Our setup has to be tilted to one side so that water will drain off... Otherwise it will trap water.
The first time we used ours we didnt put much of slope on and couldn't even open the trailer door after it rained all night... Had to find something to push up on the canopy to drain off some of the water...
One end of our awning is maybe four to fives inches lower that the other side..
I am amazed how strong the canopy material holds up when it fills up with water. Who knows how many gallons of water that is captured...
My setup is manual but I think I have read the electric ones allows to you use them both ways...
I'm pretty sure this setup on my trailer would most likely capture some rain water. One end needs to be dropped more...
This setup as shown on GOOGLE IMAGES might be a bit too much slope or tilt for me... You really need to experiment alttle to see what would would be best for you...
Roy Ken