What advantages are there for the towns to support designation which requires Section 7 review for projects which are federally assisted, construction or development, water related, and have a direct relationship to the designated section of the rivers?

Towns already have to comply with NEPA (the National Environmental Policy Act) if federal projects proposed.  Having an Advisory Committee gives a venue for towns (through their official appointees to the Advisory Committee) to comment on projects.  Comments given by the Advisory Committee can give more weight in the federal arena to local views on a federal project.