Hey there! I'm happy to help!
The Fertile Crescent is basically where human civilization started. It stretches from Mesopotamia and across the Mediterranean coast to Egypt. Early civilizations depended on agriculture. To make agriculture, you need a river because it is a good water source to help grow your crops.
If you look at the map I have provided below, you will see that there are tons of rivers. This would make it very easy for settlers to grow crops. This means that sea tides and eroding mountains aren't the answer. I don't think the rivers were flooding and natural canals is an oxymoron because canals are artificial waterways, but this all should give you and idea.
Have a wonderful day! :D
