Katrina and the Mighty Mississippi

According to Holland & Knight (an admiralty law firm) here

The U.S. Coast Guard issued an Update on the status of major waterways that were impacted by Hurricane Katrina. The Lower Mississippi River is open to deep-draft vessels from the sea buoy to mile marker 235 for vessels with drafts of 39 feet or less and for transits in daylight hours only. Vessels with drafts deeper than 39 feet may only enter with the permission of COTP New Orleans. The Gulf Intracoastal Waterway is open west of Harvey Lock, but remains closed east of Harvey Lock to mile marker 60. (9/5/05).

Explanation: Lower Mississippi

The Mississippi River is divided into three segments: the Headwaters, the Upper Mississippi River, and the Lower Mississippi River. The Headwaters is the reach from the source (Lake Itasca) downstream to St. Anthony Falls in Minneapolis, Minnesota, whereas the Upper Mississippi River extends from St. Anthony Falls downstream to the mouth of the Ohio River at Cairo, Illinois. The Lower Mississippi River flows from Cairo to Head-of-Passes in the Gulf of Mexico. The 314-kilometer segment of the Upper Mississippi River extending from the mouth of the Missouri River (near St. Louis, Missouri) to the mouth of the Ohio is often termed the Middle Mississippi River.

Location along the main channel of the river is denoted by river miles, starting with mile 0.0 at Head-of-Passes and proceeding 953.8 river miles upstream to the mouth of the Ohio River. Numbering of river miles starts at 0.0 again at the mouth of the Ohio and continues up the Mississippi to Lake Itasca (Fremling et al. 1989).(here)

The COTP is the Coast Guard officer in New Orleans who has the job of "Captain of the Port"

The COTP is designated by the Commandant to direct Coast Guard law enforcement activities within a designated area of responsibility. A Captain of the Port enforces regulations for the protection and security of vessels, harbors, and waterfront facilities; anchorages; bridges; safety and security zones; and ports and waterways.(source)