Containing the Flood Threat in the Derbyshire Town of Matlock
As Britain is once again battered by seasonal storms, the flood defences and related construction works in the Derbyshire town of Matlock completing and the town is awash with discussion about whether it will be enough to protect local homes and businesses from the ever-increasing threat of flooding.
Local environmental engineers, Simon Edwards and Mark Bradbury from environmental consultancy IDOM Merebrook based in nearby Cromford, discuss the wider flood threat for Matlock and the area.
Nestled in the heart of Derbyshire, the picturesque town of Matlock, popular with tourists for its stunning countryside and rich Victorian history is marred by the persistent risk of flooding.
This year residents have endured extensive construction works within the town centre to build back the town’s flood defences.
As the project nears completion and the Environment Agency has announced a major milestone in the completion of the flood wall, the town is awash with discussion about whether this will be enough to protect local homes and business against ever increasing threat of climate change and rising water levels in the area.
The Derbyshire town has always been susceptible to flooding; the steep hills and run off water from the Peaks pose a threat, as does the river Derwent that runs through the town.
As in other Victorian towns around country, Matlock’s heightened risk of flooding is also attributed to an antiquated Victorian drainage system - once a thought of a remarkable feat of engineering, but today struggling to cope with the increasing frequency and intensity of heavy rainfall and flash floods that climate change has bought.
Simon Edwards, Regional Director of Idom Merebrook commented:
“Flooding in Matlock is well documented back to early 1900s, in recent years Matlock has experienced a series of flooding events that have disrupted daily life in the town and left a trail of damage in their wake.”
“As we once again approach the wetter season in Derbyshire, the risk is particularly acute and causing concern to business owners and residents. From an engineering perspective, while significant investment has been made to reinstating protection to the town from river flooding, we question whether this alone will fix the problem.
The town’s drainage infrastructure needs urgent attention and so too does the town’s housing stock and future development plans.”
Mark Bradbury, Director of Engineering at IDOM Merebrook added:
“The frequency and magnitude of extreme weather events is increasingly worse as time goes on. While there is little that can be done about the sheer volume of water, measures can be put in place to better manage it by slowing the rate and controlling the flow.
Investing in a modern drainage system to better withstand the increased environmental challenge should be a priority.”
The drains that serve Matlock like many Victorian towns are known as combined sewers and do not separate foul and surface water. Combined sewers becoming overwhelmed by increased rainfall are causing a preventable environmental and public health problem by merging raw sewage with stormwater runoff.
Combined sewer overflows, whereby raw sewage and excess water is mixed and discharged into nearby rivers and lakes release harmful pollutants and creating contamination, something that could be avoided through modern drainage designs.
Addressing Matlock’s flood risk is complex and in addition to the measures that have been put in place the year by local authorities, is likely to need further investment and watercourse modelling to mitigate the risk.
In addition to an overhaul of the towns drainage system, Idom Merebrook also suggests a greater focus on Sustainable Urban Drainage Systems (SUDS). SUDS solutions such as permeable pavements, green roofs and urban wetlands can all help absorb rainfall and reduce the pressure on traditional sewage systems.
Matlock like many other northern towns, does not have good natural infiltration and natural soakaways, indeed the hilly terrain and clay soils contribute to flash floods.
Mark advised: “It is likely that engineered solutions in the case of Matlock could offer more protection than natural defences. A wider spread development of SUDS in the town could be helpful in slowing and spreading the flow of storm water.
While it may seem counterintuitive, Matlock could benefit from increased new housing developments if future proofed for climate change, and if appropriate measures are put in place at design stage to support better attenuation of flood water.
New developments can offer betterment, and effective high-performance SUDS could help address and improve Matlock’s flood risk, rather than simply not adding to the problem.”
Simon commented: “In the case of large developers’ compliancy may be less of an issue but it is essential that regulators insist upon all the necessary hydraulic analysis and adequate engineering designs. This may be more difficult to police with smaller developers and residents themselves altering the terrain by adding patios, driveways etc. to their properties and we therefore must aim for a strategic view which accommodates these effects.”
Mark concludes, “These are all undoubtedly costly and time consuming, and need to form part of an overall assessment with detailed watercourse modelling taking into account rainfall patterns and terrain data to help design and optimise flood defence systems.
The predictive capability of watercourse modelling can be an indispensable tool in the fight against flooding by helping to determine the most effective locations for flood barriers, embankments and drainage systems.
By simulating different scenarios environmental engineers can refine designs to maximise protection, while minimising environmental impact - such as putting in place measures to safeguard biodiversity if natural watercourses become altered through flood defences.”
A combination of watercourse modelling, enhanced drainage, high performance SUDS and robust flood walls along the river Derwent are all tools which, when combined can shore up the flood risk, safeguarding Matlock for future generations to enjoy.
