Wainfleet flooding

Wainfleet flooding

Image by Richard Hardesty on 14 June 2019 (@Richardesty)

On Wednesday 12 June the embanked Steeping River breached the south bank of river defences along the Wainfleet Relief Channel to the south of Thorpe St Peter in Lincolnshire.

River levels in the Steeping and across Lincolnshire had risen rapidly following thunderstorms and prolonged heavy rainfall that began crossing England from the east on Monday 10 June. All local IDB pumping stations began continuous 24 hour pumping. The area around Wainfleet received some 138mm of rainfall over just three days. That is over double the average monthly rainfall for June in the county, and significantly greater than the 68mm of rain that occurred during the summer 2007 extreme rainfall event.

By Wednesday 12 June sections of the Relief Channel were seen to be overtopping prior to the breach, which occurred around midday. In total around 100 properties and at least 550 hectares of farmland were flooded, with about 1,000 people and 580 homes instructed to evacuate. The railway line between Boston and Skegness effectively became a river.

The event was rapidly declared a ‘major incident’ by the emergency services, coordinated from the Lincolnshire Council Emergency Centre in Lincoln, and a command centre set up at the Fire & Rescue building in Wainfleet. Commendably, staff from Lincolnshire’s IDBs provided support to the emergency command throughout.

Two RAF Chinooks and a Puma helicopter from RAF Odiham and RAF Benson were called in to drop 342 one tonne bags of aggregate to plug the breach. The bags were airlifted from a local drainage board member’s land at Firsby, which still had suitable hard standing from its time as a World War Two bomber command airfield. The bags were unloaded from road transport and prepared for airlift with the assistance of local farmers, enabling a quick rotation of sorties by the helicopters.

At Thorpe Culvert a herculean effort was made to defend Lindsey Marsh Drainage Board’s (LMDB) Pumping Station and the associated electricity substation complex. Its four pumps had been at the heart of the pumping operation since the start of the crisis, lifted 430,000m3 of water every single day from the flood cell back into the Steeping River.

On the morning of Saturday 15 June, steadily rising flood water was found to be entering the substructure of the station putting its electrics at risk. The IDB team, alongside the emergency services, members of the local community, EA, Western Power Distribution, and Inter-Lec Ltd, battled to keep flood water out of the station’s structure by building temporary defences, using over a thousand sandbags. Their heroic urgent intervention remarkably kept the station operational throughout. Its loss would have resulted in a larger number of homes being affected in and around Wainfleet. In total, the station shifted in excess of five million cubic metres of water from the flooded area over 11 days.

Additionally, LMDB had a further six mobile pumps out along the banks of the Steeping to help empty the Thorpe flood cell. These were assisted by EA pumps, and 11 high velocity pumps deployed from across England by UK Fire and Rescue Services’ HVP Capability Team.

Andrew McGill, Chief Executive of LMDB, complimented his team on their dedication and commitment to do everything within their power to protect the local area during the recent event.

To relieve pressure on the breached bank the Environment Agency set up one of their ultra-high volume pumps (UHVP) at Thorpe Culvert. The temporary pump, which is able to shift 1.65 cubic metres of water per second (m3/s), replaced an LMDB 12” portable pump, pumping water from the Steeping River into the adjacent low level Bellwater Drain on the afternoon of Sunday 16 June. This main drain within Witham Fourth’s Internal Drainage District flows west 12.5km to the Lade Bank Pumping Station (Capacity: 17m3/s), and then south 14.5km to the Hobhole Pumping Station (Capacity: 38 m3/s) where it finally reaches the tidal River Haven east of Boston. To boost its capacity, a further UHVP was deployed by the EA at Lade Bank. Collectively this system was pumping over 2.5 Olympic swimming pools of water per hour, and it is estimated that around 1 million cubic metres of water was diverted from the Steeping River into the Bellwater Drain.

Peter Bateson, Chief Executive of Witham Fourth District IDB said that the IDB were pleased to be able to help with this important emergency relief effort, made possible by the excellent condition of their assets and main drainage network having already dealt with significant rainfall across their own catchment.

Initially there were concerns of a further breach or ‘crack’ in the river embankment. However, an EA Catchment Engineer was able to confirm that an erosion line that runs from the initial breach point for ~500m was superficial erosion and so should not impact the stability of the bank as a whole. The EA worked with drones from Lincolnshire Police to closely monitor the breach throughout the event.

Repairs to the breach had started by Tuesday 18 June with contractor Bentley in evidence preparing the access to the area. Initially the dropped bags were supplemented with additional ballast, to strengthen it. On Saturday 22 June the damaged area of bank was back-filled with aggregate, reinforcing the embankment and providing a platform from which to drive steel piles to cut off water flow, enabling a permanent repair.

The condition of the banks and channel had previously been of concern to the EA and IDB for some time, they had been working closely to develop a better maintenance regime. The EA stated that they spent around £80,000 on planned maintenance to the Steeping River system annually.

Embanked rivers present a set of specific maintenance challenges, such as burrowing animals. The EA reported that whilst badgers have been present along the banks in recent years, the breach itself was not affected by a badger sett. Badgers, as a protected species, were relocated from the flood bank to an artificial sett in August 2018 and further efforts had been ongoing in the area. Ruts on the surface of the embankment had recently been filled in for the EA by LMDB under a PSCA, but more substantial repairs to the embankment had been awaiting funding within the EA’s long term capital investment plan.

It has been confirmed that a lessons learned review will be set up following the event. Evidently, it is essential that we have an open dialogue to fully understand the facts after the crisis has been dealt with and, using the evidence, take the right actions to reduce the risk of this happening again.

The breach and flooding incident involved teamwork on an epic scale. Over 500 staff from the emergency services, Lincolnshire IDBs, Environment Agency, local councils and partners pulled together to tackle the incident response. Thank you to all of our members who assisted.