River Cocker Flooding & Flood Risk

River Cocker flooding is fast and it is concentrated. The Cumbrian Cocker (not the river of the same name near Cockerham in Lancashire) runs out of Crummock Water, down the Lorton Vale and into Cockermouth, where it meets the River Derwent just downstream of Main Street Bridge. Rain on the fells above Buttermere reaches the town within hours, and when the Derwent is high at the same time the Cocker has nowhere to go and the town floods from both sides. We prepare flood risk assessments and drainage strategies for land anywhere in the valley, from Buttermere down to the confluence.

The Cocker and the Derwent set their records in different storms. Every Cocker gauge set its highest level on 19 or 20 November 2009, when South Street Footbridge in Cockermouth reached 4.97 m; the Derwent's highest levels in the town came on 6 December 2015, nine to twelve hours after the Cocker had already peaked.

To talk through a site, call 01293 214444 or email enquiries@unda.co.uk.

• Course. From the head of the Buttermere valley through Buttermere and Crummock Water, then north for 14 km past Lorton and Southwaite to the Derwent at Cockermouth. The West Cumbria Rivers Trust gives the whole river as 19 km long with a catchment of 145 km², taking in Loweswater.
• Who regulates it. The Environment Agency, because the channel is a Main River all the way from Crummock Water to the Derwent. Cumberland Council handles surface water and the smaller becks.
• Gauges. Three Environment Agency gauges: Scalehill below Crummock Water, Southwaite Bridge, and South Street Footbridge in Cockermouth. All three are on the map below.
• Warnings. One flood alert area for the Cocker, Marron and Derwent, and six flood warning areas that take in the Cocker, five of them in Cockermouth.

When has the River Cocker flooded Cockermouth?

Cockermouth has recorded 15 floods since 1761, and four of the worst came within eleven years: January 2005, October 2008, November 2009 and December 2015. The Cocker set its records in 2009. In 2015 it peaked first and the Derwent did most of the damage, so the two floods were worst in different streets even though both put the town centre under water.

1. 8 January 2005. Southwaite Bridge measured 107 m³/s, and the Section 19 investigation report for the town records 261 flooded properties.
2. 23 October 2008. A smaller flood. Southwaite carried 118 m³/s and 45 properties in the town flooded.
3. 19 and 20 November 2009. Seathwaite Farm in Borrowdale recorded 316.4 mm of rain in the 24 hours to midnight on 19 November, a UK record at the time, and the Centre for Ecology & Hydrology placed the Cocker's catchment among the three with the heaviest rain. Southwaite Bridge peaked at 201 m³/s, the largest flow in a record going back to 1967, and 537 properties in Cockermouth flooded.
4. 5 and 6 December 2015, Storm Desmond. Honister Pass set a new UK 24-hour record of 341.4 mm. The Cocker peaked at 18:45 on 5 December at 4.48 m at South Street; the Derwent peaked overnight at 4.54 m at the Kingfisher gauge. The investigation counted 594 flooded properties in the town and found defences overtopped or outflanked at several points on both rivers, though none failed.
5. 28 October 2021. Southwaite Bridge carried 180 m³/s, the third-highest flow on record. High flows that winter damaged privately owned walls protecting the town centre, and the Environment Agency put temporary defences in their place.
6. 8 October 2023. Part of the Old Courthouse beside the Cocker collapsed into the river. Cumberland Council reported that the Environment Agency's flood walls nearby were intact.

The order of the peaks matters for any site in the town. A property on Rubbybanks Road or South Street sits on the Cocker alone and was hit harder in 2009; one on Gote Road or Derwentside Gardens sits on the Derwent and saw its worst water in 2015. An assessment takes the higher of the two for its own frontage and sets it against the annual probability of each flood.

The River Cocker on the map, gauge by gauge

The coral line follows the Cocker from Crummock Water to the Derwent, with its three live gauges pinned along it. Click a pin for the latest River Cocker levels, or use our live river levels map to see the Cocker beside the Derwent and the Greta. Entering a postcode screens that spot against the Environment Agency's river, surface water and reservoir mapping.

Each gauge has its own datum. A reading only means something against that gauge's own thresholds. Scalehill sits just below the lake outflow and shows how full Crummock Water is running. For the town itself, read South Street.

Source: Environment Agency gauge pages and flood-monitoring service, read on 6 November 2026. The highest South Street reading since 2009 is the 4.48 m of 5 December 2015, half a metre lower.

Why does the River Cocker rise so fast?

Because the catchment is steep, very wet and almost impermeable. Above Southwaite Bridge the fells average about 2,100 mm of rain a year, the rock beneath is old slate and granite that stores almost nothing, and the slopes average nearly 290 metres of fall per kilometre. Water reaches the channel quickly, and the Lorton Vale gives it little room to spread before Cockermouth.

Sources: National River Flow Archive station pages for Southwaite Bridge (75004) and Scalehill (75016), checked 6 November 2026. A FARL of 1 would mean no lake storage at all; 0.71 at Scalehill shows Buttermere and Crummock Water trimming the peaks, but in November 2009 the CEH found that the biggest jumps above previous records anywhere in Cumbria came at gauges below lakes.

• Rock that holds nothing. The archive describes the catchment as Lower Palaeozoic rocks and granite under moorland with deeply cut headwaters, and since almost none of the rain soaks in, a wet week on the fells turns straight into river flow at Scalehill and then at Southwaite.
• Lakes that fill up. Crummock Water and Buttermere slow the ordinary rises. A long storm fills them. After that the outflow at Scalehill tracks the rain on the fells, as it did in 2009.
• Gravel in the Lorton Vale. The river drops gravel where the valley flattens. After Storm Desmond the Environment Agency removed it at Low Lorton, Southwaite and Whit Beck, and its Lorton Valley action plan notes there are no formal defences anywhere in the valley.
• A bigger river at the bottom. The Derwent already drains 235 km² at Portinscale, between Derwentwater and Bassenthwaite Lake, twice the Cocker's catchment at Southwaite Bridge. When it is in flood the lower Cocker cannot drain freely into it, so a site near the confluence depends on both rivers' timing.

Which streets and villages does the River Cocker flood?

Most of the exposure is in Cockermouth. Upstream the valley is farmland with scattered houses and the odd mill. In December 2015 the Environment Agency counted roughly seven homes and businesses flooded across Southwaite, Lorton, Crummock and Buttermere put together. In the town the flooded streets run from Victoria Road Bridge down to the confluence, and the table below follows the river in that direction, giving each place the warning area that covers it.

A site inside one of these areas is likely to sit in Flood Zone 2 or 3 on the planning map, and our note on flood zones explains what each zone asks of an application. Check an address on our flood risk map, and for the rest of the county's rivers see the Cumbria page.

Is the River Cocker a Main River?

Yes, along its whole length below Crummock Water. On the Environment Agency's statutory Main River map the channel from the lake to the Derwent is Main River, and the designation also reaches above the lake and up several becks near Loweswater and Cockermouth. That gives the Agency powers over the river and the land beside it. A wall, an outfall, a footbridge or a building within 8 metres of the bank can need the Agency's permit as well as planning permission.

• The smaller becks. Becks and field drains off the Main River map are ordinary watercourses. Work on them needs consent from Cumberland Council as lead local flood authority, and keeping them clear falls to the riparian owners whose land they cross.
• Who decides the application. Cumberland Council for Cockermouth, still applying the former Allerdale Local Plan. Most of the valley upstream lies in the Lake District National Park, where the national park authority decides planning applications.
• When an assessment is needed. National policy, in chapter 18 of the NPPF, asks for a site-specific flood risk assessment for development in Flood Zone 2 or 3, and on larger sites or those with other flood risks in Flood Zone 1.

What do the defences on the lower Cocker mean for a site?

They cut the chance of flooding for the streets behind them. They do not take a site out of the flood zone. The planning map is drawn as if the defences were not there, so an assessment behind a wall still has to show what happens when it is overtopped or bypassed, which on the Cocker side of the town is what happened in at least four places in December 2015.

• The 2013 scheme. A £4.4 million Environment Agency scheme opened on 11 June 2013, with a 120-metre self-closing barrier that rises on the floodwater, glass panels, raised embankments and flood gates. The Agency said it protected over 400 homes and businesses.
• What 2015 showed. On the Cocker side, water went over the defences at Victoria Road Bridge, Hatters Croft, below Main Street Bridge and at Jennings Brewery, and around them at the Rubbybanks Road hump. The defences delayed the flooding and reduced the damage.
• Repairs still to come. The walls damaged in 2021 are privately owned. The Environment Agency's proposed repair scheme would restore their design life without raising them; its published timetable puts construction in 2026 or 2027, and it is still at appraisal.
• Upstream work. The West Cumbria Rivers Trust has built 516 leaky dams across the becks and reconnected floodplain at Blaze Beck in High Lorton and Dub Beck at Loweswater, all of which slows the water on its way down the valley without changing a single line on the planning map.

For a site behind the walls an assessment needs two answers: how deep the water would get if a defence were overtopped, and how quickly it would arrive. Our notes on residual flood risk and on why a site stays in a flood zone after new defences set out how an assessment deals with both.

Flood and drainage reports for land on the Cocker

A planning application, a purchase and a drainage condition each need something different on the Cocker. Three of the reports below get confused. A flood risk assessment asks whether the building is safe from the river and every other source, and whether it pushes water onto neighbours. The sequential test asks whether a lower-risk site could take the development instead. A drainage strategy deals with the rain that falls on the site itself.

• From Buttermere to the confluence. Each flood risk assessment we prepare here starts from the nearest Cocker gauge record and the warning area, then works through surface water, the becks and any defence between the site and the river.
• New homes and conversions. Most new homes in Cockermouth come forward as infill and conversion, and each one needs a flood risk assessment for planning that answers to Cumberland Council and the Environment Agency.
• Buying in the town centre. Streets that flooded in 2009 and again in 2015 show up on searches and in insurers' questions; a flood risk survey for property purchase explains what that history means for one building before exchange.
• Sites in Flood Zone 3. An unallocated site on the floodplain has had no test at plan level, so the sequential and exception test falls to the applicant.
• Getting water off the site. Cumberland Council expects runoff from new development held to greenfield rates before it reaches the Cocker, and our drainage strategy work starts from that limit.
• Infill on steep, wet ground. Thin soils over slate rarely take a soakaway, so a surface water drainage strategy usually turns to storage and a controlled outfall instead.
• After permission is granted. Where a permission arrives with a pre-commencement drainage condition, we prepare the information for the discharge of drainage conditions before work can start.
• Levels behind the walls. Where the national mapping cannot say how deep water would be if a Cocker defence were overtopped, flood modelling works out the level for that frontage.
• Homes that have flooded before. Homes on Rubbybanks Road and South Street flooded in 2009 and again in 2015; a flood risk assessment for insurance gives a broker the site's actual exposure.
• A warning service with little lead time. The 2015 investigation found the warnings did not give some streets enough time, so a flood warning and evacuation plan sets out who does what when the South Street gauge climbs.
• Shops and businesses on Main Street. Jennings Brewery, the Market Place shops and Main Street businesses flooded in 2015; a business continuity assessment plans for the next one.

Ground conditions decide what a drainage strategy can do here, and our geology and soakaway checker gives a first idea of whether infiltration is worth testing on a plot.

Where to report flooding from the Cocker, and who answers

It depends where the water comes from. The river itself, its defences and the gauges belong to the Environment Agency's Cumbria and Lancashire area, while water off the fields, a blocked beck or a culvert goes to Cumberland Council and a surcharging sewer to United Utilities, which runs the public sewers through the town. The Cocker is its own operational catchment within the Derwent North West management catchment.

• Catchment plans. Flood measures for the river sit in the North West flood risk management plan 2021 to 2027, and its water bodies are listed in the Cocker operational catchment.
• The town's plan. The Environment Agency's Cockermouth community action plan from 2016 lists the walls, floodgates and gravel work after Storm Desmond.
• Warnings. The Agency sends free warnings by phone, text or email through its warning service, and Floodline is on 0345 988 1188. In 2016 the Agency recorded 81% of at-risk properties in Cockermouth as registered.
• Funding and partnership. The North West Regional Flood and Coastal Committee approves flood investment across Cumbria, and the Cumbria Strategic Flood Partnership coordinates the councils, the Agency and United Utilities.
• In an emergency. Call 999 if life is at risk and 105 for a power cut. In a major flood the Cumbria Local Resilience Forum brings the emergency services, the councils and the Agency together.

River Cocker flooding: questions people ask

Whether the site is a barn in the Lorton Vale or a shop on Main Street, call 01293 214444 or email enquiries@unda.co.uk and our chartered consultants will say which reports it needs. Assessments for Cocker sites come from Unda Consulting Limited, a CIWEM Business Partner.