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Engineering Services

Last Modified March 14, 2024

We are the Land Drainage Authority for Hertsmere and have permissive powers granted under the Land Drainage Act 1991 and the Hertsmere Land Drainage Byelaws 1998. These powers allow us to maintain and improve existing ordinary watercourses, to construct new works and serve notices to instruct people to carry out necessary works to maintain the flow in ordinary watercourses.

Engineering Services maintains a programme of flood defence works, carries out maintenance of strategic sections of the land drainage system within the borough and provides assistance and advice on drainage related matters, including the acquisition of commercial opportunities.

Unfortunately determining the responsibility for drainage and flooding problems can be complicated.

Who's responsible for what?

Water and sewerage companies in England and Wales are responsible for private sewers. Thames Water, the sewerage undertaker for the Hertsmere area, has produced an explanatory booklet which can be downloaded from the Thames Water Utilities site.

Engineering Services can advise you on the ownership and responsibility of a particular watercourse or drain, however, as a guideline:

Public sewer

Thames Water Utilities is the Sewerage Undertaker within the Hertsmere area. A copy of the public sewer map, as issued by Thames Water, can be viewed at the council offices during normal office hours.

Private drain

A private drain is the pipework that serves an individual property until it leaves that property's boundary, (ie the pipe crosses into a neighbours property or under the public highway) or until a neighbouring property connects into the pipework (ie the point at which the pipework serves two or more properties) This applies to both foul water (from toilets and sinks) and surface water (rain water from roofs and driveways). This pipework is usually the responsibility of the property owner that drains through it. The council does not have records of any private drainage.

There are exceptions to this, blocks of flats may be treated as one property and surface water discharging to a communal soakaway or directly to a watercourse may remain private. Please check with Thames Water Utilities for clarification.

Main rivers

Major watercourses and rivers are designated 'main rivers' and are under the control of the Environment Agency, contact them for further advice and help.

Non-main rivers

Ordinary watercourses and land drainage are generally the responsibility of the owner of the land that it flows across. This person is known legally as the Riparian owner.

Highway drain

A highway drainage system collects run off from adopted highways, usually via road gullies and is the responsibility of the Highway Authority, this explanatory diagram explains the differences. Ditches that run along the side of adopted highways and collect highway run off may be the responsibility of the Highway Authority or the land owner or a combination of both. This person is known legally as the Riparian owner.

What do engineering services do?

Services provided include the following:

  1. Emergency cleaning of obstructions on sections of ordinary watercourses (including ancillary assets) where the council is the riparian owner or where it has exercised its discretionary land drainage powers.
  2. Emergency response to pollution incidents affecting watercourses, including co-ordinating with those responsible for the pollution source and liaising with the Environment Agency, sewerage undertaker (Thames Water), county council (Highways) and the emergency services.
  3. The provision of advice on flood warning, flooding related issues and drainage responsibility via the standby officers.
  4. Provision of free sandbags and assistance during flooding subject to available funding and resources to Hertsmere residents, with priority given to the most vulnerable.
  5. The provision of an emergency response service, subject to availability of resources, to fee-paying customers, including:

Drain blockage clearance
Tanker works, including gully cleaning
Over pumping
High pressure jetting
Manhole cover repairs

       6.  The provision of consultancy services to fee-paying customers including the following:


  • Land Drainage Consultation
  • Drainage Impact Studies
  • Feasibility Studies
  • Topographical Land Surveys
  • Drainage Surveys inc CCTV & Confined Space Entry
  • Sewerage System Hydraulic Modeling
  • Design of Small Drainage Systems inc Pumped Systems
  • CAD services 
  • Contract documentation and specification 
  • Project management 

Build and maintenance 

  • New build and maintenance of existing drainage systems 
  • High pressure jetting 
  • Manhole cover repairs 
  • Drain tracing 
  • Pollution tracing / studies 
  • CCTV surveys to OS20x standard 
  • Minor repairs to sewers and drains 
  • Maintenance of watercourses and control structures on behalf of riparian owner.

What is a watercourse?

A watercourse is defined as any channel through which water flows and can be open or enclosed underground as a culvert. Watercourses may be classed as either 'main rivers' or 'ordinary watercourses'.
Watercourses occur naturally, they serve to drain the land and assist in supporting flora and fauna.
Historically watercourses have taken surface water run-off from buildings and roads, as well as fields and parks. In the process of development many have been covered or changed in other ways.
In normal conditions the watercourse may be a dry channel in the ground
In storm conditions it may become a raging torrent
Continued development tends to increase the rate at which water is discharged to watercourses, (even though adequate safeguards to prevent this are available), a process that can lead to increased risk of flooding.

What is a riparian owner?

Under Common Law you are the riparian owner of any watercourse within or adjacent to the boundaries of your property. Where a watercourse is sited between two or more property boundaries each property owner is equally responsible. For clarification of any matter relating to your role as a riparian owner please contact Engineering Services who can also provide advice and assistance.

External Links:

Environment Agency

Thames Water Utilities Ltd

Affinity Water

Hertfordshire County Council (Highways)

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