Here's my transcription from the two recordings mentioned above. There's a third version online by a Biddy Rhodes who was taught it by Ruth Tongue when she was a girl. It's used as the background to a video and is only partial, though the clearest recording: Shadowlands Project at Halsway Manor - just over halfway down the page Shadow animation test for Walford's Gibbet.

I'll try and put the tune up, but it might be a few days.

Mick

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SEVERN NO MORE
(Ruth Tongue)

As I walked out by Severn side,
A brown-rigged craft came up/down the tide.

  Chorus:
  Singing, "Farewell, shore
  It's Severn no more.
  No more."
  Singing, "Farewell, shore,
  It's Severn no more"


Now/O Severn she's/is wide as the eye can scan
And/But she wrecks them under both craft and man.

There's none can ride her mighty bore
Where/When she do rise with a terrible roar


O Severn do shine and she lies still
And all come home both safe and well

  Final Chorus:
  Singing "Welcome, shore,
  It's Severn no more.
  No more",
  Singing "Welcome, shore,
  It's Severn no more"


Source: Meg Rose and Ruth Tongue

There are some slight differences in wording in the two versions. Those to left of / are Meg Rose, those to the right Ruth Tongue.

Ruth Tongue's own chorus is slightly different (and is as the first version I posted originally):
  Singing, "Farewell, shore
  It's Severn no more.
  No more. No more"

and similarly for the final Welcome shore chorus