Scottish Water seeks out sustainable sewer flooding solutions
Scottish Water has announced a new plan to reduce flooding incidents by managing storm water on the surface rather than in the country's sewers.
The strategy, launched on Monday, highlights that more effective ways of dealing with storm water above ground will substantially reduce pressure on nearly 32,000 miles of sewer network operated by the utility.
More than 43,000 homes and businesses are at risk of surface-water flooding. Sewers can be overwhelmed by surface-water flooding and can also contribute to that flooding in places.
Experts from Scottish Water assess that rather than building bigger sewers to deal with increasing volumes of surface water, more sustainable solutions are needed for the future.
A number of pilots are being considered across the country to test new methods in communities that will reduce flooding risk. These will include more natural approaches such as diverting roof and road water through channels to ponds, use of permeable paving, and property-level raingardens.
The new approach, which will be more adaptable to climate change, could substantially reduce the impact of sewer flooding on householders and businesses. Tackling sewer flooding is a high priority for Scottish Water, which is committing £190M of investment to tackle the issue in the 2015-2021 investment period.
Addressing the capacity of the sewer network will also help support economic development across Scotland by enabling new properties to connect to Scottish Water’s network.
Launching the Storm Water Management Strategy at the SNIFFER (Scotland and Northern Ireland Forum for Environmental Research) Flood Risk Management Conference at Strathclyde Technology and Innovation Centre, Dawn Lochhead, Scottish Water’s Flooding Manager, said: “Increasing urbanisation and changes in climate patterns, including more intense wet-weather events, means that many sewers can be overwhelmed with increasing volumes of surface water.
“This can result in dilute sewage flooding homes, gardens and highways and can cause pollution to streams and rivers from increased spills from sewer overflows.
“Traditionally we’ve built larger tanks and bigger sewers to deal with the increasing volumes of surface water. While these will still be needed, the aim is to build more sustainable solutions to manage water on the surface rather than putting it into pipes in the ground. This is a more sustainable approach and more adaptable to future changes from climate change.”
The sewerage system in Scotland is, for the most part, a combined system – draining both sewage and surface water. It also contains overflows that allow excess water to spill in a controlled manner from the sewerage system into water courses.
Lochhead said: “Sewer capacity continues to be impacted by factors including increased paved area run-off, groundwater infiltration, river intrusion, land drainage run-off and asset condition.
“This is just the start of a long journey to transform our approach to tackling sewer flooding. Scottish Water sewers do not work in isolation and, as such, we cannot continue to develop and deliver our strategy in isolation. Partnership working with local authorities and engagement with communities will be the key.
“This will link into the Flood Risk Management Strategies and local authority-led surface water management planning for those towns and cities prioritised as having the highest risk of surface water flooding.”
Environment Secretary Roseanna Cunningham said: “Reducing flood risk is a priority for this Government as climate change and increasing areas of hard surfaces mean more rainwater is entering the sewerage network. Scottish Water’s Storm Water Strategy is an important contribution to the collaborative efforts being made to transform the way Scotland manages surface water and flooding.”
Speaking at the WWT Wastewater conference in Birmingham last week, Scottish Water’s Wastewater Asset Strategy Manager, Gordon Reid, said “we have to act now when it comes to climate change adaptation”, particularly when taken in conjunction with predicted population growth and the challenge of fats, oils and grease (FOG) in sewer systems.
Discussing the company’s long-term plan to reduce flooding risk, he told delegates: “There may be in some catchments a need for key infrastructure elements... but the majority of this should focus on storm water removal from the combined sewer network. It’s not just going to be 25 years, probably more like 50, but we do need to start now because we’re already seeing the impact of climate change.”
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