THE Environment Agency is warning that persistent heavy rain could lead to an increased risk of flooding in the Upper River Wey valley over the next few days.
And low-lying land and roads across the Alton area are facing "several weeks" of flooding from groundwater.
The forecasted heavy rain could cause surface water flooding, see a rise in river levels, and travel disruption as roads and rail lines may be affected.
At 4.30pm on Friday, there were 53 alerts across the South East, where flooding is possible.
Groundwater levels have risen at the agency’s observation borehole in Farringdon in the Alton area.
The alert for Alton reads: "Groundwater levels are above normal for this time of year and have now reached a level where communities may be affected within the next few weeks by flooding from groundwater.
"We expect levels to rise steadily over the next few weeks in response to rainfall forecast across the area. Low-lying land and roads will therefore continue to be at risk of flooding.
"Due to the nature of groundwater behaviour, this situation could continue for several weeks or longer."
Meanwhile, river levels remain high on the Upper River Wey as a result of recent heavy rainfall overnight.
Property flooding is not currently expected, but flooding of roads and farmland is anticipated, "especially in the Shottermill, Bramshott area".
The agency’s alert for the upper Wey valley continues: "There will be a band of rain moving south-east this evening [Friday] and into tomorrow [Saturday] morning. This rain could be heavy at times.
"The band of rain will then ease and clear during Saturday morning ahead of the heavy and persistent rain associated with storm Dennis, we will be closely monitoring the situation.
"Our incident response staff have been in the area clearing trash screens and checking defences.
"Please remain safe and aware of your local surroundings."
Maria Herlihy, duty manager for the Environment Agency, said: “Heavy downpours are expected across the South East on Friday night and into the weekend, which could lead to surface water flooding and significant travel disruption.
“Current forecasts indicate a heightened risk of flooding in parts of Surrey, Kent, Sussex and Hampshire.
"The Environment Agency is making preparations to operate flood defences, flood storage reservoirs and to issue flood warnings and advice and to those at risk ahead of the incoming weather.
“Our teams have been out on the ground checking flood defences, clearing debris from rivers, and will continue to support other agencies to reduce the impacts of the heavy rain. We will issue flood alerts and warnings where necessary.
“We urge the public to prepare to take action when at risk of flooding, even if a temporary barrier is in place.
"There are a number of things you can do to prepare for flooding to keep yourself and your family safe. Find out if your home is at risk, sign-up for flood warnings and be ready to take action."
“People should remain vigilant, check their flood-risk and plan to stay safe. We urge people to stay away from swollen rivers and not to walk or drive through flood water as just 30cm/12ins of flowing water is enough to move your car.”
If you’re on Twitter, follow updates on flood-risk on the Environment Agency’s South East and national accounts, @EnvAgencySE and @EnvAgency