P.S.
My reading tells me that if you have a slope above your bed, and water runs down that slope and into your problem area, a good place to trench is ABOVE the bed.
Find an angle that will "Intercept" water running down that slope.
When water runs into the trench, the slope and angle of the trench WILL keep water going DOWN, since gravity insists on that. But if the angle is right, the water will also be guided at an angle instead of straight downhill. That angle should move it "sideways" towards some low spot OTHER THAN the spot where you hope to grow. (Also aim it AWAY from your house's foundation.)
If you divert the water off your property, consider whether the neighbor that receives it is related to lawyers. And some locations have draconian laws against seriously altering the flow of rain runoff - why, I'm not sure.
I usually trench BELOW my bed, to give water IN the bed an escape route.
But it is also smart to keep "uphill water" from ever reaching your bed.
