Background to the scheme
The primary cause of the flooding problems experienced since 2012 is ‘flood-locking’, whereby the drainage systems cannot flow into the river because of the high river levels. Surface water flooding generally happens when flows in the River Derwent exceed 80m3/s, (cubic metres per second). This corresponds broadly with the threshold at which the gravity drainage systems become impeded.
There have been seven occasions when a flow of greater than 80m3/s has occurred in the River Derwent, Malton since the Main River flood defences were constructed in 2003.
Problems experienced are:
- whilst local surface water and ground water flooding may not affect as many properties as would flooding from the River Derwent, infiltration and overloading of the combined public sewer network makes it particularly unpleasant for the residents and businesses affected
- flood warnings in Malton are based on the river levels, so warning and response surface water and groundwater flooding relies on anecdotal and eyewitness accounts
- the residual risk of surface and groundwater flooding in Malton, Norton and Old Malton is potentially too high for the emergency response procedures to fully make sense as a long-term solution, if an economically viable investment now could save costs in the longer term
In assessing potential options to reduce flood risk to businesses and communities, the study has been guided by two overriding objectives:
- to reduce flood risk in a way which represents best value for money in the short, medium and long term
- to propose solutions that are socially and environmentally acceptable to local people and statutory authorities, which respect the heritage setting and avoid disruption to local residents and businesses where possible
In partnership with other responding risk management authorities we have since this time undertaken a significant amount of work to develop the scheme over the years.
It is fair to say that delivering a solution in the location is challenging. The number of flooded properties is relatively low in flood risk terms to attract funding for a scheme. Surface water flooding is difficult to model and the interaction of the river, duration of flooding events and the groundwater element means that there is not one solution to the events that are experienced.
What the scheme will deliver
The present scheme will deliver:
- construction of permanent infrastructure for temporary pumps
- improve CCTV monitoring at key pumping locations
- local property level protection
- assessment of possible better management of groundwater conditions in the Castlegate area
- improved pump infrastructure
We are making improvements to 5 key pumping locations across the area.
These are Taylor Brown Yard, Boathouse Yard, Tate Smith Yard, The Cat Well and Lascelles Lane.
All of these are current and key locations in the Malton, Norton and Old Malton Pump Plan.
The formalizations of pump infrastructure will ensure that there are robust and safe practices carried out with increased efficiency of pump deployment. Several designs have been considered for each location however, they just would not be feasible. All designs are considered the best for the location.
CCTV is to be installed at 3 key pumping locations. This will assist with monitoring of water levels across the area allowing for pumps to be deployed effectively in these locations.
See the detailed Improved Pump Infrastructure drawings (pdf / 14 MB)
Property level resilience
Property level resilience (PLR) offers an innovative and effective response which ‘plugs the gap’ that previously existed between engineered flood protection schemes, and either sandbags or the ‘do nothing’ option. The approach aims to identify products and measures that are appropriate for the person, flood and property together, helping to reduce flood damage and increase peace of mind.
149 properties across Malton, Norton and Old Malton are eligible for the scheme and have been contacted. All those interested have received a property survey from our consultants, JBA Consulting. Each surveyed property can receive up to £5000 worth of property level resilience works.
PLR can take many different forms and often requires a combination to get the best protection. These can include any of the following plus more;
Barriers can be fitted to doors and windows, providing a seal to limit floodwater ingress.
Non-return valves can be installed to drains around a property to prevent floodwater or sewage backing-up.
Airbricks can be replaced with automatically closing airbricks to create a seal against floodwater.
Pumps can be recommended to help keep floodwater at manageable levels for those at risk of rising groundwater entering through the floor.
PLR increases the ability of your property to be more resistant to flooding and, in the case of larger floods, minimise damage so that your property can be reinstated and returned to much more quickly than would otherwise be possible.
They are not a guarantee that your home will be completely protected from all flood events.
Groundwater flooding is a challenging issue to resolve. As part of the PLR offering, NYCC is working with JBA Consulting to look at possible bespoke solutions for the Castlegate Area.
We have secured funding from 4 different stakeholders. Contributions are from North Yorkshire County Council (up to £450,000), Ryedale District Council (up to £320,000), Local Enterprise Partnership Bid (£500,000) and Environment Agency Flood Grant in Aid (£314,846).
For more information about the scheme, please contact us.