Causes of flash floods pdf

A flood is caused by a combination of heavy rainfall causing river oceans to over flow their banks, and can happen at any time. Pdf causes and consequences of flooding in nigeria. In the sense of flowing water, the word may also be applied to the inflow of the tide. Highly populated areas have a high risk for flash floods. The urban flooding in cities is mainly in the form of flash floods and water. S dollars in damage national oceanic and atmospheric administration. Every year flash floods cause the loss of a great number of lives as well as tremendous damage. Environment to prepare these guidelines on flash flood prevention and mitigation. A critical analysis revealed that many cases of flooding experienced in this. Pdf an assesment of causes and effects of flood in nigeria.

You will learn to identify various methods that are used to prevent floods and explore how preventing natural flood. Pdf recent floods and consequences all over the world are becoming too frequent and threat to sustainable development in human settlements. Flash floods can be caused by a number of things, but is most often due to extremely heavy rainfall from thunderstorms. Topography characteristics can be an indicator for areas susceptible to flash floods wmo, 2007a. These flash floods occur with little or no warning and cause the biggest loss of human life than any other type of flooding. Flash floods are defined as those flood events where the rise in water is either. Flash floods can occur due to dam or levee breaks, andor mudslides debris. The water table of a river is the area from which it gathers water, so if an unnaturally high level. Figure 1 heavy rainfallinduced flash flood from shrestha, 2008 another cause of flash floods particularly in mountainous terrain outside the tropics can be rain on snow events. In urban areas, flash flooding can occur where impervious surfaces, gutters and storm sewers speed runoff.

The causes of flooding are varied, but the effects of most causes can be managed if not prevented. When there is a lack of vegetation, however, there is little to stop water from running off. Flash floods also can be caused by dam failure, the release of icejam flooding, or collapse of debris dams. According to wikipedia, a flood is an overflow of water that submerges land which is usually dry. Unusually heavy weather at the source of a river can lead to vast amounts of water draining into the water table. Flooding can be caused by rain that falls several miles upstream and then moves rapidly downstream. Additionally, heavy rain falling on steep terrain can weaken soil and cause debris flow, damaging homes, roads, and property. Fatal flash floods hit johannesburg news al jazeera. Vegetation can help slow runoff and prevent flooding. Flash floods rank first as the cause of flood related deaths in the united states. While area residents likely welcome the rain, the lack of vegetation after the drought can cause flash flooding. Boscastle, united kingdom, flood causes and impact of flooding medc case study 1. Flooding that begins within 6 hours, and often within 3 hours, of the heavy rainfall or other cause. You will not always have a warning that these deadly, sudden floods are coming.

Flash flooding comes on so quick that people are unprepared. The main impact of flash floods is undercutting of check dams, the. Most violent storms in decades deluge gauteng, south africa. Flooding occurs in known floodplains when prolonged rainfall over several days, intense rainfall over a short period. Large rivers like the mississippi, missouri, colorado, and ohio carry so much water that a small flash flood is unlikely to cause one of these major rivers to flood, says richards. The european union eu floods directive defines a flood as a covering by water of land not normally covered by water. The worst cases of flooding may occur if there is a combination of. Coastal areas are also at risk from sea flooding, when storms and big waves bring seawater onto the land.