2007’s flooding was a sharp shock for the UK. What began as a wet washout of a gloomy summer became a three-day war against rising waters, leaving an aftermath of extensive damage that is still under repair.

More than 55,000 homes were flooded in the wettest May to July period since records began in 1776, as 16” (414mm) of rainfall hit the UK. A strong, southerly jet stream combined with uncharacteristically high Atlantic sea temperatures to create a long rainfall beginning in May and culminating in extreme rainfall in late June and late July. By mid-June the ground was saturated, and began to flood.

The rivers were not so much the problem as the drains and sewers: which were soon overwhelmed: around two-thirds of the buildings flooded were flooded by surface waters. Whilst existing flood defences helped reduce the impact, in some areas (particularly those with a lower level of flood defences), they were not sufficient.

As UK population, trade and industry continues to expand rapidly, more developers are looking to floodplains for building opportunity, but this brings with it a clear requirement for careful flood risk assessment and planning. RPS Hydrologists work with developers and businesses to help inform decisions for proposed development location, and ensure it is above the appropriate level of risk. RPS experts are also able to help set appropriate flood defences in place for existing built areas.

RPS is providing independent professional opinion for Sitecheck Flood – Landmark Information Group’s new flood report for commercial property conveyancing which launched this month. Sitecheck Flood is a significant comprehensive new reporting system bringing together expert opinion and key flood risk data from the Environment Agency, British Geological Survey, Norwich Union and RMS. The data sets includes risk from fluvial, tidal, groundwater and pluvial flooding.

Using hydraulic modelling, RPS has recently secured Environment Agency approval for two commercial properties in Brackley, Northamptonshire for the Honda F1 Team. The FRA produced by RPS successfully demonstrated that the buildings would be above flood zone 3 (the 1:100 year plus 30 per cent flood level) and not increase flood risk to third parties.

Particularly complex hydraulic modelling, including mitigation options for on and offline storage potential, was required for the EIA and FRA that RPS has now completed for a mixed-use development in South Lanarkshire. As project manager for the EIA (including hydrology, ecology and heritage consultation), RPS experts assessed the risks of downstream flooding from proposed culvert removal and diversion of a tributary watercourse, and co-designed and developed a SUDS system.

As the built environment expands, it becomes ever more crucial to not only assess the existing hydrology of a site, but also to accurately forecast potential impact, and develop appropriate mitigation. The floods of summer 2007 came only sixty years after the benchmarked severe floods of 1947, and as Britain settles into what is, so far, another wet summer, we cannot ignore the realisation that whilst ‘flood flows might only be exceeded once in 200 years, this does not mean we have 200 years before the next flood.’¹ 

Reviews after the 2007 events quickly identified that better flood defences, a more efficient flood forecasting model, more co-ordinated warning systems and improved public liaison are all key to preventing future severe flooding, and work in these areas is being implemented, with 54 new flood defences built so far, and a multi-faceted programme of co-operation between the Environment Agency, water utilities, Water UK and the Meteorological Office to extend flood research and improve flood forecasting. RPS’ extensive expertise across a range of hydrology services places the Group securely as a significant consultant in a vital field.

Contact:
Sitecheck Flood:
Neil Bagley
T: +44 (0) 161 237 9858
E: bagleyN@rpsgroup.com

Honda F1:
Amy Rix
T: +44 (0) 1902 771 331
E: amy.rix@rpsgroup.com

Lanarkshire:
Garron Owen
T: +44 (0) 131 555 5011
E: garron.owen@rpsgroup.com

¹ Environment Agency Review of 2007 Summer Floods. Figures quoted in this article are from this source also.