Understanding flood risk
Hull is at risk from multiple sources of flood risk. A summary of the main routes water takes to move through the city and associated flood risks are -
Holderness drain and Beverley and Barmston drains
High level drains carry land drainage from the mid-catchment of the River Hull through and around the city for the eventual discharge to the River Humber.
Great Culvert Pumping Station lifts land drainage into main Holderness drain.
East Hull Holderness Drain Pumping Station, which has recently completed as part of a £28 million scheme, pumps this drain into the Humber.
The pumping stations reduce the risk of river flooding. It does this by keeping water moving across the flat land when the drains are tidally locked and cannot naturally discharge.
Watercourses
There are many other watercourses that have a role in storing and conveying water. Many watercourses within the city have been in-filled and diverted to flow into the surface water drains or combined sewage system. Others have been contained in culverts. The ones that are still open watercourses are managed by risk management authorities.
The Humber Estuary
The Humber handles 14% of the UKs national trade and is the largest port complex in the country. It has international environmental significance with valuable intertidal habitats and one fifth of England's land drains through the Humber.
The Humber is under threat from tidal flood risk and rising sea levels. Areas around the Humber are currently protected by a mixture of nature flood management. These include salt marshes and flood defence walls, including the new 7km flood wall along the Humber frontage. The flood wall was recently completed by a £42 million scheme to better protect Hull from tidal surges. Hull also benefits from a tidal surge barrier. It prevents flows from the Humber traveling up the river Hull and flooding the city during tidal surges.
Sewage collection and wastewater treatment
Sewage flows to a combined system. It is taken through a large tunnel and pumped to a single wastewater treatment works in East Hull from where it flows to the Humber.
Emergency storm overflows discharge to the Humber Estuary by the East and West Hull pumping stations. 84% of Hull’s surface water flows into the sewers. That means when it rains heavily or for a long time, the sewer system can become overwhelmed, causing a risk of sewer flooding.
Surface water drainage
Most of the surface water flows into the combined sewer. Surface water from the Bransholme catchment is collected separately. It is discharged to the River Hull by the Bransholme pumping station and stormwater balancing lagoon.
Surface water storage
There are several Aquagreens built in green spaces across the city to store surface water. There are larger surface water storage reservoirs on the western edge of Hull, within East Riding of Yorkshire.
Surface water storage solutions store rainfall and reduce uncontrolled surface water flows into Hull’s drainage network when it is at capacity.
Water resources and supply
Hull is built on top of a chalk aquifer. This presents the risk of groundwater flooding when the aquifer becomes full after prolonged or heavy rainfall.
Water is supplied from both surface water abstraction and through abstraction from the underlying chalk aquifer. It is treated at Top Hill Low Water Treatment Works. Water source protection zones are in place but there is pressure from development and saline intrusion.
Long-term flood risks
You can check your long-term flood risk here for -
- rivers
- the sea
- surface water
- reservoirs
- groundwater
We have produced detailed surface water flood risk maps available in our downloads. Or visit Hull myMaps to see Hull's Flood risk zones.