Feature image probably shows flooded human habitation along Cheyyeru river after Annamayya project failure on Nov. 19. However, caption of image published in Deccan Herald report does not mention it.
India has been witnessing unusual monsoon rains in 2021. First the delay in South West Monsoon[i] withdrawal till third week of October 2021 brought heavy rainfalls in several states of North India in the first half of October 2021. Then the extreme rainfall spells during North East Monsoon[ii] have caused floods in several parts of south India in quick succession in November 2021.
In October 2021, the all India rainfall has been 33% above normal while November rainfall being record breaking 86% above normal. The formation and interactions between low depressions and western disturbances largely contributed in record breaking rainfall events during this period including the onset of La Nina phenomena.
The unprecedented rainfall has also resulted in rivers breaching of Highest Flood Levels (HFL) at 30 sites including 7 sites in North India, 1 in East and 22 sites in South India, according to Central Water Commission (CWC) Flood Forecasting site[iii] in these two months. The analysis of all such incidents in 2018[iv], 2019[v], 2020[vi] and 2021[vii] can be seen on SANDRP website.
Ganga Basin
Following unprecedented rainfall[viii] in third week of October 2021, several rivers in Ganga basin flooded dangerously in Uttarakhand and Uttar Pradesh. This heavy downpour also led to breach in HFLs at least at 7 sites of which 6 are in Uttarakhand and 1 in Uttar Pradesh.
All the 6 sites in Uttarakhand are Level Monitoring (LM) sites and the lone site in Uttar Pradesh is Level Forecast (LF) site. The highest rise of 3.97 metre (m) above previous HFL is recorded at Ramnagar Barrage on Kosi river in Nainital followed by 3 m rise above old HFL at Ghat site on Sarda river in Pithoragarh district.
Hydrographs of rivers beaching HFLs in Uttarakhand.
This event also exposed unpreparedness in CWC flood monitoring works as there were glitches at several sites where no progress in hydrographs was registered for a day while the rivers were in extreme flood situation. Moreover several sites in Sarda basin were out of work during the deluge.
So far, CWC has not updated the new HFL at any of the sites mentioned in the table below. On the contrary, in several cases, it has removed old HFL and dates for these sites. For Paliakalan site in Kheri, CWC has changed Warning Level (WL) from 152.32 m to 153.1 m and Danger Level (DL) from 153.32 m to 154.1 m.
| SN | Site/ River | District/ State | WL/ DL | Old HFL | Date | New HFL | Date/ Time of new HFL | Rise above old HFL | Level Above old HFL for hrs | HFL Up-dated? |
| 1 | Karanprayag (A) NA | Chamoli Uttarakhand | 758.3 m | 18.08.2019 | 759.92 m | 19.10.2021 15:00 hrs | 1.62 m | 22 hrs | No | |
| 2 | Devprayag (A) Alaknanda | Pauri Uttarakhand | 466.9 m | 18.08.2019 | 467.48 m | 19.10.2021 07:00 hrs | 0.58 m | 2 hrs | No | |
| 3 | Ghat Sarda | Pithoragarh Uttarakhand | 472 m | 16.08.2011 | 475 m | 19.10.2021 14:00 hrs | 3.0 m | 10 hrs | No | |
| 4 | Pancheshwar Sarda | Champawat Uttarakhand | 432.5 m | 16.08.2011 | 433.3 m | 19.10.2021 14:00 hrs | 1.9 m | 8 hrs | No | |
| 5 | Garjia Kosi | Nanital Uttarakhand | 476.89 m | 18.08.2019 | 478.79 m | 19.10.2021 22:00 hrs | 0.27 m | 23 hrs | No | |
| 6 | Ramnagar Barrage Kosi | Nainital Uttarakhand | 216.98 m | 01.06.2019 | 220.95 m | 19.10.2021 14:00 hrs | 3.97 m | 41 hrs | No | |
| 7 | Paliakalan Sarda | Kheri, UP | 152.32 m 153.32 m | 155.32 m | 21.07.2014 | 155.82 m | 20.10.2021 18:00 hrs | 0.5 m | 47 hrs | No |
Brahmaputra Basin
It’s almost after 25 years that Teesta river at Mekhliganj LF site has breached the old HFL that too in later half of October. CWC website has not updated the new HFL readings.
| SN | Site/ River | District/ State | WL/ DL | Old HFL | Date | New HFL | Date/ Time | Rise above old HFL | Above old HFL for hrs | HFL Up-dated? |
| 1 | Mekhliganj Teesta | Kochbihar W Bengal | 65.45 m 65.95 m | 66.45 m | 13.07.1996 | 66.62 m | 20.10.2021 07:00 hrs | 0.17 m | 8 hrs | No |
Cauvery Basin
In Cauvery basin HFL is breached at 4 sites of which 3 are LM and 1 LF site. Interestingly river Shimsa at Thoreshettahalli LM site has breached old HFL thrice within a month cumulatively gaining 0.69 m rise over HFL attained in October 2019. CWC lacks old HFL dates for Ayyar river at Thandalaiputhur LF site and Marudaiyar river at Varanavasi LM site. CWC has not updated new HFL recordings at its website as on December 12, 2021.
Hydrographs of rivers breaching HFL in Cauvery basin in Karnataka.
| SN | Site/ River | District/ State | WL/ DL | Old HFL | Date | New HFL | Date/ Time | Rise above old HFL | Above old HFL for hrs | HFL Up-dated? |
| 1 | Thoreshettahalli Shimsa | Mandya Karnataka | 624.41 m | 17.11.2021 01:00 hrs | 624.59 m | 21.11.2021 11:00 hrs | 0.18 m | 23 hrs | No | |
| 1A | 624.05 m | 23.10.2021 11:00 hrs | 624.41 m | 17.11.2021 01:00 hrs | 0.36 m | 14 hrs | ||||
| 1B | 623.9 m | 07.10.2019 | 624.05 m | 23.10.2021 11:00 hrs | 0.15 m | 08 hrs | ||||
| 2 | Pudunagara Uduthorehalla | Chamaraja Nagar, Karnataka | 587.71 m | 06.12.2017 | 587.8 m | 15.11.2021 07:00 hrs | 0.09 m | 25 hrs | No | |
| 3 | Thandalaiputhur Ayyar | Tiruchira-ppalli Tamil Nadu | 97.3 m 98.3 m | 98.5 m | NA | 98.735 m | 26.11.2021 10:00 hrs | 0.235 m | 07 hrs | No |
| 4 | Varanavasi Marudaiyar | Ariyular Tamil Nadu | 61.8 m | NA | 62.02 m | 26.11.2021 10:00 hrs | 0.22 m | 06 hrs | No |
Hydrographs of rivers breaching HFL in Cauvery basin in Tamil Nadu.
Pennar Basin
Old HFL is breached at 2 LM and 1 LF sites in Pennar river basin. All 3 sites have recorded new HFL on November 19-20, 2021. While at Singavaram LM site river Chitravathi has set new HFL after 33 years, the Pennar crossed old HFL at Nellore Anicut LF site after 39 years. This is the event when the record breaking rains and failure of Pincha and Annamayya projects[ix] have caused large scale flood destruction in four districts of Andhra Pradesh.
| SN | Site/ River | District/ State | WL / DL | Old HFL | Date | New HFL | Date/ Time | Rise above old HFL | Above old HFL for hrs | HFL Up-dated? |
| 1 | Singavaram Chitravathi | Anantpur Andhra Pradesh | 260.355 m | 12.09.1988 | 261.58 m | 20.11.2021 01:00 hrs | 1.225 m | 13 hrs | Yes | |
| 2 | Nandalur Cheyyeru | Cuddapah Andhra Pradesh | 137.2 m | 17.11.2015 | 138.12 m | 19.11.2021 09:00 hrs | 0.92 m | 15 hrs | Yes | |
| 3 | Nellore Anicut Pennar | Nellore Andhra Pradesh | 15.91 m 17.28 m | 18.7 m | 30.11.1982 | 19.57 m | 20.11.2021 06:00 hrs | 0.87 m | ~17 hrs | No |
East flowing rivers (EFR) between Pennar & Kanyakumari
At least 17 HFL breach incidents has been witnessed in just 18 days of November 2021 (between 12 and 29, November). 7 of the breaches are recorded in single day of November 19. Interestingly all of these are LM sites.
Hydrographs of rivers breaching HFL in EFR between Pennar & Kanyakumari in Andhra Pradesh.
At 2 sites Buggaagraharam on Nagari river in Chittoor district of Andhra and at Monnavedu site on Kosasthalaiyar river in Tiruvallur district of Tamil Nadu HFLs are breached twice while Kallar river at Poyyapakkam site in Ranipet district of Tamil Nadu registered HFL breach thrice during these days.
Hydrographs of rivers breaching HFL more than once at Poyyapakkam & Monnavedu sites in EFR between Pennar & Kanyakumari under Tamil Nadu state.
Cumulatively, the HFLs have gone up by 2.52 m at Mannavedu and 0.72 m at Poyyapakkam sites. The highest single time rise over old HFL is seen at Kumarapalayam site on Varahanadhi river in Puducherry which is 2.135 m followed by 1.78 m rise at Puduvayal site on Aranair river, 1.15 m rise at Chengalpatu site on Palar river at Chengalpattu district and 1.03 m rise at Nariyampattu site on Palar river in Vellore district.
Hydrographs of other rivers breaching HFLs in EFR between Pennar & Kanyakumari under Tamil Nadu state.
CWC lacks old HFL dates for Panneswaram Madam site on Ponnaiyar river and Ayilambedu site on Kosasthalaiyar river. It has not updated new HFL records for Poyyapakkam and Venganur site on Periyaodai river. Thirunavalur is newly functioning site on Gadilam river in Vellipuram district which witnessed significant rise on November 19, 2021 and 36.27 m is its first HFL there.
| SN | Site/ River | District/ State | WL/ DL | Old HFL | Date | New HFL | Date/ Time | Rise above old HFL | Above old HFL for hrs | HFL Up-dated? |
| 1 | Narasinga-rayanipet Poini | Chittoor Andhra Pradesh | 269.03 m | 27.11.2020 | 269.59 m | 19.11.2021 09:00 hrs | 0.56 m | 17 hrs | Yes | |
| 2 | Buggaagra- haram Nagari | Chittoor Andhra Pradesh | 95.45 m | 12.11.2021 | 96.25 m | 19.11.2021 01:00 hrs | 0.8 m | 11 hrs | Yes | |
| 2A | 94.75 m | 27.11.2020 | 95.45 m | 12.11.2021 06:00 hrs | 0.7 m | 12 hrs | ||||
| 3 | Panneswaram Madam Ponnaiyar | Krishnagiri Tamil Nadu | 447 m | NA | 447.52 m | 19.11.2021 14:00 hrs | 0.52 m | 16 hrs | Yes | |
| 4 | Thiruvalam Palar | Vellore Tamil Nadu | 197.92 m | 20.11.2020 | 198.55 m | 19.11.2021 01:00 hrs | 0.63 m | 13 hrs | Yes | |
| 5 | Vazhavachanur Ponnaiyar | Thiruvanna- malai Tamil Nadu | 138.782 m | 17.11.1991 | 139.4 m | 19.11.2021 06:00 hrs | 0.618 m | 17 hrs | Yes | |
| 6 | Poyyapakkam Kallar | Ranipet Tamil Nadu | 101.91 m | 19.11.2021 09:00 hrs | 102.38 m | 29.11.2021 04:00 hrs | 0.47 m | 24 hrs | No | |
| 6A | 101.74 m | 12.11.2021 05:00 hrs | 101.91 m | 19.11.2021 09:00 hrs | 0.17 m | 17 hrs | ||||
| 6B | 100.94 m | 10.12.2020 | 101.74 m | 12.11.2021 05:00 hrs | 0.8 m | 46 hrs | ||||
| 7 | Monnavedu Kosasthalaiyar | Tiruvallur Tamil Nadu | 101.32 m | 12.11.2021 19:00 hrs | 102.82 m | 20.11.2021 05:00 hrs | 1.5 m | 20 hrs | Yes | |
| 7A | 100.3 m | 05.12.2020 | 101.32 m | 12.11.2021 19:00 hrs | 1.02 m | 47 hrs | ||||
| 8 | Ayilambedu Kosasthalaiyar | Vellore Tamil Nadu | 97.85 m | NA | 97.97 m | 21.11.2021 12:00 hrs | 0.12 m | 07 hrs | Yes | |
| 9 | Nariyampattu Palar | Vellore Tamil Nadu | 99.75 m | 13.10.2021 | 100.78 m | 19.11.2021 23:00 hrs | 1.03 m | >110 hrs | Yes | |
| 10 | Puduvayal Araniar | Tiruvallur Tamil Nadu | 97.47 m | 27.11.2020 | 99.25 m | 12.11.2021 08:00 hrs | 1.78 m | 18 hrs | Yes | |
| 11 | Venganur Periyaodai | Cuddalore Tamil Nadu | 78.26 m | 04.12.2020 | 78.79 m | 26.11.2021 03:00 hrs | 0.53 m | 08 hrs | No | |
| 12 | Chengalpatu Palar | Chengalpattu Tamil Nadu | 28.2 m | 02.12.2015 | 29.35 m | 19.11.2021 14:00 hrs | 1.15 m | ~84 hrs | Yes | |
| 13 | Kumarapalayam Varahanadhi | Puducherry | 13.12 m | 31.12.2011 | 15.255 m | 19.11.2021 12:00 hrs | 2.135 m | 51 hrs | Yes | |
| Thirunavalur Gadilam | Vellipuram Tamil Nadu | 36.27 m | 19.11.2021 17:00 hrs |
Hydrographs of Varahanadhi river breaching HFL at Kumarapalayam site in Puducherry.
West flowing rivers (WFR) from Tapi to Tadri
The Manimala river at Pullakkayar site in Kottyam witnessed sudden rise of 3.425 m above old HFL on October 16, 2021.
| SN | Site/ River | District/ State | WL/ DL | Old HFL | Date | New HFL | Date/ Time | Rise above old HFL | Above old HFL for hrs | HFL Up-dated? |
| 1 | Pullakkayar Manimala | Kottyam Kerala | 96.2 m 98.2 m | 98.315 m | 07.08.2020 | 101.74 m | 16.10.2021 13:00 hrs | 3.425 m | 09 hrs | YES |
West flowing rivers (WFR) from Tadri to Kanyakumari
The Kodaiyar river breached the HFL at Thiruvarambhu LF site in Tamil Nadu thrice this year cumulatively rising 2.11 m higher than August 2018 HFL. CWC has not updated the new HFL so far.
| SN | Site/ River | District/ State | WL/ DL | Old HFL | Date | New HFL | Date/ Time | Rise above old HFL | Above old HFL for hrs | HFL Up-dated? |
| 1 | Thiruvarambu Kodaiyar | Kanyakumari Tamil Nadu | 11 m 12 m | 15.67 m | 17.10.2021 05:00 hrs | 15.7 m | 13.11.2021 21:00 hrs | 1.02 m | 10 hrs | No |
| 1A | 14.68 m | 26.05.2021 14:00 hrs | 15.67 m | 17.10.2021 05:00 hrs | 0.99 m | 20 hrs | ||||
| 1B | 14.58 m | 15.08.2018 | 14.68 m | 26.05.2021 | 0.1 m | 03 hr |
River Basin and State Wise Summary
In just two months of October and November 2021, rivers have breached old HFLs at least at 30 sites including 5 sites (Kodaiyar river at Thiruvarambu, Kosasthalaiyar river at Monnavedu, Kallar river at Poyyapakkam in Tamil Nadu, Nagar river at Buggaagraharam in Andhra Pradesh and Shimsa river at Thoreshettahalli site in Karnataka) where HFLs is breached twice or thrice during this period.
Out of this 24 are LM sites and 6 are LF sites. Maximum HFL breach incidents (13) have taken place in EFR between Pennar and Kanyakumari. The HFL breaching incidents were seen at 27 sites during South West monsoon 2021.
| SN | Basin | States | Level Monitoring | Level Forecast | Total |
| 1 | Ganga | Uttarakhand | 06 | 00 | 06 |
| Uttar Pradesh | 00 | 01 | 01 | ||
| Total | 06 | 01 | 07 | ||
| 2 | Brahmaputra | W Bengal | 00 | 01 | 01 |
| 3 | Cauvery | Karnataka | 02 | 00 | 02 |
| Tamil Nadu | 01 | 01 | 02 | ||
| 03 | 01 | 04 | |||
| 4 | Pennar | Andhra Pradesh | 02 | 01 | 03 |
| 5 | EFR between Pennar & Kanyakumari | Andhra Pradesh | 02 | 00 | 02 |
| Tamil Nadu | 10 | 00 | 10 | ||
| Puducherry | 01 | 00 | 01 | ||
| 13 | 00 | 13 | |||
| 6 | WFR from Tapi to Tadri | Kerala | 00 | 01 | 01 |
| 7 | WFR from Tadri to Kanyakumari | Tamil Nadu | 00 | 01 | 01 |
| Sub Total | 24 | 06 | 30 |
Month wise summary
There were 9 HFL breach incidents in Oct 2021, while Nov 2021 has seen 21 such events.
| Month | River | Basins | Total | |||||
| Ganga | Brahma-putra | Cauvery | Pennar | EFR between Pennar & Kanyakumari | WFR from Tapi to Tadri | WFR from Tadri to Kanyakumari | ||
| October | 07 | 01 | 00 | 00 | 00 | 01 | 00 | 09 |
| November | 00 | 00 | 04 | 03 | 13 | 00 | 01 | 21 |
| Total | 07 | 01 | 04 | 03 | 13 | 01 | 01 | 30 |
In addition this, there are at least 6 sites (2 LF and 4 LM) where old HFL has either been touched or missed by narrow margins, details of which is given in table below.
| SN | Site/ River | District/ State | WL/ DL | Old HFL/ Date | Highest level date/ time in Oct/ Nov 2021 | Missed HFL breach by |
| 1 | Pipalkoti Alaknanda | Chamoli Uttarakhand | 1051.86 m 27.07.2021 03:00 hrs | 1051.8 m 19.10.2021 14:00 hrs | 0.06 m | |
| 1051.78 m 19.08.2019 | ||||||
| 2 | Kachhla-bridge Ganga | Budaun, Uttar Pradesh | 161 m 162 m | 162.79 24.09.2010 | 162.79 m 23.10.2021 01:00 hrs | Touched |
| 3 | Bendrahalli Survarnavathi | Chamaraja Nagar, Karnataka | 634.7 m 13.09.2013 | 634.65 m 14.11.2021 10:00 hrs | 0.05 m | |
| 4 | Venganur Vellar | Cuddalore Tamil Nadu | 78.26 m 04.12.2020 | 78.12 m 03.11.2021 07:00 hrs | 0.14 m | |
| 5 | Ashramam Pazhayar | Kanyakumari Tamil Nadu | 45.5 m 6 m | 7.1 m NA | 7.1 m 14.11.2021 17:00 hrs | Touched |
| 6 | Kuzhithurai Thambraparni | Kanyakumari Tamil Nadu | 8.83 m 08.12.2010 | 8.31 m 14.11.2021 05:00 hrs | 0.52 m |
CWC’s flood monitoring work remains inconsistent, opaque as being highlighted regularly by SANDRP. It’s randomly updating new HFLs for some sites and skipping doing same for most of the sites. For example out of 30 HFL breach incidents as documented here, it has not updated new levels for 16 sites while 4 of these sites lack old HFL dates as on December 12, 2021.
Cumulatively, HFL breach incidents have taken place at 57 sites (at 27 sites during South West Monsoon and 30 in the month of October and November) in 2021 (38 are LM & 19 LF sites).
Bhim Singh Rawat (bhim.sandrp@gamil.com)
References:
[i] https://sandrp.in/2021/09/30/sw-monsoon-2021-district-wise-rainfall-in-india/
[ii] https://sandrp.in/2021/12/07/heavy-rainfall-in-india-in-oct-nov-2021/
[iii] https://ffs.tamcnhp.com/
[iv] https://sandrp.in/2018/11/08/hfl-crossing-flood-events-during-india-sw-monsoon-2018/
[v] https://sandrp.in/2019/10/29/rivers-that-cross-highest-flood-level-during-sw-monsoon-2019/
[vi] https://sandrp.in/2020/10/03/rivers-that-reached-new-highest-flood-level-during-monsoon-2020/
[vii] https://sandrp.in/2021/10/05/rivers-that-breached-hfl-in-south-west-monsoon-2021/
[viii] https://sandrp.in/2021/10/26/unprecedented-october-2021-rainfall-in-uttarakhand/
[ix] https://sandrp.in/2021/12/05/andhra-pradesh-dam-induced-flood-disaster-in-november-2021/
SANDRP 