Hi Tony, Your and my shed both flood!. Yep it happens to mine in a very heavy downpour, Takes a couple of days but it happens.
Yes I have a small bunded area and do have a trap. Haven't used it yet, other than to pump water out of when shed floods.
I have been working on the diversion new contour bank and piping. Wills see what happens next time it rains.
Good news is that that I got that WVO from the small shop.
Annatex