|A control method for suppressing seed germination and seedling growth of willow after loweringterrestrialized floodplains of lowland rivers by land excavation was proposed on the basis of field surveysand document investigations: the germination and establishment of willow may be prevented byfacilitating early recovery of tall grasses. The field surveys (308 sites in seven rivers) indicated willowestablished in lower land level (i.e., land areas near river level) and the relative elevation was 0.54-1.06m (first and third quartiles). In addition, occurrence probability of willow increased with decrease in therelative elevation from river level. Also, previous studies showed that increasing plant density promptlyafter the lowering terrestrialized floodplains could be effective for the suppression of the establishmentand growth of willow. These findings demonstrated that the relative elevation and plant density wereimportant for the willow suppression.