Free-ranging Ducks on a stream?

We would like to get ducks and chickens at some point. We have a stream running through our back yard which we thought would be great for the ducks. We were originally thinking of keeping the chickens and ducks in the same coop (at least until we ever decided to get a rooster or a drake). However, I don't really want to entirely free-range my chickens and let them go wherever they want. We would more than likely use movable fencing for them. If we kept the ducks and the chickens together the ducks wouldn't have access to the stream. My question is, are ducks good free rangers, or would they be like chickens (who I've heard eat up gardens and poo pretty much all over the place)? If they're messy like chickens we might consider making them a coop closer to the stream and having part of the stream in their run. (Hope that all made sense).

Thoughts?

Also, picture of the stream:

Ducks will poop and wander like chickens. They damage a garden a little differently, trampling plants as opposed to scratching them out. Bottom line, both will love your garden to death if there are too many in too small of an area.

Ducks in the creek seems really idyllic, and would be if the density was low enough. However, ducks fenced in a small area with a creek will absolutely devastate the vegetation in the creek. Duck like to muck around, pulling every little plant out by its roots. They use their bills very effectively to dabble in the muddy shorlines, destroying all vegetation in time. Once when I had about 30 ducks in an area with about 100 feet of creek, they removed every scrap of growing plant from the creek bottom in a summer. Anywhere the ground was wet, whether in the creek or along its banks, was decimated by their dabbling. It took three years to recover.

Mixing ducks and chickens is totally fine, even with a rooster or a drake in the mix. Especially if you raise them together from youth, they should all get along great.

When you think Ducks think Mud Mud Mud Mud Mud Mud Mud Mud Mud Mud Mud Mud .............

They are wonderful things
I have 7 Docks and 40 Chickens
They all live happily together seperate sheds but the same pen overnight.
The Ducks if anything are better foragers than the Chickens they certainly go further
I have an acre of paddock and shrubs for them to explore

They also tend to work together as a team and act as a family.
Definitely get a Drake or two they look after their Ducks very well
I have two Drakes one the Runner is incredibly attentive. he also hate Pidgeons and chases them all day!

The comments above about damage are spot on my large pond is not the idyllic wild life pool it once was
A steam in rock or gravel might be ideal though - we are on clay so in the winter it is Mud Mud Mud Mud Mud Mud Mud Mud Mud Mud Mud Mud .............

My Geese do the least damage to my Garden and they are the only one allowed up on the main lawn and formal garden!

What are you planing on fencing them with? Or are you using any fencing? I have 5 muskovy ducklings that I want to run on a very over grown creek. So I don't care if they are able to eat everything up, but I don't think they will, besides I have a huge yard and several shallow ponds at the ready for pasture rotation. But I want to put them on this creek that I have. My yard on a map would look like a big squared b. The creek runs a long the spine of the "b" so there are neighbors, and they have dogs. I plan on having them with the chickens so whenever they are at the creek I will herd them back to the coop at night. I'm pretty sure this will work, I'm already working with them with just a long stick. I've seen this method work with geese, and I've heard muscovys are very much like geese. I am not a afraid to make my fencing hot.

Haha duck herder... I'm trying to be a duck herder... lol.