Why The Marina Sutton Harbour is the Safest Place to Be

A stone's throw from the original castle, Sutton Harbour's sea defence continues to prove  it's unrivalled value to the maritime community.

With the passing of storm Angus and the next one on the list, Barbara, Britain is getting set for another season of battering as the Atlantic weather patterns throw their wintry worst at us – and of course the first port of call for any Sou'Westerly storm is Plymouth. In parallel Devon County Council are establishing an Extreme weather resilience report.

But with the lock gates protecting The Marina at Sutton Harbour and controlling the depth there is room for 44 million gallons of overspill from outside the lock whilst still staying within the safe flood prevention parameters. It means the safety of berth holders and businesses is assured and unlike days of old, the water will not flood the shops of the Barbican and Southside Street. This has already been acted upon this week with a multimillion pound vessel berthing in the harbour for safety before its delivery.

It is safe to say that much of Britain's Ocean City of Plymouth's maritime history is concerned with the eternal struggle against tide and tempest.

In the days when Plymouth and Sutton Pool were synonymous and Sutton Pool provided the most shelter, Sutton (the ‘South Town') was an interesting combination of a flood-pool inside a narrow ridge of limestone rock, which was naturally breached in two places allowing the small boats to pass in and out.

Over the decades, the larger gap on the National Marine Aquarium side was improved to give clearer passage; on the side nearest the Castle's Barbican tower it was rather smaller and shallower. In the middle was a small ‘island' on which a small fish warehouse was built; eventually of course the small gap was in-filled forming the area on which the Mayflower Steps now stand - and confusing tourists forever more as they realise the the original steps lurk deep under the pub!

Indeed the last couple of hundred years have seen much re-working of the sides of the Pool, to turn a muddy-beached area into the hard wharf of Sutton Harbour that we see today.

In the days when Sutton Harbour was all about trade, the combinations of gales, a flood of tide from seaward and the opposition of torrents of rain from landward, there were regularly flooding problems. Notably a certain Mr IK Brunel had looked at this undesirable state of affairs, but it wasn't until 1993 that the protective wall and lock gate was installed by Statutory Harbour Authority the Sutton Harbour Company. Yes - only 1993!

This made an enormous difference, as one local fisherman observed; "The Plymouth Lock Gates on the entrance to Sutton Harbour are worth their weight in gold after helping to stop tidal surges during the recent storms. Without them, like in the past, the Barbican would have flooded all the way up to the Parade Square! Thankfully the lock gates keep us safe".

But it wasn't simply a matter of building a wall, and opening and closing its gate at will. The whole project has 24/7 control and monitoring from the Harbour Control Centre overlooking the gates. These are the people that warn you to get off the pedestrian bridge when a boat comes along.

Sutton Harbour Master and Head of Plymouth Fisheries, Pete Bromley, explains; "The lock tower is manned 24/7 and monitors both the tide height and weather conditions. We close the lock gates at 5.7 metres above chart datum (CD) as a matter of course for flood prevention. The lock does not start operating again until the tide has turned and the depth receded to 5.6metres above CD."

This standard flood prevention procedure is also backed up with the Sutton Harbour's accurate tide depth gauges and alarms.

Pete Bromley added; "The predicted height of the tide is affected by barometric pressure and storm surges further out in the Atlantic develop a swell which surges up the channel. Areas of low pressure which are associated with bad weather have the effect of allowing the tide to rise higher than that predicted.

With a deep low pressure and a storm surge the height of the tide can be considerably higher and these are the conditions when flooding would usually occur."

"We are advised through the EA flood line when conditions are likely to put us at risk of flood but in addition we monitor all bad weather and during the last low tide before the arrival of a storm we will close the harbour and maintain a depth of around 3.5mts above CD within the pool. This action has three benefits, the boats are lower and gain protection from the wind from the Quay walls, there is no wave action within the pool and Sutton Harbour itself provides the Barbican with an overflow catchment area to protect the rest of the Barbican from flood.""

Sutton Pool has a wet area of 90,930sq metres and by holding the depth at 3.4mts+CD the harbour has room for 200,046 cubic metres or 44million gallons of overspill from outside the lock and still be within the safe flood prevention parameters.

The outer lock gate defence is 7.2mts+CD but there are three gaps in the adjoining wall on West Pier which Plymouth City Council sand bag and protect as this is in their ownership.