The story of the drowning

প্ৰাগজ্যাতিষপুৰ

FLASH FLOODS OF GUWAHATI:

CAUSES, IMPACTS ON THE PEOPLE AND THE ECONOMY AND ITS MITIGATION

-PRITOM SARMA

Background on the Problem

The city of Guwahati, lies between the banks of Brahmaputra River and the foothills of the Shillong plateau.

The Bharalu is the primary perennial river stream which has been expanding upstream and sideways since remote past. The plain portion of the southern part of the Guwahati city topographically is the valley of the river Bharalu

But in present days the river creates water logging and flood hazards within the Guwahati city.

On the other hand the fluvial characteristics of the river channels are also affected by the urban morphology of the city.

My research is based on the need of finding qualitative and quantitative causes for these flash flood and thus help in solving the problem surrounding it.

Why Floods?&Why Guwahati?

There several known causes for flash floods in Guwahati, But according to my research two of the following reasons may be counted as the most prominent ones.

Bad town planning centring the Bharalu river valley.

Heavy amount of relentless waste dumping in the Bharalu basin.

An elaborate discussion of these reason in context to my research has been presented in the subsequent slides.

Planning or rather Misplanning in the city of Guwahati

Bad town planning is one of main reason for flash flood conditions in the city. There are several sub-points under this cause.

•Nearly perpendicular turnabouts (manmade meanders) inflicted in the course of the Bharalu river due to road and developmental constructions throughout the city, causing irregular flow and thus hampering the fluvio-geomorphic processes like overall flow, flow rate etc. in the river. This in turn causes the river to overflow during even the slightest rainfall.

•Non-equivalent width of the stream at different place along with an unexpectedly high change in stream width. This leads to differential flux, as a result when the water level in the channel increases (during rainfall) the adjoining areas are bound to be flooded

•Low land cover due to rampant uncontrolled urbanization and saturation of the soil exposure due to geochemical pollution reduces the seepage ability of the incoming rainwater, as a result this rainwater collects and on a larger scale contribute to the flash flood conditions.

Heavy dumping and geochemical pollution of the Bharalu river bed•Heavy and relentless waste dumping in the Bharalu basin has increased the mean height of the river bed leading to instant overflow once in it rains

Effects of these flash floods•Disruption of households: According to a study presented by the district administration of Kamrup Metro more than two lakh households were effected during the calendar year of 2014 only due to flash floods.

•Public Health Hazards: According to statistics by the Public Health Department, 53% of the cases of directly or indirectly water borne diseases originated from the place near the banks of the Bharalu and the flash flood prone areas.

MitigationMitigation of Flash floods in Guwahati is the problem of the century for Assam. But as it is often said the solution lies within the problem. Few of these solution which can be worked out are:

•Prevention of irregular flow and differential flux: This can be achieved by diverting the channel to the downstream and increasing the channel width in places where there is a chance of overflow.

•Increase the land cover to allow proper seepage of the rainwater and stop illegal and unauthorized construction near the flood hazard area

•Also control the dumping of waste into the Bharalu, this will be a very big step toward solving this issue.

•And finally turning the entire Bharalu river valley into a water shed area is bound to completely solve the problem once and for all.

It is high time for us to realize that the ancient beautiful city of Pragjyotishpur, is now in danger, until rigid steps are not taken an unprecedented disaster is imminent.