Joshua 3:14-4:7 ~ (New American Bible)
14 The people struck their tents to cross the Jordan, with the priests carrying the ark of the covenant ahead of them. 15 No sooner had these priestly bearers of the ark waded into the waters at the edge of the Jordan, which overflows all its banks during the entire season of the harvest, 16 than the waters flowing from upstream halted, backing up in a solid mass for a very great distance indeed, from Adam, a city in the direction of Zarethan; while those flowing downstream toward the Salt Sea of the Arabah disappeared entirely. Thus the people crossed over opposite Jericho. 17 While all Israel crossed over on dry ground, the priests carrying the ark of the covenant of the LORD remained motionless on dry ground in the bed of the Jordan until the whole nation had completed the passage.
1 After the entire nation had crossed the Jordan, 2 the LORD said to Joshua, "Choose twelve men from the people, one from each tribe, 3 and instruct them to take up twelve stones from this spot in the bed of the Jordan where the priests have been standing motionless. Carry them over with you, and place them where you are to stay tonight."
4 Summoning the twelve men whom he had selected from among the Israelites, one from each tribe, 5 Joshua said to them: "Go to the bed of the Jordan in front of the ark of the LORD, your God; lift to your shoulders one stone apiece, so that they will equal in number the tribes of the Israelites. 6 In the future, these are to be a sign among you. When your children ask you what these stones mean to you, 7 you shall answer them, 'The waters of the Jordan ceased to flow before the ark of the covenant of the LORD when it crossed the Jordan.' Thus these stones are to serve as a perpetual memorial to the Israelites."
It was an instant miracle, the Jordan parted like the Red Sea. Only it wasn't so sudden, one generation of Israel had passed away, the Lord waited 40 years for the Ark to pass through the Jordan River. In the Lord's time and to serve His purpose, miracles occur. The Lord expects His people to be a holy people.
When God's time was right:
Jeremiah 29:11 ~ (English Standard Version)
For I know the plans I have for you, declares the LORD, plans for welfare and not for evil, to give you a future and a hope.
Scripture for Today Blogspot included an article interviewing Archaeologist Dr. James Pritchard, University of Pennsylvania, about the archaeology discovery of this biblical city, Zarethan. Please see - Joshua 3 ~ the waters rose in heap very far away