The second wave of floods (first wave came in around May 20-24) this year inA North East India is affecting Tripura, Mizoram and mainly Barak Valley in Assam. Worryingly, while CWC flood forecast site shows water level reaching unprecedented levels in Manu river at Kailashahar in North Tripura District, CWC seems to have NO flood forecasting site in Mizoram. At Matizuri site in Hailakandi district in Barak Valley in Assam, the Katakhal river also approaching its highest ever flood level. In Bangladesh too sites like Amalshid have crossed the HFL.
Review of IMD’s rainfall data this month shows that indeed, North Tripura district has received the highest rainfall of 346.3 mm (46% above normal) between Jun 1-13, among all the districts of Tripura. However, Serchhip district in Mizoram has received way higher rainfall of 677 mm, massive 345% above normal. In comparison, Assam as a whole has received 104.7 mm rainfall, 40% of below normal rainfall, the highest rainfall in Assam has been received by Karbi Anglong (IMD spells is as Karbi Analog!) at 166.3 mm, 101% above normal.
HIGHEST WATER LEVEL BREACHED IN TRIPURA The Manu river (flowing into Bangladesh from Tripura) water level at Kailashahar site in North Tripura district has warning level of 24.34 m, Danger level of 25.34 m and HFL (Highest achieved Flood Level) of 25.79 m, achieved way back on June 7, 1993. The water level at this site had already reached 25.95 m at 0900 am on June 13, 2018 and remained at the same level at least till 1600 hours on June 13. This means that the water level here has broken 25 years old HFL record and already overshot it by 16 cm, in the initial monsoon rainfall.
At the only other CWC FF site in Tripura state, at Sonamura in West Tripura district. The district had the highest rainfall of 101.5 mm on June 13, highest among all districts of Tripura on June 13, and that rainfall was massive 480% above normal as per IMD figures, so the Gumti river water level may go up. There is a reservoir with live storage capacity of 312 MCM (Million Cubic Meters) on this river, but this highly silted reservoir was already 74% full on June 7, 2018, as per the latest CWC Weekly Reservoir Storage Bulletin. There has been demand for decommissioning of this reservoir for long.
Among the CWC flood monitoring sites in Tripura, the river water did cross HFL at Manughat as per CWC flood hydrograph.
CWC HAS NO FLOOD FORECASTING SITES IN MIZORAM As noted above, Mizoram has received much higher rainfall in first 13 months of June, but since CWC has no flood forecasting sites in the state, we cannot know the water level in any of the numerous rivers of Mizoram. It is high time CWC includes crucial sites of Mizoram in its flood forecasting sites.
Flood level at Matizuri site close to HFL The water level of Katakhal river, a tributary of Barak River, was already at 22.4 m at 1600 hrs on June 13, 2018 with rising trend. Water level was at 22.62 m at 1400 hours on June 14, 2018, forecast to reach 22.67 m by 1800 hours on 14 June, that is within six cm of HFL. At this site the HFL (achieved in Sept 10, 2007) is at 22.73 m, so the water level is likely to reach very close to the HFL.
Tripura Floods During current floods in Tripura, as per available media reports, all eight districts are affected, at least two people are killed, 3472 are homeless, in shelters[iii]. More rain is predicted by IMD. The rain has triggered landslides in 17 locations. Eleven of the landslides occurred in Khowai district, one in Gumti and five in Dhalai. ONGC sites have been submerged[iv].
In MAY[v]: Last month, six people were killed. Floods have rendered more than 23,000 people homeless across Tripura, state disaster management officials said. West Tripura, Gumti and Khowai are the worst affected districts, and relief camps have been set up to shelter the displaced. Many have been shifted to camps in Udaipur and Sonamura due to a sudden rise in Gumti’s water level on May 20 night. The water levels of Khowai, Dhalai, Manu and Deo were on the rise.
Tripura CWC sites Besides the two flood forecasting sites (Sonamura and Kailashahar), CWC has a number of flood monitoring sites, including Amarpur, Belonia, Gajaraia, Haora, Kamalpur, Khowai, Kumarghat, Manughat, Nutanbazar. A number of site names like Kailashahar and Sonamura appear multiple times and in case of Kailashahar, both sites showing different and contradictory hydrographs.
Mizoram Floods In current episode[vi], due to heavy rains since June 11, landslides and floods have been created at various places. The land is now unstable around the hilly areas cuts across National Highway 54. It is the area located near Hunthar, Aizawl. Even areas just outside the Aizawl city located near the Tlawng river had been badly affected. Landslides have also damaged houses.
Another media report[vii] says: The disaster management department of Mizoram is trying to rescue families stranded in more than 150 submerged houses in Tlabung town in Lunglei district and Sairang village, near Aizawl, as the flood water is rising due to rains since June 10, 2018. Rain has triggered flood in Lunglei and Aizawl district of Mizoram. Over 1000 people have been evacuated to safer places in the two districts. 100 houses in Tiperabagh, 70 houses in Serhuan village and around 30 houses were submerged in Tlabung town.
On June 5, 2018, landslides in Mizoram killed ten people[viii]. Raw footage of buildings collapsing as of made of card boards, due to landslides in Mizoram[ix] can be seen on online videos (unfortunately most of them are of last year). ASSAM is also bracing for the floods[x].
Mizoram CWC sites There are no flood forecasting sites of CWC in whole of Mizoram state. CWC has some eight flood monitoring sites (Turial, TUichawng, Tuichang, Sihthangpui, Sairong, Pangkhuah, Keitum, Baily bridge Tuipui). However, no hydrographs for any of them were to be seen, except for Turial and Sairong, in both these cases, the hydrographs showed water level below HFL.
Bangladesh All this had impact on Bangladesh and report suggest widespread impact of floods.[xi] Bangladesh’s flood forecasting site[xii], in many ways (e.g. it provides a week’s hydrograph compared to three day hydrograph of CWC) better than that of CWC, provided some highlights: The Kushiyara river level at Amalshid has already reached 16.44 m, way higher than HFL. The Surma river level at Kahaighat was at 14.29 m, just 2 cm below HFL.
CWC flood forecasting The importance of the flood forecasting done by CWC cannot be over estimated. As the CWC flood forecasting site[xiii] describes, It has 226 flood forecasting sites, including 166 level forecasting sites and 60 inflow forecasting sites. The site also mentions about 700 flood monitoring sites, but they do not seem to be included in the map based forecasting tool or in the daily flood bulletins. This year, the CWC seems to have added a new feature called flood hydrogrpah[xiv], where “Station wise hourly trend for the last 72 hours can be explored here… This trend is with reference to Warning Level(WL), Danger Level(DL) and Highest Flood Level(HFL) in case of level forecast station. In respect of other flood monitoring stations trend is with reference to HFL only.”
Scope for improvement There is huge scope for improvement in CWC’s flood monitoring and forecasting mechanism, some of the suggestions are listed here.
- The name of the site should change from “CWC Flood Forecast” now to “CWC Flood Monitoring and Forecast”, since this is the only site that is also monitoring the floods in India in terms of river and reservoir water levels.
- The flood monitoring data should be separately be available, besides the forecastes.
- All the flood monitoring and forecasting done by CWC for the season should be archived, currently there is no record of what CWC had forecast earlier in the day, the previous day, previous week or previous month or year.
- Most of the Mizoram’s flood monitoring sites are not showing anything, this needs urgent attention. CWC also needs to add some key sites from Mizoram among its flood forecasting sites. They also need to add more sites in Tripura, considering the large number of rivers in both states.
- The current flood forecast sites that CWC lists at any give point of time[xv] should itself have color code of Yellow/ Orange/ Red so that one can immediately see the situation at a glance.
- CWC currently does not update its HFL till the next monsoon. The flood monitoring and forecasting site should at least record the instances for current season when the HFL has been crossed.