some really bummer erosion

This is less than 20 yards behind my current garden. Water comes down a gravel tractor path, past my garden and down into the river bed, taking tons of soil and rocks along with it. It has also invited Japanese Knotweed to move in. Sadly, the property owner doesn't see this as much of a priority. For the 5 years that we've lived here, he's been saying that he is going to "fix" the bank, and every year a few more feet of the bank goes into the river.

Is there any way to slow the water down *before* your garden? If it never gets to that tractor path, it can't erode it.

Thank You Kindly.