I am modeling runoff from some tilled farm fields and am looking for a typical value (or range) for the overland flow Mannings n. I reviewed Table 5-13 in the CHI handbooks for Hydrology that list some values from Engman (1986), but none of them say tilled farm fields. I was wondering if anyone has any experience or other references that may be helpful or some updated values.

Thanks,

Roger Leventhal, P.E.
FarWestEng@AOL.COM