Lecture on Floods (2).ppt
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Transcript of Lecture on Floods (2).ppt
Global Warming…
Global warming is the increase of the Earth’s surface median temperature over time.
Since late in the 19th century the average global surface temperature has gone up .5F and during the 20th century, surface temperatures grew by about 1F.
Predictions for the next 100 years are for a 2.7-8 degree F increase, depending on how much fossil fuels are burned and forest systems are removed.
Global Warming…
An increase in greenhouse gasses is the cause of global warming.
Some effects include: an increase in sea level, difficulties in agriculture, change in rainfall, and changes in the ecosystem which will cause animals and plants to have to adapt or perish.
Floods
• A certain surface is affected by them for an indeterminated period of time.
• They can be
seasonal or sudden.
Floods
Floods are water covering previously dry area. A flood is a very large amount of water that has
overflowed from a source such as a river, lake, and ocean.
They can also have overflowed a broken pipe onto a previously dry area.
The damages after a flood is harsh because everything or parts of things will be under water and the effects of a flood can kill many people.
Kinds Of Floods
Flooding can also be divided into different
categories according to their location:
Coastal Floods
River Floods
Urban Floods
Kinds Of Floods
1. Coastal Floods:
Coastal Floods usually occur along coastal areas.
When there are hurricanes and tropical storms which
will produce heavy rains, or giant tidal waves created by
volcanoes or earthquakes, ocean water may be driven onto
the coastal areas and cause coastal floods.
Kinds Of Floods
2. River Floods
This is the most common type of flooding.
When the actual amount of river flow is larger than
the amount that the channel can hold, river will overflow
its banks and flood the areas alongside the river.
And this may cause by reasons like snow melt or
heavy spring rain.
Kinds Of Floods
3. Urban Floods
In most of the urban area, roads are usually paved.
With heavy rain, the large amount of rain water
cannot be absorbed into the ground and leads to urban
floods.
The Effect on Floods
Higher surface temperatures and changes in precipitation cause floods in some places, and droughts in others. floods. A rise in sea level and severe rain are two causes of floods.
The Effect on Floods
Long term changes in the hydrological cycle (the flow of water throughout Earth) due to higher temperatures (more evaporation; melting of ice, more intense rain fall) contribute to more floods.
More water vapor in the atmosphere, because the atmosphere is heating up, can cause floods to happen more regularly.
Floods Continued Sea level rising will also contribute to more floods. The sea level is predicted to go up from four inches to
three feet. Sea level rises when the water warms and increases
in amount, or when glaciers and ice melt..
Floods Continued As the glaciers and ice turn into water the sea level
increases and floods could start to last for a longer
amount of time and happen more
Floods ContinuedSea level rising
will also contribute to more floods. The sea level is predicted to go up from four inches to three feet. Sea level rises when the water warms and increases in amount, or when glaciers and ice melt. As the glaciers and ice turn into water the sea level increases and floods could start to last for a longer amount of time and happen more frequently.
Examples and Predictions of Flooding
There are predictions that as a result of
climate change there will be a large increase in
famine by 2050 of 30 million people going
hungry because of less crops caused by
flooding.
One country that suffers from flooding
because of climate change is Bangladesh.
They experienced major flooding in 1998 in
which two thirds of the country was
underwater.
Examples and Predictions of Flooding
There are predictions for this to become
worse with more constant flooding and more of
the country underwater by 2100 if it continues
the same way.
Many coastal cities would be affected,
including Manhattan, San Francisco, New
Orleans, and Miami, and cities around the world
including highly populated ones like Shanghai.
BENEFITS
There are many disruptive effects of flooding on human
settlements and economic activities.
However, floods (in particular the more frequent/smaller
floods) can bring many benefits, such as recharging ground
water, making soil more fertile and providing nutrients in
which it is deficient.
Flood waters provide much needed water resources in
particular in arid and semi-arid regions where precipitation
events can be very unevenly distributed throughout the year.
BENEFITS
Freshwater floods in particular play an important role in
maintaining ecosystems in river corridors and are a key
factor in maintaining floodplain biodiversity
Urban Areas Rural Areas
Massive amounts of erosion can be
accomplished by flood waters.
Such erosion can undermine bridge structures,
levees, and buildings causing their collapse.
Flooding of farmland usually results in
crop loss.
Livestock, pets, and other animals are
often carried away and drown.
Water entering human built structures cause
water damage.
Even with minor flooding of homes, furniture
is ruined, floors and walls are damaged, and
anything that comes in contact with the water is
likely to be damaged or lost.
Flooding of automobiles usually results in
damage that cannot easily be repaired.
Transportation systems may be disrupted,
resulting in shortages of food and clean-up
supplies.
Food grains stored at home or in go-
downs get wet and start rotting.
In under developed countries food
shortages often lead to starvation
Effect of Flood on Urban & Rural Areas
Urban Areas Rural Areas
Gas and electrical service may be disrupted.
Water supply pipes/ system get damaged and
wells get inundated creating shortage of drinking
water.
The affected communities living in
temporary shelters/ resettlements have
limited or no access to safe drinking water,
food etc.
In addition, prevailing unhygienic sanitary
conditions make it conducive for spread of
food and water borne diseases.
Effect of Flood on Urban & Rural Areas
Natural Causes
• Excesive rains.
• Overflowing of rivers, lagoons,lakes,etc.
Human causes• Bad agricultural practice
• Bad infraestructure
• Deforestation
• Urban increase
Most important consequences
• Population mortality
• Economic losses
• Population evacuation
• Infraestructure destruction
Flood Management History in India• Before independence: Damodar experience• 1948: The DVC Act• 1954: National Flood Policy• 1963: Farakka construction starts• 1980: Report of National Floods Commission• 1979-80: Flood forecasting starts• 1999: Report of the National Commission on
Integrated Water Resources Development• 2002: ILR proposals to solve flood problem• 2004: PM’s Task Force on Floods• 2004: Proposal for NE River Valley Authority
The Govt responses• Embankments
• Dams
• Dredging
• Spurs, revetments
• (Flood forecasts, warning)
• ILR
• Disaster Management
• Relief, (insurance)
• Committees
How flood affected area has been going up
State Area prone to floods (m ha) as assessed by
NCF (1980)
10th Plan working Group-2002
Bihar 4.26 6.88
UP 7.34 7.34
W Bengal 2.65 3.77
Arunachal Pradesh - 0.12
Assam 3.15 3.82
Average annual damage due to floods in Bihar(Source: NCF, 1980)
Period Total Area affected, Lakh Ha
Crop Area affected, Lakh ha
Total damage at constant prices, Rs Lakh
1950-65 8.81 4.43 861.92
1966-70 10.82 5.85 1184.08
1971-78 21.30 8.85 4588.57
Average annual damage due to Floods in Uttar Pradesh
(Source: NCF, 1980)
Period Total Area affected, Lakh Ha
Crop Area affected, Lakh ha
Total damage at constant prices, Rs Lakh
1950-65 16.80 7.84 1229.48
1966-70 20.12 10.42 1730.16
1971-78 30.00 16.64 4550.81
Brahmaputra floods in IndiaPeriod Average Annual
Area flooded ( m ha)
Flooded crop area as % of total inundated area
Average Annual no of people affected, m
Average annual damage Rs MTotal Cropped
1953-59 1.013 0.1 8.85 0.86 58.6
1960-69 0.75 0.16 21.33 1.52 75.7
1970-79 0.87 0.18 20.69 2.00 151.8
1980-88 1.43 0.40 28.05 4.55 1445.2
1999-2005 1.07 0.38 35.65 4.586 7171.7