The case for automatic weirs


With hosepipe bans returning to parts of the country this summer, it’s easy to forget the disastrous floods of recent years – unless, of course, you were personally affected.

This year’s harsh winter and modest levels of spring and summer rainfall belie a growing trend of more extreme weather events hitting the UK and a pattern of warmer winters and wetter summers.

As we saw three years ago in Doncaster and Tewkesbury, torrential rain and flash flooding has become a serious threat in many parts of the country. Of course, lessons have been learned but the UK’s water management infrastructure still has some way to go.

In the Netherlands, much of which is below sea-level, we are used to managing major flood events and our system of dykes and drainage channels allows us to divert, store and control exceptional flows during flood conditions.

In the UK the infrastructure has continued with more traditional systems and, for a Dutch engineer, the widespread use of manual sluices and weirs to control water flow can seem outdated: the large-scale flooding witnessed in the UK during recent years might have been less devastating if more modern water-management systems had been in place.

Today, automatic and remotely-controlled weirs are the norm in the Netherlands and other low-lying regions of northern Europe. Combined with computerised flood monitoring, they allow timely intervention to prevent flood-water from inundating built-up areas.

The traditional design of manual weirs, which require the physical winching up and down of sluice-gates or the hoisting in and out of heavy stop-logs are not only very labour-intensive but are also extremely slow to operate. Yet these remain the norm throughout most of the UK.

Managing the UK’s flood and coastal defences is the responsibility of the Environment Agency which, this summer, reported that spending on flood management had hit an all-time high at nearly £630 million so far this year. But the Environment Agency also warned that businesses, landowners and communities are going to have to spend even more as climate change raises the risk of flooding and coastal erosion.

The priority has to be the protection of heavily populated built-up areas and of course this is where the spending is concentrated. But even so a farmer grazing sheep on low-lying marshland will rely upon several manual weirs to protect his land and his flock. When storm conditions arrive the farmer will have to venture out to the outer fringes of his land to manually close off a dozen or more weirs and he can only place one stop-log at a time.

If the flood arrives with the speed and ferocity of recent events, this farmer will be literally risking his life as he will be unlikely to get round to all the weirs and adjust them manually in the time he has available.

Automatic weirs offer a level of control that is unachievable with static designs. Modern telemetry and remote water level monitoring has made it possible to react quickly to a rapidly developing flood situation by closing or opening a network of weirs from a central location.

Automatic weirs such as those made by Kiljstra are lightweight pre-cast units featuring concealed mechanisms for added security. They are easily installed and once set up require minimal maintenance.

The weir gates are powered either by mains electricity or, when installed in a remote location, by batteries which have a service life of up to six months (which normally equates to around 28 one-minute cycles per week). They can be controlled locally or via SMS text messaging, allowing a single operator to close a whole sequence of weirs simultaneously.

Considering the advancement in technology now being employed in the UK water industry it seems a natural progression.

This type of weir is an appropriate solution given the technology already employed in the industry here in the UK. Our understanding of weather patterns and our ability to model the effects of these patterns using computer technology gives us the ability to plan ahead more effectively and to consider introducing more technology based systems rather then relying just on manual weirs to protect ourselves from flooding.

Automatic weir systems have an established role to play in modern water management technology and the latest generation of weirs not only deliver better performance but will bring significant long-term savings in reduced labour and maintenance requirements.

The Environment Agency is receptive to new technology and in fact has already specified automatic weirs on at least one project. However, the natural tendency from within the industry to view new and unfamiliar methods with caution means that automatic weirs still have a case to make in the UK.

There’s no doubt that automatic weirs are under-utilised in the UK today. But with flooding risk likely to increase during the foreseeable future and investment in infrastructure now an urgent necessity, their use can only grow in the UK.


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