Wednesday 18 February 2015

Storm Surge 2013 : One Year On - Part Two : What we Learnt

by @cloudskinner

This is the second post of our mini-series about the 5 December 2013 storm surge, and its legacy for the Humber region in particular. Last week's post highlighted some of the research that had been undertaken after the surge, and why this is important for understanding the future flood risk in the Humber, especially in the context of climate change which is predicted to bring bigger and more frequent storms, as well as a steadily rising sea level. This post looks at what we have learnt about the storm surge a year after the event, and summarises the presentations given at the 2014 Humber Conference held at Hull's Guild Hall in mid November, organised by the Humber Nature Partnership. You can view individual presentations using the links on the presenters' names.

Dr Susan Manson from the Environment Agency (EA), a co-author on the research highlighted last week, began the conference by providing some of the key scientific details about the storm surge. It has commonly been held that the devastating 1953 storm surge was the baseline for these events in the Humber - the 2013 storm surge is currently the largest on record, but there have been five other events larger than 1953 in between. The fact that the devastation and loss of life has never been as extensive is true testament to the defences and plans that have been invested in since that time. For the recorded tide from the EA gauge at Immingham, which has been recording since 1963, 2013 was the highest ever water level, and by some margin.

Immingham Dock Oil Terminal - The water level recorded here on 5 December 2013 was the highest on record (by "Chris")

Susan gave some figures about the surge. 116 flood warnings were issued. 1,170 properties were flooded around the Humber estuary, but the defences protected a staggering 156,000 further from the surge. It normally takes a tidal crest more than an hour to propagate from Spurn Point, at the mouth of the estuary, to Blacktoft Jetty along the River Ouse, but the surge covered this distance in just 15 minutes – described as “like a wall” by some.

40 km of defences were overtopped but most of them held, with only two points where the flood defences themselves were breached (south of Cleethorpes on the south bank, NE Lincolnshire, and near Skeffling, on the north bank, E Yorkshire). The EA has been busy strengthening and repairing defences as fast as they can. Philip Winn of the EA described how they are using X-Rays to check the integrity of defences to ensure they are up to standard, and how the defences at Alexandria Dock have been improved (all of the flooding in Hull City Centre emerged from overtopping the 1 km stretch here). Phillip also described how the EA are looking to the future, reconsidering the Humber Strategy drawn up before the flood and going to the Government with a request for £1bn to upgrade the estuary’s defences to a 1 in 200 year standard.

Flood defences being repaired shortly after the storm surge - Chowder Ness, near Barton-upon-Humber, on the south bank, N Lincolnshire (by Jonathan Thacker)

But for many people the misery of the storm surge continues. One of the worst affected places is the small town of South Ferriby on the south bank. The defences overtopped and flooded the majority of the houses there and depositing large quantities of silt and mud inside. One of my old school friends described on Facebook how she sat on the stairs watching the water rise as her children slept upstairs. For many it was over 6 months until they could move back into their houses.

The Cemex factory was very badly damaged and a full year after the flooding it still has not returned to production. Kevin Groombridge of the firm described how the flooding did not just bring water, but also sediment and salt. These clogged machinery and corroded the electrics of the site, which were all at ground level. Having never flooded in 75 years they nearly did not heed the flood warnings from the EA, but the Director of the site insisted the workforce move. It is possible that he saved numerous lives by that decision and thankfully that is just speculation.

The Cemex Cement Factory at South Ferriby (by David Wright)

Kevin described how immediately after the flood a ‘Blitz-spirit’ emerged among the staff, and how the factory manager had to buy new office furniture, laptops, stationery and even diesel generators on a credit card in order for them to continue working. Literally everything on the factory site had been destroyed.

Agriculture was also badly hit. Andrew Wraith of Savills UK, an Agribusiness, described some of the impacts that has struck them. On their Yokefleet Estate they have 34 residences and 22 of those flooded, and 1000 acres of their 2500 were flooded to a depth of 4 ft., and a green pea factory was flooded. Some of this land was flooded for 2 -3 weeks but was alleviated by pumps. A major issue they faced was soil erosion caused not by the flooding but the speed of the water draining away.

They lost many crops, both planted and stored, and Andrew put the cost of these losses in seven figures. But Andrew also said that they considered themselves lucky – when the surge hit they anticipated that their crop loss would be almost 100% but it was actually a loss of 5-10% of the yield. He put this down to the dry conditions prior to the surge allowing for effective drainage of the damaging salt water. The timing of the surge was also fortunate, as had it had been in the spring or the summer they would have felt a two year impact on yields.

Behind Hull's Tidal Barrier on 5 December 2013 - It the water level came within 40 cm of overtopping (by @Tom_Coulthard)

And it is this sense of being lucky that I want to end this post on. If you were one of the residents in South Ferriby, out of your home for the better part of a year, you will not feel lucky, and you weren’t. If you live in one of the 156,000 properties protected by the EA’s defences, a product of decades of work and investment, you were also not lucky but fortunate that we have invested in our excellent EA. But in many ways the Humber estuary could be described as being lucky as stories emerge of near misses and close calls. It was probably only the decision by one Director at Cemex that saved the lives of their workers. The tidal barrier at Hull came within 40 cm of overtopping and putting at risk hundreds of properties along the River Hull – if the surge was timed with the high tide, rather than 2 hours apart, it could have made the difference and spilled over. If the weather in the prior days had been wet then the salty flood water would not have drained as quickly as it did, this fact saving much farmland and properties from further damage.

In all the defences of the Humber were put under considerable strain by a massive, unusual, and largely unprecedented event, but came out on top. Just. Those responsible for them should be praised that they withstood the barrage, and that there was no loss of life. But we should not become complacent – we may never witness another event of that scale again in our lifetime, but as our climate warms, becomes stormier, and the sea level rises, the chances of another, or larger, storm surge in the Humber increases. We need to continually work to keep our defences ready.

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