Flood and Pollution Prevention for UK Highways

According to a survey by the Department of Transport in 2017, there are nearly 250,000 miles of road network in the UK.  The size of these roads and the amount of traffic they carry vary from Major Roads, motorways and highways, including the Strategic Road Network, down to small private roads that have been in existence since the 19th Century.  Major roads make up 31,400 miles, with 2,300 miles of motorway and the remainder is made up of local authority managed B, C and U categories.

These roads, which we’re adding to every year, represent a large amount of impermeable area where rainfall cannot follow a natural route back into the water cycle and must run off into either sewers or local watercourses.  This surface water needs to be managed effectively to ensure road safety and reduce flooding impacts.   It also contains a high pollutant load that should be removed to protect the water environment. 

We have over 40 years’ experience in controlling and treating surface water flows and our range of Hydro-Brake® Flow Controls and StormTrain® stormwater treatment systems have been developed and designed with performance, plug-and-play installation and easy maintenance in mind.   We've put together a short overview of the Guidelines and Regulations for the design of roads in the UK.

Control and attenuate surface water flows to prevent flooding 

Surface water runoff from roads and highways must be drained efficiently to avoid deep surface ponding that would be unsafe to drive through, but at the same time it must be controlled so that it doesn’t cause flooding to other areas.

For highway engineers, the selection of a flow control can seem a very small part of an overall drainage design, but it can have a significant effect on the performance of the system.  Choosing the right flow control can provide benefits such as a reduction in the amount of storage required, a reduced risk of blockage or a reduction in the drain down time for storage areas, ensuring that the system is ready for subsequent storm events.  Flexible installation options can also help to reduce installation time making it safer for roadside workers.

Our Hydro-Brake® Flow Controls can provide effective control and our Stormcell® and Stormbloc® Optimum modular geocellular storage and infiltration systems can store the excess flood water until it can be released back into the surrounding ground or discharge downstream at a safe and controlled rate.

Hydro International have a range of Hydro-Brake® Flow Controls so that engineers can select the most appropriate and best performing for a given scheme.  

Hydro-Brake® Optimum, our most popular and widely used vortex flow control, is precision-engineered.  Each unit is customised to help meet differing site objectives, such as to reduce the amount of storage volume required or with larger orifice size to provide a reduced risk of blockage.  The Hydro-Brake® Optimum also has a future-proof option which can provide a flow rate adjustment of plus or minus 10%.

Design your own Hydro-Brake® Optimum flow control with our online design tool: hydro-int.design

Hydro-Brake Optimum WRc and BBA logosOur Hydro-Brake® Optimum is the only vortex flow control which is BBA and WRc approved for design and performance.  Find out more about Hydro-Brake® Optimum.

Our Hydro-Brake® Flow Controls can be delivered pre-installed in a concrete chamber as a "plug-and-play" unit which is ready for rapid and easy installation, reducing the amount of time spent at the roadside and improving CDM requirements.

Stormbloc® Optimum is a resilient geocellular storage system that provides underground storage and infiltration for surface water runoff.  Lightweight materials combined with robust design make it easy to transport, quick to install and extremely durable, even beneath high-traffic areas such as roads, car parks and warehouse yards.  All systems can be installed with fully inspectable chambers including the option of a sand trap to manage sediment build-up in the tank.  With Hydro-Logic® Smart Monitoring, levels for both flow and sediment build-up can be detected, triggering alerts for maintenance and reducing the cost of unnecessary inspection visits. 

Stormcell®  is a high-capacity, low-maintenance modular stormwater and surface water storage system, which is light but strong, making it ideal for use beneath areas such as roads, car parks and industrial areas.  With a design that ensures that solids are washed through the pipework rather than into the storage area, the system requires very little maintenance.  

Stormbloc Optimum & Stormcell storage & infiltration systems


Get flood and weather warnings to enable faster response to adverse conditions

Roadside flood warning signGet early flood warning to reduce risk to road users 

Hydro-Logic® Smart Monitoring can provide accurate and early Flood Warning to reduce or even eliminate the risks to the public by providing up-to-date and accurate information around likely and current flood levels.  

Hydro International’s Hydro-Logic® Services team are the leading independent provider of flood warning systems to local authorities in the UK, with over 900 flood warning sites for over 85 councils and land drainage authorities.

Find out more about flood warning services here.

Get early snow and ice detection for rapid deployment of maintenance crews and help reduce risks for road users

Early warning is crucial to the management of risk of inclement weather in order to allow maintenance crews time to perform their essential duties and inform road users. 

Our Hydro-Logic® Smart Monitoring system with the Sommer Ice Detection System IDS-20, can provide advanced warning to maintenance teams and the general public if required.  The system is able to distinguish between water and ice, so can detect when ice has formed and its thickness.  It can also detect when the climate conditions are likely for ice to form or thaw.

Protect the water environment from the harmful pollutants in highway runoff

Surface water runoff from highways carries a high pollutant load which includes silts and grits, litter and debris, organic (PAH’s) and inorganic pollutants, other nutrients (phosphates and nitrates), salts, heavy metals and oils and hydrocarbons.

The Environment Agency summarises the problem of highway runoff:
“Highway surface runoff discharges may contain pollutants that have accumulated on the carriageway, particularly following periods of dry weather. These pollutants can then be transported via the surface drainage system to discharge to ground or receiving watercourses. Previous studies have demonstrated that highway runoff affects the quality of waters and sediments. Increased concentrations of metals, hydrocarbons and anions are associated with changes in the structure and functioning of biological structures”.

Environment Agency report: The Long Term Monitoring of Pollution from Highways Runoff: 25 June 2005

We are experts in solids / liquids separation and have developed a range of stormwater treatment devices to deliver reliable, repeatable and easy to maintain pollutant removal solutions. These devices have no moving parts, require no power and have a small footprint which enables them to be fitted into existing road drainage margins.
Our stormwater treatment systems can all be used as standalone solutions, but can also work alongside or enhance other solutions such as ponds and swales.

Pollution removal for major roads including the Strategic Road Network (SRN)

For Highways England officers and their associated road construction and maintenance contractors, our range of surface water treatment devices deliver proven, measurable and repeatable surface water runoff treatment, targeting and removing pollutants that could harm the water environment. The small footprint and modular ‘plug-and-play’ design ensure that time spent at the roadside for installation and maintenance is reduced as much as possible, greatly reducing health and safety risks and providing substantial cost savings.

Downstream Defender highway installationOur Downstream Defender® is an advanced hydrodynamic vortex separator which has been referenced within the DMRB guidance and CIRIA 753.  It is the only vortex separator that is certified by the WRc, and has also been approved and installed on a large number of Strategic Road Networks (SRN) within the UK. 

For design flexibility our First Defense®  vortex separator can offer multiple inlet options, including:

  1. up to two inlet pipes,
  2. an inlet grate feed to help fit the unit within an existing drainage line,
  3. customised inlet/ outlet pipe orientations.

The first installations of Downstream Defender® on the Strategic Road Network (SRN) were on the M25 in 2007.  Since then Downstream Defender® and First Defense® units have been installed across many areas of the SRN, providing reliable, high performance pollutant removal and protecting the aquatic environment.

Our vortex separators have a small footprint and can usually be installed within existing road margins. They can also provide pre-treatment to ponds and swales, removing litter and oils from the flows and preventing build-up of silts and associated pollutants. With the addition of Hydro-Logic® Smart Monitoring, alerts for maintenance can be sent only when required, reducing the cost and risk of unnecessary roadside inspection visits.

First Defense® can also be adapted to an inlet grate feed to help it fit within an existing drainage line.

For sites where a higher level of treatment is required, the Up-Flo™ Filter can provide multi-stage treatment, including screening and filtration all in a small footprint.

Pollution removal for principal and minor roads

For Council / Local Authority Highways Officers and their contractors responsible for construction and maintenance of the urban highway network Up-Flo™ Filter and Hydro Biofilter™ can deliver high performance pollutant removal in a small footprint which is ideal for new and retrofit schemes in space constrained sites.

For larger roads with higher runoff rates First Defense® and Downstream Defender® will provide targeted pollutant removal over a wide range of flows. With Hydro-Logic® Smart Monitoring, alerts for maintenance can be sent only when required, reducing the cost and risk of unnecessary roadside inspection visits.

Our Up-Flo™ Filter is a multiple-step surface water treatment system that combines sedimentation and screening with fluidised bed filtration to deliver exceptional surface water pollution removal.

With a small footprint it can provide protection to the water environment where there is no room for swales or ponds for treatment.  Find out more about the Up-Flo™ Filter.

Hydro Biofilter™, with its shrub or small tree can help add biodiversity while providing a high level of surface water treatment, including dissolved pollutants. Its small footprint, but high pollutant removal performance makes it ideal for urban streets and retrofit applications.
As Hydro-Biofilter™ is small and contained in a concrete chamber it can be used on brownfield sites where infiltration isn’t possible or for retrofit into small urban spaces.

Hydro Biofilter Design EguideOur E-Guide: How to Design a Hydro Biofilter for Urban Stormwater Treatment contains more information relating to the Manual for Streets & Designing Streets and also outlines some further useful reference sources relating to Sustainable Drainage Systems (SuDS) as applied in a highways context.

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