Berkshire: Flood warnings issued as more rain expected
Flood alerts mean "we're expecting property flooding directly", Mr Mansbridge said.
There are also a number of flood alerts in place, which warn rivers will break their banks and "some water will be on the floodplain where it's naturally meant to go", he said.
A yellow weather warning for rain from the Met Office will be in place until 06:00 GMT on Friday.
"We have a team of people monitoring all the river levels and the forecast and looking at where the levels might get to, so we’re ready to issue those when they’re required," Mr Mansbridge said.
He said there were "gangs of operational staff" on site clearing places that need extra maintenance to try to keep the water flowing.
Mr Mansbridge urged people to monitor the agency's website to ensure they know whether they are at risk.
"If they’re issued with a flood warning then they need to do their basic normal things like switching their electric off, moving their valuables upstairs, etcetera," he said.