Expert study predicts river erosions in northwest, seeks precaution

Expert studies predict river erosion in particular points in several northwestern and central districts this year, seeking protective measures for structures and farmlands as torrential rains and gushing waters from upstream continued to inflate the streams in upper riparian areas.

Experts at C-EGIS, a pubic trust under water resources ministry purview, said their studies on river morphology in 2020 suggested that 16 particular locations in 12 northwestern, central and southwestern districts could be exposed to erosion in coming months.

The cross-border Brahmaputra-Jamuna and Ganges-Padma river systems cover all these 12 districts which are Kurigram, Jamalpur, Gaibandha, Bogura, Sirajganj, Tangail, Manikganj, Pabna, Rajbari, Rajshahi, Faridpur and Madaripur.

According to C-EGIS the erosion could engulf about 2,385 hectares of farmland and claim settlements on 365 hectares of land alongside swallowing 5.40 km of roads, 32 educational institutions, three hats or bazaars, 29 mosques, two government and one non-governmental offices this year.

"We have conveyed our study findings to authorities concerned and those exposed to erosion vulnerability for precautionary measures," said Engineer Sudipta Kumar Hore of Center for Environmental and Geographic Information Services (CEGIS).

Hore, who is a CEGIS associate specialist of river, delta and coastal morphology, however, said resource constrains forced the agency to concentrate its studies on the two main rivers of Brahmaputra-Jamuna and Ganges-Padma systems or basins alone.

CEGIS has been carrying out the annual studies on the two river systems since 2004 as part of its research works on natural resources management.

Several other major rivers like the Teesta, Dharla, Dudhkumar, Korotoa; and Bhairab, Ichamati, however, also come under the purview of these two basins as their tributaries or distributaries but remain beyond the CEGIS study.

Hydrologists divide riverine Bangladesh in four basins of Meghna that covers northeast and some central districts, Brahmaputra for northwest and central regions, Ganges-Padma for parts of northwest and western region and Southeastern Hill Basin.

But the CGEIS report, largely-based on satellite images, came as torrential rains and gushing waters from upstream continued to inflate major rivers particularly in Brahmaputra and upper Meghna which appeared to be a prelude of a major deluge.

Bangladesh Water Development Board's (BWDB) Flood Forecasting and Warning Centre (FFWC) predicted the north and northwestern region to be exposed to a "short" or "midterm" flooding but negated possibilities of a synchronized deluge with simultaneous inflation of water levels in rivers in all four basins.

River erosions in greater northwestern and central region uprooted tens of thousands of families over the decades until early 1990s but the curse largely disappeared in the past several years as Brahmaputra-Jamuna and Ganges-Padma systems have not been abruptly changing their courses.

Experts said BWDB measures to keep the rivers in their courses through different structural and non-structural measures also contributed to halt major erosions.

The CEGIS calculated that since 1973 over 1, 56,525 hectares of land were eroded alongside the bank lines of Brahmaputra-Jamuna and Ganges-Padma river systems while the Brahmaputra-Jamuna alone swallowed 92,845 hectares.

The rate of erosion in the Brahmaputra-Jamuna was above 5,000 hectares of land per year in the 1970s while it has reduced to between 1000 and 1500 hectares in the last decade.

Fortunately erosion rate in the Ganges-Padma reduced rapidly during the period.

Officials said the CEGIS annual predictions appeared largely or nearly accurate in recent years.

In 2017 CEGIS forecast that 3,225 hectares of land would be eroded while 3,450 hectares were eroded subsequently and in the next year 2,600 hectares of land were eroded against its prediction of 2,300 hectares.

However, there was a larger gap between the prediction and actual erosion last year when CEGIS said 2,800 hectares of land could be lost in erosion but eventually the figure appeared to be 1,965.

"Our river erosion predictions are showing a matching of around 70 percent with the real erosion occurring and predictions of erosion vulnerable locations matching around 80 percent with the actual happening on an average in recent times," Hore said.

BWDB's executive engineer stationed at FFWC in Dhaka M Arifuzzaman Bhuiyan said CEGIS could deliver a more accurate prediction if it could have studied thoroughly the characters and soil structures of different riverbeds across all river basins and other related factors alongside the satellite images.

BWDB's Chief Engineer for Rangpur zone Jyoti Prosad Ghosh said the CEGIS study report would be useful to his office though "we work to prevent river erosion mainly using our own mechanisms".