Guwahati, Monday, June 19, 2017
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Man-made factors mostly behind frequent flash floods: Report
R Dutta Choudhury

 GUWAHATI, June 18 - With floods becoming a regular feature in Guwahati city, making life miserable for the people, a report of the Assam State Disaster Management Authority (ASDMA), prepared in collaboration with All India Disaster Management Institute, has outlined some of the key issues causing such havoc and pointed out that most of the reasons are man-made.

The report pointed out that most of the causes of such disasters in the city are man-made, which include lack of drainage, unmanaged solid waste, reclamation of low-lying lands and unchecked and unplanned urban growth, hill cutting, etc. Another reason is the increased intensity of rainfall occurring in a very short duration. Back flow of the water from River Brahmaputra due to blockage in the drainage system through Bharalu, Khanajan, etc., also causes floods frequently every monsoon. The Bharalu basin is the most flood-prone area in the region. This is probably because most of the drains fall on the upstream side of River Bharalu. The river is at a higher level than the level of the drains leading to the retarded outlet of the water. Moreover, there is heavy siltation and dumping of garbage in the Bharalu.

The report pointed out that human intervention and depredation in the watershed region above Guwahati also aggravated the problem. The most serious environmental problem in the hilly regions now is deforestation. Its effects, if unchecked, are sure to bring about permanent ecological harm with dramatic increase in the flash flood problem in Guwahati city. Deforestation on hill slopes leads to loosening of soil, creating massive erosion along the hill edges. Excessive rain, too, adds to the woes and it carries this loose soil down to the drain channels and causes siltation in the city.

Guwahati city faces a severe problem of landslide during monsoons, for which rain is the primary reason, but the triggering cause is excessive cutting along hills and encroachment on them by migrants. Earthquakes too add to the problem as the entire NE region falls under seismic Zone-V, the report said.

The report pointed out that Guwahati city is sitting in the midst of natural wetlands, forests, hillocks and the river edge of one of the mightiest rivers in the world. All these constitute an interlinked ecological system, which is under threat due to rapid and unplanned development. Environmental degradation is fast becoming a major threat to this sensitive arrangement on natural entities and the population, which relies on it.

Encroachment on a large number of wetlands that serve as natural reservoirs like beels, swamps and marshes around the city, has also reduced the retention capacity of the drainage system, causing the flood level to rise. The desire to have a better life and to earn good fortunes lures migrants from villages and towns towards cities. Guwahati is facing a major threat from this problem as a big portion of the migrant population illegally occupies hillocks to build their shacks. They exert pressure on the already tottering infrastructure of the city and make the flood mitigation process a difficult task.

Guwahati city faces the brunt of unplanned road building in sensitive eco-zones comprising hillocks, forests and wetlands. Because of unprecedented growth in the population of the city, construction of roads for transportation had become necessary. Since there had been very little concern for natural environment in the process, the severe effect of this negligence is now showing up in the form of frequent flash floods and landslides in and around Guwahati.

Migration has been a continuous phenomenon for Guwahati city in the past few decades. Economic opportunities along with many social and political reasons cause migration of people to the city. Better urban services as compared to other rural areas such as education and medical facilities also are factors affecting immigration. In the past few years, with a rapid increase in employment opportunities due to growth of industries and other secondary and tertiary sectors, migration has taken place from different cities and villages. In most cases these people are poor or from economically backward backgrounds and thus they tend to settle in illegal settlements and encroach on hills or fragile lands. The recent increase in slum areas is an indication of increased migration to Guwahati.

The report pointed out that the present situation in Guwahati city is not going to allow further densification of the city as the FSI (Floor Space Index) is already higher than in other cities. Thus, there is an urgent need for creation of satellite townships to reduce the burden on Guwahati city.

Moreover, external factors such as development near the Meghalaya border have also led to change in the topography. There are flash floods in the agricultural university area. A lot of industries, schools, colleges etc., have been built along the border, which not only threaten the environment of the city by aggravating and causing floods, siltation and air pollution, but are also putting pressure on the infrastructure and services of the city as this development is depending on Guwahati city for its requirements.

The report observed that uncontrolled deforestation and construction on the hills in Guwahati has resulted in more exposed slopes which are more prone to soil erosion as compared to the vegetation-covered slopes. Increased soil erosion not only results in loss of soil fertility but also causes problems of water-logging and flash flood down the slope. There is a need for regulating cutting of trees and encroachment in forest areas.

One of the important tributaries of the Brahmaputra, the Bharalu, which flows through the city, is an important channel for the drainage of the city. Due to siltation, the bed level of the Bharalu has considerably risen. A major chunk of the water discharged from the city is directly dumped into this river. Waste water from households, commercial and business establishments, small and medium industries also end up in the Bharalu River, which gets discharged into the Brahmaputra. Even in the upper reaches, the waste water from the Indian Oil Corporation Refinery at Noonmati flows directly to the river. This has resulted in degradation of the water quality of the river and it has been reduced to a drain. With choking of the natural drainage, the city has become more prone to waterlogging and urban flooding, the report added.

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