Floods The Most Often Tragedy In Bangladesh

Bangladesh is one of the most disaster prone countries in the world due to its geographical location, geological structure and population density. Bangladesh is a riverine country and about 700 small and big rivers flow through Bangladesh. This is the main reason why the incidence of floods in Bangladesh is higher than other natural disasters.
Floods usually occur during the monsoon season (June to September). About 26,000 sq km (16%) of Bangladesh is flooded every year. In the past, floods have wreaked havoc in Bangladesh, especially in 1966, 1988, 1998, 2008, 2017 and 2020. This means that every 10 years there is a big flood in Bangladesh.
There are four categories of floods in Bangladesh. They are monsoon flood, flash flood, urban flood and tidal flood. Monsoon flood is seasonal where the river water rises slowly and floods a large area causing severe damage to life and property. Flash flood caused by sudden mountain slope or short-term heavy rainfall or by breaking natural or man-made embankment. Urban flood may occur due to flash floods or river or coastal floods but in most cases it is due to excess rainfall over developed areas. Tidal flood usually has a height of 3 to 6 meters.
Both natural and man-made causes are responsible for the floods in Bangladesh. Natural causes are generally low altitude topography over which major rivers flow. Rivers have formed a densely arranged drainage network consisting of their tributaries; heavy rainfall in upstream areas outside the country and inside the country; melting of snow in the Himalayas and natural migration of glaciers; flooding of river bed / Occupancy of river side / Landslide due to siltation; simultaneous rise of water in major rivers and influence of one river over another; the back water effect of the river as a result of the reverse action of the tides and winds; response to sea surface changes; widely known as sea level rise, SLR and geo-structural disturbances (earthquakes, river flows and changes in topography).
Man-made causes are rapid urbanization, deforestation, global warming and fresh water demand. Rapid urbanization occurs due to population growth. In addition to construction of buildings and roads for the extra population, natural drainage network is blocked resulting in floods in the city due to excess rainfall. We deforest. Forests protect homes, people and livestock from flooding during floods and slow down water flow, as well as prevent river erosion and landslides. Deforestation increases the risk of flood damage. Global warming is increasing as a result of climate change, which has multiplied the risk of floods. As the population grows, so does the demand for fresh water. Due to excessive use of river water, the frozen barrier layer of river silt is lost. With the flow of water, silt falls into the deep part of the river, which reduces the depth of the river and reduces the water holding capacity of the river, increasing the risk of floods.
Some adverse effects are noticeable in both small and large floods. Economic damage includes houses, roads, farmlands that are all destroyed due to floods. People become homeless. The country’s resources are damaged and a lot of time and money is spent on rehabilitating the affected people. Environmental damage i.e. floods have adverse effects on the environment. All the chemicals in the agricultural land get mixed in the water, uproot the plants, and cause river erosion. Flood causes damage to humans and livestock: Floods kill people and livestock, destroy plant habitats and destroy bird habitats. Not enough pure water is available; people get sick due to lack of food. Production decreases due to flood. The impact of floods reduces people’s ability to produce crops and buy other necessities. Floods cause water to stagnate, making it difficult to produce anything. Flood causes migration that people move from one area to another due to floods. This puts pressure on other areas for extra people and people face a variety of problems.
Flood mitigation can usually be done in two ways. A) infrastructural and b) non-structural.
Infrastructural flood controls where physical structures have been constructed or individual features or structures have been constructed to reduce the impact of floods on the whole land.
Construction of flood control dams, bridges and other infrastructure including culverts, to develop or expand drain channels and drain infrastructure, the most important thing is to plant trees. Especially on the banks of rivers or seas shores, to make cement blocks and stick them well on the banks of the river so that river erosion does not occur during floods, to placing sandbags on the banks of the river, the sand absorbs water and sticks together to form a solid structure.
Non-structural measures refer to social adaptation to flood management. These include:
To intensify the flood forecasting and warning process for the people long before the flood waters rise so that the people can take shelter in safe places quickly; Land management to reduce the overflow of rivers. To this end, a comprehensive program of afforestation and reforestation should be adopted and its proper conservation should be done so that the level of flood water can be reduced by increasing the absorption process; change in land use and proper application of building codes, diversification of crop production i.e. identification and planting of flood resistant or flood tolerant crops and adaptation of crop planting season; To divide the floodplains into different zones and to create land use zones to control development activities. Non-structural measures can be implemented at low cost.
Identification of flood prone areas through GIS (Geographic Information System) and identify necessary actions to increase the resilience of the community against flooding is important.
Floods are a natural disaster that we cannot prevent if we want to. Therefore, tackling the effects of floods and determining adaptation strategies is possible only through integrated initiatives. To this, disaster management needs to be improved, as well as the process of providing emergency relief during floods needs to be facilitated, necessary medical assistance needs to be provided, clean drinking water supply has to be ensured and houses, roads need to be constructed. Above all, it is necessary to build infrastructure to deal with the floods in accordance with the standards and rules and people also need to be aware so that they can be protected from the loss of their lives and property.

(Dr. Md. Munsur Rahman, Professor, IWFM, BUET. Email: mmrahman@iwfm.buet.ac.bd;
and Md. Shibbir Ahmed Tashfik, Post-graduation Student and Research Assistant, IWFM, BUET. Email: shibbiriwfm.buet@gmail.com)