I lived on the northern end a few blocks from Lock and Dam number 1. You'll find the Mississippi has several distinct sections. You'll find navigable waters north to downtown Minneapolis after that it's more for canoes for about 250 miles. From the Twin Cities south to the junction with the Ohio
River (in Iowa) there is a system of lock and dams that help maintain a 9 ft channel. So draft
won't be an issue at any time but there is a channel to observe some places more than others. I would say that section would be considered the only section that is scenic but it is very scenic any time of the year. Lots of birds and animals
and scenery of high bluffs and thick trees. South of the Ohio
the river widens a great deal and the topography flattens. The scenery drops to almost nothing though some towns along the route
would prove interesting. Personally, I would suggest the Ten Tom Waterway:
Tennessee-Tombigbee Waterway Maps Page
for the lower section of your trip. There is more scenery and I think from the water
is a better trip.
really is not a problem any time of the year but debris is. Spring time brings lots of debris from the winter snows. Whole floating trees can be in your path. Currents are only a problem in a few spots where the river is at the narrowest points that are very short sections. A 6 knot
current in spring would be common in the worst places. When the river widens the current slows but in flood stages you will have a LOT of debris and I would worry more about that in early spring. The fine soils of the upper Midwest erode easily and so the water is dark and many trees are washed down.
There is commercial
traffic in the whole river. Except during winter in the northern most sections in MN/IA traffic runs all year long. You would plan a trip down that would leave no later than early November from MN/IA. Maybe early October as it will freeze in November and snow storms can hit any time in November but generally don't. Fall color on the northern end begins early October and proceeds on down.
When dealing with locks no recreational traffic is permitted inside the lock with commercial
traffic - period. A commercial boat has priority over any recreational traffic always. They generally open on demand though some times there may be a schedule when busy with recreational traffic. You always hail the lock when you are nearing. Bridges open on demand most of the time but you would want to check.
from the Army Corps of Engineers as they manage all the inland rivers as well as all the locks.