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Urban flooding, an alarming phenomenon in Bangladesh

Standfirst: It also increases water pollution, and roads become blocked, so much so that several water borne diseases like cholera, diarrhea, typhoid, etc. break out
Farzana Akter
Urban flooding, an alarming phenomenon in Bangladesh

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 plain 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 flood 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.

This city is on the bank of the river of Buriganga. Many cities are 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.

Causes of urban flooding

It can be caused by flash flooding, coastal flooding, river floods or rapid snow melt, pollution in cities, water inflow from upstream catchment, 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 it can't pass the water from heavy rain.

As there is little open soil that can be used for water storage nearly all the precipitation needs to be transported to surface water or to the sewage system. High intensity rainfall can cause flooding when the city sewage 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. Yet if eight to 10 inches pour down in an hour or two, roads usually are severely flooded and canals overflow.

Despite these reasons, there is another big reason for urban flooding, and 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 turns 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.

Impact of urban flooding 

Urban flooding is making our life difficult day by day. It hampers city dwellers too much. People can’t move, students can’t go to school, business is disrupted, cars damaged, transport system hampered, health hazards occur. It also increase water pollution, and roads become blocked and so much so several water borne diseases like cholera,  diarrhea,  typhoid, etc. break out. 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, and vegetation becomes 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 gets mixed up over the street simultaneously. Life becomes so difficult. In fact, sometimes it takes our life too. On the other side, houses of slum areas get submerged due to urban flood. The current research indicates a trend to more intense precipitation, which could result in more urban flooding.

The main culprit of this situation is no other than we. We people try to be smart, modern, but we don't know actually what a healthy and modern life in a developed country means. We are the main reason of drainage blocking. We throw our wastes consciously to drain, whereas in Japan, people use their street drains for cultivation of fish, and we proudly throw our wastes on the street. These activities should be banned here. 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 problems. And these are lack of resiliency in their drainage and sewer infrastructure and the need for progressive and sustainable alternatives for filtering, receiving and storing rainwater. Government should take necessary step to 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.  

The writer is a student of Environmental Science and Engineering, Jatiya Kabi Kazi Nazrul Islam University, Trishal, Mymensingh

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Editor : M. Shamsur Rahman

Published by the Editor on behalf of Independent Publications Limited at Media Printers, 446/H, Tejgaon I/A, Dhaka-1215.
Editorial, News & Commercial Offices : Beximco Media Complex, 149-150 Tejgaon I/A, Dhaka-1208, Bangladesh. GPO Box No. 934, Dhaka-1000.

Editor : M. Shamsur Rahman
Published by the Editor on behalf of Independent Publications Limited at Media Printers, 446/H, Tejgaon I/A, Dhaka-1215.
Editorial, News & Commercial Offices : Beximco Media Complex, 149-150 Tejgaon I/A, Dhaka-1208, Bangladesh. GPO Box No. 934, Dhaka-1000.

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