An estimated 200 properties were flooded in the north west of Northern Ireland following heavy rain over the weekend.
Some political representatives have criticised the response from the authorities.
DUP MLA Gary Middleton described “chaos” in some areas of Derry waiting for sandbags to protect property.
Read more: Family business "devastated" after flooding hits for second time in five years
But the Department of Infrastructure has defended its response, insisting it was well prepared, with staff on standby despite a “short notice” weather warning.
It described a “significant event”, and said staff were extremely busy with more than 350 flood-related calls and over 8,000 sandbags were deployed.
A departmental spokesperson said that the Met Office has estimated that 70mms of rain fell in the area in five hours on Saturday evening.
It said that compares with a situation in the North West in August 2017 when some 60-70mm of rain fell over an eight to nine hour period, resulting in the flooding of around 400 properties.
“As a result of the efforts by the department through Saturday evening and into the early hours of Sunday morning, many homes were protected from flooding,” they added.
Clean-up efforts continued across Derry and Strabane on Monday in the aftermath of the floods.
An emergency assistance scheme, which can award a flooded household £1,000, is open for applications.
It is not yet known how many applications that Derry City and Strabane District Council have so far received for the Department of Communities assistance.
Six people were rescued by emergency workers on Saturday evening.
The Northern Ireland Fire and Rescue Service said it received more than 100 calls and responded to 49 incidents.
NIFRS group commander David Doherty told the BBC that the priority as they received calls was lives over property.
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