North coast Orkney, Scotland Flood
Scapa Flow and the Churchill Barriers: a hundred square miles of sheltered water with a wartime history
Scapa Flow is the largest sheltered harbour in the British Isles: 120 square miles of water enclosed by Orkney, with the best kayak camping in Scotland and a set of tidal channels between four islands that were joined by concrete barriers in the 1940s. It is also where the German High Seas Fleet scuttled itself in 1919, and seven of its ships are still on the seabed.
- Distance
- 8.8 nm
- Tide window
- 2.6-4.2 m springs, 1.4-2.2 m neaps
- Wind limit
- 14 kt
- Grade
- Sheltered
- Published
- 25 Aug 2026
What Scapa Flow is
The Flow is a natural basin 13 miles across, protected from the Atlantic by Hoy and from the North Sea by the eastern islands. The British Grand Fleet used it in both world wars because it is deep, sheltered and easily defended, and the defences — booms, batteries, and the Churchill Barriers — are still visible around its shores.
For a kayaker the Flow is the most forgiving water in the north of Scotland. There is almost no tidal stream in the centre, the swell never gets in, and there are landing beaches on six of its islands. It is the correct place to be on a day when the Pentland Firth is closed, which is most days.
The Churchill Barriers and their channels
The four barriers were built in the 1940s after a German U-boat sank HMS Royal Oak inside the Flow in 1939. They link the Orkney mainland to Lamb Holm, Glims Holm, Burray and South Ronaldsay, and they turned four islands into a causeway with a road on top.
Between the barriers there are four channels, each 60 to 120 m wide, and the tide runs through them at 1.5 to 2.5 knots on springs. Each channel has its own slack window, roughly 20 to 30 minutes after Stromness high and low water, and each has a set of eddies at either end that can be used deliberately. This is the most entertaining paddling in the Flow.
Wildlife and camping
Scapa Flow holds about 1,000 grey seals, with pupping on the barrier islands in October and November, and black guillemot — the small, black-and-white, red-footed auk that is the Orkney speciality — breed in the stone walls of the barriers themselves. Otters are common along the Houton and Orphir shores.
Camping is permitted on several of the islands with the landowner's permission, and the standard Orkney practice is to ask at the nearest farm. The islands inside the Flow are low, green and free of the wind that makes camping on the outer coast difficult, which is why this is considered the best multi-day kayak destination in northern Scotland.
Planning a day or a week
A single day from Houton can cover 8.8 nm: south along the Hoy shore, through the Sound of Hoxa, east across the Flow to the barrier channels, and back north on the flood. That takes four hours with a stop, and it uses two opposing streams, which is what makes it work as a round trip.
For a longer trip, the Flow is the base and the outer islands are the objective: Hoy, Rousay, Shapinsay and the string of small islands in the north. Every one of them has a landing beach and a route that can be done between weather systems. The limiting factor is not the water, it is the wind, which in Orkney is a permanent feature and which closes the outer routes for days at a time.
Plan table
Before departure
- 01
Check the wind forecast, not the tide
The Flow has almost no stream in the centre; the wind is the deciding factor in Orkney.
- 02
Calculate slack in the barrier channels
Slack is 20 to 30 minutes after Stromness high and low water.
- 03
Ask permission before camping on any island
Standard Orkney practice is to ask at the nearest farm.
- 04
Confirm the seal pupping closures on the barriers
October and November on the barrier islands; 100 m from any haul-out at all times.
En route
- 01
Use the eddies at the barrier channel mouths deliberately
Each channel has a usable counter-current within 100 m of the shore.
- 02
Keep off the concrete faces of the barriers in any swell
The barriers are vertical and reflect everything; the clapotis there is worse than the open Flow.
- 03
Watch for the Houton and Lyness ferries
Both run regular routes across the Flow and through the barrier area.
- 04
Return north on the flood through the Sound of Hoxa
It is the widest of the northern channels and the least affected by the stream.
Key numbers
- 8.8 nm day from Houton including the barrier channels, 4 hours.
- Almost no tidal stream in the Flow centre; 1.5 to 2.5 kt in the barrier channels.
- Wind limit 14 kt, but the wind is the real factor in Orkney, not the tide.
- 1,000 grey seals and black guillemot breeding in the barrier walls.
- The best multi-day kayak base in northern Scotland, with camping by permission.
Bail-outs
- B1 Houton pier, all states of tide
- B2 St Mary's pier on Holm, a small pier on the south side of the barriers
Return leg：Return north through the barrier channels on the opposite stream, or round the outside of Lamb Holm if the channels are running hard.