A huge cleanup effort is under way across the northwest following a catastrophic series of thunderstorms which washed away roads and bridges in Donegal and Derry.

More than 100 people had to be rescued in the northwest after heavy rain flooded homes and left Derry City virtually inaccessible by road.

The torrential conditions - which saw a month’s worth of rain fall in just a few hours - forced some to abandon their cars and homes and seek emergency shelter overnight, while more than 25,000 homes were left without power at the height of the storm.

There were no reports of deaths or serious injury.

The scene in Claudy after overnight weather caused major disruption. Several people were forced to leave their homes after serious flooding in Derry and the north west on Tuesday night. Photograph: Matt Mackey / Press Eye.

Statistics from Met Éireann, which had issued a status orange thunder warning and a status yellow rainfall warning, show almost 10 centimetres of rain fell in some parts of Donegal over just a few hours, with lightning activity also concentrated in northern areas.

The UK Met Office said two-thirds of the average rainfall expected in Northern Ireland for the entire month of August fell on Tuesday night.

Houses in Donegal were destroyed, trees were blown down and roads were washed away due to the force of the floods. Hundreds of people were left stranded and many of the roads into and out of Derry city were impassable for a time on Tuesday.

Damage to the main Derry to Moville road in Co Donegal caused by the force of a flooded river overnight. Photograph: Brian Hutton/PA Wire

Two Government Ministers travelled to Donegal to assess the scale of destruction. Following their assessment, it is expected an emergency relief fund will be announced to assist communities affected and to fund repairs to local infrastructure.

Minister for State at the Office of Public Works Kevin “Boxer” Moran rejected the criticism and insisted his intervention had enabled important flood relief works to be sanctioned more promptly.

Mr Moran said he had monitored the storm, keeping contact with those affected. “Sudden flooding like that is a frightening experience that I have had firsthand experience of. You could sense the concern in peoples’ voices,” he added.

The OPW would examine the particular circumstances of these floods, he said. It was “easy target” for criticism but Mr Moran said he had changed the system for approved flood relief works, so fewer schemes were being turned down.

He confirmed he would be briefing the Minister for Finance and the Taoiseach on the scale of damage to the region and expected an emergency relief fund would follow that process.

Minister for Transport Shane Ross arrived in the area on Wednesday night to assess damage to roads “first hand”.

“We understand that the local authorities are still responding to the issues on the ground and they are not yet in a position to fully assess the impact,” he said. “We deeply sympathise with all those who have been so terribly affected by flooding and other consequences of the recent weather.”

Damage to the main Derry to Moville road in Co Donegal caused by the force of a flooded river overnight. Photograph: Brian Hutton/PA Wire

Earlier local TD and Minister of State for the Gaeltacht Joe McHugh visited Burnfoot and Buncrana which experienced extensive damage to homes and businesses.

Donegal County Council confirmed on Wednesday that two bridges either side of Quigley’s Point on the R238 and R240 collapsed as mountain streams turned to torrents, and two bridges near Carndonagh which sustained serious structural damage may take weeks to replace.

Diversions and traffic calming measures are also in place for roads which were badly flooded over the course of the deluges on Tuesday.

Speaking on RTÉ News, Donegal county engineer Brendan O’Donnell described the weather as “extreme” and said there was no possible way of preparing for the freak conditions.

He added that Donegal’s road network was not built to cope with such a sudden dump of rainwater, and that drainage systems were overwhelmed.

This is how it all unfolded last night. Thunder, lightning, and torrential rain. pic.twitter.com/D8sJgsgny3 — Barra Best (@barrabest) August 23, 2017

A man looks at a tractor which has fallen into a river after a road collapsed in Iskaheen, Co Donegal after heavy rain left a trail of destruction. Photograph: Niall Carson/PA Wire

The Coast Guard at Malin Head and the Rescue 118 helicopter from Sligo assisted in a number of rescues over the course of the evening, including search operations for people who were cut off by rising flood waters.

In a Twitter message early on Wednesday Donegal County Council urged the avoidance of unnecessary travel “as there is significant flood damage affecting all routes”.

It continued: “Major flooding in Inishowen area. Many roads washed away and bridges down, all routes affected. Please be careful and avoid travel.”

Power outages

Northern Ireland’s Fire and Rescue Service said that at the height of the flooding on Tuesday night it was receiving an emergency call every 45 seconds.

Assistant Chief Fire & Rescue Officer, Alan Walmsley, said they rescued 93 people from either cars or property who had been trapped by the floodwaters.

“Our Regional Control Centre (RCC) received 402 emergency 999 calls between 7pm and 4am.

“At its peak time between 9pm and 11pm, RCC handled an emergency call every 45 seconds.

“Firefighters worked in extremely challenging circumstances to reach people.

“A number of roads were impassable due to flooding, and crews had to take alternative routes to attend some incidents.

“This was a very busy and challenging night for fire crews and our regional control centre personnel, and I commend them for their professionalism in responding to such challenging circumstances as efficiently as they did throughout the night,” he said.

Up to 25,000 ESB customers lost power on Tuesday evening mainly across the northwest, midlands and in parts of Dublin due to lightning strikes, and around 1,600 customers on the Inishowen peninsula were still without power on Wednesday afternoon.

The ESB said crews are working to restore supply within the area and hope to do so over the coming hours. A spokesman for the company said power may be slower to return in badly flooded areas as crews must allow the water to subside before rebooting the grid. Anyone who notices damage to an electricity network is asked to report it to 1850 372 999.

Donegal County Council was forced to implement an emergency action plan as hundreds of people sought help following the flooding. Many were left trapped in cars as flood waters surrounded many motorists.

The Buncrana Road, between Donegal and Derry, was covered in water as stranded motorists had to be rescued by the emergency services.

Hundreds of people posted videos online of the chaos including cars and other vehicles being washed down streets under the force of flooding waters.

One of the worst areas hit was the Inishowen Peninsula along the border with Co Derry where villages and towns including Burnfoot, Burt, Bridgend and Buncrana were badly hit. Other areas hit with heavy flooding included Ballybofey, Raphoe and Lifford.

Storms over the course of Tuesday also caused a mudslide in the Grainne’s Gap area of Donegal.

Fianna Fáil called on Mr Ross to make emergency funding available, with the party’s transport spokesman Robert Troy describing it as an “exceptional situation which requires an exceptional response”.

“Local communities in Donegal have been left isolated as a result of the damage to transport infrastructure. They are not in a position to wait weeks for repairs to be carried out as the council follows standard procedures to allocate funding for repairs,” he added.

‘I’ve never seen flooding like it’

The Northern Ireland department of communities has already opened an emergency assistance scheme offering £1,000 towards renovating flood-affected homes.

In Derry the Foyle Arena and a number of community centres were opened, and many people spent the night in hotel lobbies or with friends or family.

All flights into and out of Derry City Airport were cancelled on Wednesday due to flooding of the airport building.

Brian Kernohan spent five hours trying to travel from Belfast to Derry, and had to spend the night in the lobby of a hotel outside Derry.

“I’ve never seen flooding like it.

“We were turned back by the police on the main road, then cut across to Limavady and were turned back again at Greysteel.

“We passed cars which had got stuck in the water.

“We’re now stranded in Drumahoe, the river looks to have burst its banks and the road is completely flooded.

“All the roads into Derry are closed, I have no idea how to get home.”

Main A6 road into Derry completely flooded at Drumahoe. Photograph: Freya McClements

Janet Lynch from Drumahoe said many of her neighbours had been flooded.

“They’re sitting upstairs and their houses have been flooded downstairs, so they’re waiting to find out what the damage is.

“I’ve never seen anything like it in my life.

“There’s so much water, its like a river across the road.

“They’re now saying the Faughan bridge is in danger of collapse, that’s how bad it is.”

Sarah Moore, who had travelled by bus from Belfast, got off in Drumahoe to find her father’s car submerged.

“We only live about five minutes away but the car is in the park and ride and it’s completely flooded, even the roof is completely covered.

“The house is only round the corner so we thought we’d try and get there on foot, but the firemen told us to go back.

“They told us to go to the hotel so we’ll have to sit there for the night and come back and see about the car tomorrow.”