The River Sidon had two forks which ran along each side of the City of Zarahemla:
East
And now it came to pass that when Alma had made these regulations he departed from them yea from the church which was in the city of ZARAHEMLA and went over upon the EAST of the RIVER SIDON into the valley of Gideon (Alma 6:7)
West
And now it came to pass that Alma…returned to his own house at ZARAHEMLA…Alma departed from thence and took his journey over into the land of Melek on the WEST of the RIVER SIDON (Alma 8:1,3)
This fact excludes 99.9% of all Book of Mormon geography models so far. If a model does not have a river with two forks on either side of the City fo Zarahemla, it’s not true Book of Mormon lands.
In the following account, you will notice that it doesn’t make sense unless there were two branches of the River Sidon:
15 And it came to pass that the Amlicites came upon the hill Amnihu, which was east of the river Sidon, which ran by the land of Zarahemla, and there they began to make war with the Nephites.
16 Now Alma, being the chief judge and the governor of the people of Nephi, therefore he went up with his people, yea, with his captains, and chief captains, yea, at the head of his armies, against the Amlicites to battle.
17 And they began to slay the Amlicites upon the hill east of Sidon. And the Amlicites did contend with the Nephites with great strength, insomuch that many of the Nephites did fall before the Amlicites.
18 Nevertheless the Lord did strengthen the hand of the Nephites, that they slew the Amlicites with great slaughter, that they began to flee before them.
19 And it came to pass that the Nephites did pursue the Amlicites all that day, and did slay them with much slaughter, insomuch that there were slain of the Amlicites twelve thousand five hundred thirty and two souls; and there were slain of the Nephites six thousand five hundred sixty and two souls.
20 And it came to pass that when Alma could pursue the Amlicites no longer he caused that his people should pitch their tents in the valley of Gideon, the valley being called after that Gideon who was slain by the hand of Nehor with the sword; and in this valley the Nephites did pitch their tents for the night. (Alma 2)7 And now it came to pass that when Alma had made these regulations he departed from them, yea, from the church which was in the city of Zarahemla, and went over upon the east of the river Sidon, into the valley of Gideon, there having been a city built, which was called the city of Gideon, which was in the valley that was called Gideon, being called after the man who was slain by the hand of Nehor with the sword. (Alma 6)
21 And Alma sent spies to follow the remnant of the Amlicites, that he might know of their plans and their plots, whereby he might guard himself against them, that he might preserve his people from being destroyed.
22 Now those whom he had sent out to watch the camp of the Amlicites were called Zeram, and Amnor, and Manti, and Limher; these were they who went out with their men to watch the camp of the Amlicites.
23 And it came to pass that on the morrow they returned into the camp of the Nephites in great haste, being greatly astonished, and struck with much fear, saying:
24 Behold, we followed the camp of the Amlicites, and to our great astonishment, in the land of Minon, above the land of Zarahemla, in the course of the land of Nephi, we saw a numerous host of the Lamanites; and behold, the Amlicites have joined them;
25 And they are upon our brethren in that land; and they are fleeing before them with their flocks, and their wives, and their children, towards our city; and except we make haste they obtain possession of our city, and our fathers, and our wives, and our children be slain.
26 And it came to pass that the people of Nephi took their tents, and departed out of the valley of Gideon towards their city, which was the city of Zarahemla.
27 And behold, as they were crossing the river Sidon, the Lamanites and the Amlicites, being as numerous almost, as it were, as the sands of the sea, came upon them to destroy them.
28 Nevertheless, the Nephites being strengthened by the hand of the Lord, having prayed mightily to him that he would deliver them out of the hands of their enemies, therefore the Lord did hear their cries, and did strengthen them, and the Lamanites and the Amlicites did fall before them.
29 And it came to pass that Alma fought with Amlici with the sword, face to face; and they did contend mightily, one with another.
30 And it came to pass that Alma, being a man of God, being exercised with much faith, cried, saying: O Lord, have mercy and spare my life, that I may be an instrument in thy hands to save and preserve this people.
31 Now when Alma had said these words he contended again with Amlici; and he was strengthened, insomuch that he slew Amlici with the sword.
32 And he also contended with the king of the Lamanites; but the king of the Lamanites fled back from before Alma and sent his guards to contend with Alma.
33 But Alma, with his guards, contended with the guards of the king of the Lamanites until he slew and drove them back.
34 And thus he cleared the ground, or rather the bank, which was on the west of the river Sidon, throwing the bodies of the Lamanites who had been slain into the waters of Sidon, that thereby his people might have room to cross and contend with the Lamanites and the Amlicites on the west side of the river Sidon.
35 And it came to pass that when they had all crossed the river Sidon that the Lamanites and the Amlicites began to flee before them, notwithstanding they were so numerous that they could not be numbered.
36 And they fled before the Nephites towards the wilderness which was west and north, away beyond the borders of the land; and the Nephites did pursue them with their might, and did slay them.
37 Yea, they were met on every hand, and slain and driven, until they were scattered on the west, and on the north, until they had reached the wilderness, which was called Hermounts; and it was that part of the wilderness which was infested by wild and ravenous beasts. (Alma 2)
Summation
The Hill Amnihu was on the east. The Valley of Gideon was on the east. Yet somehow, the enemy got around to the west. If there were only one river, that would have meant they were already on the city side of the river. But they were not. The reason they were contending at the river was that they were on the west side of the west fork of the River Sidon.