SITE TABLE OF CONTENTS
Flood Forecast Display Tool
The Flood Forecast Display Tool currently covers the Fargo-Moorhead area. There have been discussions to expand the extents of this tool in the future depending on available funding.
The FFDT consists of two main parts tailored to the two types of forecasts issued by the National Weather Service, the probabilistic and deterministic forecasts. For more information on the NWS forecasts click here.
Realtime Flood Forecast
This “widget” displays flood inundation maps for the 7 day deterministic flood forecast from the NWS for the Red River of the North at Fargo gage. The user can select play and view the flood forecast through time. The forecasts are displayed in the viewer in near realtime (as the forecasts are issued).
Peak Flood Inundation Layer
The Peak Flood Inundation layer displays the peak flooding from the 7 day deterministic forecast for the area along with the time of the peak flooding at specific locations along the river. The deterministic forecast for the Fargo gage can be found here.
Because deterministic forecasts are issued as needed during times of high water, and are not routinely available, this part of the tool will only have data when a deterministic forecast is issued.
Static Flood Inundation Maps
This “widget” displays flood inundation maps for various flood stages of the Red River of the North at Fargo gage. These inundation maps have been created in advance allowing users to select what a particular flood stage will look like. This information is best used in conjunction with the probabilistic, or long term, forecasts from the NWS. The two parts of the probabilistic forecast for the Fargo gage can be found here and here.
Uncertainties and Limitations for Use of Flood-Inundation Maps (language provided by USGS)
Although the flood-inundation maps represent the boundaries of inundated areas with a distinct line, some uncertainty is associated with these maps. The flood boundaries shown were estimated based on water stages (water-surface elevations) and streamflows at selected USGS streamgages. Water-surface elevations along the stream reaches were estimated by steady-state hydraulic modeling, assuming unobstructed flow, and using streamflows and hydrologic conditions anticipated at the USGS streamgage(s). Unique meteorological factors (timing and distribution of precipitation) may cause actual streamflows along the modeled reach to vary from those assumed during a flood, which may lead to deviations in the water-surface elevations and inundation boundaries shown. Additional areas may be flooded due to unanticipated conditions such as: changes in the streambed elevation or roughness, backwater into major tributaries along a main stem river, or backwater from localized debris or ice jams.
The accuracy of the floodwater extent portrayed on these maps will vary with the accuracy of the digital elevation model used to simulate the land surface.
If this series of flood-inundation maps will be used in conjunction with National Weather Service (NWS) river forecasts, the user should be aware of additional uncertainties that may be inherent or factored into NWS forecast procedures. The NWS uses forecast models to estimate the quantity and timing of water flowing through selected stream reaches in the United States. These forecast models (1) estimate the amount of runoff generated by precipitation and snowmelt, (2) simulate the movement of floodwater as it proceeds downstream, and (3) predict the flow and stage (water-surface elevation) for the stream at a given location (AHPS forecast point) throughout the forecast period (every 6 hours and 3 to 5 days out in many locations). For more information on AHPS forecasts, please see.