Report Published Into Alyth Flooding
A joint report into the devastating flood that caused major damage to homes and businesses in a Perthshire town has been published.
Authorities say the flooding in Alyth on July 17 was caused by "extreme rainfall" and high river flows.
Analysis of rainfall data has shown that approximately 55 to 60 mm fell over a six hour period, with the highest intensity occurring between 4am and 8am, resulting in what the report says was a “once in 200-year event”, causing a peak flow in the Alyth Burn of around 40 m3/s.
Locals believed the fallen wood from the Den of Alyth may have caused the problem but officials deny it was the main contributor.
There were also concerns beavers may have played a role in what happened.
The Royal Zoological Society of Scotland looked into the claims. The report states: “All beaver dams located along the stream network feeding into the Alyth Burn above the Den of Alyth were found to be intact with only minor damage to a few which beavers had repaired with mud.
“There was no sign of current beaver activity in the Den itself. While much of the flood borne timber had been debarked and could appear to have been associated with beaver felling, close inspection found an absence of characteristic beaver tooth marks on the wood.
“This indicated that the loss of bark had been caused by abrasion against rocks and trees rather than by beavers.
“RZSS concluded that beavers made little or no significant contribution to the flood.”
SEPA says the findings provide a valuable starting point to develop measures to prevent it happening again.
Pascal Lardet, SEPA flood unit manager, said: “Our joint investigations have shown that this event seems to have been the largest flood in Alyth over the last 140 years and was triggered by a very intense period of rain in the early morning of 17 July.
“The flows resulting from the sheer volume of rainfall not only exceeded the capacity of the Alyth Burn, but also caused significant erosion to the banks of the watercourse throughout the catchment, with trees and other debris washed down the river.
“The joint report provides a valuable starting point from which to develop sustainable measures to mitigate the impact of severe flooding in the future.”
Leader of Perth & Kinross Council, Councillor Ian Miller, said: “I would like to take this opportunity to thank local residents for all the photographs, videos, eyewitness accounts, information on flow paths and completed questionnaires they provided which enabled the council and its partnership agencies to complete the detailed investigations which were necessary to compile the report.
“It is only through improving our understanding of the causes and impacts of the flooding that we will be able to manage it in future.”
David Bale, SNH area manager for Tayside & Grampian said: "The objective approach has been essential in coming to an understanding of the complexity of the flood’s cause and effects.
“It has also enabled us to answer many of the questions posed by those who have been affected by such a traumatic event.”