Interesting, so it depends greatly on what was built here and where....that only requires approval by the Army if whatever is built impacts course, location, condition, or physical capacity of the water. Obviously, a fence wouldn't change the course, location or physical capacity of the river, the question would be does it change the "condition" and what "condition" means. Geez, I never got permission from them when I built a dock at the lake house....Have a ball.
Essentially it boils down to navigatable waters.
Complaint – #1 in United States v. Abbott (W.D. Tex., 1:23-cv-00853) – CourtListener.com
COMPLAINT (Filing fee $ 402.), filed by UNITED STATES OF AMERICA. (Attachments: # 1 Exhibit U.S Army Corps of Engineers Navigable Waters List, # 2 Exhibit U.S. Coast Guard Navigability Determination, # 3 Exhibit U.S. Coast Guard Authentication Declaration, # 4 Exhibit U.S. Customs and Border...www.courtlistener.com