14-09-2012, 11:21 AM
Natural Disasters
Natural Hazards.ppt (Size: 653.5 KB / Downloads: 347)
Natural Disasters are disasters that occur in this world naturally.
Natural disasters can happen at any location at any time throughout the universe.
Natural disasters can destroy cities, or sometimes a whole country if it is that severe.
They can occur on land, in the water, and with the weather.
The Nature of the Hazard
a. Rapid Onset vs. Slow Onset
At one extreme earthquakes, landslides, and flash floods give virtually no warning. Less extreme are tsunamis, which typically have warning periods of minutes or hours, and hurricanes and floods, where the likelihood of occurrence is known for several hours or days in advance. Volcanoes can erupt suddenly and surprisingly where as hazards such as drought, desertification, and subsidence act slowly over a period of months or years.
b. Controllable Events vs. Immutable Events
For some types of hazards the actual dimensions of the occurrence may be altered if appropriate measures are taken(Eg floods). For others, no known technology can effectively alter the occurrence itself(Eg earthquakes,volcanoes,etc.).
c. Frequency vs. Severity
Some hazards like floods occurs every year or every few years, the hazard becomes part of the landscape, and projects are sited and designed with this constraint in mind. Unlike tsunami which may strike any time in 50 or 100 years, it is difficult to take up mitigation measure..
d. Mitigation Measures to Withstand Impact vs. Mitigation Measures to Avoid Impact
Earthquake-resistant construction and flood proofing of buildings are examples of measures that can increase the capacity of facilities to withstand the impact of a natural hazard. Measures such as zoning ordinances, insurance, and tax incentives, which direct uses away from hazard-prone areas, lead to impact avoidance
Fundamental Concepts Related To Natural Hazards
Natural process have service functions.
Hazards are predictable.
Linkages exist between hazards and physical and biological environment.
Hazards that previously produced disasters are now producing catastrophes
Risks from hazards can be estimated.
Adverse effects can be minimized.
Kinds Of Floods
Flooding can also be divided into different categories according to their location:
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.
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.
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.
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. Freshwater floods in particular play an important role in maintaining ecosystems in river corridors and are a key factor in maintaining floodplain biodiversity
Education and Training Activities
Education and training, both formal and informal, prepare people at all levels to participate in hazard management. Universities, research centers, and international development assistance agencies play the leading formal role in preparing individuals to face natural hazards. These activities are also carried out by operational entities such as ministries of agriculture, transportation, public works, and defense.
Natural Hazards.ppt (Size: 653.5 KB / Downloads: 347)
Natural Disasters are disasters that occur in this world naturally.
Natural disasters can happen at any location at any time throughout the universe.
Natural disasters can destroy cities, or sometimes a whole country if it is that severe.
They can occur on land, in the water, and with the weather.
The Nature of the Hazard
a. Rapid Onset vs. Slow Onset
At one extreme earthquakes, landslides, and flash floods give virtually no warning. Less extreme are tsunamis, which typically have warning periods of minutes or hours, and hurricanes and floods, where the likelihood of occurrence is known for several hours or days in advance. Volcanoes can erupt suddenly and surprisingly where as hazards such as drought, desertification, and subsidence act slowly over a period of months or years.
b. Controllable Events vs. Immutable Events
For some types of hazards the actual dimensions of the occurrence may be altered if appropriate measures are taken(Eg floods). For others, no known technology can effectively alter the occurrence itself(Eg earthquakes,volcanoes,etc.).
c. Frequency vs. Severity
Some hazards like floods occurs every year or every few years, the hazard becomes part of the landscape, and projects are sited and designed with this constraint in mind. Unlike tsunami which may strike any time in 50 or 100 years, it is difficult to take up mitigation measure..
d. Mitigation Measures to Withstand Impact vs. Mitigation Measures to Avoid Impact
Earthquake-resistant construction and flood proofing of buildings are examples of measures that can increase the capacity of facilities to withstand the impact of a natural hazard. Measures such as zoning ordinances, insurance, and tax incentives, which direct uses away from hazard-prone areas, lead to impact avoidance
Fundamental Concepts Related To Natural Hazards
Natural process have service functions.
Hazards are predictable.
Linkages exist between hazards and physical and biological environment.
Hazards that previously produced disasters are now producing catastrophes
Risks from hazards can be estimated.
Adverse effects can be minimized.
Kinds Of Floods
Flooding can also be divided into different categories according to their location:
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.
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.
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.
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. Freshwater floods in particular play an important role in maintaining ecosystems in river corridors and are a key factor in maintaining floodplain biodiversity
Education and Training Activities
Education and training, both formal and informal, prepare people at all levels to participate in hazard management. Universities, research centers, and international development assistance agencies play the leading formal role in preparing individuals to face natural hazards. These activities are also carried out by operational entities such as ministries of agriculture, transportation, public works, and defense.