Since you are on waterfront property you should speak with your local Conservation District in Alcona as there can be legal issues related to shoreline changes. Janet Reins (firstname.lastname@example.org) is the District Manager. Additionally you have an organization called Huron Pines that deals with phragmites removal. I can't confirm that this is invasive phragmites from the pictures. I believe that Huron Pines does site visits and should be able to confirm if it is indeed invasive. I've also linked you to an informational page.