Flooding can affect mental health for years after the event, the Environment Agency warns.
Victims of extreme weather have a 50% greater chance of suffering issues such as PTSD, stress and depression.
A quarter still suffer such issues two years on, research found.
Low-income households are eight times as likely to live in tidal floodplains.Yet 61% of low-income tenants have no home contents insurance – risking a huge financial shock if floods hit.
Speaking during its Flood Action Week, the Environment Agency urged householders to “prepare, act, survive” – sign up for flood alerts, move valuables upstairs and keep a grab bag of vital medicines and documents.
Pam Webb, whose home and spa business in Fishlake, South Yorks, were badly damaged in last November’s floods there, had underestimated the mental impact it could have.
She said: “Doncaster Council suggested getting in mental health teams after the floods and I thought that was over the top – but how wrong I was.
"I’ve had the stress of trying to build a business back up, to provide income for my staff and to recover my home.
"But I was one of the fortunate ones – so many are still displaced from their homes.”
Flood resilience campaigner Mary Dhonau, 58, of Worcester, has been hit by at least 12 floods, including one that filled her family home with waist-high sewage.
She said: “Living through a flood is the most appalling experience and compounds issues you are already dealing with.
"Every time it rains hard your heart rate goes up. When you lose your home that layer of safety is taken away from you.”
Caroline Douglass of the Environment Agency said:“It’s not just the financial stress, it’s the loss of irreplaceable sentimental belongings and the strain on those affected.
“We are already seeing more frequent and intense flooding as a result of climate change, so we would urge everyone to know the simple steps to take to help reduce the damage and keep yourself and your family safe.”