Flood control methods are used to reduce or prevent the detrimental effects of flood waters. Flooding can be caused by a mix of both natural processes, such as extreme weather upstream, and human changes to waterbodies and runoff. Flood control methods can be either of the structural type and of the non-structural type. Structural methods hold back floodwaters physically, while non-structural methods do not. Building hard infrastructure to prevent flooding, such as flood walls, is effective at managing flooding. However, best practice within landscape engineering is more and more to rely on soft infrastructure and natural systems, such as marshes and flood plains, for handling the increase in water.
A weir was built on the Humber River (Ontario) to prevent a recurrence of a catastrophic flood.
Relationship between impervious surfaces and surface runoff
Emergency flood barrier
Flood protection for town of Ybbs along the river Donau
A flood is an overflow of water that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant concern in agriculture, civil engineering and public health. Human changes to the environment often increase the intensity and frequency of flooding. Examples for human changes are land use changes such as deforestation and removal of wetlands, changes in waterway course or flood controls such as with levees. Global environmental issues also influence causes of floods, namely climate change which causes an intensification of the water cycle and sea level rise. For example, climate change makes extreme weather events more frequent and stronger. This leads to more intense floods and increased flood risk.
Urban flooding in a street in Morpeth, England
View of flooded New Orleans in the aftermath of Hurricane Katrina
Flooding of a creek due to heavy monsoonal rain and high tide in Darwin, Northern Territory, Australia
Flood in Jeddah, covering the King Abdullah Street in Saudi Arabia