A hydrograph shows how the river level changes over time at a specific location. Forecast hydrographs are displayed when flooding is expected, otherwise the hydrograph for the past few days is provided, if the data are available. At key river gages, such as along navigable rivers, daily forecast hydrographs are provided, whether or not flooding is anticipated. For some locations, probabilistic outlooks for extended periods of up to 90 days are provided.
In cold regions, the hydrograph may seasonally show the effects of the formation of an ice cover. Gauges may either malfunction due to cold weather and/or show sporadic readings due to formation of ice cover on a river or movement of ice. The amount of ice effects can be determined at a site by comparing the gauge forecasts (which is based on open water flow) to the observed stages.
Links to past and forecast precipitation, river level impact and historical flood information are also included on this page.
The following terminology is used when describing floods:
The term Minor Flooding is used to indicate minimal or no property damage. However, some public inconvenience is possible.
The term Moderate Flooding is used to indicate the inundation of secondary roads. Transfer to higher elevation may be necessary to save property. Some evacuation may be required.
The term Major Flooding is used to indicate extensive inundation and property damage, usually characterized by the evacuation of people and livestock, and the closure of both primary and secondary roads.