Factors affecting River Flooding
Rivers flood for a variety of different reasons, and very few rivers have the same background characteristics. The reasons why rivers flood can be divided into HUMAN and PHYSICAL (or Natural) characteristics.
The physical reasons for flooding
River flooding by By Rob and Stephanie Levy from Townsville, Australia (Queensland floods) via Wikimedia Commons
Human reasons for river flooding
Humans cause changes in LAND USE which can impact upon river flooding.
1. Urbanisation can cause flooding because many of the surfaces in towns and cities are Impermeable. The whole urban system is designed to move water from the surface into underground pipes and away from urban areas which have value. This can lead to floods in other regions.
2. Deforestation (the removal of trees) can increase soil erosion, reduce interception and increase flood risk.
3. Increases in population density can also have an impact as it places more people in flood risk areas. It is for this reason that we are building on floodplains and flood risk areas in the UK, this just increases the likelihood of a flood.
Historically floods were reasonably unusual events in the UK and mainly occurred during the winter season. This pattern is changing, with major floods becoming more frequent in the UK and many are now occurring in summer. Our case study of a flood in an MEDC, in Morpeth, occurred in early September. If these patterns continue it will cost a lot of money to protect the vulnerable people in flood risk zones. Winter rainfall is becoming more prolonged and heavier as well. This is shown wonderfully below, using statistics from the Met Office website for 2012;
This resulted in extensive flooding in the UK, even in Newcastle upon Tyne on "Thunder Thursday". It has been noticed across the UK that flooding is increasing in intensity (how large the floods are), frequency (how often they occur) and are becoming more common in ALL seasons of the year. This is nicely revealed by the graph from flooding over time in York in Northern England below.