I poked around some Civil War maps, and found a skirmish named the Battle of Dranesville occurred around 2 miles south of this spot.
This was after Ball’s Bluff, and both armies were set in for winter...and essentially competing foraging parties ran into each other. Result: 300 casualties. And (I find these types of tid bits interesting) it was the first time in the eastern theater that the Union won.
So we have Ball’s Bluff 11 miles northwest of the Trump site, and Dranesville 2 miles south of the Trump site. Its not unreasonable to believe that some of the wounded may have indeed ended up on this river bank...perhaps to be evacuated, or just to drink water. Its also not unreasonable to believe that local lore includes stories of blood in the river.
This is the coordinate of the battle:
39.0006130, -77.3451880
When placed in Google Maps, just pan a little north, and there’s Lowes Island.
That whole section of the Potomac was the site of all sorts of skirmishing. It’s going to be hard to find a point where shots _weren’t_ fired ...