Staff gauge
From Glossary of Meteorology
staff gauge
A graduated scale placed in a position so that the stage of a stream may be read directly therefrom; a type of river gauge.
Staff gauges may be painted on bridge piers and pilings, and painted wooden scales or enameled metal scales may be mounted on bridge piers, docks, trees, or specially constructed supports to be partially submerged by the stream at all times.
