Joshua 3:13, 15-17 (RSV) And when the soles of the feet of the priests who bear the ark of the LORD, the Lord of all the earth, shall rest in the waters of the Jordan, the waters of the Jordan shall be stopped from flowing, and the waters coming down from above shall stand in one heap.” . . .  and when those who bore the ark had come to the Jordan, and the feet of the priests bearing the ark were dipped in the brink of the water (the Jordan overflows all its banks throughout the time of harvest),  the waters coming down from above stood and rose up in a heap far off, at Adam, the city that is beside Zar’ethan, and those flowing down toward the sea of the Arabah, the Salt Sea, were wholly cut off; and the people passed over opposite Jericho.  And while all Israel were passing over on dry ground, the priests who bore the ark of the covenant of the LORD stood on dry ground in the midst of the Jordan, until all the nation finished passing over the Jordan.
Joshua 4:18, 23 And when the priests bearing the ark of the covenant of the LORD came up from the midst of the Jordan, and the soles of the priests’ feet were lifted up on dry ground, the waters of the Jordan returned to their place and overflowed all its banks, as before.. . .  For the LORD your God dried up the waters of the Jordan for you until you passed over, as the LORD your God did to the Red Sea, which he dried up for us until we passed over,
The Scottish evangelical Protestant Egyptologist and archaeologist Kenneth A. Kitchen (b. 1932), is author of the magisterial On the Reliability of the Old Testament (Grand Rapids and Cambridge: William B. Eerdmans Publishing Company, 2003). He wrote in this book:
[T]he river’s flow stopped, leaving a dry crossing, as the waters had piled up at a town named Adam near Zarethan (3:16). . . . This phenomenon directly reflects known reality, and is not fantasy. Some sixteen miles north of a crossing opposite Jericho, Adam is present-day Tell ed-Damieh. It is specifically in this district that the high banks of the Jordan have been liable to periodic collapses, sufficient to block the river for a time. Thus in December A.D. 1267 a high mound by the rover collapsed into it, stopping its flow completely for sixteen hours. In 1906 a similar event occurred, and then during the earthquake in 1927. That time the west bank collapsed, taking the road with it, while just below this a 150-foot section of riverside cliff fell across the river, damming it completely for twenty-one hours. Such an event in antiquity would have readily facilitated the crossing by the early Israelites. (p. 167; for further documentation of these three events, see J. Garstang, Joshua Judges [London: Constable, 1931], 126, 136-138)
The Israel Tours web page, “Earthquakes in History and Archaeology” observed in agreement: “Historically known quakes have dammed the Jordan River repeatedly, sometimes for several days, in 1160CE, 1267, 1534, 1834, 1906 and 1927.”
Robert M. Bowman, Jr. comments on this naturalistic explanation:
By the way, the fact that the river was stopped by an earthquake and mudslide does not in any way undermine the Bible’s giving God the credit for it. There is nothing wrong with thinking that at least some of the Old Testament wonders may have involved natural processes over which the Lord exercised dramatic sovereign control. Mudslides damming the Jordan did not happen every day; from what we can tell such an event happens there on average once every couple of centuries or so. Yet the river was stopped at just the right time for the Israelites to cross over into the Promised Land and march on Jericho. Ironically, by using such natural processes to bring about some of his dramatic provisions for the people of Israel, God left behind “clues” to the veracity of the biblical accounts that we can examine and verify millennia later.
Photo credit: Joshua passing the River Jordan with the Ark of the Covenant (1800), by Benjamin West (1738-1820) [public domain / Wikimedia Commons]
Summary: At least six known times in history (1160, 1267, 1534, 1834, 1906, and 1927), the parting of the Jordan River (or obstruction of its flow) occurred, on the basis of entirely natural causes.