SUDS/LID Control Types
Sustainable Urban Drainage System (SUDS) in InfoWorks networks and Low Density Development (LID) control objects in SWMM networks are specified as part of the Subcatchment data and are used to define the parameters which model the outflow from the SUDS/LIDs structures which are located within a subcatchment.
One of these parameters is the type of SUDS or LID control. This can be selected from the Control type property dropdown list and contains the following options:
Bio-retention cell
Biological retention cells/facilities are landscaped depressions used for the storage and infiltration of storm water through plants, soil and micro-organisms in areas with relatively lower ground level before draining to a drainage bed usually comprised of gravel. A bio-retention cell may optionally contain some form of under-drainage system.
The following diagram illustrates how a bio-retention cell structure is modelled in InfoWorks ICM:
Rain garden
Rains garden are similar to a bio-retention cells but without a gravel bed (storage layer). They typically have a small shallow depression (about 100 mm to 300 mm deep) which is designed to overflow into a piped drainage system. Beneath this, flow can percolate through to the underlying soil.
The following diagram illustrates how a rain garden is modelled in InfoWorks ICM:
Green roof
Green roofs are essentially a vegetated surface which provide retention and attenuation of flow and encourage evapo-transpiration. A drainage mat allows excess percolated flow to drain off the roof. Outflow (down-pipes)from a green roof are rarely designed to be a constraint.
The following diagram illustrates how a green roof is modelled in InfoWorks ICM:
Infiltration trench
These are linear excavations filled with stone aggregate or other void-forming material used to capture runoff from upstream impermeable areas and encourage infiltration for underground water recharge.
The following diagram illustrates how an infiltration trench is modelled in InfoWorks ICM:
Permeable pavement
Permeable pavements are block paving or permeable asphalt on top, high voids geo-grid in the middle or stone media, and the base can be lined or soil. A large majority of rainfall will pass through the pavement into a storage layer below where it can infiltrate into the soil below. A layer of soil may optionally be included between the permeable pavement and the storage layer. The outlet is usually a form of hydraulic control.
The following diagram illustrates how a permeable pavement is modelled in InfoWorks ICM:
Rain barrel
Rain barrels are an enclosed overground or underground stormwater collection facilities that collect roof runoff during storm events. They can either slowly release flow into the system or allow the re-use of rainwater during dry weather periods.
The following diagram illustrates how a rain barrel is modelled in InfoWorks ICM:
Rooftop disconnection
Rooftop disconnection is when roof drain pipes drain to pervious areas and lawns instead of directly into the drainage system. In some cases, the roof drain pipes can drain to a permeable pavement.
The following diagram illustrates how a rooftop disconnection is modelled in InfoWorks ICM:
Vegetative swale
There are many variations in the design of swales. In general terms a swale is a vegetation covered overground channel, of any depth between 500mm to 2m or more. It can collect, transport and convey stormwater. Conveyance within the swale is usually restricted and allows more time for water to infiltrate into the soil below. It can be used as connection with other urban drainage facilities. When it is full, it will spill from the surface at the bottom end and cause overland flow.
The following diagram illustrates how swale is modelled in InfoWorks ICM:
The SWMM Reference Manual, Volume III, Water Quality contains further information about types of LID controls.
