Brahmaputra basin faces unprecedented flood wave in August 2017

Screen shots of CWC flood forecasting sites as on Aug 11 2017

In case of at least one site, namely Raidak-I river at Tufanganj site in Cooch Behar district of W Bengal, the site was already red as I write this, signifying that the river water level has already crossed the HIGHEST EVER FLOOD LEVEL for that site and had attained a new HFL. The river here has already crossed the earlier recorded highest ever flood level of 36.36 m, attained 24 years back on Sept 21, 1993. So the flood here was worst ever, worst in any case in a quarter century.

Assam and parts of W Bengal that had already experienced several waves of floods earlier this monsoon, were thus facing the prospects of even higher, unprecedented floods. Neither the state nor the centre is ready to face this new wave, from all available indications.

In the table below I have given an overview of these sites where water level has already come within half a meter of highest ever recorded flood levels, of the water level attained, water level forecast and HFL recorded on CWC’s flood forecasting site.

FLOOD MONITORING SITES WHERE RIVER WATER LEVEL REACHED CLOSE TO HIGHEST FLOOD LEVEL AT RESPECTIVE SITES

(unit: Meters)

Ganga Basin to face unprecedented floods next? That the Ganga basin could also face similar unprecedented flood situation in coming days is also apparent from the flood forecast at Basua site in Supaul dist in Bihar along Kosi river (Ganga Basin), already on Aug 12, 2017. The HFL for this site is 49.17 m (reached on Aug 25, 2010). Actual river water level here at 2300 hours on Aug 12 was 49 m, forecast to reach 49.23 m at 0700 hours on Aug 13. This means the river water level here is expected to achieve new HFL on Aug 13 morning already.

Damage in Assam The full dimensions of the impact of this particular wave of flood is not known as yet it will take at least a couple of days to get clear picture. However, the extent and intensity of the impact is only likely to be greater than the earlier wave. As per the latest available Flood report from Assam Disaster Management Authority[iv] the damage in this round of flood assessed so far is given below. These numbers are so far lower than earlier rounds of floods, but these numbers are likely to go up rapidly in next few days.

• Districts affected: 19 (66 circles, 1752 villages)
• Crop area affected 1 lakh ha
• Population affected 99 lakh
• No of people in relief camps 63800 In 268 camps
• No of people dead 5
• No of houses damaged 56 (fully) + 13 partially
• No of people rescued 2615

This flood wave, when it reaches Bangladesh, along with all the heavy rains in that country, the flood situation in Bangladesh could also worsen in days to come.

Questions about dams and other interventions in North East During the earlier rounds of floods in Assam & rest of North East India, the role of dams, hydropower projects and embankment breaches had come into focus and questions were raised about efficacy of these structures. Similarly, the govt attempt at dredging the river, creating waterways, building roads cum embankments on both sides of Brahmaputra were also questioned in the context of floods. There is already demand for decommissioning of Ranganadi Hydro in Arunachal Pradesh and Loktak Hydro Project in Manipur, in addition to Dumbur Dam in Tripura earlier and also demand for scrapping of Lower Subansiri Hydro in Arunachal Pradesh Assam border. The role of CWC had also come into sharp focus with questions about how useful its flood forecasting is since many areas where floods occur, there is no flood forecasting by CWC and at other locations, their flood forecasting is too late, erroneous or just not available to right people at right time.

SANDRP (ht.sandrp@gmail.com)

END NOTES:

[i] https://trmm.gsfc.nasa.gov/publications_dir/instant_2.html

[ii] http://www.india-water.gov.in/ffs/current-flood-forecast/

[iii] Explanation: 30.51-R / 10-1208: 30.51 is in meters, as all levels are. R stands for Rising, similarly S stands for steady and F stands for Falling. This shows that trend of this site at this location, both in terms of actual level and forecast level. 10 means 10 hours, 1208 means 12 Aug.

[iv]http://www.asdma.gov.in/pdf/flood_report/2017/Daily_Flood_Report_12.08.2017.pdf