists]>·        <![endif]>Export Model to SWMMLive - Exports the active InfoSWMM SA model for SWMMLive (InfoSWMM SA) to create a baseline model.  All essential information about the active InfoSWMM SA model is exported into the given inp file.  If current InfoSWMM SA model contains scenario data, this option can be used in conjunction with selected scenarios to export scenario based models with overriding operational scenario data.  All scenario based model inp files will be exported to their respective scenario sub-folders under the baseline model path.

<![if !supportLists]>·        <![endif]>Extend Scenario Data to SWMMLive - Exports additional InfoSWMM SA scenario models based on a provided SWMMLive baseline model.  The operational data from the selected scenarios will be merged into the given SWMMLive reference model to form different scenario models, to be used in SWMMLive.  All scenario based model inp files will be exported to their respective sub-folders under the given baseline model path.

<![if !supportLists]>·        <![endif]>Diagnose SWMMLive Model - Diagnoses a given SWMMLive model using the full utilities available from InfoSWMM SA.  The given SWMMLive model is imported into InfoSWMM SA for any diagnosis analysis in InfoSWMM SA.

Export Model to SWMMLive

In the box of Export Model File to SWMMLive, a inp file is specified for InfoSWMM SA SWMMLive Manager to store the InfoSWMM SA model information. 

 Browse for a folder location and specify a inp file name.

If the InfoSWMM SA model is blank, SWMMLive Manager will not export.  Otherwise, SWMMLive Manager exports the active scenario as the baseline model to SWMMLive.