The flood process:-
Most floods take place hours or even days to develop, giving residents plenty of time to evacuate. other floods occur suddenly and with little warning. These flash floods can be extremely dangerous, instantly turning a calm river into a thundering wall of water that sweeps everything in its path downstream.
Causes of floods:-
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.
Drain and Sewer
Floods
Sewer flooding may result from a failure of the sewerage system. It may also happen when the sewer system does not have enough capacity to take water entering the system from heavy rainfall or river or highway flooding.
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.
Groundwater
Floods
Resources:
Most floods take place hours or even days to develop, giving residents plenty of time to evacuate. other floods occur suddenly and with little warning. These flash floods can be extremely dangerous, instantly turning a calm river into a thundering wall of water that sweeps everything in its path downstream.
Causes of floods:-
Flooding can happen anywhere, at anytime, and be caused by more than just rain. Even if people don't live near a river or a creek, different types of flooding may still happen in the area from other causes. Occasionally,
floods occur unnaturally; they result when a stream runs out of its confines
and submerges surrounding areas; these are usually the result of human
activities. Such activities include:
- Blasting - this causes landslides in the
slopes of hills and mountains which may result in the unintentional
damming of rivers and streams.
- Construction of temporary
dams - this produces
an impediment to the flow of a river or stream which then results in an
overflow;
- Failure of hydraulic and other
control structures -
accidents like the breaking of a dike result in the entry of an enormous
quantity of water in a protected area; and
- Mismanagement of hydraulic
structures - control
structures like dams which are utilized for various purposes are usually
operated according to what is known as an "operation rule" and
mismanagement which results in the violation of the rule may necessitate
an untimely and sudden release of large amounts of excess water.
Developed VS
undeveloped (countries)
- In less developed countries, humans are particularly
sensitive to flood casualties because of high population density, absence
of zoning regulations, lack of flood control, and lack of emergency
response infrastructure and early warning systems.
- In industrialized countries the loss of life is usually
lower because of flood control structures, zoning regulations that prevent
the habitation of seriously vulnerable lands, and emergency
preparedness. Still, property damage and disruption of life takes a
great toll, and despite flood control structures and land use planning,
floods still do occur.
The Poor The Rich
VS.
The Impact of Flooding:-
On a small scale in the UK, the major impacts of flooding are......
- Damage to Property
- displacement from homes
- the loss of personal valuables (these include buildings, infrastructures, agriculture, open recreational space and the natural world)
- There will be fewer shoppers
- business may lose stock, patronage, data, productivity and disruption to utilities
- The public realm is often badly affected through damage and the deposit of potentially large quantities of ruins.
- Tourism, farming and livestock can be equally affected
- Land contamination may also be transported and spread during floods
- Electricity and gas supplies can be interrupted.
- The build environment may be damaged which will result in high pay cost
- Road links, railways, canals may be blocked causing disruption to transport, network and accessibly
- ongoing fear of insecurity caused by the experience
- water supplies may be lost or contaminated which can cause immediate health effects
Types of Floods:-
Flooding can be devided into different categories according to their duration:
Slow-Onset
Floods
Slow-Onset
Floods usually last for a relatively longer period, it may last for one or more
weeks, or even months. As this kind of flood last for a long period, it can
lead to lose of stock, damage to agricultural products, roads and rail links.
· Rapid-Onset
Floods
Rapid-Onset
Floods last for a relatively shorter period, they usually last for one or two
days only. Although this kind of flood lasts for a shorter period, it can cause
more damages and pose a greater risk to life and property as people usually
have less time to take preventative action during rapid-onset floods.
· Flash
Floods
Flash Floods may occur
within minutes or a few hours after heavy rainfall, tropical storm, failure of
dams or levees or releases of ice jams. And it causes the greatest damages to
society.
Flooding can also be divided into different
categories according to their location:
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. River
flooding is generally caused by prolonged, extensive rain. Melting snow can
worsen flooding. Flooding can also occur if fallen trees; natural overgrowth or
rubbish blocks the free flow of a river.
Sewer flooding may result from a failure of the sewerage system. It may also happen when the sewer system does not have enough capacity to take water entering the system from heavy rainfall or river or highway flooding.
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.
Arroyos Floods
A arroyo is river which is normally dry. When
there are storms approaching these areas, fast-moving river will normally form
along the gully and cause damages.
Groundwater
flooding can occur when water levels underneath the ground rise above normal
levels approaching the surface. It is usually caused by prolonged periods of
rainfall. Groundwater flooding can last for weeks and months.
Resources:
- http://adamworld.typepad.com/blog/page/37/
- http://www.floodsite.net/juniorfloodsite/html/en/student/thingstoknow/hydrology/floodtypes.html
- http://kidlat.pagasa.dost.gov.ph/genmet/floods/cause_types.html
- http://www.sepa.org.uk/flooding/be_flood_aware/types_of_flooding.aspx
- http://library.thinkquest.org/03oct/02054/floodtype.htm
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