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Water Course – how climate change is changing drainage systems

28 Sep 2018

Water Course – how climate change is changing drainage systems

Climate change is the talk of the moment, with consumers being encouraged to reduce and monitor their water consumption.

Summer 2018 saw record temperatures across the UK with higher than average temperatures predicted to last until October and a hosepipe ban in full effect across parts of the UK. As a result we are becoming more conscious of water usage than ever.

During the summer months it can be easy to forget about the rainy, cold days of autumn and winter. However just last year, unprecedented levels of rainfall brought devastating flooding to areas of the UK, destroying homes, belongings and livelihoods.

Last year’s floods, and those in preceding years, have many causes and it would be wrong to lay the blame on one single reason. However, there is no doubt that the laying of impermeable ground surfaces such as concrete and tarmac in areas of the country has reduced permeability, and rainwater has had nowhere to escape to. The British drainage and sewer system is at its maximum capacity in many areas, particularly in the regions where the highest level of flooding has been experienced.

Worryingly, recent research shows that extreme flooding may become more frequent in the UK due to climate change, with almost five times more heavy rainfall events predicted to exceed 28mm in one hour in the future than currently.

In the UK there is a growing acceptance that a more sustainable approach is needed to managing rainfall and flooding. If flood water is effectively managed it can be recycled and used when needed.

Through a Sustainable Urban Drainage (SuDS) system storm water can be absorbed by permeable paving through enlarged joints, which are filled with grit instead of sand which is used in conventional paving, and stored in a special sub base beneath the paving. This acts like a huge tank, and the aggregate that is used for the sub-base filters out most of the pollution that may have been washed off the roads and roofs.

Of course the question of cost always raises its head when considering SuDS solutions. There is a general consensus that permeable paving is a highly expensive solution. However, when the overall drainage costs are taken into consideration permeable paving can be a very cost effective solution compared to traditional methods.

It is also worth bearing in mind that unlike some other SuDS solutions, permeable paving does not require any additional land take, and so does not reduce the number of viable units on a housing project.

Today, few would disagree with the principle that SuDS and techniques such as permeable paving are needed to help fight flooding and pollution – particularly with overloaded sewers, urbanisation and climate change.

In April 2015, the government introduced new planning guidelines for the use of SuDS on any new housing site with more than ten units. The aim of the guidelines is to ensure that any new development has measures in place for combating potential flooding issues.

A good example of this is in Wales. From January 7 2019 proposed new developments must be served by sustainable drainage systems which comply with the Welsh minister’s standards and is approved by the SuDS Approving Body (SAB).

Furthermore, the Environment Agency recommends that where appropriate, storm water source control measures, which also improve water quality, should be incorporated into a development proposal. They are essential for any new development in areas where existing sewerage systems are at full capacity.

With the recent flash floods in parts of England, it appears highly likely that this legislation will be adopted throughout the rest of the UK.

Article & Image Source: Housebuilder

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