Shorty many times in high water events BG and LMB go to cover to avoid the current. I would say that as a % of total BG that size a very small % went out. So what does that mean. If that many went out then there must be many times that still there. Further if you saw that big of an increase in 2-3in BG #s due to LMB removal last year then what will you see this year. Those LMB are gone and the BG that produced those #s are still there minus any natural morts.

Our outflow pipe on one pond is IIRC 48in. (big enough for me to easily climb down to the bottom on the ladder welded inside). I have watched from a boat as that pipe head went 2 ft underwater. The 3in BG could easily escape the flow as long as they stayed about 10 ft from the intake. Fifty yards from the pipe intake there was no current effect on the fish at all. All this is said to help you not to worry. The only time I have seen high water effect fish #s in a pond are when an emergency spillway event occurs ( water going out via a 30 ft wide and 3 feet deep spillway). Even then only a small % of the fish were effected.

I would still go salvage what I could .