The winter 2015 floods are the most recent of many to have hit Calderdale. During the summers of 2012 and 2013 there were four major floods in Calderdale. In 2012 more than 900 properties and 253 businesses were flooded. The Upper Calder Valley was cut off and the main trunk road up the valley and the Leeds to Manchester rail link were impassable.
During the floods of Boxing Day 2015, Calderdale was the worst affected borough in the UK following sustained and heavy rainfall. Todmorden, Walsden, Hebden Bridge, Mytholmroyd, Sowerby Bridge and Elland were all struck by serious flooding. Over 2,000 homes in the Calder Valley were badly affected and over 1,000 businesses were also hit.
Bridges at Elland and Mytholmroyd collapsed, disrupting communications. Several electricity sub-stations failed, causing power cuts across the valley. No lives were lost but that may partly have been due to the timing of the flood striking over the holiday period when schools and businesses were closed. The flood was the worst in living memory.
Flood and Water Management Act 2010
The Flood and Water Management Act 2010 received Royal Assent on 8th April 2010. The Act implements those recommendations made by Sir Michael Pitt which require primary legislation including the recommendation for local authorities to establish and maintain a record of assets.
Section 19 requirements:
1 - On becoming aware of a flood in its area, a lead local flood authority must, to the extent that it considers it necessary or appropriate, investigate:
(a) Which risk management authorities have relevant flood risk management functions, and
(b) Whether each of those risk management authorities has exercised, or is proposing to exercise, those functions in response to the flood.
2 - Where an authority carries out an investigation under subsection (1) it must;
(a) publish the results of its investigation, and
(b) notify any relevant risk management authorities.
Section 21 requirements:
• establish and maintain a “register of structures or features, which in the opinion of the authority are likely to have a significant effect on a flood risk in its area” and;
• establish and maintain “a record of information about each of those structures or features including information about ownership and state of repair”.
Section 21 of the Act also requires that a Lead Local Flood Authority (LLFA) to “arrange for the register to be available for inspection at all reasonable times”.
Types of flood risk in Calderdale
Historical flooding events have proven that the nature and extent of flooding in Calderdale is a result of a complex interaction of different sources of flooding. These sources include the following:
Groundwater flooding - occurs when levels of water in the ground rise above the surface.
Surface water flooding - caused by high intensity rainfall ponding on hard-standings or soils with low infiltration.
Sewer flooding - occurs when the capacity of sewers is exceeded.
Ordinary watercourse flooding – flooding from all watercourses not designated as main rivers, including rivers and streams, ditches, drains, cuts, culverts, dikes, sluices, sewers (other than public sewers within the meaning of the Water Industry Act 1991) and other passages through which water flows.
Main river flooding – flooding from main rivers, which are larger streams and rivers or smaller watercourses of strategic importance. This map shows which rivers in England are designated as 'main rivers'.
Highway flooding – flooding of the highway resulting from the discharge of flows on to the highway or overwhelmed drainage infrastructure. Flooding from the highway can occur where adjacent properties are at a lower elevation.
For more information on types of flooding, click here.
What does Calderdale Council’s Flood Risk Management Team do?
One of Calderdale Council’s first actions after the Boxing Day event of 2015 was to bring together various activities to increase flood resilience and reduce flood risk. Under the Flood and Water Act 2010, the Council is the Lead Local Flood Authority for our area and is responsible for the following activities:
• Establishing a flood risk asset register
• Inspecting flood risk assets and intervening where necessary
• Investigating incidents of local flooding
• Working with partners to develop flood resilience measures
• Developing a surface water management plan (SWMP)
• Development control
• Supporting natural flood management
• Supporting flood alleviation schemes
Flood risk asset data register
Completion of a register is a statutory requirement. The register is essential to understand what infrastructure affects flood risk in Calderdale, determine a management strategy for those assets and define maintenance procedures. A clear understanding of watercourses and assets is critical to understanding and redressing flooding.
Activities include upkeep of the flood risk data asset register, integrating output from surface water management plans and other studies into the database, prioritising flood risk assets and flooding hotspots, developing and updating asset maintenance schedules, mapping assets in the geographical information systems and establishing a web based flood asset register map to publish on the Council website for the public domain.
Flood risk asset inspection
The asset inspection process is part of an overall cycle of risk and performance based asset management being developed by the Environment Agency. This programme is being carried out in partnership with JBA Consulting and applied via GISmapp assessment methods to integrate key activities in the assessment cycle, directing inspectors to the appropriate level of activity according to the level of risk.
Using this method, inspections can be targeted to need and interventions can be timed relative to the risk of asset failure, rather than dictated by routine inspections. Inspections are driven by a considered balance of investment and flood risk, offering the greatest impact on risk reduction and cost efficiency.
Investigating incidents of local flooding
Events of flooding reported via the Council website are followed up by investigating the extent to which intervention is considered necessary or appropriate and where required, taking action to resolve the issue or carry out works in response to an incident.
This may mean looking at the involvement at various risk management authorities and any actions that have been taken or proposed. Where formal investigation is carried out, the results of the investigation will be published and any relevant risk management authorities notified of the findings.
Surface water management plans
Surface water runoff causes flooding problems across Calderdale. A major area of work identified in the Calderdale Flood Risk Management Strategy is the need for improved understanding of surface water flooding across the whole of Calderdale.
Completed plans will assist in identifying the measures required to minimise the effects of flooding, including natural flood management interventions. They will also help to define critical drainage areas, which is an important first step to developing robust management of runoff from new developments identified within the Local Plan.
Partnership and flood resilience
This involves liaison with external stakeholders, education of landowners and completion of funding applications for schemes and is delivered via the Calderdale Flood Recovery and Resilience Programme.
The programme brings together a number of partners including the Council, the Environment Agency, the Canal and River Trust, local flood groups, Yorkshire Water, Network Rail and the voluntary sector. The aim of the partnership is to work together to substantially reduce the impact of flooding in Calderdale as well as supporting the local community to build its resilience against future flood events.
As the Lead Local Flood Authority, Calderdale Council is a statutory consultee on planning applications for major developments and the flood risk manager is consulted on applications that have drainage implications. It is important that new developments don’t increase the flood risk to the environment or indeed the development itself and, where possible, developers should seek to improve the existing situation.
The flood team reviews all of these applications and suggests planning conditions requiring the developer to manage the disposal of surface water from their site. For example, this may involve using a flow restriction device, underground tanks or other sustainable drainage solutions such as swales, ponds or permeable paving.
Natural flood management
Sympathetic land management techniques can help reduce flood risk. Locations across Calderdale are mapped to show where such measures may be most effective and this is used as a basis for engagement with major stakeholders regarding land management initiatives with the greatest chance of success. The NFM project officer’s role involves:
• Supporting existing NFM schemes and applications for funding
• Supporting organisations to carry out suitable NFM interventions in appropriate locations to maximise benefits to the environment and minimise risk to properties and other receptors
• Developing a new grant scheme to help farmers and landowners to deliver NFM measures.
• Supporting monitoring of NFM interventions to fill knowledge gaps and inform future decision making
• Working with NFM Operational Group, one of the core groups that reports into the Flood Recovery and Resilience Programme Board, to implement NFM related actions in the Calderdale Flood Action Plan.
Flood alleviation schemes
Several potential flood risk resilience and alleviation schemes have already been identified. Evaluation of these schemes and their benefits is needed to allow the most cost effective schemes to be advanced by the Environment Agency and the chosen contractors.
Presently, two Flood Alleviation Schemes (FAS) are underway for Hebden Bridge and Mytholmroyd to increase protection following the flooding of Boxing Day 2015. In addition, a number of smaller flood risk reduction schemes (FRRS) are in development to provide important flood relief measures.