EART 2 Lecture 22: Great Natural Floods
Document Summary
Floodplain is part of the river an area of low-lying ground adjacent to a river, formed mainly of river sediments and subject to flooding. Humans tend to build on floodplains because they want to have access to water. Silt and clay deposited on flood plain; coarse fraction adds to levee (builds up natural levees) Amount of water put in upstream determines flood, because water needs to drain out. Flooding tends happen in lower-level channels (downstream) because water piles up. Too much water - rivers spill into floodplain. Floods happen when the channel/levee system is overwhelmed. Engineering augmentation of levees - 1 flood every 100 years. Without augmentation - once every 2 to 3 years. Natural dam failures have caused the largest floods. Build up of lake/sea above surrounding level due to large dam. Dam collapse (or uplift); massive draining flood. In 1970 the drilling ship glomar challenger collected the first set of ocean floor cores spanning the mile-deep mediterranean sea.
