and when those who bore the ark were come to the Jordan, and the feet of the priests who bore the ark were dipped in the brink of the water (for the Jordan overflows all its banks all the time of harvest),
The waters standing up in a heap is, of course, exactly what waters always do behind a dam, and, since this miraculous stoppage took place miles above where the Israelites were, they might not have known exactly where the waters were gathered together in a heap until some time later. Joshua's knowledge of this came in advance from a direct revelation of God. Significantly, the place identified as Adam is the precise location of the tallest of those great mud cliffs that line the banks of the Jordan.