Possible Clues:

• 'Sounds as if the top knot stops the flow (4,4)'
• Flood cause
• The flood finished in a knot up there, by the sound of it
• The water, by the sound of it, is not tied down
• How the 19 across may get knotted up, by the sound of it
• It's right in and knotted, by the sound of it, up there
• When the foreshore is covered
• Got in a knot, by the sound of it, up there with water in
• Sounds not at the top but it's full in
• Time between flood and ebb