During ongoing North East monsoon season at least six rivers have breached highest flood levels (HFLs) at their respective flood monitoring sites in December 2023. All of these HFL breach incidents have taken place in two states of Andhra Pradesh (3) and Tamil Nadu (3). Interestingly, all of these rivers are part of East Flowing Rivers (EFR) between Pennar and Kanyakumari basin. The details of HFL breach sites and rivers are given in table below.
| SN | Site/ River | District/ State | Old HFL/ Date | New HFL/ Time/ Date | Rise over Old HFL | Above Old HFL for hours |
| 1 | Pallamala/ Kalangi | Chittoor/ Andhra Pradesh | 100.05 m/ 12.11.2021 | 100.8 m/ 08:00 hour/ 05.12.2023 | 0.75 m | ~35 hours |
| 2 | Verupaksha-puram/ Swarnamukhi | Chittoor/ Andhra Pradesh | 57.835 m/ 14.12.2020 | 57.88 m/ 22:00 hour/ 05.12.2023 | 0.045 m | ~02 hours |
| 3 | Sullurpet/ Kalingi | Nellore/ Andhra Pradesh | 6.65 m/ 16.11.2015 | 7.4 m/ 07:00 hour/ 05.12.2023 | 0.75 m | ~37 hours |
| 4 | Puduvayal/ Araniar | Tiruvallur/ Tamil Nadu | 99.25 m/ 12.11.2021 | 99.42 m/ 07:00 hour/ 05.12.2023 | 0.17 m | ~04 hours |
| 5 | Murappanadu/ Thambraparani | Tuticorin/ Tamil Nadu | 21.35 m/ 14.11.1992 | 23.595 m/ 16:00 hour/ 18.12.2023 | 2.245 m | ~36 hours |
| 6 | Irrukkankudi/ Vaippar | Virudhunagar/ Tamil Nadu | 51.1 m/ 15.12.1998 | 51.5 m/ 17:00 hour/ 18.12.2023 | 0.4 m | ~02 hours |
While most of the Old HFLs were attained in recent past years, the Thambraparani river at Murappanadu and Vaippar river at Irrukkankudi site have crossed old HFLs after 31 and 25 years respectively.
It’s worth mentioning that the hydrograph for Murappanadu site did not record hourly water level for about 13 hours (between 17:00 hour 18.12.2023 to 09:00 hour 19.12.2023) because the site was completely inundated by Thambraparani floods and unapproachable for CWC staff. Hence, the peak level attained there could possibly be higher than 23.595 meter.
Sites Where Rivers Touched or Reached Close To HFLs
In addition, there have been at least three sites where the rivers have either touched or narrowly missed crossing the respective HFLs. All these three sites are in Tamil Nadu.
Two of these sites namely Monnavedu and Kallidaikurichhi are part of EFR between Pennar and Kanyakumari basin while Odendurai site is part of Cauvery basin where the Kallar river has touched the HFL on November 23, 2023. The details of these sites is given in table below.
| SN | Site/ River | District/ State | HFL/ Date | Peak Flood Level/ Time/ Date | Missed Crossing HFL by Meter |
| 1 | Odendurai/ Kallar | Coimbatore/ Tamil Nadu | 331 m/ 02.12.2019 | 331 m/ 10:00 hour/ 23.11.2023 | Touched |
| 2 | Monnavedu/ Kosasthalaiyar | Tiruvallur/ Tamil Nadu | 102.82 m 20.11.2021 | 102.77 m/ 05:00 hour 05.12.2023 | 0.05 m |
| 3 | Kallidaikurichhi/ Tambraparani | Tirunelveli/ Tamil Nadu | 78.1 m 13.01.2021 | 77.47 m/ 12:00 hour/ 18.12.2023 | 0.63 m |
The details of all the sites where rivers have crossed their respective HFLs in pre-monsoon months and during South West monsoon season 2023 can be seen here.
Bhim Singh Rawat (bhim.sandrp@gmail.com)
SANDRP 