It comes as the Met Office has issued a yellow weather warning for both rain and wind in the region.
The Environment Agency has warned of flooding for Mansbridge and Riverside Park, with water levels in the River Itchen increasing.
This comes after after 35mm of rainfall was recorded in the last 24 hours in Otterbourne – the equivalent of half a month’s rain.
Lane restrictions are also in place on Westquay Road, outbound to Mountbatten Way, due to flooding.
As much as 30mm of rain are expected today with the Environment Agency also issuing a flood alert for Monks Brook in Eastleigh.
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In a statement, a spokesperson for the Environment Agency said: “Flows in the Lower River Itchen at Mansbridge are high and increasing. In the last 24 hours, 35mm of rain has been recorded at Otterbourne, which is almost half a month’s rain.
“It is currently high tide at Southampton, which is preventing the river from flowing to the sea.
“This may cause the river to flood the access road and affect the car park near to the White Swan Pub at Mansbridge. Footpath flooding may also affect Riverside Park.
“Storm Bert brings further rainfall with at least another 20-30mm expected. Water levels in the river will remain much higher than normal until at least Tuesday, November 26.”
The spokesperson added: “The water level in the Monks Brook is high and rising.
“The river may rise to bankfull and will be deep and fast flowing. The recreational ground at Fleming Park may flood, and the river will be high at Kingfisher Road.”
The flood alerts coincide with flooding that’s already affected Southampton city centre.
