Talk Report: 2017-11-08
Report on Rivers: A natural and not so natural history, by Paul Raven
On the 4th of February 1967 12-year-old Paul Raven drew an owl in Wells Museum. Last Wednesday 8th November the careful drawing appeared on the screen as Dr Paul Raven PhD began his lively and fascinating talk in Wells Museum. This was about the formation and character of Britain’s rivers.
Paul took early retirement from the Environment Agency in 2011 after 15 years as Head of Conservation and Ecology. His talk to members was based on the book which he wrote with his friend Nigel Holmes: Rivers a natural and not-so-natural history. Owls were never mentioned again! but along the way we heard about a great deal, from the formation of rivers since the first Ice Age to the damage man has done and is still doing to our waterways, and from the aurochs which once roamed our land to the myriad life forms which still inhabit our rivers.
Britain has only been an island for about seven and a half thousand years. The great rivers which flowed across the land mass of Europe would have once continued into our lands and the some of the species of fish which swam in them have survived to this day in British rivers.. The huge, cow-like aurochs have long since gone but our rivers still flow, although often dramatically changed over the years. Changes occur by natural processes but most often they have been altered and adapted by our ancestors for their own uses.
Their names for many rivers exist to this day: Avon means river…Derwent means oak fringed stream…Ouse means water. Rivers were essential not only for fresh water but for transport and food and - later - for power and drainage. The Romans were the first to move earth to alter the flow of rivers; monks cleared local river’s banks and sometimes changed the course for their own purposes. We were shown images of mediaeval mills and Saxon fish traps. We heard how, from ancient times, man has used the flora which grows besides rivers: reed for thatch roofing, rushes for flooring and willows (withies) to make fish traps, baskets and, much more recently, seats for early automobiles and aeroplanes.
Adapting rivers for fishing, transport, drainage and power often means altering their course and character. Through history and still today rivers have been and are over-widened and artificially deepened. Trees are cut back and banks are cleared, altering the flow and width. Rivers are forced between concrete walls to avoid buildings, culverted beneath towns, embanked to reclaim land and over-manicured to enable easy fishing. Only about 10% of our rivers remain as they originally flowed.
A river is essentially a jerky conveyor belt carrying materials from higher ground down to the sea. Rocks and pebbles, sand and clay travel down river, tumbling down in foaming swirls or slipping slowly along as sediment beneath the rippling water. Woody debris and tree roots beside the river bank make ideal sanctuaries for wildlife, as do the wet woodlands and marshy areas which often board the river’s edge. We were shown photographs of meandering rivers, rivers through peaceful woodland, rivers in full flood and rivers which have dried away to a mere trickle of water. The Industrial Revolution speeded up the desecration of our rivers and contemporary paintings and engravings show the grim, polluted waterways which flowed through towns in the 19th and early 20th century.
It is not all doom and gloom. With knowledge, great expense and care rivers are being re-claimed as clean waterways. Wildlife once again flourishes in and alongside our rivers. Hobby fisherman work to preserve fish in their natural habitat and otters are flourishing again now they are no longer hunted. Now we are more worried by invasive species introduced from other lands to threaten our native flora and fauna. The American Signal Crayfish, introduced in the last century, has more or less obliterated our native crayfish and the ever-threatening Japanese Knotweed and the pretty but invasive Himalayan Balsam are often seen smothering our natural river banks.
Paul was asked many questions by the audience. How do we “ration” the water extracted from rivers by farmers? There are strict and carefully organised percentages of water which any landowner is allowed to take from the river boarding his fields. What is the perfect rate of flow for a river? The natural pace at which any one river flows within its banks is the right rate of flow for that particular river. There were many more questions and the speaker was thanked very much for such an unusual, interesting and well-illustrated talk.