80 Nautical Notes
Introducing an occasional feature about what goes on the River Dart and its estuary, an explanation of some of the activities/actions of the many boats that we may take for granted or perhaps don’t notice, how the river‘s infrastructure works and other odd bits of knowledge that you can use to explain or show off to your friends and family!
T DARTMOUTH’S TIDES
he River Dart arises 550 metres above sea level on the high moors of North
Dartmoor at its most distant (52 miles) and flows to the sea passing through Dartmeet, Buckfastleigh and Totnes, then Dartmouth & Kingswear either side of the estuary mouth. The estuary is the tidal extent
where the freshwaters of the river meet and mix with the tidal seawater of the coast. The Dart is tidal up as far as Totnes weir, just upstream of the estuary’s first bridging point 12 miles from the mouth. Like most South West estuaries,
the River Dart estuary is a drowned river valley or a Ria type estuary. The original deep carved river valley was formed through the ice age and believed to meet the coast just east of Start Point.
After the ice age receded, the sea level rose (c120m) drowned and inundated the river valley with the characteristic steep sides and deep waters of a Ria and providing the deep harbour that we have today. The River Dart has a relatively
large water catchment to the size of the estuary and is typically freshwater dominated, particularly during heavy rain periods If you are going to use a boat,
kayak or paddleboard on the river, it’s important you understand the difference between neap and spring tides. A ‘Spring Tide’ means ● A big change in level from High Water to Low Water
● High tide in the range 4.8m - 5.3m indicates a spring tide
● Lots of water has to get in and out of the river
● Currents will be quite strong except at high and low water
● At low tide there will be beaches and areas of mud
● Spring Tides occur when the moon is full or at no moon
‘Neap Tides’ are the opposite ● The water height at high tide is much less
● The water does not go so far down at low tide
● High water 3.6m - 4.2m indicates a neap tide
● Not much water has to go in and out of the river
● Currents will not be very strong ● Neap tides occur when there is a half moon about 7 days after Springs
If it’s spring tides one weekend it will be neap tides the next weekend. It changes that fast.
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