[Animals] Waves of dead animals washing up in NSW.

[ʟᴜᴄɪ፝֟ꜰᴇʀ]

Everything from bandicoots to tiny turtle hatchlings have been washing up dead in NSW, with wildlife rescuers fearing po[CENSORED]tions already ravaged by prolonged drought and catastrophic bushfires will plummet further.

Large tracts of NSW went underwater in the past week as rivers filled by torrential rain broke their banks.

Tens of thousands of people were evacuated across the state, with Sydney's Hawkesbury-Nepean Valley and the mid-north coast the hardest hit.

As the waters recede, calls to help injured wildlife are flooding in.

"We're seeing kangaroo joeys coming in whose mums have drowned, wombats displaced and taking shelter under cars, possums with head injuries, very small hatchling turtles being washed up on beaches," International Fund for Animal Welfare (IFAW) spokeswoman Josey Sharrad told AAP.

"We're even getting reports of bull sharks attacking cattle in the floodwaters."

Orphaned animals are coming in hard and fast, as are many animals with hypothermia, shock, pneumonia and exhaustion.

"We won't really see the true impact for a few days (but) we anticipate there will be an influx of animals coming in," Ms Sharrad said.

Ground-running and burrowing animals like echidnas and wombats are particularly vulnerable, but tree-dwelling animals haven't been spared.

One mid north coast resident found a Eastern pygmy possum curled up in torpor - a coma-like state - in one of her pot plants.

That tiny critter, which weighs less than a golf ball and is declared vulnerable in NSW, is one of the luckier ones though, John Grant says.

It, and many of the animals that survived the floods, will recover without intervention.

"They really just need sorting out and drying off," the NSW Wildlife Information Rescue and Education Service (WIRES) spokesman told AAP.

"Some of them might need fluids, but most of them will come good of their own accord."

But with more animals out and about in search of new, drier habitats, WIRES has been receiving an influx of reports of car strikes.

Domestic pets are also an increased problem.

Anyone who spots wildlife that may be injured should leave it be and call their local rescue organisation.

Mr Grant is hopeful wildlife po[CENSORED]tions, particularly on the mid-north coast, won't be as drastically affected as during the bushfires.

"Animals that live in flood prone areas, almost know the drill, so to speak," he said.

"But there are situations where the native animals will go to higher ground and it'll be the one-in-100 year flood where the water just gets higher and higher so they become trapped."

But Ms Sharrad says there's only so many extreme weather events the po[CENSORED]tions in the area can take.

Action to protect and insure them against increasingly-frequent extreme weather is desperately needed.

"Three billion animals are estimated to have been impacted by the bushfires and they had no chance to recover before this," she said.

"They've just been reeling from disaster to disaster without any time to come up for air."