Because of the persistent flooding of the Tennessee River, and the expanse of water-logged terrain in vicinity of Union-controlled Fort Henry, that position was deemed unsuitable for loading significant numbers of troops. So, when the time arrived for the thousands of Federal troops camped in vicinity of Union-held Fort Donelson to "march to the Tennessee River and board steamers for the Expedition" (ultimately destined for Pittsburg Landing), those troops were not marched to Fort Henry; instead, they took the Ridge Road until three miles west of the Furnace, turned left, and continued southwest to Metal Landing (a point on the Tennessee River about three miles south of Fort Henry.) The first Federal troops to reach Metal Landing belonged to Brigadier General McClernand, arrived about March 4th. As steamers arrived, they were loaded, then joined the convoy led by Brigadier General Sherman's new division (dispatched from Paducah, and protected by a timberclad gunboat.) To expedite loading of soldiers at Metal Landing, Colonel Jacob Lauman was sent on detached duty from the Second Division, to act as Transport Organizer (Lauman was in place by March 10th.) And on March 13th, with the Federal troops mostly departed, Metal Landing was deemed suitable for holding Army livestock: pens were ordered constructed that could hold 1000 head of cattle. Metal Landing remained in use through the build-up of forces at Pittsburg Landing.
References: Papers of US Grant volume 4, pages 312, 322, 323, 342, 351 and 356.
[Map showing Metal Landing south of Fort Henry, from Papers of US Grant, volume 4.]