Distribution, Causes and Consequences
INTRODUCTION
A flood is an overflow of water that submerges land that is usually dry. Floods can occur due to heavy rainfall, melting snow, and ice, as well as coastal storm surges and tsunamis. They can cause significant damage to homes, businesses, and infrastructure, as well as lead to loss of life. Floods can also lead to secondary hazards such as landslides, fires, and disease outbreaks. Floods can be predicted and monitored through various means such as weather forecasting, satellite imagery, and on the ground observation. Preparedness and mitigation measures can also be taken such as building flood barriers and early warning systems, and having emergency plans in place.
Floods can be categorized into two types: flash floods and river floods.
Flash floods occur quickly and unexpectedly, usually as a result of heavy rainfall or a dam or levee failure. They can happen in urban or rural areas and can cause significant damage to buildings, roads, and infrastructure. They can also be very dangerous, as the fast-moving water can easily sweep away cars and people.
River floods occur when the water level in a river rises and spills over its banks. They can be caused by heavy rainfall, snowmelt, or a combination of both. They can take several days or weeks to develop, giving people more time to prepare and evacuate. However, river floods can still cause significant damage, especially to homes and businesses located near the river.
Floods can also be caused by coastal storm surges and tsunamis. Coastal storm surges occur when a storm’s winds push water onto the shore, causing the sea level to rise. Tsunamis are huge waves caused by earthquakes, volcanic eruptions, or underwater landslides. Both can cause significant damage to coastal communities and infrastructure.
Preparedness and mitigation measures can include building flood barriers, such as levees and dams, developing early warning systems, creating emergency plans and educating people about what to do during a flood. Planning and zoning regulations to minimize the risk of flood damage and reducing the amount of impervious surfaces such as pavements and buildings can also help reduce the impact of floods.
It is important to note that floods can be dangerous and life-threatening, so it’s important to stay informed and follow the advice of local authorities during a flood event.
Another important aspect of flood management is insurance. Many homeowners and business owners purchase flood insurance to protect themselves from financial losses caused by flooding. Flood insurance is typically separate from standard homeowners or business insurance, and is offered through the National Flood Insurance Program (NFIP) in the United States, which is administered by the Federal Emergency Management Agency (FEMA).
Flood insurance policies can cover the cost of repairing or rebuilding a home or business, as well as the cost of personal property such as furniture and appliances. It’s important to note that standard homeowners and business insurance policies do not typically cover flood damage, so it’s important to purchase separate flood insurance if you live in an area at risk of flooding.
In addition, it is also important to take proactive steps to protect your property from flooding. This can include installing sump pumps, backflow valves, and elevating electrical and heating systems above flood level. Building a floodwall or levee around your property, or elevating your home or business on stilts, can also help protect it from flooding.
As climate change is leading to more severe weather events, floods are becoming more frequent and severe. Therefore, it is important for communities to plan for flood risk, prepare for floods, and take steps to reduce their vulnerability to flooding.
Floods can have wide-reaching impacts on communities, and it is important to be prepared and take steps to reduce vulnerability to floods:
Preparedness
It is important to be aware of the flood risk in your area and to have a plan in place in case of a flood. This can include knowing your community’s evacuation routes, having an emergency supply kit ready, and staying informed about the latest weather forecast and flood warnings.
Flood Insurance
Many homeowners and business owners purchase flood insurance to protect themselves from financial losses caused by flooding. Flood insurance is typically separate from standard homeowners or business insurance, and is offered through the National Flood Insurance Program (NFIP) in the United States.
Mitigation Measures
Preparedness and mitigation measures can include building flood barriers, such as levees and dams, developing early warning systems, creating emergency plans and educating people about what to do during a flood. Planning and zoning regulations to minimize the risk of flood damage and reducing the amount of impervious surfaces such as pavements and buildings can also help reduce the impact of floods.
Proactive steps
It is also important to take proactive steps to protect your property from flooding. This can include installing sump pumps, backflow valves, and elevating electrical and heating systems above flood level. Building a floodwall or levee around your property, or elevating your home or business on stilts, can also help protect it from flooding.
Emergency response and recovery
Emergency responders such as police, fire, and paramedics may be called upon to rescue people who are trapped or in danger during a flood event. After a flood, recovery efforts begin to help people and communities get back on their feet. This can include providing temporary housing, food, and other basic needs to those who have been displaced by the flood, as well as cleaning up debris and repairing or rebuilding homes, businesses, and infrastructure that were damaged by the flood.
Examples
In 2017, Hurricane Harvey caused widespread flooding in the Houston, Texas area, damaging or destroying more than 200,000 homes and causing an estimated $125 billion in damage.
The 2011 Missouri River floods in the United States caused an estimated $2 billion in damage and affected more than 3,000 homes and businesses.
The 2010-11 Queensland floods in Australia affected more than 200,000 people and caused an estimated $2.38 billion in damage.
In summary, floods can have significant impacts on communities and it’s important to be prepared and take steps to reduce the risk of damage and injury.
CAUSES OF FLOOD
Flood can cause due to any of the following or combination of the following reasons:
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Excessive Precipitation
Heavy precipitation or rainfall in an area than normal along with poor drainage system can cause flood like situation. Flood can occur in both cases of heavy rainfall for shorter duration and continuous light rainfall for many days.
River Runoff
Excessive supply of water in the upstream due to heavy rainfall or otherwise can cause the downstream river water to run into the land or flood plain areas causing inundation.
Strong Coastal Wind or Cyclone or Tsunami
Strong coastal winds have the capacity to carry water from the sea to the land causing inundation in the coastal areas. Besides, Cyclones and strong winds can also bring heavy rainfall, causing flood on inland areas as well.
Breakage of Dams or Embankments
Embankments or levees are built alongside the river to prevent overflowing of water or avoid flood like situation on the adjoining land.
However, breakage or leakage on the embankment can lead to overflowing of river water on the flood plain also heavy water flow can break embankment and cause flood.
Similarly, dams, which are built to capture water flowing down from upland can cause floods if broken due to excessive pressure of the stored water, even at times extra water from dams are knowingly released to avoid possible breakage or leakages, which can also cause flood like situation in the lower lands.
Breakdown of Ice Dam
Ice dams occurs when glaciers or ice blocks restrict flow of river water during freezing weather. This stored water behind ice sheets/ blocks when released due to ice melting is more powerful than normal river water flow and can cause inundation at the lower catchment areas. e.g The Flood in Russel Fjord in Alaska USA in 1986 caused due to breakage of Ice dam.
Volcanic Eruptions
Volcanic eruptions has caused floods in country like Iceland where volcanic vent covered by thick layer of ice/ glacier got melted due to emission of hot lava. The melting glaciers turns into fast flowing water down the steep volcanoes causing inundation in the nearby areas.
TYPES OF FLOODS
Flash Floods
Flash Flood appears very fast and due to its sudden arrival, the term flash has been added to this types of flood. Flash flood cover smaller area but with high intensity, usually due to heavy rainfall or breakdown of Ice dams. Because of its higher speed and sudden appearance this flood causes more damages and is dangerous. Flash flood can even transport heavy rock, boulders and other heavy items due it its high speed.
Boulders and other heavy items due it its high speed. Besides, its capacity to carry debris makes this flood more dangerous as can damage both life and property.
Slow on-set Flood
This type of flood last long and spread over larger areas and occurs mainly due to over flowing of rivers or other water bodies. Since many coastal areas and flood plains frequently get inundated during rainy seasons, people for safety moves up to higher grounds during this period. The after effect of this flood is more dangerous as people die due to diseases and famine.
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Rapid On Set Flood
This type of flood occurs fast and last for a shorter period almost for a day or two. This flood is associated with heavy rainfall and as it appears fast the chances of damages to property and life are high as people get less time to prepare before the flood appears.
THE OTHER TYPES OF FLOODS ARE
Ice Dammed Flood
Ice Dam Flooding happens when flowing water, which were initially restricted by block of ice flow again due to melting of ice or spilling over of the piled up water above the ice wall into the nearby plain areas.
This flowing water is more powerful and dangerous than simple flowing river as this water carry big pieces of ice and thus with flooding of the plain area, this ice loaded water can damage property and life.
Coastal Floods
This is a common type of flood in coastal areas. This flood is caused by high storms and waves in the oceans and mainly the area near the ocean boundaries get inundated.
Even Tsunamis, cyclones, hurricanes and tornadoes with low pressure center, which pulls the water from the ocean towards the center of the storm carries the dome of water while moving towards the land and when reaches the coast this water loaded storm causes flooding and resultant damages.
Even fast moving waves or storms are destructive at times breaks past beaches and causes flooding at the coastline.
Storm Surge Flood
This is more devastating than the coastal flood as the storm rises above normal high tides mainly due to strong winds and lower atmospheric pressure.
Storm surge the causes huge damages to large areas near the coasts. These storm surges up to a height of 20 feet or more. Major hurricanes with huge storms have caused damages to property and life in the past including the recent past, where hurricane Katrina caused huge damages along the gulf coast in Texas and state of Florida.
PROBLEMS OF FLOODING
The Economic Impact of Flooding
Floods like flash flood, storm surge causes huge damages to properties and infrastructure of the affected areas. Houses, bridges, farms, roads, electric poles and vehicles are mostly destroyed causing huge economic losses to both public and government.
Many people losses their livelihood due to floods impact on agricultural fields, industries etc. Due to damages in communication lines, infrastructure and transport networks business takes hit not only in the flood affected areas but also in the adjoining localities.
The long time after effects of flood are felt in terms of lack of clean drinking water, disruption in power supply, reduction in purchasing power of people due to loss of income, rise in prices of basic items etc. Even rebuilding the infrastructure, rehabilitation of people and bringing the normalcy in economic activities takes lot of time causing further economic losses.
Environment Impact of Flooding
Flooding has its impact (both negative and positive) on the environment. Unlike the economic impact of flooding, which is mainly negative, flooding has some positive impact on environment. Such as refueling of surface and ground water storage.
This replenishment of water supply helps in improving the soil quality and thus crop production. But the negative impact of flooding on the environment is quite dangerous as the flood water brings along with it different types of pollutants, chemicals, debris including uprooted trees, stones etc. This polluted water contaminates the clean water due to breakdown of water pipes and drainage systems.
Besides, due to flooding many animals loses their natural habitats and contaminated water impacts the health of livestock as well as wild animals. Reduction in biodiversity level happens due to death and displacement of many animals during and after flood. As noticed in Australia’s Queensland in 2011, where heavy flooding resulted in death of many animals. The flood water once receded leave behind debris and sediments, which also hampers the water quality.
In 2011, Tsunami struck Japan and many coastal areas got flooded including the Fukushima, where waves caused level 7 meltdown of the power plant and release of radiations due to cooling system failure by Tsunami. Nuclear radiation release has long term negative impact on the health of people, animals and the environment.
Impact of Flooding on Human and Animal
The direct impact of flooding is experienced maximum by humans and animals. Flash flooding or sudden arrival of huge floods causes many damages to people and animal including loss of lives and properties.
Many animals and people are forced to migrate to safer places. Post flooding rise in diseases also impacts human and animals badly. Many people become homeless due to flood havoc. In addition to the physical impacts people also suffers psychologically.
The flood victims can remain disturbed for longer period of time as they see all the devastation in front of their eyes. Also, by losing home and other properties the security level of people decreases they become vulnerable to many threats. The stress to rebuild the life post devastations takes further toll on human’s life.