Graphical representation of flood inundation for NWS flood categories are based on steady state hydraulic modeling of water surface elevations for incremented discharges. Map shows approximate inundation areas for given water surface elevations and should not be used for navigation or permitting or other legal purposes, but strictly as a planning reference tool.
The purpose of a flood forecast inundation map is to communicate flood risk based on best available information at the time of map development. This flood forecast inundation map has been compiled using the best information available and is believed to be accurate; however, its preparation required many assumptions. Actual conditions during a flood event may vary from those modeled in the map. The limits of flooding shown should only be used as a guideline for emergency planning and response actions. Actual areas inundated will depend on specific flooding conditions.
The risk of flooding behind flood risk management (FRM) structures (such as levees, floodwalls, closures, etc.) depends on many factors that cannot be entirely predicted in advance. These factors include whether the FRM structure overtops, length of time the structure overtops, and whether the overtopping leads to breach formation.
Two distinct approaches to mapping flooding behind FRM structures have been applied to best address the uncertainty, documented flood risk management systems and undocumented flood risk management systems. No specific level of protection is implied for any FRM structure depicted on these maps.
The mapping is based on the PASDA ground elevation data from 2006-2008.
Documented Flood Risk Management Structures (red lines) – Includes Autoneum FRM project. Area behind the FRM structures is not shown as being flooded until the structure is over-topped.
Documented Flood Risk Management Risk Area (yellow shaded area) – Shows the areas with flood risk reduced by documented flood risk management structures
Undocumented Flood Risk Management Structures (orange lines) – Includes Kawneer FRM project. Area behind FRM structures is shown as flooded, although the structure may provide some level of flood risk reduction
Undocumented Flood Risk Management Risk Area (pale orange shaded area) – Shows rough approximation of FRM area that would have flood risk reducted by the undocumented flood risk management structure if it functions properly
The detailed project report can be found here
If you have questions related to any of the flood risk management/levee projects in Columbia County, call Eric Stahley, Columbia County Resiliency Office, at 570 389-9146 Ext 9.