 The flood is an overflow of water that submerges lands that is usually dry. The European Union EU Floods Directives defines a flood as a covering by water of land, not normally covered by water. In the sense of flowing water, the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrology and are of significant concern, in agriculture, civil engineering and public health. Flooding may occur as an overflow of water, from water bodies, such as river, lake, or ocean, in which the water over-talks or breaks levees, resulting in some of that water escaping its usual boundaries, or it may occur due to an accumulation of rainwater on saturated ground in an aerial flood. While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, these changes in size are unlikely to be considered significant unless they flood property or drown domestic animals. Floods can also occur in rivers when the flow rate exceeds the capacity of the river channel, particularly at vents or knee-enters in the waterway. Floods often cause damage to homes and businesses if they are in the natural flood plains of rivers. While river-rime flood damage can be eliminated by moving away from rivers and other bodies of water, people have traditionally lived and worked by rivers because the land is usually flat and fertile and because rivers provide easy travel and access to commerce and industry. Some floods develop slowly, while others such as flash floods can develop in just a few minutes and without visible signs of rain. Additionally, floods can be local, impacting the neighborhood or community, or very large, affecting entire river basins.