The new series of Coast continues with a journey around the great estuaries of Britain where 20 million people live, and a dazzling variety of animals thrive. The team visit the most dynamic and dramatic of our waterways to discover surprising stories that emerge where rivers and seas collide.
Nick Crane explores the wealth of wildlife and industry that are attracted to the Firth of Forth, the mighty estuary that feeds Edinburgh. To reveal the secrets that made this coastline famous for salt production Nick must answer a deceptively tricky question that intrigues children and baffles adults: Why is the sea salty? Nick also investigates a remarkable natural phenomenon discovered accidentally on this coast in 1834. First seen in the water of a canal near Edinburgh and dubbed the 'Soliton', it's a rare type of wave that appears to travel endlessly, without losing energy and without breaking up, even when it collides with another Soliton wave. Now engineers have created tiny Soliton light waves, which could revolutionise the next generation of fibre-optic communication by transmitting messages effortlessly between continents.
Miranda Krestovnikoff witnesses the extraordinary transformation that salmon must make to their bodies to avoid death by dehydration as they migrate from freshwater to saltwater. This complex lifecycle made farming salmon practically impossible. So how, in 1971, did Scottish fish farmers discover the secret of managing salmon in captivity? Scotland's pioneering efforts created a business worth around half a billion pounds a year, making the noble salmon Britain's favourite fish dish.
It's a dirty job, but someone's got to do it; Tessa Dunlop reveals how the Victorian zeal for cleanliness turned the Thames into a giant self-flushing toilet bowl. It was an ingenious system that relied on the power of the tide to wash the capital's sewage out to sea, a visionary scheme that ended in triumph - and tragedy. The sewage tunnels themselves are still used, but in 1878 the tragic deaths of 600 day-trippers aboard the SS Princess Alice, a pleasure ship wrecked in the Thames, caused such outrage that London's twice-daily tidal flush was abandoned. The unfortunate victims had plunged into a toxic soup of raw sewage, where they perished. London's mighty 'Tidal Flush' was replaced by a fleet of purpose-built ships, carrying human waste from the capital out to the North Sea. Known to locals as 'the Bovril boats' these unsung heroes continued with their vital daily task right up until 1998.
Mark Horton discovers the astonishing struggle to build a rail tunnel deep under the Severn estuary between England and Wales, a challenge that was finally accomplished in 1886. Commuters on the 450 trains that now use it each day are unaware that a vast spring of underground water still pours continuously into the tunnel. Construction was halted for years as Victorian engineers tried to stem the underground spring, but they failed. Even today the rail link is only kept dry by powerful pumps that stop the rising waters.
And multi-award winning folk-singer, June Tabor, returns to Coast to conjure up the haunting 'Brean Lament'. June explores the superstitions surrounding the burial of shipwrecked sailors at the Somerset village of Brean, sited at the mouth of the mighty River Severn - where rivers and seas collide.