Kurt, you might contact your local NRCS agent. In my case he came out and laid out our pond and also laid out a terrace to capture water adding to my watershed area. My pond, like yours, is located close enough to the top of a hill it also has limited runoff. The terrace about doubles the runoff area.
In the picture below the sheds tend to be at about the top of the hill. So everything to the right of the picture the water flows down to the terrace and the terrace enters the pond towards the bottom of the picture just below the south most shed.
Even though your project might be much smaller, the NRCS agent could determine and lay out a lot for you if he will. Save you some experimenting time.
Also here is a thread about my sediment pond recently built. You might need something more like what I call my pre-sediment pond towards the end of the thread.
snrub's sediment pond direct link to pre-sediment pond Water from the field terrace enters the pre-sediment pond via the double culverts in the picture where a farm road goes over the tops of the culverts.
