Highway drainage systems

Following recent rainfall, for the next few weeks we will be prioritising reports of floods that are a risk to road users or property. This means it will take longer than usual to investigate other drainage reports. We apologise for this delay.

Highway drains are designed to:

  • remove surface water run-off from the highway to help keep roads safe and minimise problems
  • prevent damage and make roads last longer through effective drainage
  • minimise surface water from the highway affecting properties or land.

Our highway drains are not usually designed to provide drainage for other areas outside of the highway boundary.


How we look after our drains

We use a risk-based approach to maintain over 250,000 highway drains and we aim to cleanse all highway drains every 3 years.

Our approach considers many variables including:

  • road classification (A-road, B-road)
  • speed limit
  • if it is a known flood zone.

Strategic and locally important roads are cleaned yearly, whilst our minor roads are cleaned either yearly, every 2 years or every 3 years.

Find out more about our approach for managing highway infrastructure.

Drains on high-speed roads are checked once a year between April and September.

If a gully is causing flooding or concern, please report it to us so we can investigate the problem.

We aim to carry out non-emergency drainage cleansing in 28 to 90 days, but during extreme weather or periods of high demand this can take longer.

If flooding from the highway is causing internal property flooding or making the highway impassable for users, then we will attend as an emergency within 2 hours where possible. During extreme events of flash flooding this is unfortunately not always possible.

If we find any defects during routine maintenance these are passed to a drainage engineer for further assessment.

Park your car somewhere else if you see signs telling you that cleansing will take place. We can't clean the drains if your car is in the way.

Don't tip waste, such as concrete and oil, down the drains as this can block the pipes and contaminate nearby streams, rivers and land.

Remove fallen leaves covering gully grills if you can do this safely. When doing this:

  • wear gloves if you are clearing leaves by hand
  • put leaves in your normal rubbish bin or in a compost bin
  • be careful not to step into traffic on the road and be aware of pedestrians
  • don't lift the drain covers or put your hands into the drain as there might be sharp objects you cannot see.

To repair or improve our drainage systems, our work includes:

  • investigation work
  • minor works
  • broken pipe repairs
  • installing and enhancing drainage systems.

Our drainage engineers can carry out specialist work such as CCTV investigations and root cutting in order identify defects and remedy them with the appropriate repairs.

If flooding keeps happening in the same place, we will investigate how the situation can be improved and when we will do the work.

These works are prioritised according to the risk to highway safety and risk to internal property flooding.

If a blocked drain or flooding on a road is causing you concern report it to us.

Other parts of our drainage system

We look also look after ponds, lagoons, pumping stations and soakaways which drain water from the road.

Ditches and grips

Ditches are generally the responsibility of landowners, although these ditches may take highway surface water. If a ditch needs maintenance works we can request landowners to do the required work.

Find out more about  owner responsibility for rivers and ditches

Ponds and lagoons

Some highway drainage systems drain to roadside ponds and lagoons. These are inspected and maintained in response to reports of flooding.

Pumping stations

We own 15 highway pumping stations. These are serviced every 12 months with additional maintenance if needed.


Soakaways are large underground tanks. Water drains from roadside drains, through pipes and into these chambers where it gradually soaks into the ground. If cleaning roadside drains doesn’t clear the flooding, we investigate if nearby soakaways may also need cleansing.