It works out to 0.11 Sverdrups, which is a bit over half the discharge of the Amazon, but greater than any other river, about seven times the discharge of the Mississippi or St. Lawrence.
The atmospheric flux must have been much higher.
SC area 83e3 km2 = 83 e9 m^2depth of flood = 0.25 m
total water = 20e9 m3
time = 2 days
10e9 m3 /day
= 115740 m3 / s