Future of Stormwater Lagoon Hull LAGOON HULL A1165 N HULL 1km River front development A1033 opportunity areas BALANCED Victoria Dock Consent ready outer A63 harbour development 26-41% REDUCTION IN New four lane highway TRAFFIC ON THE A63 (9.6km) Outer harbour DEFENCE (2km!) 100% The ambitious Lagoon Hull project aims to protect Hessle IMPOUNDED LAGOON (5KM!) Tidal flood protection the city from flooding, while improving transport for at least 100 years connectivity and reinvigorating the local economy. Y £300M U A R Journey time savings Nadine Buddoo reports. E S T E R M B 1,600 100% THROUGH TRAFFIC H U MOVED TO LAGOON ROAD Construction jobs ull is one of the cities estuary – on the southern edge of in the UK which are Hull – compounds its vulnerability £1bn Gross value added most vulnerable cities KEY FACTS to flooding. per annum to coastal flooding “The city is almost trapped by Bridge Humber and rising sea levels. £1.5bn water,” says Hatley. “There has been But the proposed pluvial flooding, which we saw in Lagoon Hull project aims to change Cost of Lagoon 2007, where a massive downpour one or two types of flooding, but Hull is Hall that. into saturated land led to surface vulnerable to all of them. It is a perfect The £1.5bn scheme will involve the water runoff just pooling everywhere storm of all the risk factors.” construction of an 11km causeway in throughout the city before it even got Lagoon Hull aims to deliver a holistic the Humber estuary, creating a non- 11km to the drains. The devastation was solution that alleviates all of these risks. tidal lagoon along Hull’s waterfront. Length of immense.” “There’s no point fixing pluvial A four lane highway will also be built Hatley explains that the city also flooding, if people are still at risk along the causeway in the Humber Lagoon Hull remains at risk of fluvial, tidal surge and of flooding from something else,” estuary for 9.6km, relieving congestion groundwater flooding. says Hatley. on the A63, currently the main route “It is relatively unusual because in The project has also been designed into the city. most places the area is vulnerable to to consider the needs of the city, as well Construction is expected to take 10 as the requirements of the Port of Hull. years, and the completed lagoon could The scheme is divided into two parts: provide flood protection for at least 100 the 5km2 impounded lagoon and the years. Lagoon Hull project director Paul 2km2 outer harbour development. Hatley says the scheme is primarily water For the outer harbour development centred on providing the best solution – which has already received for local people, as well as for the attenuation, we are development consent and includes environment. more than 84ha of land for quayside Hull sits in what was originally dealing with a vast operations – the main requirement is swamp land and is mostly below ease of access for shipping vessels, large sea level. During heavy rain, surface amount of water. A areas of quay space and water berths. water from neighbouring areas drains “ But the needs of the city are towards the city. The River Hull runs fundamentally different to those of the through the centre, while the Humber is about 5M.m3 port. The impounded lagoon borders the 34 NEW CIVIL ENGINEER ! SEPTEMBER 2020 LAGOON HULL A1165 N HULL 1km River front development A1033 opportunity areas Victoria Dock Consent ready outer A63 harbour development 26-41% REDUCTION IN New four lane highway TRAFFIC ON THE A63 (9.6km) Outer harbour (2km!) 100% Hessle IMPOUNDED LAGOON (5KM!) Tidal flood protection for at least 100 years Y £300M U A R Journey time savings E S T E R M B 1,600 100% THROUGH TRAFFIC H U MOVED TO LAGOON ROAD Construction jobs £1bn Gross value added per annum Humber Bridge Humber city and will play a vital role in providing Lagoon Hull aims The University of Hull found that had a comprehensive flood defence. to address all of There’s no the lagoon been in place during the “It will also allow us to regulate the the flood risk tidal surge that hit the area in 2013, the water levels,” Hatley says. “With flood types affecting city would have had 100% protection water attenuation, we are dealing with the city and the rest of the estuary would have a vast amount of water. A metre level seen an 80% reduction in flood volume. difference is about 5M.m3.” people are still at risk According to Hatley, these results are By lowering water levels in the caused by the fact that the estuary is lagoon, it can be used to store not a contained body of water. As such, stormwater and alleviate the risk of the proposed causeway would reduce flooding in the area. “ the volume of water entering it from something else the sea in the event of a tidal surge. COMPLEX MODELLING This is because the causeway would Around five years of design and counter to traditional engineering narrow the estuary, reducing volumes planning have already gone into the logic. Traditional thinking assumes of water that can pass into it before project, but submitting an application that constructing the causeway in the the surge ends. for planning permission is still Humber would cause a coastal squeeze As the average depth of the Humber some way off. While the modelling effect, with the causeway displacing estuary is a relatively shallow 6.5m, undertaken so far is promising, there flood water onto the south bank of the the ability of the causeway to reduce is more work to be done. “We’ve been Humber estuary. But modelling carried tidal surge impacts is expected to be in discussion with the Environment out independently by the University of greater than that of deeper rivers and Agency and it is intrigued, but not Hull and marine consultancy service estuaries, as less water can enter it completely convinced,” Hatley admits. ABPmer suggests that the causeway during a tidal surge. The sticking point is that the will, in fact, protect both sides of the “The model is effectively showing proposed scheme seems to run estuary from flooding. us that by introducing a restriction SEPTEMBER 2020 ! NEW CIVIL ENGINEER 35 Future of Stormwater Lagoon Hull It is not about “ in a certain part of the river, less water flows in because there is more resistance,” he says. “It’s not a barrage or a barrier, it’s a constriction that seems to have the potential for wider flood protection benefits.” Hatley is, of course, encouraged by the modelling data but remains cautious. “There is more work to be done to prove that this effect would really happen,” he says. The Environment Agency has The project brighter future.” If we get it agreed to undertake further modelling includes a Building the new highway on the work and, before delays caused by causeway estuary would not just expand the right, we will the coronavirus pandemic, the team incorporating a city’s traffic capacity, it would improve behind Lagoon Hull was expecting to 9.6km relief road access for cyclists and pedestrians. meet environment secretary George Highways England has also Eustice to discuss the need for undertaken traffic modelling which has government investment to fund further demonstrated that 100% of through modelling and research. traffic in the city would be transferred engineering and nature “Worst case scenario: if the design to the lagoon road, which would ease “ doesn’t make flooding any worse, the congestion on the A63 and improve overall lagoon project would still be access to the port. hugely beneficial in terms of supporting Improving connectivity to the a range of other outputs including region would also position Hull as the CHALLENGES AHEAD placemaking, economic regeneration, Northern Powerhouse’s gateway to The future of UK trade and energy port growth and improved transport Europe. Driving the region’s economic might rely heavily on the Humber and links,” Hatley insists.“Even if there was renaissance is a focus on green energy. the Lagoon Hull development, but the just a 5% estuarial flood protection Historically, the Humber estuary economic benefits must be aligned benefit, quite frankly, it’s worth the has been the heart of the UK’s coal with a considered approach to the investment to at least do the research.” powered energy industry with coal surrounding ecology and the river’s brought in by rail and river to nearby characteristics. ECONOMIC DRIVER power stations including Drax, “Trying to find ways of building Further in-depth feasibility studies Ferrybridge and West Burton. in harmony with nature is a major require a cash injection of around £25M But with energy production in challenge, but this project takes it to a from the government, so ultimately the the Humber region slowly being completely different level,” says Hatley. funding for the project will be a mix of transitioned away from high carbon “The construction phase will involve public and private. towards green energy and offshore lots of dredging and reclamation, but Hatley describes the funding model renewables, Hatley believes the region there’s nothing massively complicated for the scheme as particularly unusual. will play a vital role in producing the in terms of the construction techniques.” “It isn’t a public scheme, so it is energy of the future. But Hatley says the real engineering currently entirely backed by private “That transition is really important challenge will be balancing the organisations in the region,” he for the role the Humber will play in development of the project with the explains.