River Severn & Bristol Channel Tides

Tides

Severn boating

River Severn Tides

Before the construction of locks and weirs, the effect of the tide reached as far as Worcester.

Today, weirs near Gloucester hold back the daily tides except at high Spring tides *.

The high Spring tides overtop the weirs and make the River Severn tidal as far as Upper Lode Lock, near Tewkesbury.

Around high water, severe turbulence occurs near the approach to Gloucester lock.

Boats should avoid passage at this time.

* Spring tides occur twice each month around the full and new moon.

Bristol Channel & Severn Estuary

The Severn Estuary has the second highest tidal range in the world. Currents are strong with Spring rates of upto 8 knots in the vicinity of the Second Severn Crossing. The funnel-shape of the Estuary and River produces the regular, sometimes spectacular, Severn bore.

The water is deepest at High Water Springs and shallowest at Low Water Springs.

Tidal currents are strongest at the Spring Tides.

At Low Water Springs many harbours may dry out.

The entrance lock to Portishead marina. Here the ground is soft mud.

This photograph was taken at around Low Water Springs.

Later the same day the High Water tide will reach the top dark line on the walls.

Because of the great tidal range, careful planning is required for any passage in the Bristol Channel or Severn Estuary.

sharpness approach at low and high tides

Many ports are only accessible at or near high water.

The tidal window at Sharpness, for example, is very limited.

Craft should arrive no earlier than 1 hour before, and not after high tide Sharpness.

The Youtube timelapse video, coypright Andrew Syred, shows rocks and shoals revealed by the ebbing tide.

Because of the fierce currents, anchoring or taking the ground in the upper reaches of the Estuary is not advised.

Remember also, tidal currents will have a considerable effect on your steering track, fuel consumption and speed over ground.

For safe boating on the Severn Estuary and Bristol Channel, an understanding of the tides and access to daily tide tables are essential.

Tides