Flood Risk Assessment in Mytholmroyd

Three separate flood defence schemes have now been built in Mytholmroyd, and all three have already been tested by real storms. Unda prepares flood risk assessments in Mytholmroyd for planning applications, property purchase, mortgage and insurance queries, and BREEAM submissions, alongside sequential and exception tests and surface-water drainage strategies, for sites across this stretch of the Upper Calder Valley where the Calder meets Cragg Brook.

Every one of these reports has to account for the same combination of sources: the River Calder and Cragg Brook themselves, the Rochdale Canal running through the village, surface water shedding off the steep valley sides in heavy rain, a hillside-instability risk around Scout Road that is unusual even for this catchment, and groundwater, which is assessed as standard within any flood risk assessment. Whichever report you need, call 01293 214444 or email enquiries@unda.co.uk for a fixed-fee, no-obligation quote, usually within 60 minutes.

On Boxing Day 2015 the Calder at Mytholmroyd reached 5.74m, its highest level on record, against a typical range of 0.4m to 2.7m. The same flood triggered a landslip that blocked Scout Road and forced the temporary relocation of a school. Three funded schemes have since been built to answer that event directly, and all three are now complete.

Flood risk assessment in Mytholmroyd at a glance

The table sets out the headline position. Every figure is sourced and expanded on, with its origin, further down the page.

Check flood risk in Mytholmroyd

The map below shows the Calderdale district outlined in coral. Enter a Mytholmroyd postcode to see the Environment Agency's current flood risk data for that specific location, alongside any live flood warnings.

Flood risk and hydrology in Mytholmroyd

Mytholmroyd sits at the confluence of the River Calder and Cragg Brook, in the same steep-sided Upper Calder Valley as Hebden Bridge nearby, where the surrounding moorland sheds rainfall quickly into a narrow valley floor. That geography produces several distinct flood sources rather than one, and a site-specific assessment has to look at all of them together.

• Fluvial flooding. The River Calder and Cragg Brook both pass directly through the village centre, and the two watercourses meeting close together concentrates flow at exactly the point where the built-up area is most dense.
• Canal flooding. The Rochdale Canal runs alongside the river through Mytholmroyd and can contribute to flooding when it rises with the watercourses it parallels.
• Surface water (pluvial) flooding. The valley's steep sides mean heavy rainfall reaches the village quickly as runoff, independently of river levels, and this was a major contributor to the depth of flooding recorded in 2015.
• Hillside instability and landslip risk. The slopes above Scout Road are prone to instability in prolonged or intense wet weather, a risk distinct to Mytholmroyd within the wider valley and one that a site assessment near the hillside needs to consider specifically.
• Groundwater. Assessed as a matter of course within any flood risk assessment, rather than as a separate report, groundwater can raise water tables and reduce how well infiltration-based drainage performs on valley-floor sites.

The Calder at Mytholmroyd typically runs between 0.4m and 2.7m. On Boxing Day 2015 it reached 5.74m, its highest level on record, illustrating how far outside the typical range this catchment can move within hours of sustained heavy rain.

History of flooding in Mytholmroyd

Mytholmroyd has flooded repeatedly and severely within living memory, and each event has directly shaped the flood defences and planning policy that now apply to development in the village.

2012: back-to-back flash floods

Mytholmroyd was hit twice within a few weeks during the summer of 2012, on 22 June and again on 9 July, when flash flooding struck the Upper Calder Valley alongside Hebden Bridge and Todmorden. The clustering of two significant events in such a short space of time was a major factor in the flood-resilience work that followed across the valley.

Boxing Day 2015 (Storm Eva): the worst flood on record

The floods of 26 December 2015 remain Mytholmroyd's worst on record. The Calder and the adjoining canal rose to cover the valley floor and the village centre, with water reaching as much as 2m above street level in places.

• Around 300 properties and 70 businesses flooded in Mytholmroyd itself, alongside a church, a church hall, two schools and the community centre.
• A row of shops north of County Bridge – the Grade II-listed bridge dating to 1684 and widened in 1823 – partially collapsed into the river.
• A landslip blocked Scout Road, forcing the evacuation of around 20 nearby homes and the temporary relocation of Scout Road Academy.

9 February 2020 (Storm Ciara): the second-worst flood on record

Storm Ciara delivered the second-worst flood in the Calder Valley on record, a 1-in-75-year event with an annual probability of around 1.33%. Calderdale received more than a month's typical rainfall in 48 hours – 129.8mm – making it the wettest February on record in the Calder catchment. This fresh, serious flooding episode struck Mytholmroyd and the wider valley while the main flood alleviation scheme was still under construction, a reminder that risk does not pause for a scheme to finish.

Mytholmroyd's flood defences: three completed schemes

Unlike some neighbouring parts of the valley where major flood alleviation work is still going through planning, Mytholmroyd's response to the Boxing Day 2015 floods is finished, funded and already in place. Three separate schemes, each addressing a different part of the damage, have all been completed and tested by subsequent storms, as set out in Calderdale Council's flood recovery and resilience programme.

The Mytholmroyd Flood Alleviation Scheme (£41m, opened 2021)

The main scheme cost £41m, took around three years to build and officially opened in 2021, protecting an estimated 400 homes and businesses. It was delivered by the Environment Agency and Calderdale Council with the VBA joint venture (VolkerStevin, Boskalis Westminster and SNC-Lavalin's Atkins), officially opened in 2021 with funding support from the West Yorkshire Combined Authority. Eye on Calderdale has followed the scheme's progress in detail throughout construction.

• New and raised flood walls, up to around 1.8m high, on both banks of the Calder and Cragg Brook.
• New wall units on Burnley Road downstream of New Road Bridge.
• Relocation of Caldene Bridge to improve how flows pass through the village.
• Channel widening at two locations to increase the capacity of the watercourses through the village.
• Flood-proofing of riverside buildings to reduce damage from any residual risk that remains.

The Scout Road flood recovery scheme (£6.5m, complete)

This £6.5m scheme repaired the hillside above Scout Road that failed in the Boxing Day 2015 landslip, which had blocked the road and forced the evacuation of nearby homes. The completed works replaced and upsized the drainage along the road and hillside, and built a new stone-faced retaining wall in keeping with the surrounding streetscape, as confirmed when the works were finished.

The Burnley Road Academy flood resilience scheme (£450,000, complete)

A £450,000 partnership between the Department for Education, the Environment Agency and Calderdale Council, delivered by contractor Watertight, protects the school that was badly damaged in both 2015 and February 2020. The works fitted puddle pumps, sump pumps, air brick covers, flood barriers, flood gates and a flood door, along with non-return valves and re-pointing and rendering to the building's walls, under a scheme announced by the Department for Education.

Three completed, funded schemes is a genuinely different position from many Pennine towns still waiting on defences to be built. It does not remove the need for a site-specific flood risk assessment. New defences are generally excluded from the Environment Agency's Flood Map for Planning, which is drawn as though they are not there, so land behind even a recently completed scheme can still sit within a mapped flood zone, and residual and off-site risk still has to be assessed for any new development.

Planning policy and the Lead Local Flood Authority

Calderdale Metropolitan Borough Council is the Lead Local Flood Authority for Mytholmroyd, responsible for surface water, groundwater and ordinary watercourses, while the Environment Agency remains responsible for the main rivers, including the Calder. Development is assessed against the Calderdale Local Plan's Policy TP25 (Flood Risk Management) and Policy TP26 (Water Environment), supported by the Calder Catchment Strategic Flood Risk Assessment, first produced jointly by Calderdale, Kirklees and Wakefield councils in 2005 and refreshed in 2016.

A site-specific flood risk assessment is required for any development of one hectare or more, even where the site sits in Flood Zone 1; for any development in Flood Zone 2 or 3; and for any development within a designated Critical Drainage Area, regardless of flood zone. Calderdale also has an adopted Flood Risk and Drainage Supplementary Planning Document that sets out its expectations for surface-water drainage.

A conservation area still classified "at risk"

Mytholmroyd's village centre sits tightly between the River Calder and Cragg Brook, threaded by New Road, which passes beneath the Caldervale Line railway viaduct and over the Grade II-listed County Bridge, built in 1684 and widened in 1823. The scale of damage from the 2015 floods, the demolitions that followed, some unsympathetic rebuilding, high vacancy and poor shopfronts, together with the physical impact of the flood-defence works themselves, led Historic England to classify the Mytholmroyd conservation area as "at risk" in 2018.

That heritage status sits alongside the completed flood defences as a genuine planning consideration for any development or shopfront change in the village centre. Village-centre redevelopment since 2018 has cleared some buildings to create new public space and a more clearly defined centre, and any scheme in this area needs to satisfy both the conservation-area context and Calderdale's flood risk and drainage policy.

A flood risk assessment, a sequential or exception test and a drainage strategy are three distinct reports. They often travel together in a planning submission for a Mytholmroyd site, but they answer different questions: is the site safe, should the development be here, and where does the surface water go.

Local development context in Mytholmroyd

New Road is the spine of the village centre, running under the Caldervale Line railway viaduct and over County Bridge, with the River Calder and Cragg Brook close on either side. That tight geography, combined with the conservation-area-at-risk status and the recently completed flood defences, shapes almost every development or refurbishment proposal in the centre of the village, whether it is a shopfront change, a residential conversion or a larger site.

• Village-centre sites sit within metres of the Calder, Cragg Brook or the canal, and typically need to demonstrate how the completed flood walls interact with the specific site rather than assume blanket protection.
• Heritage-sensitive schemes around County Bridge and New Road need to work within the conservation area's "at risk" status alongside flood risk and drainage requirements.
• Hillside sites near Scout Road need to reflect the ground stabilisation and drainage works completed after the 2015 landslip.
• Any site of a hectare or more, even outside the mapped flood zones, needs a flood risk assessment under Calderdale's Local Plan.

Flood risk assessments for every situation in Mytholmroyd

Whatever the reason a Mytholmroyd site needs a flood risk assessment or a related report, Unda prepares it against the right framework for that purpose.

• Flood risk assessments for planning for developments across Mytholmroyd and the wider Calder Valley, satisfying the NPPF and Calderdale's Local Plan.
• Flood risk surveys for property purchase for buyers and homeowners who want a clear picture of a specific building's risk, beyond a standard conveyancing search.
• Flood risk assessments for insurance where cover has been restricted, premiums have risen, or an insurer needs more detail after a flood event.
• BREEAM flood risk assessments, structured around BREEAM's flood and surface water management credit rather than planning safety criteria.
• Sequential and exception tests where a site's location, rather than its safety alone, needs to be justified against lower-risk alternatives.
• Surface-water drainage strategies (SuDS) for managing runoff from Mytholmroyd's steep valley sides in line with Calderdale's adopted Flood Risk and Drainage SPD.
• Discharge of drainage planning conditions to satisfy pre-commencement or pre-occupation conditions once a scheme has permission.
• Preliminary drainage design at the early, outline stage of a scheme, before layout and land value are fixed.
• Flood modelling where national mapping alone is not detailed enough for a confluence site like this one, feeding accurate levels, extents and flow paths into an assessment.
• Groundwater assessment, carried out as part of every flood risk assessment rather than as a separate report.
• NPPF flood risk guidance for developers and agents who want the national policy position explained clearly for a specific site.

For sites elsewhere in the county, Unda also prepares flood risk assessments across Yorkshire, including Bradford and Rochdale, a comparable Pennine catchment that was also badly hit on Boxing Day 2015.

Local flood risk management and emergency contacts in Mytholmroyd

Several organisations share responsibility for flood risk management around Mytholmroyd, and there are free tools and local groups worth knowing about too.

• Calderdale Council is the Lead Local Flood Authority and leads the borough's flood recovery and resilience programme.
• The Environment Agency manages the main rivers, including the Calder, and operates the flood warning service.
• West Yorkshire Combined Authority has been a funding partner for flood alleviation work in Mytholmroyd.
• Yorkshire Water manages the sewerage network that interacts with surface water drainage in the village.
• The Yorkshire Regional Flood and Coastal Committee oversees strategic flood risk investment across the wider region.
• Slow The Flow Calderdale, a charity founded in 2016, has built more than 859 leaky woody dams at Hardcastle Crags on Hebden Water, slowing the flow of water into the valley, including into Mytholmroyd further downstream.
• Mytholmroyd's own flood group is part of the same valley network as neighbouring flood groups, formed after the 2012 floods with support from the Defra Flood Resilience Community Pathfinder Scheme, backed by more than 60 trained flood warden volunteers across the Calder Valley.

Sign up for flood warnings on gov.uk, and check live conditions using Unda's own Flood Risk Map and Live River Levels Map. In a flood emergency, call 999. To report a power cut, call 105. For general flood advice, Floodline is available on 0345 988 1188.

Frequently asked questions

To find out more about how Unda works and the sites we cover, visit our about page, browse coverage of our work in the media, or explore every area we serve. Related reading: why you can still be in a flood zone after new flood defences have been built, natural flood management explained, how leaky dams reduce flood risk, beavers as a flood-risk solution, the different types of flooding explained, fluvial flooding and its planning implications, surface water flooding explained, critical drainage areas and planning, riparian ownership rights and responsibilities, Flood Re, the UK flood insurance scheme, record UK flood insurance claims in 2024, understanding flood risk before a property purchase, flood risk and mortgage lending, flood history declarations when selling a property, how to prepare for a flood, and Unda's free ground conditions and soakaway map, drainage calculators and BRE 365 infiltration rate calculator.

You can also find one of our experienced flood risk consultants via our flood risk consultants page, or browse the full range of flood risk assessment services Unda provides across England and Wales.