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Discover The Next-Generation of Drainage Design

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Next-Generation Drainage Design

Causeway Flow provides next-generation drainage design capabilities without high costs, initial licence fees or feature trade-offs.

Flow is a hydraulic modelling package for the design and analysis of an optimal, compliant and cost effective storm or foul water drainage networks. Built on state-of-the-art technology, it is designed to be a robust, intuitive and affordable alternative to what the market currently offers, capable of seamlessly integrating with existing solutions to take your drainage design to the next level.

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Designed By Industry Specialists, For Industry Specialists

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Optimise the resources you have

Provide the team with the licences they require to work as efficiently as possible without breaking the bank.

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All of the tools your team needs

Access all of the tools your team is likely to need, including network analysis, storage and SuDS design, simulation, CAD integration and BIM.

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BIM compliance

Deliver the BIM outputs clients require.

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No need to wait for an available license

All engineers can have access to licences on demand.

PDS modules

Access all of the modules you need

The new subscription bundles mean that the extra packages you would have liked but could not justify could now be available as standard in one of our bundles.

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BIM outputs without changing your workflow

BIM tools allow you to design as usual, but deliver BIM outputs as required.


Network licencing as a standard

Gain a licence manager hosted by Causeway. All licences are wide area networked and ensure optimisation.

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CAD agnostic

Use SmartDrainage to integrate Flow with AutoCAD. Alternatively, integration with PDS will allow you to read and write DWG files as standard, therefore if you run AutoCAD LT it will still work for you. Full MicroDrainage integration support also included.

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Rationalise your supply chain

If you currently have legacy software, Flow will provide your engineers with the latest tools. This will allow you to cut the annual maintenance you pay to other suppliers, saving money on your overall annual spend.

A New Way To Buy Drainage Design Software

Flow Bundle packages offer a new way to design drainage networks and a new way to buy software. They are designed to offer you all the drainage design capabilities you need, without the unnecessary costs of those you don't.


For those needing straightforward hydraulic design capability
  • Flow
  • Flow+
  • Drainage Layout and Annotation (SmartDrainage and PDS Drainage)
  • Flow and MicroDrainage Integration
  • BIM Design


For those needing to deliver BIM outputs
  • Flow
  • Flow+
  • Drainage Layout and Annotation (SmartDrainage and PDS Drainage)
  • Flow and MicroDrainage Integration
  • BIM Design
Training courses

At Causeway, we are committed to providing ongoing support for our products. We offer a range of training courses that cover everything from the latest tips and techniques for getting the most from Flow Drainage Design, to the practicalities of effective and seamless Flow / MicroDrainage integration.  


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Book Your Free, No-Obligation Demo

Whether you want to experience Flow's state-of-the-art features for yourself, to get a personalised quote, or need help deciding on the most suitable bundle package for your needs, our experts are on-hand. Simply fill in the form to get started. 

Causeway Flow Features


Flow is a complete drainage design and modelling software built on the Modified rational method for sizing any conveyance system and the state-of-the-art 1D SWMM engine for hydraulically analysing any storm drainage system. Flow empowers engineers, consultants, developers and approving authorities to delivers an optimal and compliant design at micro or macro catchment level.

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Whether working on a greenfield site or on a brownfield re-development project, Flow will empower you with an advanced software to deliver an optimal preliminary or detailed drainage design. Design storm water networks using the Modified Rational Method, and design foul networks in accordance with the requirements of BS EN 752:2008. Flow enables designers to combine new design with existing networks seamlessly to conduct integrated hydraulic analysis, including negative falls or backdrops, throttle pipes and bifurcations.


Automated calculation of falls to give minimum velocity. Pipe diameters selected from a pre-defined set of pipe sizes, manholes sizes calculated in accordance to Sewers for adoption or user definable conduits. Automated backdrop removal and design for capacity to give optimum cover depth or to meet known outfall level. Lock nodes and links to prevent the design engine making any changes to specific parts of the network.

SuDS Design

SuDS can be designed and modelled to satisfy the latest guidance (SuDS Manual C753) via templates, then cascaded with flow-back to upstream structures in the event that downstream structures fail. SuDS can also be designed at the detailed design stage independently or combined with traditional storm water drainage network, to help manage quantity, quality, amenity and biodiversity to comply with latest guidance.


Define network as a set of nodes and links making designing multiple links possible, with the added spinoff of not needing dendritic numbering system meaning great flexibility. With Flow+ this will allow the modelling of multiple outfalls, bifurcations, linear drainage and many more complex models.

Pre-development Calculation

Calculate pre-development runoff rates and volumes to show equity or betterment to post-development runoff rates and volume. All of the latest UK-specific greenfield and brownfield runoff calculation methods are covered. For SuDS feasibility analysis, quickly estimate storage sizes to begin designing infiltrating structures in detail.


Define or import rainfall data by specifying FSR, FEH99 and FEH13 rainfall data or directly specify rainfall profiles and add a climate change factor. Automatically generate time varying rainfall using UK 50 percent summer profile from 15 minutes to 7 day duration. Analyse one or multiple storm durations in single run with result collated and critical durations automatically identified at every node.

Hydraulic Simulation

Simulate the design using cutting-edge 1d dynamic wave routing over multiple storm durations for a range of return periods and profiles. Hydraulically analyse drainage systems to identify and solve issues with any design swiftly and effortlessly. Dynamic wave routing takes account of node and link storage, backwater effects, entrance and exit losses, flow reversal, and pressurised flow. The engine solves the complete one-dimensional Saint Venant flow equation to simulate the transport of water through the drainage systems, producing the most theoretically accurate results.


Model open manhole, sealed manhole and junctions. Design Flow controls composite inline controls, overflow and multiple controls to set a range of discharge rates. Model storage and infiltration structures as on online or offline arrangements, loops and additional losses, to control flooding. Drain down time can be adjusted to check the feasibility of each SuDS option.


Model flow controls composite inline controls, overflow and multiple controls to set a range of discharge rates. Several manufactured controls such as Hydro-Brake, ACO Q-Brake and hydroslide are supported. Flow also supports all types of storage and infiltration structures as on online or offline arrangements, loops and additional losses, to control flooding. Drain down time can be adjusted to check the feasibility of each SuDS option. Multiple flow storage and infiltration structures can be designed and simulated seamlessly. Use our unique Flow Through Pond (FTP) technology designed to closely mimic natural flows through conveyance storage or infiltrating structures.

Easy Import/Export

Import/Export functionality supports several formats including the capability to copy and paste from any Excel spreadsheet. Supports industry file formats: .SWS .EWS and .MDX formats

Live 2D and 3D visualisation

Graphically visualise any drainage network in longsection and plan forms and detect crossings and clashes. Allows longsection, graph and plan graphics to all be displayed simultaneously or any combination thereof. Design any drainage network whilst visualising live in both 2D and 3D global view, giving you unparalleled capability to achieve a design objective efficiently. View real-time animation of water levels on longsection, graph and 3D view all synchronised, using standard controls and intuitive navigation through the simulation results via live graphs or output hydrographs.

Compliance Audit

Conduct automatic compliance audit to check against approval authorities requirements before submission for consent. Perform up to 16-compliance test that determine whether a design is suitable for approval based on a set of user definable pre-defined criteria. This will allow you to identify, understand and resolve any problem with a drainage network automatically, speedily and effortlessly.


User customisable Report of the design output data to formats such as Excel and PDF.

Flow +

Flow+ empowers engineers with the ability to model complex existing systems including negative falls or backdrops, throttle pipes and bifurcations. This capability allows seamless integration of existing models with new compliant design. Model links/pipes with negative falls and/or backdrop, links/pipes with insufficient capacity to carry the design flow, complex non-dendritic network containing nodes/manholes with multiple outgoing links/pipes, bifurcations, parallel runs or looped systems, separate online controls for each outgoing link and ability to mix and match designed and existing network segments and simulate seamlessly. Flow+ is designed to allow any design to either follow design ‘best practice’ or to brake guidelines in order to model existing network. These complex models can be engineered using Flow’s tabular format or graphically via SmartDrainage. Visualisation of multiple link/pipe connections and all the complex models allowed in Flow+ is possible on the longsection and plan view.

Drainage Network Layout and Annotation

Storm and foul drainage networks are laid out, manipulated and edited with tools that will automatically sense manhole locations and apply depth rules appropriately. Catchment areas can be identified with multiple areas and different permeability factors applied, loaded and recorded for reference purposes. Drainage sections, combined road / drainage sections, manhole schedules and powerful user controllable annotation styles are all included.

Integration with MicroDrainage

The layout completed in PDS is exported to Causeway Flow for hydraulic analysis of the network. A dynamic link is established and any changes made in Flow will automatically be highlighted in PDS, giving the user the opportunity to accept the changes or investigate further. Importantly, all aspects of the Flow design are carried back to PDS, including flow controls and storage devises, which are essential for a complete design and BIM output. 3D networks are generated automatically in PDS from the hydraulic design. Support for MicroDrainage integration is also included.

Utilities / Services / Under and Round Building Drainage

This module addresses the growing need for our customers to model all underground utilities, not just drainage. The services module includes specific tools to aid the user model under and round building drainage, bridging the gap between the structure and surrounding infrastructure.


SmartDrainage translates a plan view of a drainage layout, constructed from standard AutoCAD/Civil 3D graphic entities, into a network of nodes and links ready for Causeway Flow to analyse. The user has only to select the outfall node; One click of the outfall node will mean SmartDrainage automatically finding all the connected nodes and links, their cover levels and catchment areas, removing the unnecessary step to re-tracing CAD drawings. The layout may be drawn specifically for this purpose, or may be a legacy CAD drawing. SmartDrainage is very versatile in interpreting the CAD structure of drawings. After analysis in Flow, SmartDrainage annotates the results and draws longsections and schedules. SmartDrainage embeds the Flow data within the AutoCAD/Civil 3D file, complete with all its non-graphic information. This keeps graphics and analysis within a single file, of a type handled by major document management systems.

SmartDrainage in AutoCAD/Civil 3D

Draw networks of nodes and links from standard CAD entities. Click on the outfall – SmartDrainage will find the network. Design non-straight links where required. Define node and link types in your own standard library. Use any layering/naming standard to assign the node and link types. Automatically assign drawn catchment areas to the appropriate nodes. Assign impermeability factors to catchment areas. Apply multiple areas to the same node if needed. Derive levels using the SmartSurface tool, or from the CAD entities. Set numbering and annotation styles. Embed multiple networks within AutoCAD/Civil 3D file and output to Flow for design and analysis with one click.

Iterative Design Cycle

Re-Import designed and analysed Flow data with one click. SmartDrainage will hold all Flow data, including ancillaries and non-graphic attributes and amend the network in CAD or in Flow as SmartDrainage will automatically synchronises both. Maintain current design as single standard dwg file per network or group of networks, suitable for all sizes of design team from one designer to joint-ventures. Manage easily on any document management system that handles dwg files. Due to all these reasons, SmartDrainage combined with Flow will significantly reduce risk of errors, saves time, money and delivers an optimal and compliant drainage design.


After analysis in Flow, update network drawing annotation, draw longsections, manhole and pipe schedules for graphical setting out, scheduling and the production of sections.

BIM Design

BIM compliance demands much more than 3D model output. All packages in the Flow & PDS Enterprise Bundle contribute to the BIM workflow with user controllable attribute data attached when generating outputs for BIM collaboration.

Network Licencing

Standardised wide-area network licencing offering our customers maximum flexibility and optimum licence utilisation for all of the functionalities of Flow Bundles. Licencing is controlled via a cloud-based licence manager hosted by Causeway, allowing access by users from any location with an internet connection. Licence borrowing is a feature that allows a licence to be borrowed from the network to a local PC for a given period of time, after which it is automatically reverted to the network pool.

Customer efficiency gains and cost savings

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Boost productivity thanks for Flow's intuitive, friendly interface

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Streamlined processes and engineer utilisation

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Save in upfront investment thanks to a subscription delivery

Partner with us

At Causeway, we pride ourselves on being more than a provider. We pride ourselves on being your partner.

We work closely with customers and listen attentively to their feedback to understand their challenges and identify the solutions that work for them. Watch how we partnered with Jacobs to develop a fully integrated solution.

Proud partners
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Get your personalised quote

Gain access to Flow Drainage Design by getting in touch with us. One of our team members will be happy to create a personalised quote for you.

Frequently asked questions

    • Flow Drainage Design is offered as a subscription service because it is a very efficient way to utilise software while minimising the impact on cash flow and providing maximum tax benefit.
    • As a customer, you are able to pick the bundle that best suits your needs and gain access to many productivity tools at a compelling price point.
    • You need to pay for the annual subscription based on the minimum term that was discussed when you purchased Flow Drainage Design Bundles.
    • No, the prices quoted for the Bundles are based on an annual invoice.
    • Yes, you can always upgrade. For example, if you pick the Professional Bundle as best meeting your immediate needs, then find customers requesting BIM outputs, you can move to the Enterprise Bundle at the difference in cost.