Experts have been assessing the damage to wildlife and habitats, following the biggest tidal surge to hit the Norfolk and Suffolk coasts for 60 years.
The RSPB said nature reserves had been affected by the flood water in varying degrees.
There was significant damage at the Snettisham reserve in Norfolk, and the island of Havergate in Suffolk was now vulnerable to high tides.
Damage includes salt water flooding fresh water habitats.
Damage to RSPB reserves
RSPB Snettisham: Significant damage, now closed to the public
RSPB Titchwell: Damage to walkways and fresh water habitats, but no significant damage
RSPB Minsmere: Damage mainly to beach and sand dunes. Still some flood water on reserve
Dingle Marshes: Significant damage. Shingle sea banks breached. Reed beds inundated with sea water
RSPB Havergate: Whole of the island breached. The sea walls need repairs.
At Snettisham, access roads have been completely flooded and badly damaged.
The shingle bank was breached and the lagoons that wintering birds use are full of seawater.
Warden of the reserve Paul Eele, said: "We used to have four hides where people could watch the wading birds roosting.
"After Friday night, we've now only got one hide.