Sorry, Internet Explorer is not supported. 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. Additional uncertainties and limitations pertinent to this study are described in the document accompanying this set of flood inundation map plates.
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.
Flood inundation map services can be found here. More information about the Flood Inundation Mapping Program can be found here. Inundated areas shown should not be used for navigation, regulatory, permitting, or other legal purposes. Although USGS intends to make this server available 24 hours a day, 7 days a week, timely delivery of data and products from this server through the Internet is not guaranteed.
