Sunday afternoon's meeting at Plumpton has been called off after the third race following rain on the track.
The course had passed an inspection shortly before racing, but a decision was taken to abandon the rest of the card after a second check.
Jockey Andrew Thornton told At The Races: "We're all for racing, but unfortunately the water is as much as a foot deep in places.
"It's getting worse and the rain doesn't look like stopping."
Nicky Henderson-trained L'Ami Serge had earlier galloped through the desperately wet conditions on his debut over fences to win the At The Races App On iPhone Novices' Chase by 27 lengths from Doctor Harper.