advice for swale off-contour

I'm designing a swale on a client's site located in Virginia's Appalachian foothills, and would appreciate any recommendations you all have from your experience. We want to channel water coming from a spring that travels around 50 ft. across grass (with about a 10 foot decrease in elevation) before hitting an old degraded pond (now dry). Average rainfall peaks at 3.83" in May and Sept. The spring enters into a dry creek bed that continues to the upper and low edge of the property. I would like to dig a swale that channels the water allowing for water loving plants to fill in densely on the sides. I've read it's best to cut the channel slightly off contour at a 1-3% drop rather than allow it to run straight down. Do you all have any more recommendations or online resources that could inform this design? thanks!

Good luck with the project.
You are correct a gentle slope is all thats required.
If the water speed gets above about 3 ft a second erosions starts.
With such a low rainfall, what is the purpose of shifting the water?
What volumes are you looking at?

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thank you! We're still in the process of observing the site during the rainy season, so I'm not sure exactly where we're at with volume. We want to channel and sink the water so it isn't getting this flat, lower point on the land soggy. We also want to utilize the space for water-loving plants by redirecting the water.

I know opinions differ on this, but I usually think of a swale as a tree-planting system, and it is dead level on contour. So what you're planning I would just call a ditch or a channel or a stream.

To avoid erosion completely (always a good idea), I would generally keep the fall of your channel to 2% max, and preferably closer to 1%. If it's heavily planted with water-loving plants with good root systems, you could maybe get away with a bit more, but only once those plants are established, so you'd have to devise a way to keep the flow gentle in the initial stages. Do you know what the maximum possible flow is out of that spring? Combined with a 100-year rain event for the area? (Like hurricane leftovers  blowing through after 3 weeks of solid rain, or some such thing.) That's what you want to plan for.

Meandering around the property gently like that it can do a lot of good. I'm sure there's a limit to how much digging you want to do though, so if you want to drop it down a few feet at a time, you might want to create some infrastructure. Maybe vetiver grass or something if you want to go all-natural.