In 2021, the U.S. Geological Survey (USGS), in cooperation with the National Geological and Geophysical Data Preservation Program, cataloged and scanned notes and calculations for indirect measurements taken during flood events in Montana. This product provides a publicly available catalog of the field notes, photos, survey information, and calculations for indirect measurements at selected sites. Indirect measurements are surveyed by the USGS after floods by identifying high water marks along rivers indicating the maximum stream stage. These high water marks are used to estimate the peak discharge through standardized methods. Estimates of peak streamflow from the indirect estimates were were added to the National Water Information System. The estimates from the measurements can be used to calculate peak-flow frequencies, inform floodplain management, or add information to flood databases. Flood events are organized into child items by water year.