Thanks esshup.

After I posted, I realized I could make the size of the passage somewhat "adjustable". I should put in a larger culvert and then use stop boards to alter the size and flow as needed. I have some pieces of 18" plastic double-wall culvert that should work just fine. I think blocking the top 50% would be a good size to start experimenting.


I still don't understand why fish swim upstream during floods or even moderately rising creek levels? Google returns me articles on why salmon swim upstream (which we all understand).

If I was a fish and the waters in my home started to diminish, I think I would swim downstream to find more water. But fish are certainly much smarter on fish behaviors than I am.

If anyone knows the reason, or wants to speculate, I would still like to read it.