Will landowners be reimbursed for vandalism to their property associated with trespass?

No. Federal agencies do not have the authority to reimburse landowners for damage to their lands as a result of public use. However, wild and scenic river designation is unlikely to increase or invite vandalism. Granting access remains the owner’s responsibility and vandalism is handled by local law enforcement authorities. Federal river-administering agencies do, however, work closely with landowners to minimize problems through brochures and maps, signs, etc., and many landowners feel they are better off with the agency taking some responsibility.

Source
Interagency Wild & Scenic Rivers Council