HFL crossing flood events during India SW Monsoon 2018

Even as the rainfall during South West Monsoon of India during June Sept 2018 was 9.4% below normal, a number of HFL (Highest Flood Level) crossing flood events were recorded on CWC’s (Central Water Commission) Flood Forecasting (FF) website[i]. Since CWC’s FF site does not provide archived information or comprehensive list of such events, we are here putting together a list of such events that we had noted during the SW monsoon, for future records and also understanding trends of high floods.

TRIPURA[ii]

1. Site: Manughat: River: Manu; Basin: Naochchara and others; North Tripura district. HFL: 46.6 m; HFL date: 5.6.2001;

Crossed HFL on 12.6.2018 at around 0800; reached new HFL of 48 m around 1600 hrs on 12.6 and came below HFL level by 2230 hours on 12.6.2018.

2. Site: Kailashahar; River Manu; Basin: Naochchara and others; North Tripura district. WL: 24.34 m; DL: 25.34 m; HFL: 25.79 m; HFL date: 7.6.1993;

HFL crossed at 0900 hrs on Aug 13, Level at 1800 hrs on 13.6.2018: 25.95 m, above HFL till 0000 hrs on 14 Aug.

ASSAM:

1. Site: Sivasagar: River: Dikhow; Basin: Brahmaputra: Dist: Sibsagar; WL: 91.4 m; DL: 92.4 m; HFL: 94.19 m (June 25, 1998) 94.21 m at 0600.

Crossed HFL at July 31, 2018, reached 94.23 between 0400 and 0500 hours on Aug 1, 2018 as per CWC response to SANDRP on twitter[iii].

2. Site: Numaligarh: River: Dhansiri (South); Basin: Brahmaputra; Dist: Golaghat; WL: 76.42 m; DL: 77.42 m; HFL: 79.87 m (on 24.9.1985).

Water level crossed HFL at 0500 on Aug 2, 2018, reached peak of about 80.18 m on Aug 3[iv], which was huge 31 cm above the previous HFL. There was clearly a role of Doyang Hydropower in this event[v]. The level came back below HFL by 1800 hours on Aug 4, which means it remained above HFL for about 61 hours.

KERALA

Site: Kidangoor: River: Meenachil; Dist: Kottayam; HFL: 8.015 m;

HFL was crossed on July 16, but we have only information that Water level dropped below HFL at 0200 hours on July 17.

– HFL was crossed at 1200 hrs on Aug 16, 2018, reached about 8.15 m and water level dropped below HFL at 0800 hrs on Aug 17,2018.

Site: Perumannu; River: Valapatnam; Dist: Kannur; HFL: 14.75 m (07082012);

Water Level crossed HFL at 1800 hours on Aug 8, 2018, reached new HFL of around 15.55 m at 2300 hours on Aug 8. It is likely to have remained above HFL till around 2200 hours on Aug 9, 2018, which means river water went 80 cm above previous HFL and remained above HFL at least for 28 hours.

– HFL here was again crossed just after 1900 hrs on 14.8.2018. Water level returned below HFL by 0600 hrs on 15.8.2018.

– HFL was again crossed around 1200 hrs on 16.8.2018, returned below HFL at 2300 hrs on 16.8. On both these occasions (14-15 Aug and 16 Aug), the water level did rise HFL, but did not cross the new HFL achieved on Aug 8.

Site: Mankara: River: Bharathapuzha; Dist: Palakkad; HFL: 51.55 m;

HFL crossed at about 0820 hours on Aug 9, 2018. Reached new HFL of 52.11 m at 1300 hours on Aug 9, 2018.

Site: Kumbidi: River: Bharathapuzha; Dist: Palakkad; HFL: 9.76 m (18.07.2007)

Crossed HFL at 0300 hrs on Aug 16, 2018, reached 11.3 m and remained above HFL till 0600 hrs on Aug 18, 2018.

Site: Muthankera: River: Kabini; Basin: Cauvery; Dist: Wyandu; HFL: 712.735 m (22061992); HFL crossed at 1900 hours on 09.08.2018, reached 713.49 at 0700 hours on 10.9.

HFL crossed at 0600 hours on Aug 16, reached upto 713.26 m (0600 hrs on Aug 17) and remained above HFL till 1000 hrs on Aug 18.

Site: Arangali: River: Chalakudy; Dist: Thrissur; HFL: 7.61 m;

HFL crossed at just after 0800 hrs on Aug 15, 2018; at 9.2 m at 0800 on 17 Aug 2018.

Site: Kalampur: River: Muvattupuzha (also known as Kaliyar); Dist: Ernakulam; HFL: 14.96 m;

HFL crossed at 1400 hrs on Aug 15, reached upto 17.5 m, and remained above HFL till 0700 hours on Aug 18.

Site: Ramamangalam: River: Muvattupuzha (also known as Kaliyar); Dist: Ernakulam; HFL: 8.42 m;

Crossed HFL at 0600 hours on Aug 16, 2018, reached upto 9.4 m with rising trend at 1600 hrs on 16.8.18.

Site: Vandiperiyar: River: Periyar; Dist: Idukki; HFL: 793.8 m;

River Periyar at Vandiperiyar in Idukki district of Kerala flowed above HFL between 6 and 8 hours of 11^th June 2018.

-Crossed HFL just before 2200 hours on Aug 14, reached till 797.3 m and remained above HFL till 2200 hours on Aug 19. The new HFL was 4.5 m above the previous HFL and water level remained above HFL for over five days!

Site: Neeleeswarm: River: Periyar; Dist: Ernakular; HFL: 11.105 m (27.7.1974)

HFL crossed at 2200 hours on Aug 15, attained about 12.4 m and remained above HFL at least till 0800 hrs on Aug 17.

Site: Kuttyadi: River: Kuttyadi; Dist: Kozhikode; HFL: 8.32 m (18.7.2009)

HFL crossed at 0600 hours on Aug 16, 2018, reached 8.36 m, remained above HFL for only two hours.

Site: Pulamanthole: River: Pulanthodu; Dist: Palakkad; HFL: 19.07 m (14.7.1994);

HFL crossed at 1400 hours on Aug 16, reached new high of 19.95 m and reached above HFL till 0700 hours on Aug 17.

Site: Malakkara; River: Pamba; Dist: Pathanamthitta; HFL: 8.2 m;

HFL crossed just before 1800 hrs on Aug 15, 2018, reached upto 8.5 m, in next two hours, further information is not available.

KARNATAKA

Site: Shimoga: River: Tunga; Basin: Krishna; Dist: Shimoga; HFL: 568.28 m (15.7.1994);

HFL crossed at just after 1100 hours on Aug 14, 2018, reached upto 568.45 m, and came back to HFL by 1500 hrs on the same day.

Site: Holehonnur: River: Bhadra; Basin: Krishna; Dist: Chickmagaluru; HFL: 561.04 m (6.8.2004);

HFL crossed just after 1100 hrs on Aug 14, 2018. Reached 563.6 m at 2300 hours on Aug 15, 2018 and remained above HFL at least till 1200 hrs on Aug 17, 2018.

Site: Chunchunkatte: River: Cauvery; Dist: Mysore; HFL: 757.35 m;

HFL crossed around 2130 hrs on 14 Aug 2018 and reached a peak of 759.44 m and remained above HFL at least till 1800 hrs on 18 Aug 2018.

Site: Kudige: River: Cauvery; Dist: Kodagu; HFL: 820.41 m;

HFL crossed at 2200 hours on Aug 14. It dropped below HFL 16 hours later, again went above HFL at 0500 hrs on Aug 16, 2018. It attained new HFL of 822.35 m and remained above HFL at least till 0900 hrs on Aug 18. This site is downstream of Haranagi-Cauvery confluence. Harangi dam on Harangi river is just upstream of this confluence.

TAMIL NADU

Site: Nellithurai: River: Bhavani; Basin: Cauvery; Dist: Coimbatore; HFL 308.25 m (7.2.1989);

Crossed HFL in a steep climb at 0900 hrs on Aug 16, 2018, reached new HFL of almost 309.5 m in next two hours, remained above HFL till 1700 hrs on same day.

Site: Savadapur: River: Bhavani; Basin: Cauvery; Dist: Erode; WL: 184.5 m; DL: 185.5 m; HFL: 186.878 m (5.11.1978);

HFL crossed just before 0100 hrs on Aug 17, reached about 187.8 m, dropped below HFL in next 12 hours. The Water level again crossed HFL around 2200 hrs on same day and remained just above HFL for about seven hours. This site is downstream of Bhavani Sagar Dam.

Site: Kodumudi: River: Cauvery; Dist: Erode; WL: 125.325 m; DL: 126.325 m; HFL: 127.83 m (25.10.2005);

HFL crossed at 0800 hrs on Aug 17, 2018, reached close to 128.15 m at 1900 hrs on same day and remained above HFL till 0300 hrs on Aug 19.

Site: Sevanur: River Chittar; Basin: Cauvery; Dist: Erode; HFL: 172.38 m (10.12.2009);

HFL crossed at 0100 hours on Aug 19,2018, reached new HFL of 173 m and remained above HFL till 2200 on Aug 19.

Summary This list thus has 25 sites where the Highest Flood Levels earlier recorded has been breached as per Central Water Commission Flood Forecasting website among the level forecasting/ level monitoring sites of CWC during June-Sept 2018, the period of SW Monsoon. We request that anyone (including CWC FF team) having additional information in this regard to kindly share the same.

This list may have covered most, though not all such sites. Unfortunately, CWC’s FF website does not provide either archival information or compiled information of such events. It is interesting to note that there are no Extreme Flood level events in any of the Ganga Basin states or sites this year. Majority (21 of 25) sites are from south India, traditionally not considered flood prone. Thirteen of these sites are in one state (Kerala), while rest of the sites are distributed among Karnataka (4), Tamil Nadu (4), Assam (2) and Tripura (2). The Rivers at both the Tripura sites crossed HFL during June 2018, the rest of the events happened in Aug 2018, none during July and Sept 2018.

SANDRP (ht.sandrp@gmail.com)

Acronyms:

CWC: Central Water Commission

DL: Danger Level

FF: Flood Forecasting

HFL: High Flood Level

WL: Warning Level

END NOTES:

[i] http://www.india-water.gov.in/ffs/current-flood-forecast/, https://www.facebook.com/CWCOfficial.GoI/

[ii] https://sandrp.in/2018/06/14/floods-in-tripura-mizoram-barak-valley-in-june-2018/

[iii] https://twitter.com/CWCOfficial_FF/status/1024522008661352448

[iv] https://twitter.com/CWCOfficial_FF/status/1025226483453677569