Flood Types & Floods in Paksitan

BAHRIA UNIVERSITY 09

FLOODS

FLOOD TYPES & FLOODS IN PAKISTAN

Jawad Bashir

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[FLOODSS] September 16, 2009

1. FLOODSA flood (in Old English flood, a word common to Teutonic languages; compare German Flut, Dutch vloed from the same root as is seen in flow, float) is an overflow of water, an expanse of water submerging land, a deluge. In the sense of "flowing water", the word is applied to the inflow of the tide, as opposed to the outflow or "ebb". ORA flood is an overflow of an expanse of water that submerges land, a deluge. 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, with the result that some of the water escapes its normal boundaries. It is recognized world over that floods are the most destructive of natural hazards and the greatest cause of large-scale damages to lives and property. Over the years, major floods have occurred in almost all the South Asian countries, causing huge loss of life and property.Despite the investment of millions, even billions of dollars in efforts to tame the rivers of the region, the frequency of major flood disasters has actually increased over the past 25 to 30 years. There is a growing consensus that the impacts of climate change may well lead to anincrease in both the frequency and the magnitude of floods.

Types of Flooding

Flooding can be divided into different categories according to their duration:

1. 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.

2. 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.

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3. 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.

Flood Types(Location)

Flooding can also be divided into different categories according to their location:

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.

2. 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.

3. 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.

4. 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.

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CAUSES OF FLOODS

Natural causes of floods:

1.High rainfall

Heavy rainfall raises the water level. When the water level is higher than the river bank or the dams, the water comes out from the river, there will have a flooding.

2.Snowmelt

Because of the global warming, the temperature of this year is higher than the temperature of many years ago. The ice caps melt in spring, many water go into the sea. The water raises the sea level, and makes the river level raise. When river level raises, flooding may cause.

3.Relief

Flooding often occurs in lowland. This is because rivers flow more slowly in low-lying area. If the water volume increases suddenly, floods occur.

4.Coastal flooding

Flooding always occur in coastal areas. Because there have high tides orstorms,the sea level will raise. If the sea level is higher than the level of the coastal lowland, flooding will occur.

5.Tsunamis

Tsunamis are high, large waves, typically caused by undersea earthquakes or massive explosions, such as the eruption of an undersea volcano. They can also bring the floods in near costal areas.

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Human causes of floods

1.Deforestation

Large areas of forests near the rivers have been cleared. The lands use to make room for settlement, roads and farmland. Less vegetation protect the soil, the soil is quickly lost to rivers and sea. This raises the river bed, so the river overflows its banks easily.

HOW DEFORESTATION LEED TO FLOODING

No trees to soak up water, so more water flows into the rivers.

No trees to build the soil together, so soil erosion takes place. Large amounts of soil are washed by rain into the rivers.

Because of silting, riverbed shallower. The water volume increases, the river cannot hold all the water and overflows its banks.

2. Poor farming

Some farming practices can damage the vegetation cover, so the soil will be washed into the river easily.

Overgrazing

People want more food and money, they graze too many animals on the land and the pasture is eaten away quickly. Less vegetation cover, soil washed into the rivers easily.

Over cultivation

When a piece of land has been used for farming for a long period of time, the soil may became so infertile that no vegetation can grow on it. The land less fertile than before, so the soil washed into the rivers more easily.

3.Poor water management

When the dams are poorly constructed or maintained ,they can easily collapse and this results in flooding.

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4. Population pressure

Because of large amount of people, everything need more, like wood, land and food……Soil erosion happen more often, it increases the risk of flooding.

Methods Use For Flood Discharge Control

1 Stream Hydrographs

Graphs of stream stage or flow over time are called stream hydrographs. Hydrographs show fluctuating water levels over differing time scales. Over a period of days, a storm hydrograph shows the stream's response to a rainfall event. Over a year, an annual hydrograph shows the seasonal fluctuations in stream flow. Over multiple years, annual variations in stream flow due to variations in rainfall patterns can be viewed.

2 Airborne synthetic aperture radar

A special type of device is use to capture and record the stream stage flow and for this purpose a air vehicle such as plane or helicopter is use.

3 Manual stage height MethodA manual-stage-height method does not produce a continuous record but is typically only a single point in time measurement. Stage height is directly read from either a standard staff gage, wire weight gage (WWG) or measured from a reference point (RP). .

Satellite 2D Modeling

In this method latest satellite equipped with various tools are use to measure floods and stream discharge rate very accurately.

Flooding Precautions

Following steps should be taken before and after the flood for safety purposes

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Before a flood

Before building, check the area for signs or history of flooding and find out how many feet above flood level you need to build your house. Do not throw garbage into drains and rivers. Put sandbags by exposed openings. Turn off gas and electricity. Unplug electrical appliances. Put dangerous, flammable or explosive liquids in a safe place and close containers securely. Seal important personal, legal and business documents in watertight containers and place above flood height. Take furniture to upper floors or raise on a sturdy table. Secure vehicles.

During a flood

Turn on a battery-powered radio. Evacuate and avoid flooded areas. Do not try to cross water courses. If your car gets stuck, abandon it immediately.

Before Flooding - Have the following

supplies ready at a safe place:

Drinking water Food First Aid/Hygiene Kit Flashlight and extra batteries Portable radio and extra batteries A fully charged cellular phone if you own one Saw Hammer Wooden planks Nails Sand bags Plastic sheeting Have a plan using plastic sheeting and sand bags to seal doorways to prevent water entering your home. Move vehicles to high ground Tie down containers with inflammable or combustible material.

During the Flooding:

Listen to a portable radio. Move belongings to an upper floor or to safe ground if time permits. Move appliances off floor level. Turn off electricity and gas. Turn off gas at the tank and electricity at the mains switch. Avoid areas that you know flood easily. Release animals and poultry. Keep children indoors and upstairs.

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If your car stalls, or becomes stuck, abandon it and climb to higher ground or onto the vehicle's roof. Do not move at night unless absolutely necessary. Do not go into fast-moving water that is more than a few inches deep.

After the flooding:

Check on your neighbours. Inspect building for damage. There can be danger from collapsing buildings. Stay away from all fallen wires. Stay away from water with fallen wires in it or nearby. Do not turn on your electricity if the water has come even close to plug height. Do not turn on electricity while there is water in your house. Do not turn on electricity standing barefoot on a wet floor. Do not turn on appliances that have been in the floodwater. Let them dry out completely and spray motors, switches, and connectors, with CRC. Appliances can take several days to dry out. Switch on with great care. Do not use food that has come in contact with floodwater. Do not drink, cook with or bathe in floodwater. Remember damaged sewer systems, septic tanks and latrines are very, very serious health hazards. Take photographs of your property, if damaged, for insurance purposes.

How to inspect for gas,

electricity, water and sewerage

problems in your home:

Gas: If you smell gas or hear blowing and hissing noises, open a window and door and turn off the gas at the tank. Do not turn off lights or appliances. Get out of the building fast and stay out. After about an hour of allowing the gas to dissipate through open doors and windows, if you still smell gas, call the Fire Service at 991. Do not re-enter the building until it has been checked by a professional. Electrical Systems: If you smell burning, see sparks or broken and frayed wires switch off the electricity at the mains panel. Make sure you are wearing dry rubber soled shoes and you are not standing in water. Proceed with extreme care. Sewerage and Water Line Damage: If the water lines are damaged, do not drink water from the tap, use your emergency water supply. Damaged water lines can lead to contaminated water. To check for damaged sewer lines try flushing your toilet. If it backs up the line is not good.

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Effects Of Flooding

Primary effects 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 diseases.

Secondary effects 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.

long-term effects Economic - Economic hardship, due to: temporary decline in tourism, rebuilding

costs, food shortage leading to price increase etc.

How To Control Flooding

1. To control the water level Dam and pumping station. 2. Build barriers. 3. Alter the river’s channel. 4. Control land use. 5. Flood plain zoning. 6. By taking Emergency measures. 7. By making structure compacted. 8. Construction of Retention Ponds.

FLOODS IN PAKISTAN

Pakistan is one of the five South Asian countries with the highest annual averagenumber of people physically exposed to floods, which occur normally due to storm systemsthat originate from Bay of Bengal during the monsoon from July to September. The stormsoriginating in Bay of Bengal passing over lower Central India and Rajputana, enter Pakistan and continue towards North into Kashmir. The mountain ranges in the extreme north of Pakistan provide a perennial source of inflow into the rivers.

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Floods particularly hit Punjab andSindh while hill torrents tend to effect the hilly areas of North Western Frontier Province,Balochistan and the northern federally administered areas. Flood events of 1950, 1992 and1998 caused many deaths and huge losses to the national economy. According to official sources, floods in Pakistan during the decade 1991 to 2001 caused an estimated damage of over Pak Rs 78,000 million to property.

Year Live lost Villagers Affected

1950 2910 10000

1955 670 6945

1956 160 11609

1973 474 9719

1975 126 8628

1976 425 9150

1978 393 9199

1988 508 10000

1992 1008 13208

1995 591 6852

1998 47 1610

2001 202 0.4 million

2004 435 4900

2006 789 67990

2007 204 1.1 millionRainfall during the period occurs due to the monsoonal systems (Lows or depressions) coming either from the Arabian Sea or from the Bay of Bengal.

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The frequency of monsoon depressionsformed in Bay of Bengal is about 80% of the total number of depressions formed in theSouth Asia monsoon region .Relatively few monsoon depressions form in the east Arabian Sea and over land in monsoon trough region. The average annual frequency of monsoon depression is seven, of which one occurs in June and two each in July, August and September. The monsoon depression normally takes a west-northwesterly course during the peak monsoon months of July and August, while they move in a northwesterly direction during the transition period in early June and late September. The depression generally weaken after crossing the central parts of India, owing to the cut-off in the moisture supply, the move further northwest and merge in the seasonal low over west Rajasthan and adjoining Pakistan. When the depressions are fed by fresh moisture supply from the Arabian Sea branch of the monsoon, the depression may retain their intensity and take a westerly course to reach Gujarat state of India, causing very heavy rains in the region. On some occasions the westerly wave passing over the north of Pakistan may take the depression under its grip and it may move in the north ward direction, causing heavy rains in the upper areas of Punjab and adjoining areas of NWFP and Kashmir.

MAJOR FLOOD EVENTS IN PAKISTAN

1992 FLOODS

During the summer monsoon season in 1992 heavy rainfall occurred over the JhelumRiver basin (Fig.1) in the month of September which caused severe flooding in theJhelum River. This was the worst event recorded since 1959 and brought in its wake largeEconomic losses and infrastructure damage in Pakistan. This severe flooding event wasinduced by the severe precipitation event associated with the summer monsoondepression traveling from Bay of Bengal through India to upper parts of Punjab andadjoining areas of Kashmir and North West Frontier Province of Pakistan.

CAUSE OF 1992 FLOODING:

Cause of this flooding is heavy precipitation during 1990-1992.During the month of June rainfall over Pakistan occurred due to the passage of westerlywave in the north of Pakistan. A trough developed in the upper air at 500hpa in north ofPakistan and moderate rainfall occurred on two occasions in the northern divisions.

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Moderate to heavy rainfall also occurred in Bangladesh, eastern coast and western Ghattsof India. During July, the weather activities over Pakistan were mainly due to thepresence of a trough in the north of Pakistan at 500hpa. There were three spells in thismonth. The first spell was weak. It caused rainfall of light to moderate intensity where asthe last two spells gave moderate to heavy rainfall over almost all catchment’s areas of the rivers.

Floods in 2007

At least 241 have been killed and 204 missing in the flood related incidents, A total of 111 died in southwest province of Baluchistan, 100 in south province Sindh and 30 in North West Frontier Province, Some 1.1 million people have been affected in Baluchistan and 100,000 displaced. A total of 15 out of 29 districts across Baluchistan have been affected while five districts in Sindh have been affected. Infrastructure has been severely undermined with roads and bridges damaged or destroyed and telecommunications out in many area.

Causes of 2007 Floods:

This flood was caused due to over flow of water and Heavy rain Flood waters have been flowing from Baluchistan into Sindh causing flood canals to overflow and inundate villages and farmland. Heavy rains lashed different parts of Baluchistan in the wake of a tropical cyclone which hit southern Pakistan's coastal areas on January 24.

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AUGUST 2008 Flood in N.W.F.P

On August 4, 2008, the torrential rain water flooded a local stream (Thara Khur) which flows from Landi Kotal to Charsada causing great havoc in Peshawar district. The affected area includes Shalman, Bara and Tatara, Ali Masjid, Takhtabaig, Lal China and Sur Kamar of Khyber Agency. About 50 villages in the upper part of Peshawar district were inundated which include Pir Bala, Potohar bala, Mathara, Ashab baba, Sheikhano kalay, Dag, Khushal Bagh, Warsak Road, Hassan Garhi, Babo Garhi, Alizai, Qanriza, Baram Khel, Garhi Muqam Shah, Harayana, Khaderkhel, Bakhsho Pul, and Nasapa Bala 15 Union Councils and 700,000 population ofdistrict Peshawar are badly affected.

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COMPOSITION OF PUNJAB SOIL

The fertile plains of Punjab boast of producing more than two-third of the food grains produced annually in pakistan. This is largely owing to the fertile soil of Punjab. Climatic differences result in a variety of soil which ultimately culminates into a wide range of crops and vegetation in Punjab. South-western Punjab is mainly dominated by calcareous soil which includes desert soil and sucrose soil. The pH value in this zone ranges from 7.8 to 8.5 and also have grey and red desert soil, calisoil soil, regosol soil and alluvial soil. The soil of central Punjab ranges from sandy loam to clayey with pH value from 7.8 to 8.5 making alkalinity and salinity problematic for this place. The alluvial soil of this zone can be widely described as arid and brown soil or tropical arid brown soil. The soil in Eastern Punjab is loamy to clayey.

COMPOSITION OF SINDH SOIL

Sindh soil is mainly composed of highly silica content and that’s why it is permeable, allowing the un compacted structures to fall quickly. The Indus deltas and tributaries bring different type of soils in this area, and that’s why the rate of water consumption is various at various places, At northern part of Sindh the soil is some how compacted, but as we move down to south the compaction of soil loss, This allowing the water to runoff quickly and cause floods near tributaries. The area near Gawadar is consist of Compacted and highly porous rocks.

COMPOSITION OF BALOUCHISTAN SOIL

In Balouchistan mainly the floods are caused due to the Arroyos floods, this is because of the relief ,less vegetation, gradient and surface runoff water.Soil in Balouchistan is mainly consisting of lithified soil types.The Major part of Balouchistan consist of permeable rocks,soil here support massive flooding due to water runoof specially in regions of Chaman,loralai and Kholu.

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FLOODS PREVENTION METHODS IN PAKISTAN ACCORDING TO PROVINCE

PUNJAB

1. The flood protection bunds have been generally constructed either to protect headwork’s and other irrigation structures, or to safeguard certain towns and villages.

2. Due to general topography of the area sloping towards the south west, the embankments along headwork’s and irrigation structures have been constructed in such a way that breaching sections are provided on the right marginal bunds to give relief to water heading up against the left marginal bunds and keep the flow through the Barrages within safe limits for the hydraulic structures.

3. In order to protect areas from erosion, spurs have been constructed. These spurs have protected the areas and in some cases even the eroded lands have been recovered.

SINDH

1. The Indus River flows on a ridge in Sindh Province, and surrounding areas are generally lower than the river bed hence, water once spilling over the bunds does not return back..

2. Sindh is situated on a receiving end of drainage of all the rivers and if flood protection measures adopted in the upper reaches are not properly planned, severe damages are likely to occur in the Province, To minimize such eventualities, double line of flood embankments has been constructed along almost both the banks from Guddu to few kilometers short of sea. The embankments have been further compartmentalized to contain widespread inundation.

BALOUCHISTAN

1. Due to peculiar physiographic and climatic characteristics in Balouchistan, mostly embankments and flood walls have been constructed to protect orchards or abbacies from flood damages.

2. Some bunds have also been constructed to serve as flood diversion/abate ment measures.

N.W.F.P

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1. In NWFP, the floods are mainly due to flashy hill torrents having steep bed slopes, which greatly increase flood velocity and severely erode the banks.

2. Mostly spurs have been constructed to save the areas from erosion.

DETAILS OF STRUCTURAL MEASURES EXECUTEDProvince No. of SchemesPunjab 33Sindh 23NWFP 20Balochistan 12Total 88

IRRIGATINONAL SYSTEM OF PAKISTAN

The Irrigation System of Pakistan is the largest integrated irrigation network in the world,Serving 42 million acres of contiguous cultivated land. The system is fed by the waters of Indus rives and its tributaries.

Structure No.Major Storage Reservoirs 3Barrages 19Inter-River Link Canals 12Independent Irrigation Canal Commands 14Large Dams (Approx. 3.00 MAF) of 15 meter and above 82

The major storage reservoirs include Tarbela (existing Live Storage Capacity = 6.948 MAFagainst original 9.70 MAF), Chashma (existing Live Storage Capacity = 0.435 MAF against

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original 0.70 MAF) on River Indus and Mangla (existing Live Storage Capacity = 4.542MAF against original 5.30 MAF) on River Jhelum. The total length of main canals/distributaries and minors is 64,000 KM. Watercourses comprise another 1,621,000 KM.

ESTABLISHMENT OF FEDERAL FLOOD COMMISSION IN PAKISTAN

1. After creation of Pakistan, a Central Engineering Authority was constituted under Chief Engineering Adviser to deal with the issues of water, power and allied engineering matters At National level.

2. In 1977 Federal Flood Commission was established for the purpose of integrated

flood management at national level.

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3. In 1982 a Federal Coordination Cell (now re-designated as FID Cell) was established to coordinate activities of the Provincial Irrigation Departments in particular in the drainage sector

4. In 1987 Dam Safety Council was established to carry out inspection of existing dams and plans for new dams etc.

Flood Types & Floods in Paksitan

Documents

river floods

coastal floods coastal

water level

urban floods

flash floods flash floods

major floods

rain water

magnitude of floods