Welcome to PondBoss!
That youtube video of the river in a flood stage is a eye opener, it will take a massive amount of free board and a massive overflow structure to handle that kind of water volume and speed, to the point of I'm not sure that's doable without some serious engineering expertise.
That may be able to be dammed up with an earthen dam but the overflow structure will have to be made of concrete or some other means, the speed and velocity of the water in the video will be multiple times faster and more erosive when its headed down the elevation of a 10m tall dam in the few meter distance to the toe of the dam.
Water is an extremely powerful force and will need to be handled as such.
It can be done but it will not be an easy or inexpensive task, damn failure is almost not an option, as it would take a vast amount of your dirt with it when it goes, making rebuilding a vastly more expensive project.
Good Luck! keep us posted and let us know how it goes, would love to see some pictures of the work being done as you are building it.
