Aim: How do channel characteristics change with the long profile in the River Wandle? Background: In south – east England the River Wandle lies as a tributary to the river Thames running through south west London at 9 miles long. The names of the river and of wandsworth have been seen to derive from old the old English “Wendlesworth” meaning “Wendle’s settlement.” Rain falls on the North Downs, filters through the chalk and emerges on the spring line at the wandles two main sources. The river has been used since roman times and was heavily industrialised in the 17th and 18th century. At one big point it was one of the most polluted rivers in England. The main industry was tobacco and textiles. The original course of the river still runs underground beneath Liberty Avenue, surfacing at Runnymede as the pickle ditch and re-joining the modern river outside sainburies. Since the industrial revolution there has been a massive clean-up of the river which has led to a dramatic improvement in the cleanliness of the river which has seen the return of the famous brown trout and other fish. On 17th September 2007, a chemical was accidently flushed into the Wandle from Thames water’s Beddington sewage works. This resulted in the death of over 2,000 fish of various species. The company was fined £125,000 for the incident on 26th January 2009, with the costs of £21,335. The river is very influenced by human activity. Man – made wooden barriers have been constructed on the banks to avoid flooding and more downstream there is a section on the river which is separated into two parts. Theory: For GCSE geography I have been studying water on the land and the long profile of a river. The theory of a river profile is that the gradient will become less steep as you get towards the river’s mouth. The average depth, channel velocity, load quality and discharge will all increase as the river gets closer to the mouth. However the load particle size and channel bed roughness will follow suite and decrease downstream. Downstream of the river there will be more erosion as the velocity will begin to increase and it will form meanders. Through the high velocity there will be a large amount of transportation of the bed load which downstream will be deposited on the outside of the meander of the river. In my investigation I will be looking to see if the River Wandle fits the pattern shown in the Bradshaw model. The Wandle is a river in Wandsworth, and was once the hardest working rivers in the world because of its location and steep gradient. It’s also a tributary of the river Thames, and we as a school are a mile away from the river. We have conducted an investigation into the river and we are seeing how closely it fits into the Bradshaw model. The Bradshaw model shows that the river flows downstream the discharge, occupied channel width, channel depth, average velocity and load quantity increases. The model fits our hypothesis, which is-
How and why do channel characteristics change with distance downstream?
To collect the data for the project I went to each site along the river Wandle and carried out various tests. For each site I followed the same procedure to ensure my results were fair. I measured the width, depth, gradient and pebble roundness. I went to each site starting at Beddington Park and worked my way towards the thames.
In my data I studied the velocity along the river Wandle and tested the results against the Bradshaw model. The Bradshaw model suggests that the velocity will increase as the river goes further and further downstream, which makes logical sense for any river, because the further downstream the water gets the longer distance it has travelled and gaining speed all the time, so at the mouth of the river the water should be flowing fastest. And at site 10 the water was flowing the fastest of all the sites, however there was not a clear...