Saturday, September 19, 2020 | ePaper

Urban Flooding

An Alarming Phenomenon In Bangladesh

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Farzana Akter :
Bangladesh is a densely-populated, low-lying, mainly riverine country located in South Asia with a coastline of 580 km on the northern littoral of the Bay of Bengal. The delta consists of the Ganges (Padma), the Brahmaputra (Jamuna) and the Meghna rivers. Bangladesh has a tropical monsoon climate. It is less than 5 meters above from the Mean Sea Level (MSL). For these criteria, Bangladesh faces tremendous floods every year during June - August. There are different categories of floods. They are called as Flash flood or pluvial flood (hilly area), River Flood also called as fluvial flood (throughout the river), Rainfall flood, Monsoon flood (during monsoon), Coastal flood (for storm surge). But there is another type of floods we usually don't realize which is involved with the urbanization and our modern life. The consequences are very devastating. Nowadays this is another type of disaster which happens almost daily at maximum cities in our country and people suffer a lot every year. The main important fact is that, there is no improvement in our country. But government should take a look on this and take immediate measures.                
Most of the people of our country are unknown with the term of urban flooding.  Urban flooding is one kind of flood that occurs when water flows into an urban region faster than it can be absorbed into the soil or run off to and stored in a lake or reservoir. It generally happens in low elevator city like Dhaka. The city is on the bank of the river of Buriganga. Many cities are also facing this phenomenon for the last few years. It's caused by excessive runoff in developed areas where the water doesn't have anywhere to go. Urban flooding can be linked to a major disaster. Urban flooding is a natural disaster but it takes furious form by the foolish activities of us. It is now an alarming phenomenon, so we should take it seriously. Otherwise whether we like it or not it is getting worse day by day.
It can be caused by flash flooding, coastal flooding, river floods or rapid snow melt, pollution in cities, water inflow from upstream catchments, indiscriminate encroachment of waterways, and inadequate capacity of drains and lack of maintenance of the drainage infrastructure. We have to admit that, in our country the drainage infrastructure is very poor. There are unplanned constructions everywhere. That's why water from heavy rain can't pass. As there is little open soil that can be used for water storage. Nearly all the precipitation needs to be transport to surface water or to the sewage system. High intensity of rainfall can cause flooding when the city sewerage system and draining canals do not have the necessary capacity to drain away the amounts of rain that are falling. In general, two or three inches of rain per hour create only minor street flooding. If eight to 10 inches pours down in an hour or two, roads are usually flooded and canals overflow severely.
Despite of these reasons, there is big reason for urban flooding, that is, Urbanization. World is getting faster than ever, people are more socialized, modern than ever before. But with this achievement and progress we are creating our own problem by our own hand, still we don't realize how much we harm our environment, we are threatening our own existence. By the name of development we are getting worse. There are too many problems we create by the name of urbanization. Common consequences of urban development include the removal of vegetation which turn our land into desert, and an increase in impervious surfaces and drainage networks, all of which increase precipitation runoff into streams and rivers. It makes soil very compact thus reduces the rate of infiltration of rain water to ground. As a result the GWT (ground water table) can't recharge. If this doesn't recharge, we won't find our drinking water. It happens in Dhaka and other developed cities. Aquifers have gone too far from the surface. It will be a day when we won't get any drinking water from ground. As the surface rain water can't infiltrate into soil because of concrete cement or simply urbanization the water remains in surface and for the lack of proper drainage in our cities, this water can't pass through city to the downstream or reservoirs, it may result in more flooding. The water remains in same place for 2/3 days. In fact the duration of urban flooding is increasing comparatively last years.
Urban flooding is making our life difficult day by day. It hampers city dwellers too much. People can't move, students can't go school, business disrupts, damage cars, hamper transport system, health hazards, Increase water pollution, Roads became blocked and so much several water born diseases breaks out like cholera,  diarrhea,  typhoid etc.  People get stocked in their building. In fact it affects all environmental process. Due to lack of infiltration rate, there happens unavailability in ground water where vegetation is waterless. Water may even enter the sewage system in one place and then get deposited. Thus water pollution occurs. And many times we see that sewage water and rain water are dancing over the street simultaneously. Life becomes so difficult. In fact sometimes it takes our life too. On the other side the house of slum area submerged due to urban flood. Current research indicates a trend to more intense precipitation, which could result in more urban flooding.
The main culprits of this situation are no other than we. We people try to be smart, modern, but we don't know actually what healthy life, modern life, and developed country is. We are the main reason of drainage blocking. We throw our wastes consciously to drain, where there in Japan, they use their street drain as cultivation of fish, and we proudly through our wastes on the street. These activities should be banned from our society. Drains should be kept clean. City dwellers should be more conscious. Although many cities try to be proactive by issuing storm warning alerts, we should focus our root problem. The lack of resiliency in the drainage and sewer infrastructure need for progressive, sustainable alternatives for filtering, receiving and storing rainwater. Government should take necessary step to come forward and solve this tremendous problem. If we follow the eco balance issues we can live a better life.
Otherwise this will make us suffer too much.          

(Farzana Akter, Environmental Science and Engineering, Jatiya Kabi Kazi Nazrul Islam University).

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