Modifications were made to Great Lakes topobathy data to interpolate areas of missing near shore elevation data. Areas with missing elevation data were not interpolated where there was low confidence in the underlying depth. This included rivers, canals, harbors, lakes, reservoirs, etc. Areas important for targeting Phragmites australis management often lie within these aquatic/terrestrial transition zones. The original topobathy data were created as part of the National Oceanic and Atmospheric Administration Office for Coastal Management's efforts to create an online mapping viewer called the NOAA Lake Level Viewer. It depicts potential lake level rise and fall and its associated impacts on the nation's coastal areas. The base elevation data were the best available lidar and US Army Corps of Engineer dredge survey data known to exist at the time of DEM creation that met project specifications. Water depths were modeled using the updated topobathy data set and a low water datum (https://tidesandcurrents.noaa.gov/gldatums.html) used to denote a static water surface elevation. Low water datums (LWD) are a stable water surface elevation that doesn't change over time based on fluctuating water levels. Water depths were modeled at levels 3 feet below to 10 feet above the LWD in 1/2 foot increments. Units are in centimeters, the larger the negative value, the deeper the water. These water depths do not consider natural processes such as erosion, subsidence, or future construction. Water extent is as it would appear on a calm day with no wind-driven waves or seiche effect. The mapping may not accurately capture detailed hydrologic/hydraulic features such as canals, ditches, and stormwater infrastructure, resulting in inundated areas that are not connected to a lake. A more detailed analysis may be required to determine an area's actual susceptibility to flooding. The data should be used only as a screening-level tool (https://coast.noaa.gov/llv).