But Commander Selfridge was a vocal proponent of a "lighting strick" of Gunboats to run the hazzards of the Arkansas River to get at the Ponchartrain. This even included the running past the fortifications and Guns at Fort Pleasent. He even went so far as to get regular reports from Fort Smith about the water levels on the upper Arkansas R. so as to plan his assualt. he knew when the waters would be high enough for him to get over the shoals and when there wouldn't be enough. So this intel would have given him the information he needed to make such a strick. So for this reason I discount the Shoals on the lower Arkansas as being any real obstuction for any serious military operations.

NOW this is not to say tha Selfridge didn't have a little bit of self interest in proposing this raid. First of all he wanted to get back into the "Game". He had commanded the USS Cairo when it was sunk and he did not like being assigned to the Timberclad USS Constoga and being assigned to the mundain duty of patroling the mouth of the Arkansas and White R. He seem to figure that If the CSS Ponchartrain was destroyed while it was at Little Rock there would be no need to guard the Arkansas River to keep her from breaking out into the Mississippi and playing havoc with Grants supply boats. Which was why he and the USS/CSS General Bragg and the USS Rattler were there.

The Ponchartrain was even less likely to break out into the Mississippi than it was for the Union Ironclads to go up the Arkansas. The Ponchratrin drew 10 or 11 feet of Water because of her construction design had it engines and boilers placed below the main deck waterline. While the Union City Class Ironclads engines and boilers were constructed on the main decks and those ships only drew 6 to 7 feet of water.

6 to 7 Feet was indeed too deep for the lower Arkansas in low water to be sure. But not if you had knowledge of higher waters coming downstream.