The Importance of Good Drainage Design

We walk over manhole covers everyday, without sparing a thought for the incredible feat of engineering far below. Advancements in drainage design is something we all take for granted.

What 5000-Year-Old Invention Do You Still Use Every Day?


At your feet lies one of the most important innovations in history. It shepherds the world’s most precious resource and is an essential component in the efficient functioning of society.


Without it disease would spread, landscapes would fall apart and our roads would become untraversable.


What is this remarkable invention?


Drainage design.


Every time it rains, you take a shower or flush the toilet, thank the drainage system that you are not up to your ankles in fouled water.  So many of the tasks you carry out daily rely on the complex network of surface and sub-surface drainage systems to maintain a sanitary environment.


It’s easy to take for granted, but rewind to just the 19th century and you will discover that inadequate drainage led to disastrous consequences, including outbreaks of cholera that killed tens-of-thousands of people in the UK alone.


These days, aqueducts act as little more than attractive landmarks.  But while the grunt work of modern drainage is carried out by far less glamorous fixings, the mechanics are more intricate than ever before.


The Unheralded Workhorse of Civilisation


Drainage design is one of the foremost concerns of any new development.  Developers must consider not only the increased flows created by new buildings, but also the impact their new construction will have in terms of flood risks to itself and the vicinity.


The impact of poorly implemented drainage design can be catastrophic. At a domestic level, inadequate drainage can lead to damp, mould and termites. Long term it can weaken the foundations of your home and cause the dreaded subsidence. On a larger scale, drainage issues can cause serious flooding and the erosion of the landscape.


In North West England and North Wales in 2017, unprecedented levels of rainfall caused severe flooding after resident’s pleas for the local council to address blocked drains went unanswered.


Yet most of the time, our drainage system functions exactly as it was designed to do allowing us to go about our lives in ignorant bliss. This, of course, is no accident. It’s all down to an intricate network of surface and subsurface drainage systems that have been meticulously calculated.


If you’re of the opinion that drainage is a wonder of the modern age, you are sorely mistaken.  Evidence of flushing toilets and advanced water waste disposal mechanisms has been dated as far back as 3000 BC.


It’s likely that, even then, drainage needed to accommodate dozens of factors including sources and volume of excess water, soil composition and land elevation, just as it does today.

Drainage Design for the 21st Century


SuDS (sustainable drainage systems ) is the pinnacle of modern drainage design


One of the biggest developments to this ancient craft has come in recent times. To keep pace with urban development’s effects on the natural order of the world, governments are increasingly insisting on drainage systems that mimic the natural management of rainwater by dealing with rainwater where it falls.


Typically, urban drainage systems carry surface water away from sites as quickly as possible to either be treated at specialist treatment plants or returned to streams and rivers. But there has been an increasing realisation that these practices are unsustainable.


Not only is the treatment of effluent water expensive, but also alteration of natural flow patterns can cause problems elsewhere in the catchment area.


Sustainable Drainage Systems (SuDS), as they are called in the UK, are designed to be environmentally friendly and cause minimal long-term damage by managing surface water run off for maximum benefit.


They achieve this by considering four pillars of design:


  • Control the quantity of runoff to support the management of flood risk and maintain the natural water cycle
  • Manage the quality of runoff to prevent pollution
  • Create and sustain better places for people
  • Create and sustain better places for nature


The development of SuDS has resulted in a new way of thinking about runoff. What was merely a nuisance for hundreds of years is now being considered a resource that needs to be managed for maximum benefit. It has also opened up the possibility for new developments in already urbanised areas where previously, developments were limited due to the capacity limits of sub surface drainage systems.


The Future of Drainage Design


HLN Engineering Ltd utilised advanced drainage design techniques as part of the company's involvement in the Roath Basin regeneration project, Tiger Bay, Cardiff


Humans, being the ingenious beings that we are, have created a number of innovative solutions that aid the implementation of SuDS.  But some of the main features of sustainable drainage have been with us for thousands of years and are simply coming back into fashion.


Modern technologies such as permeable paving, which allows rainwater to infiltrate and be returned to the environment gradually, are being augmented with ancient practices like rain gardens and filter drains.  The result?  Radically reformed drainage systems that take into account long term environmental and social factors.


By incorporating such practices, urban areas are being transformed into conscientious habitats that appreciate not only the quantity and quality of run-off, but also the amenity and aesthetic value of surface water in the urban environment.


Since its inception, drainage design has been a cornerstone of a functioning society. When it goes wrong, it’s big news, causing illness epidemics and rampant flooding.  But done right, it’s a valuable ecological resource that serves millions of people with nary a second thought.


Your Drainage Design Solution


As certified civil engineers with over 20 years experience in drainage design, HLN Engineering Ltd offers a comprehensive set of expertise that can maximise the efficiency of your development, whilst minimising the effects on the environment.


We’ve consulted on a variety of drainage projects including both commercial and residential developments, from single dwellings to multi-dwelling developments.  If you’re in need of an expert consultant in drainage design, please call 020 8099 6388 or email us at

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