Cause and Effect

What causes floods?

       A flood is caused by a combination of heavy rainfall causing river / oceans to over flow their banks, and can happen at any time of the year, not just in the winter. Floods generally develop over a period of days, when there is too much rainwater to fit in the rivers and water spreads over the land next to it (the ‘floodplain’). However, they can happen very quickly when lots of heavy rain falls over a short period of time. These ‘flash floods’ occur with little or no warning and cause the biggest loss of human life than any other type of flooding. Coastal areas are also at risk from sea flooding, when storms and big waves bring
seawater onto the land. The worst cases of flooding may occur if there is a combination of storms, ‘spring tides’ and low atmospheric pressure.

What are the effects of flooding?

Flooding can be very dangerous – only 15cms of fast-flowing water are needed to knock you off your feet! Floodwater can seriously disrupt public and personal transport by cutting off roads and railway lines, as well as communication links when telephone lines are damaged. Floods disrupt normal drainage systems in cities, and sewage spills are common, which represents a serious health hazard, along with standing water and wet materials in the home. Bacteria, mould and viruses, cause disease, trigger allergic reactions, and continue to damage materials long after a flood. Floods can distribute large amounts of water and suspended sediment over vast areas, restocking valuable soil nutrients to agricultural lands. In contrast, soil can be eroded by large amounts of fast flowing water, ruining crops, destroying agricultural land / buildings and drowning farm animals. Severe floods not only ruin homes/ businesses and destroy personal property, but the water left behind causes further damage to property and contents. The environment and wildlife is also at risk when damage when damage to businesses causes the accidental release of toxic materials like paints, pesticides, gasoline etc. Floodwater can severely disrupt public and personal transport by cutting off roads and railway lines, as well as communication links when telephone lines are damaged. Unfortunately, flooding not only disrupts many people’s lives each year, but it frequently creates personal tragedies when people are swept away and drowned.