October 5, 2010

Floods & Causes & Effects - APPSC MAINS PAPER4 SECT-3 Unit -2

Flood is overflow of the huge amount of water onto the normally dry land. Flood occurs when the overflowing water submerges land and causes deluge. It is a cruel and violent expression of water.

Floods are often deadly, damaging and devastating. They kill lots of people, damage houses and crops, and cause extensive destruction. In broader terms, floods are of two types; Natural floods and Catastrophic floods.

Natural floods are the floods that are caused naturally by the overflow of the huge volume of water, from rivers, lakes, oceans, or by heavy rains or downpours, hurricanes, cyclones, or tsunamis, etc. Natural floods could be Riverine floods – caused by rivers; Estuarine floods – caused by a combination of sea tidal surges and storm-force winds; or Coastal floods – caused by cyclones, hurricanes and tsunamis. These are one of the most common natural disasters.

Catastrophic floods are the floods that are caused by some significant and unexpected events, for instance dam breakages.


Heavy rainfalls are one of the major causes of floods. The level of water in rivers or lakes rises due to heavy rainfalls. When the level of water rises above the rive banks or dams, the water starts overflowing, which causes floods. The water overflows to the areas adjoining to the rivers, lakes or dams, causing floods or deluge. The flood water causes havoc and great destruction in the areas where it flows. Floods occur more in the regions that get heavy rainfalls.

Floods are also caused due to heavy snow melting. Global temperature is rising due to global warming. The rising temperature makes the snow caps melt faster. Continuous and fast melting snow raises the level of oceanic water, which consequently raises the level of water in rivers, and when the level of water in rivers rises above the rive banks, it causes floods.

Generally, floods occur more in the low-lying areas or the areas below the sea level. One of the main reasons is that rivers flow slowly in these areas. The volume of water increases in the low-lying areas. When the level of water rises in these regions, it causes floods.


Floods also occur more in the coastal regions. Floods, in the coastal regions, are caused due to high tides, storms, cyclones, hurricanes, or tsunamis. When the level of water rises above the sea level, it causes floods in coastal areas or coastal lowlands.

There are also several human causes of floods. Deforestation is one of the major causes of floods. Trees are being cleared fast from large areas. As result, soil is easily eroded, and the eroded soil gets settled at the bottom of rivers and seas, which raises the level of water in rivers and seas, which consequently causes floods.

Sometimes floods are caused due to poor dams that can not hold great volume of water and they give up causing floods in adjoining areas. Hence, there are always different causes of floods. However, human causes of floods can be avoided. Humans should let the nature go its own way.



Primary effects

  • Physical damage - Can damage any type of structure, including bridges, cars, buildings, sewer systems, roadways, and canals.
  • Casualties - People and livestock die due to drowning. It can also lead to epidemics and waterborne diseases.

Secondary effects

  • Water supplies - Contamination of water. Clean drinking water becomes scarce.
  • Diseases - Unhygienic conditions. Spread of water-borne diseases.
  • Crops and food supplies - Shortage of food crops can be caused due to loss of entire harvest.[4] However, lowlands near rivers depend upon river silt deposited by floods in order to add nutrients to the local soil.
  • Trees - Non-tolerant species can die from suffocation.[5]

Tertiary/long-term effects

Economic - Economic hardship, due to: temporary decline in tourism, rebuilding costs, food shortage leading to price increase, etc.



Steps to Control Impact of Floods:



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