Flood Resilience: A flood risk engineer's personal views
Principal Consultant at RPS
Most of my career has been spent working for water companies, firstly for a local authority in the days when they managed the sewer network on the sewerage authority’s behalf, and then for various consultancies in Scotland and England. And most of that has been spent working with computer models of sewer networks, which are used to identify areas for improvement.
A large part of my current work relates to the city of Hull and the surrounding area. My current employers, RPS, have been involved in this since 2010, working on the development of the large surface water management schemes (WADFAS, COPFAS and AEEFAS) that East Riding of Yorkshire Council have constructed since the 2007 floods. We’re now working for Yorkshire Water with the Living with Water Partnership, investigating blue/green solutions to reduce flood risk from sewers and surface water.
My team also works on flood risk assessments and drainage design for new developments, mostly in Yorkshire and the Midlands.
Until a couple of years ago, we lived in a mid-terraced house overlooking the River Aire in Baildon, a suburb of Bradford. The Loadpit Beck which runs down Shipley Glen runs past the western end of the terrace and joins the Aire. A bridge near the eastern end provides a good walking route to Saltaire. I bought the house for its easy access to trains for Bradford and Leeds, and out to Shipley Glen and Ilkley Moor beyond.
The front of the house looked out onto a strip of grass about 1.5m below house level and a “beehive” structure at the end of an aqueduct carrying water mains over the river. I’d looked at the records and knew this area had been flooded in 1978 and 2000, and the front garden of the house is within the 1:1000 flood zone.
We were relatively unaffected by the 2007 and 2012 floods, although the Loadpit Beck broke its banks and took a shortcut into the river, and the upstream weir at Hirst Mill was damaged. But on Boxing Day, December 2015 we watched the river inundate the grassed area and levels rise to almost cover the beehive. Several large objects swept past in the main river beyond, and we could see the water overtopping the wall into the flats at Hirst Mill opposite. We moved valuables upstairs, and took a walk over the footbridge – with water lapping at the deck and cutting across the footpath at the far end – before nervously going to bed.
We were lucky, and by morning levels had subsided. Residents in the flats on the opposite side of the river, the rowing club upstream and the sports club at Saltaire hadn’t been so fortunate.
For those who have been flooded, the question of who to turn to for help can be difficult – responsibility for flooding is complex and not easy to understand, particularly when you’re directly affected; and not everyone has relatives or friends who would be able to offer help. Over the years I’ve dealt with residents and businesses who have been flooded from sewers, rivers and overland flow -and sometimes by all three.
I was working in Glasgow when it was affected by a series of flash floods in 2002. At the time, the data and technology didn’t exist to analyse the complex interactions of sewers and watercourses to apportion responsibility between the local authority and Scottish Water. Institutional boundaries also acted as barriers to the flow of information which made understanding harder, with no single party being responsible. After the 2007 floods the Pitt Review illustrated that the situation in England and Wales was even more complex with privatised sewerage undertakers “owning” part of the problem.
The publication of CiWEM’s Integrated Urban Drainage Modelling Guide in 2009, and various reports from Defra and the Environment Agency, have provided industry standard guidance. The Flood and Water Management Act 2010 addressed some of the institutional barriers. And advances in computing power and software capabilities have allowed us to better tackle the technical issues. Across the industry there’s an increased understanding of the complexity and the need for different parties to work together and share knowledge, understanding and data. There’s also better attempts to deal with the uncertainties that come from incomplete data and the limitations of the computer packages we use.
Climate change projections show the risk of flooding increasing, with higher peak rainfall in summer more likely to overwhelm sewers and overall wetter winters leading to higher river flows. We need a range of measures to both maintain and improve flood protection. But whatever standard flood defences – natural, or conventional – are designed for, a bigger storm is still possible.
Property flood resilience is one of the many pieces in the jigsaw of flood protection, both in areas where other measures would be uneconomic and as a last line of defence. My hope would be that basic resilience measures are built into new buildings as a matter of course, and previously flooded properties are “built back better” to reduce the cost and disruption associated with flooding.