Recorded rainfall happens once in 172 years

March 5, 2023

Recorded rainfall happens once in 172 years

PETALING JAYA: The highest rainfall recorded in the current flood in Johor is in Segamat, one of the locations severely hit by floods, which is 430mm for over 24 hours, says the Irrigation and Drainage Department (DID).

In a statement, it said this measurement called Average Recurrence Interval or ARI happened once in 172 years.

ARI means the long-term average number of years between the occurrences of a flood as big as or larger than the selected event.

ARI is a way of explaining how rare an event is by comparing how often on average the particular event has occurred in the past.

“The total rainfall recorded at the Air Panas station in Segamat from Feb 28 until March 3 was 731mm over four days.

“The second highest rainfall recorded was at the Liang Batu station in Muar, which was 404mm on March 1. Its total rainfall from Feb 28 until March 3 is 548mm,” it said yesterday.

DID said the rainfall recorded was beyond the average long-term monthly rainfall for March for Johor, which was 195mm a month.

“The rainfall recorded during this episode is the highest ever, in comparison with the recorded monthly rainfall of 621mm in December 1991 and 599mm in December 2006.

“The episode this time has affected all districts (in Johor). A total of 105 flood locations were reported in Johor as of March 3.

“The Batu Pahat district has the highest number of flood locations at 24. The depth in all areas is between one and three metres,” it said.

Other areas with high rainfall readings in Johor were the station in Bekok dam with a cumulative 322mm of rain over 24 hours on Feb 28 and on March 1; Sembrong dam (260mm) over 24 hours on Feb 28 and on March 1; and Machap dam in Kluang at 395mm of rain over 24 hours on Feb 28 and on March 2.

Due to the high rainfall, water had to be released from the three dams in accordance with the standard operating procedures.