How will the federal government monitor and evaluate activities on private land?

Wild and scenic river status does not provide federal authority to regulate private lands. The river-administering agency will cooperate with state and local agencies to appropriately monitor and evaluate activities on private land. If such activities (existing or potential) threaten or are incompatible with the values that contributed to the river’s designation, then, to the extent necessary, mitigation will be accomplished in cooperation with landowners and federal, state and local agencies.

Source
Interagency Wild & Scenic Rivers Council