River Thames

Physical Geography

The Thames river is not one of the largest rivers in the world only spanning a length of 346 km, however there is a large amount of history in this region showing the relationship with humans and the fluvial environment. Below we will analyse the physical characteristics of the River Thames to understand how this system developed, throughout the large historical record of human occupation in this region.

Formation/Geology

The River Thames is a fluvial system that can date its origins to between 170 and 140 million years ago during the Jurassic period, when the region was submerged by the sea, with the formation of the limestone that would act as the building blocks of the system. This limestone would form the base for the Cotswold Hills where the source of the Thames is located. As the early seas regressed leaving much clearer water many organisms moved into the region including corals and mollusks, with their shells, with these species being the basis for the chalklands that are found within the basin.

Approximately 40 million years ago the seas of the region receded leading to the land that had been formed over millions of years emerging. The Thames would begin to gradually develop over the next 37-38 million years until the much larger Proto-Thames would form a tributary to what is the current Rhine, with a course that would have flowed more northward than its current setting. This connection with the rhine continued until the last ice age, which occurred 110,000 years ago, with the encroaching ice moving southward along the British Isles forcing the course of the Thames further south to a similar setting to that of the current Thames.

At this point the Thames continued to flow on a more southward course eroding the London Clay valley creating a series of geomorphological landforms including gravel and sand terraces along the course of the river. This vertical erosive behavior continued until the end of the last ice age, sea levels beginning to rise with the release of large volumes of water that was previously locked within the glaciers that had formed. With the increase in sea level, the erosive nature of the Thames changed, reducing the formation of the terraces that had been formed with the vertical erosion of the river leading to the current setting of the Thames.

Climate

The Thames basin is much smaller than relative to the other rivers in this series, as such the climate across the entirety of the basin is much more uniform. The climate of the basin can be described as a Maritime climate, much like the rest of the U.K, with mild summers and cool to cold winters. The Thames basin is located within one of the driest regions of the U.K. with an average annual precipitation of 690 mm while the average for the entirety of the U.K. is approximately 885 mm. The temperature across the basin is also mild, as described by the maritime climate, with an average summer temperature of 23°C with an average winter temperature of 5°C while freezing temperatures are not uncommon in the basin.

Human Geography

Modern urbanisation has been occurring throughout the Thames basin for hundreds of years since the beginning of the Industrial Revolution in the 18th century, however, a large human population has been situated within the boundary of the Thames basin for thousands of years since the Roman occupation of the British Isles. As such anthropogenic actions have been impacting the Thames for a long period of time, influencing the natural function of the region and affecting the Ecosystems and services that a natural environment provides. Agricultural practices are also very common throughout the catchment with the upper and middle course of the Thames flowing through agricultural land that use the water resources of the Thames to irrigate their fields. The region has also been the site of extensive industrialisation since the 18th century, with the sprawl of industry throughout London. With industrialisation there were many changes within the basin with losses of the natural environment that were previously situated in the area, an increase in air and water pollution, as well as changes to the permeability of the basin reducing the amount of recharge to the groundwater resources of the Thames. 

The Thames itself has been a major source of resources for those that are situated within the catchment, providing Food, Water, Habitats, tourism, Sports, Leisure as well as in modern times hydro-electric energy, as such there has been a dependence on the river itself for the growth that has been seen within the catchment over the past 300 years.

Pollution 

Pollution is a key issue for the sustained health of the River Thames with many sources being found throughout the basin, the pollution of the Thames has many sources from agriculture along the upper and middle course, industry within London for hundreds of years, transportation along the river and the discharge of wastewater. As such, there is a large amount of both diffuse and point sources of pollution along the course.

Agricultural activity is a major diffuse source of pollution within the River Thames basin, this is primarily found in the upper and middle course of the river and is the primary source of pollution along the river Thame, a tributary of the Thames. As a result of the misuse of products such as fertilisers and pesticides as well as poor practices for preventing the flow of these materials into the river itself, there can be a key issue for the environmental health of the river. An abundance of nitrates, phosphates and pesticides within the channel can lead to major negative impacts to biodiversity within the river with the potential for eutrophication.

The discharge of wastewater into the Thames has been an issue for the health of those in the catchment for hundreds of years with the earliest noted negative impacts occurring from 1830-1860 where tens of thousands of people died as a result of cholera stemming from the discharge of untreated sewage. Treatment methods have drastically improved since then, however, with the invention of modern treatment techniques to prevent occurrences like this. The discharge of treated wastewater into the Thames still occurs with the potential to negatively impact the health of the river if the treated water does not reach the standards outlined for them.

A major issue for the environmental health of the Thames comes from a much different source than those that have been seen before with the discharge of substances into the river, this source is plastics that enter the Thames through littering. These materials breakdown further and are found within the river as Microplastics, these plastics severely impact the environmental health of the river and the biota that lives within the Thames with the potential for bioaccumulation of these microplastics within the tissues of living organisms. It has been noted that the Thames gas some of the highest record levels of microplastics of any river globally, with an estimated 94,000 microplastics per second flow as some sites along its course. This issue of pollution is not easily managed as the diffuse pollution source can originate from a multitude of places including packaging, plastic bottles, gloves and masks to name a few, as such in order to achieve a reduction in this form of pollution it would take fundamental change on an industrial level for businesses to move away from the use of plastics. Some efforts have been made on a governmental level to reduce this form of pollution with the ban of single-use plastics such as plastic straws, however, much more is required to reduce the impact of plastics of the natural environment.

Climate Change

Climate change poses a major threat to areas within the Thames basin, with London itself extremely susceptible to flooding. The increase in the frequency and intensity of storm events within the basin as well as increases to Sea-level itself pose a major threat to the long-term stability of London going into the future. In order to reduce the threat that is posed by climate change, hard engineering strategies such as the Thames Barrier have been employed to manually regulate the water level within the Thames to prevent flooding from both the overflow of the banks but also reducing the risk of Storm surges travelling along the course of the Thames from the North Sea. However, the hard engineering solution of the Thames barrier can only function for a finite period of time with the original design of the barrier accounting for its use up to 2030, while the barrier has now been deemed sufficient protection until the 2060s. As such, there is a large air of uncertainty that hangs over the Thames and how climate change will impact the area from not only an environmental standpoint but also the societal and economic implications associated with climate change.