River Stage Reference Frame	Gauge Height	Flood Stage	Uses
NWS stage	0 ft	0 ft	Interpreting hydrographs and NWS watch, warnings, and forecasts, and inundation maps
Vertical Datum	Elevation (gauge height = 0)	Elevation (gauge height = flood stage)	Elevation information source
NAVD88	N/A	N/A	Survey grade GPS equipment, FEMA flood plain maps, newer USGS topographic maps
NGVD 29	N/A	N/A	Older USGS topographic maps, NGVD29 benchmarks
MSL	N/A	N/A	Older USGS topographic maps, MSL benchmarks
Other	1390	N/A

Other Data Sources: U.S. Geological Survey (USGS) Data and Site Info for Madras