What is "pierhead line"

n. (context US English) A line in a navigable waterway established by the http://en.wikipedia.org/wiki/Army%20Corps%20of%20Engineers, beyond which a pier cannot project.

A pierhead line is, in essence, a legal boundary beyond which artificial structures (such as piers) may not be built into navigable waters. ( New Jersey v. Delaware (2008) 552 U.S. 597, 642 [128 S.Ct. 1410, 1438, 170 L.Ed.2d 315, 345].) As part of the Rivers and Harbors Act of 1899, the United States may fix pierhead and bulkhead lines as part of its supreme powers to regulate navigable waters. (33 U.S.C.S. § 400, et. seq.) Many states have also established their own pierhead or bulkhead lines at various locations.,