Rain is threatening to wreck Sunday's racing with Towcester already abandoned and Exeter's card subject to an inspection.
The adjacent River Tove has burst its banks following heavy overnight rain at the Northamptonshire circuit and left standing water along the bottom of the track.
Towcester clerk of the course Robert Bellamy said: "I've been in office here six years and have never seen the River Tove as deep as this before.
"It's starting to recede now, but every forecast you look at indicates there is another band of heavy rain coming tomorrow. We were left with little option but to abandon now."
Meanwhile, Exeter have delayed a planned inspection by 24 hours with more heavy rain forecast in Devon on Saturday.
Exeter clerk of the course Barry Johnson said: "We'd be fine tomorrow, so it's pointless inspecting on Saturday morning.
"We are worried about a band of rain later on Saturday - we could see 40mm - but, at this moment in time, I'd be quietly confident we'd be OK. The course is taking the rain fantastically well."
Navan are also planning to inspect at 3pm on Saturday ahead of their National Hunt meeting on Sunday.