Shhhhh, people might be reading this!
By "dry", you mean low and not intermittent I'm assuming? We simply make our structures a bit higher than we would for flows below seasonal average. I just had to do that on the Black River where 20 cfs is the norm for the time we worked, but we had flows as low as 6.8 cfs. I had to guesstimate elevations, and you get good at it over time. We do the opposite when working in high flows. We did get rain the one night and the river bumped up to 38 cfs and dropped to 25 later the next day as we were working, but the structures we had already built upstream looked great with normal (seasonal norm, that is) flows.
The DEP does have us digging a temporary bypass channel on river left through that one point bar so we can work "in the dry" for a day and a half. So dumb. But that's NJ DEP under this Governor and DEP Commissioner. Completely inept permit reviewers now fully in charge, and not one of them has field experience.
What is weird to me is that the current DEP Commissioner who is in his final months in the job decided over the last 12-18 months to reinvent the entire permit review process. And reinvent he did as it is now far more time consuming, far costlier, and far slower than it had ever been. NJ went from the easiest state to work in of the 7 states we do river restoration in currently to the worst.
