Human activity (Edexcel GCSE Geography A): Revision Notes

Human activity and river landscapes

Human activities have dramatically changed how our river systems work. When people modify the land through building cities, farming, and industrial development, these changes create significant impacts on river behaviour, water flow patterns, and the natural landscape. Understanding these connections is essential for managing our water resources effectively.

How urbanisation affects rivers

Urban development transforms natural landscapes in ways that significantly alter river systems. When towns and cities expand, they create fundamental changes to how water moves across the land surface.

The growth of urban areas means that large portions of the natural ground become covered with impermeable surfaces like concrete, tarmac, and rooftops. These artificial surfaces prevent rainwater from soaking into the ground naturally. Instead, water runs quickly across these hard surfaces and flows directly into rivers, dramatically increasing the volume of water reaching river channels. This increased surface run-off leads to higher discharge rates and more frequent flooding events.

Urban expansion also creates pressure for new housing developments, which are often built on floodplains - the natural areas where rivers spread out during high water periods. Building on these areas removes the river's natural flood storage capacity and puts communities at greater risk during heavy rainfall events.

To accommodate urban development, rivers are frequently channelised or even forced to flow underground through pipes and tunnels. While this creates space for buildings and roads, it prevents the natural processes of erosion and deposition that help rivers maintain their healthy equilibrium. Channelised rivers lose their ability to meander naturally and become more prone to rapid flow and flooding downstream.

Agricultural impacts on river systems

Farming practices create multiple pathways for changing how water moves through river landscapes. Modern agriculture involves various techniques that modify natural water cycles and affect river behaviour in complex ways.

Field drainage systems are installed to improve farmland productivity by removing excess water from soil. While these drains help crops grow better, they also act like fast highways for moving water directly into streams and rivers. This rapid water movement can destroy natural wetland habitats that normally help philtre water and provide flood protection.

Deforestation for creating farmland removes trees that naturally intercept rainfall before it reaches the ground. Trees normally slow down water movement and help reduce surface run-off. When forests are cleared, rainwater reaches rivers much more quickly, increasing the risk of sudden floods and carrying more sediment with it.

Water abstraction for irrigation reduces the natural flow and velocity of rivers. When farmers pump water out for crop irrigation, it leaves less water flowing in the river channel. This reduced flow means that rivers deposit more sediment and can become shallower over time.

Ploughing activities disturb soil across large areas, loosening earth and making it easier for rainfall to wash sediment into river systems. This increased sediment load can change river channel shapes and affect water quality downstream.

Industrial effects on river environments

Industry creates significant demands on river systems while also introducing potential pollution sources that can transform river landscapes and ecosystems.

Industrial processes require large quantities of water for cooling, cleaning, and manufacturing. This high water demand can substantially reduce the amount of water flowing in rivers, leading to lower discharge rates and reduced erosion capacity. When rivers carry less water, they deposit more sediment and may become shallower or change course more easily.

Industrial activities also pose risks of chemical pollution when waste materials or processing chemicals accidentally spill or are deliberately discharged into river systems. Chemical contamination can kill aquatic plants and animals, disrupting the natural balance of river ecosystems. Polluted rivers may also change colour, develop unusual odours, or become unsafe for human use.

The combination of water abstraction and pollution potential means that industrial areas often experience significant changes to their natural river landscapes, transforming once-pristine waterways into heavily modified environments that require careful management and monitoring.

Understanding land-use change impacts

When examining how human activities affect rivers, it's important to focus on the broader concept of land-use change rather than just looking at individual river modifications. Land-use changes create cascading effects that influence multiple aspects of river behaviour.

Converting natural land surfaces to artificial ones, such as paving over gardens to create car parks, increases the amount of impermeable surface area. This change means that less rainwater can infiltrate into the ground, so more water becomes surface run-off that reaches rivers faster than before. The increased speed of water movement leads to higher discharge rates and greater flood risks.

Deforestation represents another critical type of land-use change that affects rivers. Removing trees reduces the amount of rainfall interception, allowing more water to reach the ground surface directly. This creates increased surface run-off and faster water movement towards river channels.

Building developments on floodplains eliminate one of the natural ways that rivers manage flood water without causing damage. Floodplains normally provide space for rivers to spread out safely during high water periods, but construction in these areas increases flood risks for both new developments and areas downstream.