The once a week idea would be nice but it takes a lot of moving water to move gold,
Only after spring run off will you get anything more than silt, fish poo, and leaves.
Unless you shovel dirt over it, but at that point your just sluicing.
A trap will only semi work, your just making a false bedrock and hoping for the best. you cant control water speed, material feed etc, so you may lose more gold than recover.
most guys I have talked to said it washed away after spring run off as it was not bogged down enough. Or people stole them or vandalized it.
If you do this, and you want to get a good amount of gold, it will have to be staked down hard. Tied and marked so you can find it again.
Also, figure on doing a lot of digging to recover it. The only streams that are really worth reprospecting are the ones whos courses change a bit every year, If you reconize the same spot year after year. no new gold is accumulating. dont waste your time. most streams in the US are so controlled anymore you dont get much movement of sand and dirt expect in the mid channel. In most cases, its better off to just work the same gold traps in bedrock each year rather than to fleece it. the guys who are doing the culverts have the right Idea. get what you can out of the traps that are already there, either natural, or man made. Much more productive.