The biblical scale of the flooding last month was underlined by Jonathan McKee, Director of Development at the Rivers Agency, who, on Friday, told members of Derry City and Strabane District Council, that the disaster was worse than that which struck the North West 30 years ago and was regarded as a benchmark worse case scenario for many years.
Mr. McKee was among a range of officials from various statutory agencies and council directorates that laid bare the magnitude of the flooding and outlined progress to date on the response to the emergency at a specially convened meeting of the local authority in the Guildhall.
Over 60 council staff were tasked to inspect flooded properties in the immediate aftermath of the disaster with 200 staff, in total, involved in coordinating the response, according to the council Chief Executive John Kelpie.
Seamus Donaghy, head of Health and Community Wellbeing, said 510 properties were affected, and 370 of these had been deemed eligible for a Scheme of Emergency Financial Assistance (SEFA), as of Friday.
The council's lead finance officer Alfie Dallas said staff worked over the bank holiday weekend immediately after the disaster to ensure 300 cheques could be cashed on the Tuesday.
Environment chief, Conor Canning, said 200 tonnes of waste were lifted from flood affected properties.
He also advised 26 council properties, including the Tullyally community centre and the Donemana civic amenity centre, were directly affected.
Director of Business and Culture, Stephen Gillespie, said the coordination of the response at two incident centres at Eglinton and Drumahoe had provided an "unprecedented example of partnership working".
Karen McFarland, the director of Health and Communities, said her department liaised closely with both the Department for Communities and the Department of Agriculture, Environment and Rural Affairs (DAERA) during the flood response.
It's also been engaging with SportsNI over damaged sports pitches.
Barry O'Hagan, head of Community Development and Leisure, said a total of £9,500 in funding relief had been administered to a range of organisations including Institute FC, Donemana FC and Creevedonnell cricket club.
Mr. Kelpie said David Sterling, the acting head of the civil service in the North was phoned after the flooding was elevated to a level 2 emergency at 4.30 a.m. on the morning after the disaster.
Brian Doherty, of DAERA, said aerial photographic surveys of local farm land, usually conducted every 3 years for the purpose of allocating EU farm payments, were called in early and the pictures landed at the department on Friday.
Mr. Doherty said DAERA had received 85 force majeure applications for emergency funding from farmers.
An extraordinary 6,500 hectares of local farmland were actively impacted, he said.
Numbers were also put on escapes from fish farms: 25,000 trout were released into the Foyle system by flood waters.
Mr. Doherty said that the quality of water at the Mobuoy dump site and Faughan were being monitored rigorously and that no significant elevations had been detected.
Perpetua McNamee, from DAERA's veterinary service, told the committee that 61,000 chickens were drowned on one broiler farm.
DAERA also received 13 calls from farmers reporting 325 missing sheep and 8 missing cattle.
Some of these may have ended up as gruesome flotsam on Culmore bay were there was a clean-up of animal carcasses.
Mr. McKee, from the Rivers Agency, said the priority was to keep culverts, grills and watercourses free from debris and that 30 staff were being employed to do this but the work would take months.
He said over a mile (1,700 metres in total) of damage to flood defences had been detected and that this was "very significant".
Repair works at the Faughan and the Burn Dennet were ongoing, although many smaller watercourses fell outside the agency's remit, Mr. McKee indicated.
The committee was told how the hydraulic models that informed the Rivers Agency's North Western Flood Risk Management Plan, published in late 2015, had accurately predicted Drumahoe, Tullyally and Ivy Mead would be inundated in a flood of this magnitude.
Mr. McKee said flood alleviation measures outlined in the plan needed to be implemented.
The true magnitude of last month's disaster was also brought home when Mr. McKee advised it was worse than when the Mourne burst its banks in 1987.
That had been seen as a mother-of-all floods benchmark but the Faughan was two foot higher than that in August 2017.
Divisional roads boss, Conor Loughrey, said 600 bridges in the west had to be inspected for potential damage.
Sixty roads had had to be closed due to the floods but that was down to 22, 12 of which were in Derry and Strabane.
He said the bridge collapse in Claudy was caused when one of four piers was wiped out by the force of the river causing two of five arches to collapse.
A further 140 roads were damaged but deemed passable.
Bridge collapses also took out NI Water supply lines in six instances, including a back up supply to Altnagelvin hospital, although all of these were swiftly replaced by stringers and loops and no outages were reported.
Dympna Gallagher of NI Water, said that the stoppage of drinking water abstraction at Carmoney on the Faughan for five days, resulted in water for the city being pumped from Banagher and Coleraine.
Ms. Gallagher also said the testing of water in the Faughan had given no cause for concern.
Chief Inspector Alan Hutton of the PSNI told the committee his priorities had been ensuring public safety and protecting property.
He said that in an average week night the PSNI at Strand Road normally dealt with about 100 calls.
On the night of the great flood they dealt with 191 with a further 184 the day after.
Eddie Doherty of the Northern Ireland Housing Executive (NIHE) said that of 28 tenants who had been placed in emergency accommodation, just two remained there as of Friday.
He also revealed 11 mobile homes at St. Canice's would be used to house those rendered temporarily homeless by the flooding in Eglinton.