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Surface Water Alleviation Schemes - SWAS

Surface Water Alleviation Schemes

Essex County Council has lead local responsibility for reducing the risk of flooding from surface water, groundwater and ordinary watercourses and to work closely with other organisations under the Flood and Water Management Act 2010.

The County Council has two key teams with responsibility for dealing with flooding. ECC’s Flood and Water Management Team are responsible for identifying broader flood risks, developing strategies for mitigating them and working with various partners, such as the Environment Agency, utility suppliers, landowners, developers and third-sector organisations to reduce potential and actual flooding.

Day-to-day flooding, on the highways that Essex County Council are responsible for, is generally managed by Essex Highways, using gully cleaning teams and/or our Surface Water Alleviation Scheme (SWAS) process.

If flooding is known to be caused by off-highway problems, or if the flooding affects areas (homes, businesses etc) off the highway, then ECC’s Flood Management team will get involved. You can read more about their work, and report off-highway flooding, on the Essex flood and water management site.

 

Essex Highways flooding work

Essex Highways takes surface water drainage and flooding issues very seriously as they are likely to generate safety and environmental problems. However a flood on a highway is also likely to be a symptom of a root cause elsewhere, often off-highway, so resolution may take more than a simple intervention that removes the immediate puddling that follows after significant rain or high tides.

Often, local flooding occurs during particularly heavy rain over a short period. In such circumstances, once drain and pipe capacity is exceeded, some flooding is inevitable. It is the same as pouring water into a funnel – if you pour in faster than the spout can let it out, an overflow will occur. As water runs naturally downhill, lower lying areas may also generate puddles once run-off water can’t be piped away. In such circumstances we simply have to wait for the drains to recover.

A puddle or flooded area can also be due to a simple highway defect such as a blocked gully (drain) or pipe. This type of problem can sometimes be resolved via basic maintenance, for instance a gully cleanse, when we have a team available.

 

‘SWAS’ Schemes

Sometimes however a flooding problem is far more complex and needs a solution that in the first instance requires a thorough investigation on site by a drainage engineer. The drainage engineer will identify the root cause, which may be some distance away and probably involve private owner land. The engineer will determine a solution in broad terms, then submit an application for a Surface Water Alleviation Scheme (SWAS for short).

Applications for SWAS schemes are made in a consistent format to ensure all relevant site information is recorded. This information is stored in a ‘Risk Register’ and conforms to set criteria which enables a risk score to be generated, largely in terms of risk to road safety. The risk to property flooding is also taken into account, however, and Essex Highways works closely with the county council Flood & Water Management Team.

SWAS schemes which reflect the highest risk to road safety are prioritised for the limited funding available. This list may change over years, both as schemes are delivered and as priorities change, for instance when a new flood risk is identified which ranks higher than previous known risks. This approach is in keeping with our obligation of duty of care under with the Highways Act 1980.

SWAS schemes can sometimes be relatively straight forward such that our delivery team can be instructed to undertake the works without any further investigations being required.  In the majority of cases, though, far more planning is required.  On occasions schemes may require detailed assessment to identify options in terms of problem resolution, followed by an appraisal of the options to identify the one most appropriate, and then a detailed design before works can be undertaken. Schemes may also involve detailed discussions with landowners, which can take a long time.

Generally speaking the majority of schemes prioritised for funding are subject to design in one year prior to works delivery the following year. Schemes which are very complex, though, can take more than two years from initial assessment to works completion.