Many of us have this idea that floods (or flooding) are simply, too much water around your house. People think that can be fun. Wrong, flooding is a lot more than that. Flooding is extremely dangerous and has the potential to wipe away an entire city, coastline or area, and cause extensive damage to life and property. It also has great erosive power and can be extremely destructive, even if it is a foot high. It is a natural event or occurrence where a piece of land (or area) that is usually dry land, suddenly gets submerged under water.
Some floods can occur suddenly and recede quickly. Others take days or even months to build and discharge. When floods happen in an area that people live, the water carries along objects like houses, bridges, cars, furniture and even people. It can wipe away farms, trees and many more heavy items. Floods occur at irregular intervals and vary in size, duration and the affected area.
It is important to note that water naturally flows from high areas to low lying areas. This means low-lying areas may flood quickly before it begins to get to higher ground. In this lesson, we shall see more about what causes flooding, the types of flooding, some effects of floods and what we can do before, during and after floods occur. CITATION Ros10 \l 1033 (Jha, 2010)
Each time there are more rains than the drainage system can take, there can be floods. Sometimes, there is heavy rain for a very short period that results in floods.
In other times, there may be light rain for many days and weeks and can also result in floods.
Rivers can overflow their banks to cause flooding. This happens when there is more water upstream than usual and as it flows downstream to the adjacent low-lying areas (also called a floodplain), there is a burst and water gets into the land.Hurricanes, Strong winds in coastal areasSea water can be carried by massive winds and hurricanes onto dry coastal lands and cause flooding. Sometimes this is made worse if the winds carry rains them. Sometimes water from the sea resulting from a tsunami can flow inland to cause damage.
Dams are man-made blocks mounted to hold water flowing down from a highland. The power in the water is used to turn propellers to generate electricity. Sometimes, too much water held up in the dam can cause it to break and overflow the area. Excess water can also be intentionally released from the dam to prevent it from breaking and that can also cause floods. Ice and snow-meltsIn many cold regions, heavy snow over the winter usually stays un-melted for some time. There are also mountains that have ice on top of them. Sometimes the ice suddenly melts when the temperature rises, resulting in massive movement of water into places that are usually dry. This is usually called a snowmelt flood.
Some would like to see the causes of floods as types of floods, but on this page we shall look at three major flood types: Flash floods, Rapid on-set floods and Slow on-set floods. Flash floodsThis kind occurs within a very short time (2-6 hours, and sometimes within minutes) and is usually as a result of heavy rain, dam break or snow melt. Sometimes, intense rainfall from slow moving thunderstorms can cause it. Flash floods are the most destructive and can be fatal, as people are usually taken by surprise. There is usually no warning, no preparation and the impact can be very swift and devastating. CITATION Hit12 \l 1033 (Saikia, 2012)
Rapid on-set floodsSimilar to flash floods, this type takes slightly longer to develop and the flood can last for a day or two only. It is also very destructive, but does not usually surprise people like Flash floods. With rapid on-set floods, people can quickly put a few things right and escape before it gets very bad. Slow on-set floodsThis kind is usually as a result of water bodies over flooding their banks. They tend to develop slowly and can last for days and weeks. They usually spread over many kilometres and occur more in flood plains (fields prone to floods in low-lying areas). The effect of this kind of floods on people is more likely to be due to disease, malnutrition or snakebites.
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 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 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.
Urban flooding is the inundation of land or property in a built environment, particularly in more densely populated areas, caused by rainfall overwhelming the capacity of drainage systems, such as storm sewers. Although sometimes triggered by events such as flash flooding or snowmelt, urban flooding is a condition, characterized by its repetitive and systemic impacts on communities that can happen regardless of whether or not affected communities are located within designated floodplains or near any body of water. Aside from potential overflow of rivers and lakes, snowmelt, storm water or water released from damaged water mains may accumulate on property and in public rights-of-way, seep through building walls and floors, or backup into buildings through sewer pipes, toilets and sinks. CITATION Ros18 \l 1033 (Borah, 2018)
Assam has been always in the headlines of national news channel for last five to ten years for flood which takes place every year and that is a great headache for the people of Assam and loss of life and property is witnessed every year. There are many factors for the cause of flood they are both natural and manmade. Assam is the land of two mighty rivers – Brahmaputra and Barak. Each year these two rivers and their tributaries cause floods in vast areas of Assam which leads to human misery and devastation of nature. This year, more than 30 districts including lower and upper Assam have been severely affected. Several factors including natural and artificial are responsible for the re-occurrence of floods in Assam.
First and foremost, Assam lies in the heart of monsoon belt and so gets overburdened with rainfall every rainy season. Due to this, the river along with its tributaries such as Subansiri, Manas, Kopili, Jia-Bhoroli etc. get flooded and their banks overflow flooding the vast plain of the state. Secondly, the existence of long ranges of mountains on its northern and eastern boundaries compels the water to flow down into the vast plain causing the rivers to swell. Thirdly, every year due to heavy natural as well as artificial land sliding, Assam loses hundreds of kilometres of its land area. This soil erosion makes the river shallow, which later helps in the creation of a heavy flood. There are also human-induced factors like destruction of wetlands, deforestation, and encroachment on river banks.
Most cities and towns suffer due to poor urban planning. Drainage congestion due to man-made embankments is one of the crucial factors responsible for urban floods that can be visible every year in cities like Guwahati, Chennai, and Mumbai. The havoc caused by the flood in Assam is beyond describable. The destruction of properties and loss of life is visible every passing year. Lakhs are rendered homeless, standing crops are damaged and roads and communication links are interrupted, hence affecting the economic condition of the state. Some of the worst affected areas include MSME sector, tea industry, wildlife and biodiversity of Assam. Increase in rhino poaching during flood is one of the alarming factors for the decline of rhino population in Assam. The floods also increase the spread of water-borne diseases like cholera, typhoid, dysentery, etc. No doubt, the government has taken several flood control measures to lessen the menace and effects of flood in the state. Immediate assistance of NDRF and SDRF, flood relief measures including setting up of relief camps, free distribution of food, clothes, medicines, cash compensation for the lost property, etc. are undertaken by the government. The chief flood control measure has been the construction of embankments along the banks of rivers in the affected areas. In recent years, India signed a treaty with China in which the latter has agreed to provide hydrological data of the river Brahmaputra during monsoon. Although it is not possible to flood-proof all of Assam, several measures should be undertaken for a long-term solution. Increasing the water holding capacity of Brahmaputra and its tributaries by dredging will be an effective solution to eliminate the havoc of flood from the state. It will decrease the rate of disaster by almost 70%. A flood is caused due to the riverbed rising. Today, technology has risen to great heights, so it is not impossible to mitigate the flood problem. Besides, dredging will also contribute to the development of water highway in the Brahmaputra, which will be a good option to develop our economy.
Moreover, the rejuvenation of wetlands, afforestation, decentralization of weather forecast, construction of more micro and scientific reservoirs and dams, establishment of river valley projects, etc. may reduce the problem considerably in the long run. Embankments should be constructed away from the rivers so that the free-flowing state of the river is maintained. Certain areas should be reserved for water retention to level off the peaks during extreme floods. The recently announced Kaleshwaram project on river Godavari is an example for the mitigation of flood and proper utilization of water in Telangana.
Launched in 1954, different methods of flood protection structural as well as non-structural have been adopted in different states depending upon the nature of the problem and local conditions. Structural measures include storage reservoirs, flood embankments, drainage channels, anti-erosion works, channel improvement works, detention basins etc. and non-structural measures include flood forecasting, flood plain zoning, flood proofing, disaster preparedness etc. Since then more than 35,000 km of embankments has been constructed and more than 39,000 km of drainage channels improved which could absorb and regulate peak floods when necessary.
It was set up by government of India to evolve a coordinated, integrated and scientific approach to the flood control problems in the country and to draw out a national plan fixing priorities for implementation in the future. Major recommendation made by RBA includes flood plain zoning and management to regulate man made activities.
It was set up to review the impact of the recommendations of the RBA and to suggest short term and long term measures Their measures included among other administrative measures, construction of large flood moderation projects, particularly in the North- East and following up the enactment of Flood Plain Zoning Act so as to tackle encroachment by people in the flood plains.
It had also observed that storage dams and embanks provided effective protection to large flood prone areas. It also suggested the urgent need to enact flood plain zoning act.
The objective of the National Water Policy is to take cognizance of the existing situation, to propose a framework for creation of a system of laws and institutions and for a plan of action with a unified national perspective. It had suggested that reservoir operation procedures should be evolved and implemented in a manner so as to have flood cushion and to reduce trapping of sediment during flood season. It has suggested incorporate coping strategies for possible climate changes, such as increasing water storage capacity in dams.
Storage dams are only meant for flood control. The planning would be to maintain a low reservoir level during high flow months and use the storage capacity to absorb the incoming flood peaks. Soon after a peak passes down, the reservoir is brought down at a controlled rate to the low level to be ready to face the next flood. Such projects would not be usually economically justifiable. Multipurpose projects are basically for irrigation and power benefits. They could be planned to also include moderation benefits as well, storing water for the non-monsoon period. CITATION Duk19 \l 1033 (Buragohain, 2019)
This programme which provided flood control benefit are dams of Damodar Valley Corporation (DVC), the Hirakud Dam on the Mahanadi , Ukai dam on the Tapi and the Bhakra Dam across Sutlej. Hirakud Dam:A major earth cum masonry dam across Mahanadi River. Damodar Valley Corporation: a series of four dams on the Damodarand Barakar rivers, namely Konar, Maithon, Panchet and Tilaiya. Ukai dam: Tapi River Bhakra Dam: Sutlej River Tehri hydro project: Bhagirathi River Sardar Sarover Project: on the Narmada River Assam Government Initiative for Flood After the unprecedented floods in the country in 1954, the Govt. of India announced a National Policy on Floods comprising three phases viz. :
The flood control activities in Assam started mainly after the announcement of National Water Policy. Subsequently, "outlined plan for flood control in Assam" along with various comprehensive plans were prepared and the priority areas, which need immediate and urgent attention were identified. Till date, the Water Resources Department has taken up works primarily for the general development of the rural sector and for the protection of major townships in both the Brahmaputra and Barak valley. Schemes have also been taken up to relieve the drainage congestion in the cities and other important areas. Construction of Embankments and Flood walls River training and bank protection works Anti-erosion and town protection works River channelization with pro siltation device Drainage improvement/ Sluices Raised Platform Flood forecasting and warning Flood zoning No long-term measures have been implemented so far to mitigate the flood and erosion problems of the state. Till date only Immediate and short-term measures are implemented by the state Water Resources Department. About 16.50 Lakh Hectares of flood affected areas out of the total 31.05 Lakh Hectare of flood prone area as identified by the R.B.A. for the state. This flood prone area of 31.05 Lakh hectares comes to about 39.58 % of the total land area of Assam. Whereas the flood prone area of the country as a whole comes to about 10.2 % of the total area of the country, it signifies that the flood prone area of Assam is four times the national mark of the flood prone area of the country. CITATION Pra13 \l 1033 (Hazarika, 2013)
Flood is one of the major natural epidemic all around the globe and this problem should very seriously be dealt with. Flood may occur due to various reasons and in India it occurs in a very severe manner in which a lot of property and life are lost and caused havoc all around the country. In India Bihar, Assam and Tamil Nadu are most prone to flood because of its geographical location and moreover flood is a common problem occurring every year in Assam and causing a lot of problem to the people. Since the last 5-10 years the severity of flood is gradually growing and more districts are drowning. According to this year report more than 100 people died and thousands of people displaced. After the flood occurring in Assam various factors plays important role like three major dams constructed by China releases massive amount of water and moreover rapidly developing Assam due to which deforestation take place and that is also a major issue and the growing population which is acquiring the river bank which is more prone to flood.
Moreover, it is not just the problem of human being animal also suffer a lot because of flood, Kaziranga National Park is every year effected by flood due to which the voiceless have to die because of our fault. Flood in Assam is a growing problem for which government have to take certain strong and rigid decisions to stop this annual problem and develop the living standard of the flood hit people. Climate change is also a major factor for the occurrence of natural disaster in the recent past. If we human beings keep on ignoring the issue of climate change and rapid occurrence of natural disaster then we will be in the verge of extinction in next 100 to 200 years.