Brandi,
Hay or straw probably wouldn't work anyway with fast runoff water. I did that on a shallow swale I dug a few years ago to protect new grass seed. After 4 hours work of putting a nice layer of hay down a heavy thunderstorm 2 days later swept the hay away in a few minutes
and lodged most of it in a 2 foot culvert pipe under my lane. That created another 4 hours work cleaning out the culvert.
I guess that's where the expression, " Your just making more work for yourself" came from.
The swale did divert the water just as planned though.
I think your idea of a few small pine trees might help. Did you have to clear some trees for the new pond?
I am still a little confused after looking at a lot of your pictures as to where your new pond is located? It must be NW of your old pond and close to the white fence poles. The picture of the neighbor's house in the background in some pictures confuses me.
Could you take a picture of the new pond from the front of your barn sometime with your lens zoom set at 50 mm equivalent and post it?
That will give a more realistic depth distance.
Lot's of luck on the wash out.
Ron