Areas of application

StormTac Web is a user-friendly stormwater and recipient model, a tool for action planning (such as watershed management plans within the Water Directive) and design. By using the application, your investigations and design process will be carried out in accordance with the latest data and methods.

The quantity calculation of design flow and required flow detention volumes takes into consideration the design rain duration, rain return time, safety factors, updated runoff coefficients and current climate factors.

The quality pollutant calculation takes updated land use specific concentration data into consideration.

Typical applications include the following:

• Calculate stormwater flows, pollutant concentration and loads of more than 80 substances in the (sub)watershed outlets and from more than 100 land uses, by employing land use specific runoff coefficients and concentrations from a large amount of flow proportional data.

• Design transport conduits such as sewers, ditches, gutters and channels.

• Design and calculate both the treatment and/or flow detention effects of up to 10 optional BMPs (SUDS) in series. The design considers site specific parameters such as the share of submerged vegetation area, inlet pollutant concentration and flow detention volume. The following facilities can be designed in StormTac Web:

– dry ponds and underground basins with cassettes for flow detention
– wet ponds (ponds with permanent pool)
– constructed wetlands
– sedimentation basins (screens in ponds/wetlands or in the recipient water body)
– biofilters (bioretentions facilities, rain gardens)
– macadam ditches (infiltration trenches, open ditches fully or partly filled with macadam)
– swales (open grass ditches with a sloop less steep than 1:2)
– grass ditches (open grass ditches with a sloop of 1:2 or more steep)
– structural soil (macadam mixed with soil)
– dry ponds (ponds without permanent pool, with bottom outlet and dry between rain events)
– biochar (optional addition)
– underground retention basins
– macadam basins (soakaways)
– underground vault structures with filter (baffle boxes)
– drain inlets (filters located at catch basins, gully pot or well filters)
– oil separators (including lamella oil separators)
– filter strips (buffer strips)
– green roofs (designed as a land use)

• Estimate allowable pollutant loads on the recipient, the required load reduction and changed recipient concentrations to meet the water quality criteria of the receiving water.

Strategic stormwater management – stormwater facilities where they give the best effect! Based on site specific parameters, StormTac Web simulates which type of facility that gives the best effect in terms of reduction efficiency and flow detention. This provides the opportunity to develop a strategic stormwater management for large areas such as an entire municipality.Since it is possible in StormTac Web, to simulate stormwater flows and pollution transport for over 100 different land uses, areas of future development can also be included in the strategic stormwater management plan.StormTac Web has been used to development a strategic stormwater management plan for the city of Lund in southern Sweden. Based on calculated stormwater flows and pollution transport for the urban areas, strategic locations were developed for facilities to achieve the best possible pollutant reduction and flow detention. “StormTac Web has been a useful tool for us when developing a plan for our stormwater management strategy. Results regarding annual pollution load per sub watershed area provides an overview of the pollution situation from the urban areas, which makes it possible to locate measures where they have the best effect.” Ebba Waernbaum, VASYD

Stormwater investigation – from flow and pollution calculation to stormwater management The impact of an exploitation in terms of both stormwater flows and pollutants can be calculated with StormTac Web, which makes it an effective tool during a stormwater investigation.With StormTac Web, it is possible to calculate the required flow detention and pollutant reduction in order not to worsen the situation for the receiving water. Based on site-specific parameters, StormTac Web simulates which type of facility that gives the best effect in terms of reduction efficiency and flow detention. Which type of facility that is best suited depends on site-specific conditions such as available surface, the degree of pollution and requirements regarding treatment and detention. A facility’s ability to decrease pollution and stormwater flow depends on facility-specific parameters such as the size of the facility in relation to its watershed area, the pollutant concentration in the inlet etc.In an exploitation area in Vagnhärad, Trosa municipality, StormTac Web was used for the necessary stormwater investigation. Based on simulations with StormTac Web, the best stormwater measurements could be developed so that the planned development does not impact the recipient negatively or increase the risk of flooding in or downstream of the development area. “Through simulated results from StormTac Web regarding stormwaterflow and pollutant load, pre- and post-exploitation, we were able to adapt the exploitation and the stormwater management to achieve the required pollutant reduction and flow detention. We were able to show that the exploitation with the planned stormwater facilities will decrease the pollutant load to the recipient and reduce the risks of flooding.” Rasmus Regnstrand, Kanvas Projekt AB