note Alternately, drive a piece of pipe into the river bed and attach the staff guage. Easiest if you predrill the holes. Of
course, in either case installation has to be done at very low water. Same for painted gauges.

Sometimes, the highway department doesn't look kindly on people drilling holes in the concrete piers as it can introduce rust and cause the pier to deteriorate more quickly. Technically, you need permission before you can install anything on highway right-of-way.