Dr. Muhammad Mahtab Hossain Mazed

River erosion is a type of natural disaster. Generally, the water of the river is accelerated when it falls into the sea. In this, the water broke the river bank. This condition of breaking the bank of the river by the flow of water is river erosion. One of the reasons for this is flooding and river erosion is a threat to coastal residents. Hearing the word, the image of some helpless people who lost everything appeared in the corner of the eye. Every year, miles and miles of land in sub-urban areas are washed away by rivers. A survey shows that every year about 6 thousand hectares of land goes under the river. Due to this, thousands of families have lost their homes and land and become destitute. Various institutions including streets, markets, schools, colleges, mosques, madrasas are disappearing.

> Natural causes of river erosion

* Bangladesh is a delta:- As Bangladesh is a delta, the land here is made of alluvial soil. This makes the structure of the soil very weak. This weak soil cannot always withstand the flow of river water. Due to this, when a little strong current comes, the river breaks.

* Flood:- Flood is one of the reasons for river erosion. Generally, the incidence of floods in our country increases during the rainy season. As the flow of water in the river is very high during the flood, the current of the water acquires enough force to break the soil layer. During this time, the speed of the water on the river bank is high and the water hits the land along the bank and causes the river to break. This increases the severity of river erosion during floods.

* Heavy rainfall:- As a result of heavy rainfall, the flow of water in the river increases and the water in the river is turbulent due to the effect of wind. This causes strong waves in the river during heavy rainfall. Then the waves of the river exert additional pressure on its banks. Due to this, the soil in the weak part of the river bank collapses and gradually this erosion process increases.

* Sediment accumulation in the river bed:-Due to various deviations in nature, sediment accumulates in the river bed. This reduces the water holding capacity of the river. Due to this, the water level of the river increases and creates pressure on the bank and the river bank breaks and changes the course of the river. Thus, river erosion is accelerated.
* Rivers with strong currents:- Some rivers are strong currents due to the amount of water flow or hill slopes. Due to the rapid flow of water in these rivers, the river may break. If the structure of the river bank in these places is not strong, the river erosion is accelerated.

* River breadth:- River breadth is related to river erosion. If the width of the river is more, the possibility of the river breaking also increases.

* Formation of new silt in the river:- Silt accumulates in the river and silt is formed. Many times the course of the river changes when new char is created in the middle of the river. This causes a breach on one side of the river and the river changes its course to the other side.

> Man-made causes of river erosion

* Deforestation:- The roots of trees go deep into the soil and strengthen the soil structure. This strengthens the foundation of the soil along the river. Day by day people cut down the forest for their own needs and the soil along the river becomes weak. Due to this, unable to handle the shock of the strong current of the river, the soil collapses and the river breaks.

* Construction of houses and structures on the banks of the river:- As a result of the construction of houses and various structures on the banks of the river by people, the bearing capacity of the soil decreases and it collapses quickly. It is therefore a cause of embankment and river erosion.

* Extraction of sand from rivers:- We often see extraction of sand from rivers. This sand extraction upsets the balance of the river and causes river erosion. Hence responsible for sand lifting from rivers and river erosion.

* Damping the river:- Many times we try to control the flow of river water by damming the river. We build power plants, irrigation projects. By doing this we benefit temporarily but it creates long term problems. The dams created in the river obstruct the natural course of the river and cause river embankment.

* Construction of city protection embankments:- Over the ages, the banks of various public ponds have been built around the banks of the river. Many times, people build city protection embankments to protect the cities located on one side of the river. By doing this, the failure of one side of the river is prevented, but the failure is caused on the other side.

* Unplanned dredging:- We see regular dredging in rivers. Dredging is not always beneficial. Unplanned dazing results in imbalance between the depth and width of the river. This causes the river to break.

Finally, I would like to say that river erosion has started in different districts at the beginning of monsoon. Vast areas go under the river. Many villages, towns, crop lands are lost due to river erosion. Thousands of people are homeless and destitute.

River bank erosion has become a regular occurrence at this time of the year. As if it is the destiny of the countrymen. Newspapers and TV channels are reporting the river breach. The news of erosion will come in a few more months. And almost 80 percent of the total area of Bangladesh is included in the three main river basins. Apart from the three main rivers Padma, Brahmaputra and Meghna, the number of small and big rivers in Bangladesh is about 410. The length of the coastline of these rivers is about 24 thousand 14 kilometers. At least 12,000 km of coastline has been identified as an area prone to river erosion. About 1.5 million people are directly affected by river erosion. As a result, Bangladesh is facing a loss of about 200 crore rupees every year. Apart from this, about 8,700 hectares of land is destroyed by river erosion every year. And river erosion occurs in about 100 upazilas of the country. Land owners are the most affected by river erosion due to heavy rains caused by monsoonal winds from June to September. Because they can never reclaim that land. And river erosion in this country is a very old and terrible problem. The erosion continues throughout the rainy season. After the end of the monsoon, the incidence of erosion has decreased somewhat, but it continues to a greater or lesser extent throughout the year. And in this flood too, thousands of people have become homeless due to the river erosion. This time also the people who are victims of river erosion have echoed the previous words 'we don't want relief, first prevent river erosion'. In fact, the government does not have a separate allocation for the prevention of river erosion and the rehabilitation of people affected by the river and the provision of necessary assistance.

Although some charitable assistance is provided to Namkawaste from the disaster funds of the government in the districts or upazilas, it is not very effective due to insufficient funds. In order to free them from the constant suffering of the people affected by the river, the government must have some specific plans. And for the rehabilitation of the people affected by the river, the districts and upazilas need to have specific funds from the government. Similarly, all development organizations working in flood prone areas will have a consolidated fund system from which they will be able to quickly take effective action in disaster areas.

Flooding, river erosion is not new at all in our country surrounded by rivers. But we have not yet demonstrated the ability to prevent river erosion and control floods. As a result, our flood damage is increasing every year.

Similarly, due to river erosion, the low-income Char residents have to suffer. Remember that the 10 million people living in Char region are one of our greatest assets. To protect these 1 crore people, we have to decide the right strategy. And it is a matter of concern that the arable land in Bangladesh is decreasing every year. People are growing. River flood refugees are putting pressure on big cities. What is the future where the situation is going? Even if you want to plan, even with great planning, it is not possible for people to prevent such a big disaster of nature. Still, utmost precautions must be taken now to minimize river erosion. For this, not only national, but also international support, advice and planning should be taken.

The writer is a, organizer, columnist & researcher Founder and Chairman, Jatiya Rogi Kallyan Society.