Flooding
River Flood Stage Explained: Action Stage, Minor, Moderate, and Major Flooding
What river flood stages mean, how gauges are used, and why impacts depend on local terrain, roads, homes, and levees.
Quick answer: River flood stage is a gauge level where water begins to create defined local impacts, from nuisance flooding to major property or road flooding.
Gauge levels
Action stage means water is rising toward concern, while minor, moderate, and major flood categories reflect increasing impacts.
Each gauge has local thresholds based on nearby roads, buildings, farmland, and flood defenses.
Forecast timing
River flooding can crest hours or days after heavy rain, especially downstream from the storm area.
Snowmelt, ice jams, and reservoir operations can also affect timing.
Safety
Do not enter flooded roads, trails, or riverbanks.
Water can rise, undercut surfaces, or carry debris even after rain ends.