Lower Savannah River Valley: Estill to Hilton Head Island is a 97 mile point-to-point trail located near Estill, SC. The trail is primarily used for scenic driving.
Like Tom said, the terrain makes a dramatic change. The vegetation does too.
We followed the river by car and got to see it several times.
Have driven many times from Augusta to Hilton Head using 321. It is a long drive, but if you are interested enough to notice, the terrain is completely flat from HH to Estil. Suddenly just north of Estil, the terrain gets noticeably more hilly. This continues until Augusta, where the fault line creates some bluffs and hills which you can see along the river.