Conceptual
Framework
Framework
Flood as a situation where a
river channel is inadequate to accommodate discharge from its catchments. It
can also be regarded as unusual high rate of water discharge which often lead
to inundation of land adjustment to the river; where the flyer overflow both
its natural and artificial banks. Flooding has become a common feature in all
the geographical region of Nigeria in recent times as well as other parts of
Africa and the entire world.
river channel is inadequate to accommodate discharge from its catchments. It
can also be regarded as unusual high rate of water discharge which often lead
to inundation of land adjustment to the river; where the flyer overflow both
its natural and artificial banks. Flooding has become a common feature in all
the geographical region of Nigeria in recent times as well as other parts of
Africa and the entire world.
Ajayi (2003) defined flooding
as the accumulation of excessive quantity of water in an area without flowing
away easily.
as the accumulation of excessive quantity of water in an area without flowing
away easily.
A flood is an overflow of
water that submerges land which is normally dry. The European Union (EU) flood
directive defines flood as a covering by water of land not normally covered by
water. In the sense of “flowing water” the word may also he applied to the
inflow of the tide. Flooding may occur as an overflow of the water from water
bodies such as river or lake in which the water overtop or break levees,
resulting in some of that water escaping its usual boundaries or it may occur
due to an accumulation of rain water on saturated ground in an area flood.
While the side of the lake or other body of water will vary with seasonal
changes in precipitation and snow melt, these changes in size are unlikely to
be considered significant unless the flood property or drawn domestic animals. (Powell,
2009).
water that submerges land which is normally dry. The European Union (EU) flood
directive defines flood as a covering by water of land not normally covered by
water. In the sense of “flowing water” the word may also he applied to the
inflow of the tide. Flooding may occur as an overflow of the water from water
bodies such as river or lake in which the water overtop or break levees,
resulting in some of that water escaping its usual boundaries or it may occur
due to an accumulation of rain water on saturated ground in an area flood.
While the side of the lake or other body of water will vary with seasonal
changes in precipitation and snow melt, these changes in size are unlikely to
be considered significant unless the flood property or drawn domestic animals. (Powell,
2009).
The
Common Causes of Flooding
Common Causes of Flooding
a.
Flooding
occur mostly when there is heavy rainfall in an area
Flooding
occur mostly when there is heavy rainfall in an area
b.
Dumping
of refuse along culverts which eventually block channels of flow.
Dumping
of refuse along culverts which eventually block channels of flow.
c.
Poor
drainage system within an area
Poor
drainage system within an area
d.
Inadequate
urban planning
Inadequate
urban planning
e.
Erection
of buildings along the drainage channels e.g culvert roads and on water shed.
Erection
of buildings along the drainage channels e.g culvert roads and on water shed.
f.
Establishment
of settlement along river channels as in case of Lagos metropolis
Establishment
of settlement along river channels as in case of Lagos metropolis
g.
Poor
construction of embankment and dams may result in flooding as in the case of Ogunpa
River in ibandan. (Ajayi, 2003).
Poor
construction of embankment and dams may result in flooding as in the case of Ogunpa
River in ibandan. (Ajayi, 2003).
The causes of flooding as
cited by (Olorunda et al 2007) include:
cited by (Olorunda et al 2007) include:
1.
The
collapse of water reservoir and dams failures
The
collapse of water reservoir and dams failures
2.
Family
activities very close to river bank course.
Family
activities very close to river bank course.
3.
Sea
tides high storm surge also causes floods in coastal towns and cities.
Sea
tides high storm surge also causes floods in coastal towns and cities.
4.
Indiscriminate
dumping of drainage systems meant for the free — flow of water.
Indiscriminate
dumping of drainage systems meant for the free — flow of water.
5.
Deforestation
activities exposing the soil to the intense force of rainfall causing erosion
and secondarily leading to flooding.
Deforestation
activities exposing the soil to the intense force of rainfall causing erosion
and secondarily leading to flooding.
Welch et al, (1977) cited the
causes of flooding to include heavy rainfall, highly accelerated snow melt,
severe wind over water, unusual high, tsunamis or failure of dams, leeves,
retention ponds or other structures that retained the water. Flooding can be
exacerbated by increase amounts of impervious surface by other natural hazards
such as wild fires which reduce the supply of vegetation that can absorb
rainfall.
causes of flooding to include heavy rainfall, highly accelerated snow melt,
severe wind over water, unusual high, tsunamis or failure of dams, leeves,
retention ponds or other structures that retained the water. Flooding can be
exacerbated by increase amounts of impervious surface by other natural hazards
such as wild fires which reduce the supply of vegetation that can absorb
rainfall.
Runoff from sustained
rainfall or rapid snow melts exceeding the capacity of the river’s channel.
Causes include heavy rains from monsoons, hurricane and tropical depression,
foreign wind and warm rain affecting snow peak. Unexpected drainage
obstructions such as landslides, ice, or debris can cause slow flooding
upstream of obstruction (USEPA, 2002).
rainfall or rapid snow melts exceeding the capacity of the river’s channel.
Causes include heavy rains from monsoons, hurricane and tropical depression,
foreign wind and warm rain affecting snow peak. Unexpected drainage
obstructions such as landslides, ice, or debris can cause slow flooding
upstream of obstruction (USEPA, 2002).
Principal
Types of Flooding
Types of Flooding
Tidal Flooding: This result
when both sea and river dense may be overtopped or breached by a combination of
low pressure weather system and peak high tides. Storm with high wind speeds
cause tall and powerful wave and low pressure fronts cause sea levels to raise
above normal levels. High tide levels vary through the lunar and solar cycle
when supper imposes upon other tidal variations exceptionally high tides
result. The onset of flooding from the sea and tidal rivers is often sudden and
the extreme forces driving it present a significant danger to life. (Dance &
Hyne, 1980).
when both sea and river dense may be overtopped or breached by a combination of
low pressure weather system and peak high tides. Storm with high wind speeds
cause tall and powerful wave and low pressure fronts cause sea levels to raise
above normal levels. High tide levels vary through the lunar and solar cycle
when supper imposes upon other tidal variations exceptionally high tides
result. The onset of flooding from the sea and tidal rivers is often sudden and
the extreme forces driving it present a significant danger to life. (Dance &
Hyne, 1980).
Fluvial
flooding:
The flooding occurs in flood plain of rivers when the capacity of water courses
is exceeded as a result of rainfall or snow and ice melt within catchment area
further upstream. Blockage of water courses and flood channels or tide locking
may also lead to ponging and rising water levels (Thompson, 1964).
flooding:
The flooding occurs in flood plain of rivers when the capacity of water courses
is exceeded as a result of rainfall or snow and ice melt within catchment area
further upstream. Blockage of water courses and flood channels or tide locking
may also lead to ponging and rising water levels (Thompson, 1964).
Flash
Flooding:
This result from connective precipitation (intensive thunderstorms) or sudden
release from an upstream impoundment created behind a darn, landslide or
glacier. Flood 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.
Flooding:
This result from connective precipitation (intensive thunderstorms) or sudden
release from an upstream impoundment created behind a darn, landslide or
glacier. Flood 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.
Muddy
Flooding: A
muddy flooding is produced by an accumulation of runoff generated on crop land.
Sediment are then detached by runoff and carried as suspended matter or bed
load. Muddy runoff is more likely detected when it reaches inhibited areas.
Muddy flood are therefore a hill slope process and confusion with mudflows
produced by mass movements should be avoided. (Esu, 1999).
Flooding: A
muddy flooding is produced by an accumulation of runoff generated on crop land.
Sediment are then detached by runoff and carried as suspended matter or bed
load. Muddy runoff is more likely detected when it reaches inhibited areas.
Muddy flood are therefore a hill slope process and confusion with mudflows
produced by mass movements should be avoided. (Esu, 1999).
Pluvial
flooding:
This is surface water flooding caused by rainwater runoff from urban and rural
land with low absorbency. Increased intensity of development in urban areas has
given rise to land with a larger proportion of non – permeable surfaces a
problem often exacerbated by overloaded and out dated drainage infrastructure.
These circumstances combine with intense rainfall, can give rise to localized
flooding. (David et al, 1981).
flooding:
This is surface water flooding caused by rainwater runoff from urban and rural
land with low absorbency. Increased intensity of development in urban areas has
given rise to land with a larger proportion of non – permeable surfaces a
problem often exacerbated by overloaded and out dated drainage infrastructure.
These circumstances combine with intense rainfall, can give rise to localized
flooding. (David et al, 1981).
The
Effect of Flooding on Surface Water Quality
Effect of Flooding on Surface Water Quality
–
Surface
water temperature increase
Surface
water temperature increase
–
Salinity
reduces
Salinity
reduces
–
Dissolve
oxygen increases
Dissolve
oxygen increases
–
Conductivity
increases
Conductivity
increases
–
Turbidity
increases
Turbidity
increases
–
PH
increases
PH
increases
–
Biochemical
oxygen Demand BOD increases
Biochemical
oxygen Demand BOD increases
–
Total
dissolved solids in water increases
Total
dissolved solids in water increases
–
Depth
increases
Depth
increases
–
Current
increases
Current
increases
–
Plankton
s reduces
Plankton
s reduces
–
Nektons
Reduces determining the insects which survive in a stream. (Dance & Hynes
1980).
Nektons
Reduces determining the insects which survive in a stream. (Dance & Hynes
1980).
The
Identifiable Effects of Flooding
Identifiable Effects of Flooding
Olorunda
et al (2009) cited that flood causes havoc and serious damages to the
environment and the populace. Flood damages ranges from destruction of
properties, farmlands, electrical installation, buildings and structures to
displacement of persons and loss of human lives. Damages caused to buildings
and properties are usually very terrible to estimate. Major examples in Nigeria
were the Lagos bar beach flooding in 1984, 1988, 1995 and 2002 respectively as
well as the Indic gore flood of 1981
in Aba, Gombe flood disaster and other across the
country. The effect of flooding is thus divided into two viz; Primary effects
of flooding includes physical damage that can damage any type of structure,
including bridges, cars, buildings, sewerage systems, roadways and canals. The
secondary effects of flooding include water supplies that result in
contamination of water (water pollution). Clean drinking water becomes scarce.
Unhygienic conditions and spread of water – borne diseases result. The effects
of flooding from the sources outlined above are felt by various receptors.
These include people, buildings, infrastructures, agriculture, open
recreational space and the natural world. In extreme cases flooding may result
to a loss of life. At least 102 people are now thought to have been killed by
floods in and around the South – Western Nigeria City of Ibadan.
et al (2009) cited that flood causes havoc and serious damages to the
environment and the populace. Flood damages ranges from destruction of
properties, farmlands, electrical installation, buildings and structures to
displacement of persons and loss of human lives. Damages caused to buildings
and properties are usually very terrible to estimate. Major examples in Nigeria
were the Lagos bar beach flooding in 1984, 1988, 1995 and 2002 respectively as
well as the Indic gore flood of 1981
in Aba, Gombe flood disaster and other across the
country. The effect of flooding is thus divided into two viz; Primary effects
of flooding includes physical damage that can damage any type of structure,
including bridges, cars, buildings, sewerage systems, roadways and canals. The
secondary effects of flooding include water supplies that result in
contamination of water (water pollution). Clean drinking water becomes scarce.
Unhygienic conditions and spread of water – borne diseases result. The effects
of flooding from the sources outlined above are felt by various receptors.
These include people, buildings, infrastructures, agriculture, open
recreational space and the natural world. In extreme cases flooding may result
to a loss of life. At least 102 people are now thought to have been killed by
floods in and around the South – Western Nigeria City of Ibadan.
Flooding took a deadly toll
in Northern Nigeria in August 2011. Torrential rains push rivers over their
banks, collapse mud houses and wash away livestock. Floodwater resulting from
heavy rains damaged three bridges and caused a darn to overflow, submerging
buildings across the city. Most of the victims were children.
in Northern Nigeria in August 2011. Torrential rains push rivers over their
banks, collapse mud houses and wash away livestock. Floodwater resulting from
heavy rains damaged three bridges and caused a darn to overflow, submerging
buildings across the city. Most of the victims were children.
The
Benefits of Flooding
Benefits of Flooding
There are many destructive
effects of flood on human settlements and economic activities. However, floods
(in particular the more frequent! smaller floods) can also bring many benefits,
such as recharging ground water, making soil more fertile and providing
nutrients in which it is deficient. Flood water provides much water needed
resources in particular in arid and semi-arid regions where precipitation
events can be very unevenly distributed throughout the year.
effects of flood on human settlements and economic activities. However, floods
(in particular the more frequent! smaller floods) can also bring many benefits,
such as recharging ground water, making soil more fertile and providing
nutrients in which it is deficient. Flood water provides much water needed
resources in particular in arid and semi-arid regions where precipitation
events can be very unevenly distributed throughout the year.
Freshwater floods
particularly play an important role in maintaining ecosystems in river
corridors and are key factor in maintaining floodplain biodiversity. (Abowei &
Sikoki, 2005).
particularly play an important role in maintaining ecosystems in river
corridors and are key factor in maintaining floodplain biodiversity. (Abowei &
Sikoki, 2005).
The
Appropriate Measures in Flood Control
Appropriate Measures in Flood Control
The three feasible measures
for combating flood menace in man’s environment are: flood adjustment, flood
prevention and flood minimization. There is a point we must all note and that
is the fact that since flood is a natural phenomenon. It is not possible for us
to have an absolute control measures for flood.
for combating flood menace in man’s environment are: flood adjustment, flood
prevention and flood minimization. There is a point we must all note and that
is the fact that since flood is a natural phenomenon. It is not possible for us
to have an absolute control measures for flood.
i Flood Adjustment: Flood involve accepting the
loss, public relief and other emergency action taken immediately after any
flood incidence. Immediately a flood disaster occurs, the victims must first
accept the loss arising from its occurrence after which what follows is the
establishment of a relief fund by the government, the non – governmental
organization and private individuals. The relief fluid must be used to procure
food items, clothing materials and beddings, drugs supplies, roofing and
building materials and be distributed to the victims.
loss, public relief and other emergency action taken immediately after any
flood incidence. Immediately a flood disaster occurs, the victims must first
accept the loss arising from its occurrence after which what follows is the
establishment of a relief fund by the government, the non – governmental
organization and private individuals. The relief fluid must be used to procure
food items, clothing materials and beddings, drugs supplies, roofing and
building materials and be distributed to the victims.
ii Flood Prevention: These are efforts that is
meant to prevent flood hazards rather than curing it. Such efforts include
modification of cropping practices, reforestation (revegetation), terracing,
contour ploughing and disallowing bush burning. Other are the proper enforcement
of all town planning and environmental laws in construction of buildings,
layouts, mapping, construction of drainage and other channels for free flow of
water as well as prosecution of offenders caught dumping refuse on water
courses and channels, and all laws regulating free feeling and deforestation
activities, furthermore, enforcement of appropriate setbacks legislature on
river courses and drainages, there most be minimal or no cultural and political
pressures on the officers of the relevant enforcement agencies.
meant to prevent flood hazards rather than curing it. Such efforts include
modification of cropping practices, reforestation (revegetation), terracing,
contour ploughing and disallowing bush burning. Other are the proper enforcement
of all town planning and environmental laws in construction of buildings,
layouts, mapping, construction of drainage and other channels for free flow of
water as well as prosecution of offenders caught dumping refuse on water
courses and channels, and all laws regulating free feeling and deforestation
activities, furthermore, enforcement of appropriate setbacks legislature on
river courses and drainages, there most be minimal or no cultural and political
pressures on the officers of the relevant enforcement agencies.
iii Flood Minimization: Flood minimization is mainly
concerned about the river or stream channels, and the purpose is to control the
flood and minimize the damage it causes by regulating its flow or diverting it
away from damaging structures or properties. The process may involve
construction of strong flood walls, damage or reservoirs, channel, improvement,
dredging and dykes.
concerned about the river or stream channels, and the purpose is to control the
flood and minimize the damage it causes by regulating its flow or diverting it
away from damaging structures or properties. The process may involve
construction of strong flood walls, damage or reservoirs, channel, improvement,
dredging and dykes.
Ajayi,
(2003), cited the following measures of controlling flooding. They are:
(2003), cited the following measures of controlling flooding. They are:
–
Flooding
can be controlled through channelization of floods from city centre.
Flooding
can be controlled through channelization of floods from city centre.
–
Through
the construction of bridges, wider culverts and dams
Through
the construction of bridges, wider culverts and dams
–
Avoiding
refuse dumping along water channels
Avoiding
refuse dumping along water channels
–
Carrying
out public enlightenment campaign on the effects of flooding.
Carrying
out public enlightenment campaign on the effects of flooding.
–
Legislation
against indiscriminate dumping and erection of buildings in swampy areas.
Legislation
against indiscriminate dumping and erection of buildings in swampy areas.
–
Proper
urban planning to avoid urban flooding
Proper
urban planning to avoid urban flooding
–
Providing
forest reserves on strategic water sheds
Providing
forest reserves on strategic water sheds
–
Environmental
sanitation to drain culverts
Environmental
sanitation to drain culverts
The
Role of Government and Non – Governmental Agencies in Flood Disaster Management
Role of Government and Non – Governmental Agencies in Flood Disaster Management
The role of government and
non – governmental agencies in flood disaster management as cited by NEMA
coordinator includes:
non – governmental agencies in flood disaster management as cited by NEMA
coordinator includes:
–
The
federal government set – up a national committee on flood relief and
rehabilitation of victims.
The
federal government set – up a national committee on flood relief and
rehabilitation of victims.
–
Rescue
operation by Nigeria Red Cross Society and other non — governmental agencies
Rescue
operation by Nigeria Red Cross Society and other non — governmental agencies
–
Ensuring
provision of portable water supply, latrine accommodation and proper
environmental sanitation and adequate sanitary management by ministry of
environment.
Ensuring
provision of portable water supply, latrine accommodation and proper
environmental sanitation and adequate sanitary management by ministry of
environment.
Challenges
of Flood Disaster Management
of Flood Disaster Management
Financial Constraint: Flood
disaster management require huge amount of money; thus it is difficult to
satisfy victims of flood disasters in terms of provision of relief material.
disaster management require huge amount of money; thus it is difficult to
satisfy victims of flood disasters in terms of provision of relief material.
Population Growth: This is
another problem resulting from high increase of individual affected by the
flood disasters authorities to meet up with the demand of the populace or
victims of flood disaster.
another problem resulting from high increase of individual affected by the
flood disasters authorities to meet up with the demand of the populace or
victims of flood disaster.
iii. Sexual Abuse and Rape: This mostly
concerned the women and girls, particularly in disaster situation where they
are vulnerable to domestic violence in their camps.
concerned the women and girls, particularly in disaster situation where they
are vulnerable to domestic violence in their camps.
iv. Gender
Issues: Poor understanding of gender issues in disaster risk reduction is
widespread among most countries, showing that it is high time government and communities
take more action.
Issues: Poor understanding of gender issues in disaster risk reduction is
widespread among most countries, showing that it is high time government and communities
take more action.
Flood Disaster
Personnel and Management for Flood Disaster Victims
Personnel and Management for Flood Disaster Victims
Flood disaster personnel
include the following:
include the following:
–
National
Management Agency (NEMA)
National
Management Agency (NEMA)
–
High
personnel
High
personnel
–
Social
Welfare personnel
Social
Welfare personnel
–
Security
para – military and military agencies
Security
para – military and military agencies
–
International
and national relief agencies
International
and national relief agencies
–
Non
– governmental organization
Non
– governmental organization
Immediate needs of victims of
disasters and emergencies. They include:
disasters and emergencies. They include:
–
Food
Food
–
Water
Water
–
Shelter
Shelter
–
Hospitalization
Hospitalization
–
First
Aid
First
Aid
–
Sport
(material and financial)
Sport
(material and financial)
–
Psychological
counseling
Psychological
counseling
–
Assurances
of self – belongings
Assurances
of self – belongings
Remedy
to the Challenges of Flood Management
to the Challenges of Flood Management
The challenges facing flood
disaster management can be remedied as given below:
disaster management can be remedied as given below:
i Government
and all sectors should gear their efforts towards making money available to
support flood disaster victims at every point in time.
and all sectors should gear their efforts towards making money available to
support flood disaster victims at every point in time.
ii In
the allocation of funds, materials and aids to flood disaster victims, the
authority in charge should first consider the population, provisions are to
serve.
the allocation of funds, materials and aids to flood disaster victims, the
authority in charge should first consider the population, provisions are to
serve.
iii Domestic
violence against women and girls, particularly in disaster situation cannot be
tolerated and perpetrators must be held accountable.
violence against women and girls, particularly in disaster situation cannot be
tolerated and perpetrators must be held accountable.
iv It’s
not gender but gender inequality that put girls and women in harm’s way when
disaster strikes. While, women are often hardest hit by disaster and take
longer to recover from their impacts, they can make a powerful and positive
contribution in reducing the impacts and risks. Thus, gender issues should be
given utmost consideration, since women and girls require much security in
flood disaster situations.
not gender but gender inequality that put girls and women in harm’s way when
disaster strikes. While, women are often hardest hit by disaster and take
longer to recover from their impacts, they can make a powerful and positive
contribution in reducing the impacts and risks. Thus, gender issues should be
given utmost consideration, since women and girls require much security in
flood disaster situations.
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