Introduction - Background to Flood Risk in Northern Ireland

Flooding is a natural phenomenon that cannot be entirely prevented. There are four main sources of flooding. Flooding from rivers or fluvial flooding occurs when the channel capacity is exceeded and flood waters overtop the river banks. Coastal flooding occurs when inundation of land takes place due to a combination of high tides, wave action and storm surge. Surface water or pluvial flooding occurs as a result of high intensity rainfall which can overwhelm drainage systems or cause water to collect in low lying areas. Finally, flooding from impounded water bodies such as reservoirs and dams can arise as a result of overtopping or failure of the impounding structure which in turn may result in a sudden uncontrolled release of flood water into downstream areas. The effects of flooding on human activity are wide ranging. Floods have the potential to cause fatalities and injury, displacement of people, pollution and health risk, loss of drinking water, damage to buildings and the environment and to severely compromise economic activities. If not properly managed, flooding to property will also impact on property prices, the ability to get a mortgage agreement and the availability of affordable property insurance.