Floods: formation, impacts and preventive measures

  • Created by: nicola
  • Created on: 23-04-11 10:47

Weather = a set of all the phenomena occurring in a given atmosphere at a given time.

  • Most weather phenomena occur in the troposphere 
  • Generally, temperature and precipitation activity at a certain place and time.

Climate = long-term conditions in the atmosphere patterns, averages, and extremes (most/maximum and least/ minimum)

  • i.e. the average of weather conditions in a place

Climate Change

When the climate is altered over time for a long time as a result of human or natural influences. Examples of effects of climate change:

  • Rise in sea level during the past century from four to eight inches
  • Increase in precipitation by approximately one percent
  • Changes in the ecosystem altering the amount of snow in the north
  • Rise from five to ten percent in rainfall
  • Summers becoming increasingly dry while ice in the Arctic Ocean decreases
  • Extending the growing season in areas with short seasons

Rapid changes don't give living systems enough time to adapt

Higher surface temperatures and changes in precipitation cause floods in some places, and droughts in others = from L/T changes in hydrological cycle

Global Warming

An increase of the Earth’s surface median temperature over time - caused by an increase in greenhouse gas concentrations.


  • Increase in sea level
  • Difficulties in agriculture
  • Change in rainfall
  • Changes in the ecosystem which will cause animals and plants to have to adapt or perish

Air-Sea Interactions

Walker circulation:

  • East-west (zonal) circulation pattern in the tropics
  • Characterized by cells of rising and sinking air, connected by horizontal movement along latitudes

El Niño:

  • Weakening / breakdown of “normal” Walker circulation in tropical Pacific Ocean
  • Warm surface waters in eastern tropical Pacific

La Niña:

  • Strengthening / intensification of “normal” Walker circulation in tropical Pacific Ocean


  • El Niño Southern Oscillation
  • Oscillation between El Niño and La Niña conditions
  • 3-to 7-yr cycle (5 yr on avg.)
  • Associated with floods, droughts and other weather disturbances in many regions of the world - vary with each event
  • Developing countries dependent upon agriculture and fishing, particularly those bordering the Pacific Ocean, are the most affected


A flood is an overflow or accumulation of an expanse of water that submerges land.

Flooding may result from the volume of water within a body of water, such as a river or lake, which overflows or breaks levees, with the result that some…


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