At the close of the twentieth century, natural hazards and disasters are one of the most common forms of disasters around the world. Natural disasters cause in significant loss of life and serious economic, environmental and social impacts that greatly retard the development process. Careful hazard assessment and planning, and a range of social, economic and political measures, can significantly contain these threats.
Most commonly, there are three components in a natural disaster plan: monitoring and early warning; risk assessment and mitigation and response. Given the improved tools and technologies available today, it is possible to provide disaster information and minimize the potential damage of disasters.
So, the national early warning systems would be discussed, as one of the important component of natural disaster risk management.
Different types of natural disasters occur, such as drought, flood, earthquake, sea-level rise, dust storm, and etc, but Flood hazard and disaster is one of the most frequent and damaging types of natural disasters. They have been the most common type of geophysical disaster in the latter half of the twentieth century in India, generating an estimated more than 20 percent of all disasters from 1950 to 2003.
Various kinds of natural disasters.
There are various kinds of natural calamities in the world,
Rapid Climate Change and Agriculture.
A flood is an overflow or accumulation of an expanse of water that submerges land. In the sense of "flowing water", the word may also be applied to the inflow of the tide. 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 of the water escapes its normal boundaries. While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, it is not a significant flood unless such escapes of water endanger land areas used by man like a village, city or other inhabited area.
Floods can also occur in rivers, when the strength of the river is so high it flows out of the river channel, particularly at bends or meanders and causes damage to homes and businesses along such rivers. While flood damage can be virtually eliminated by moving away from rivers and other bodies of water, since time out of mind, people have lived and worked by the water to seek sustenance and capitalize on the gains of cheap and easy travel and commerce by being near water. That humans continue to inhabit areas threatened by flood damage is evidence that the perceived value of living near the water exceeds the cost of repeated periodic flooding.
Various types of floods.
Slow kinds: Runoff from sustained rainfall or rapid snow melt exceeding the capacity of a river's channel. Causes include heavy rains from monsoons, hurricanes and tropical depressions, foreign winds and warm rain affecting snow pack. Unexpected drainage obstructions such as landslides, ice, or debris can cause slow flooding upstream of the obstruction.
Fast kinds: include flash floods resulting from convective precipitation or sudden release from an upstream impoundment created behind a dam, landslide, or glacier.
Commonly caused by a combination of sea tidal surges caused by storm-force winds. A storm surge, from either a tropical cyclone or an extra tropical cyclone, falls within this category.
Caused by severe sea storms, or as a result of another hazard (e.g. tsunami or hurricane). A storm surge, from either a tropical cyclone or an extra tropical cyclone, falls within this category.
Caused by a significant and unexpected event e.g. dam breakage, or as a result of another hazard (e.g. earthquake or volcanic eruption).
A muddy flood is generated by run off on crop land.
A muddy flood is produced by an accumulation of runoff generated on cropland. Sediments are then detached by runoff and carried as suspended matter or bed load. Muddy runoff is more likely detected when it reaches inhabited areas.
Muddy floods are therefore a hill slope process, and confusion with mudflows produced by mass movements should be avoided.
Effects of flood.
Physical damage - Can range anywhere from bridges, cars, buildings, sewer systems, roadways, canals and any other type of structure.
Casualties - People and livestock die due to drowning. It can also lead to epidemics and waterborne diseases.
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.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.
Economic - Economic hardship, due to: temporary decline in tourism, rebuilding costs, food shortage leading to price increase etc.
More problems of flood.
Flood-water drains are the dirtiest parts of most cities
Waste from apartments or slums is thrown into them
They are used as public toilets
Keepers of street pigs break drains and man-holes to create mud-wallows in nalas for their pigs
Sewage is let out into nalas by new buildings, contaminating drinking-water lines nearby.
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. Earthquakes are recorded with a seismometer, also known as a seismograph. The moment magnitude of an earthquake is conventionally reported, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale .
At the Earth's surface, earthquakes manifest
themselves by shaking and sometimes displacing
the ground. When a large earthquake epicenter is
located offshore, the seabed sometimes suffers
sufficient displacement to cause a tsunami . The
shaking in earthquakes can also trigger
landslides and occasionally volcanic activity.
In its most generic sense, the word earthquake is used to describe any seismic event whether a natural phenomenon or an event caused by humans that generates seismic waves. Earthquakes are caused mostly by rupture of geological faults, but also by volcanic activity, landslides, mine blasts, and nuclear experiments. An earthquake's point of initial rupture is called its focus or hypocenter. The term epicenter refers to the point at ground level directly above the hypocenter
Earthquake fault types
There are three main types of fault that may cause an earthquake: normal, reverse (thrust) and strike-slip. Normal and reverse faulting are examples of dip-slip, where the displacement along the fault is in the direction of dip and movement on them involves a vertical component. Normal faults occur mainly in areas where the crust is being extended such as a divergent boundary.
Reverse faults occur in areas where the crust is being shortened such as at a convergent boundary. Strike-slip faults are steep structures where the two sides of the fault slip horizontally past each other; transform boundaries are a particular type of strike-slip fault. Many earthquakes are caused by movement on faults that have components of both dip-slip and strike-slip; this is known as oblique slip.
Earthquakes away from plate boundaries.
Where plate boundaries occur within continental lithosphere, deformation is spread out a over a much larger area than the plate boundary itself. In the case of the San Andreas fault continental transform, many earthquakes occur away from the plate boundary and are related to strains developed within the broader zone of deformation caused by major irregularities in the fault trace (e.g. the Big ben