Data Management Plan

These data were created as part of the National Oceanic and Atmospheric Administration Office for Coastal Management's efforts to create an online

mapping viewer depicting potential water level increase and decrease in the coastal areas of the Great Lakes. The lakes included are: Erie, Huron, Michigan,

Ontario, St. Clair, and Superior. The purpose of the mapping viewer is to provide coastal managers and scientists with a preliminary look at lake level

change and potential coastal impacts. The viewer is a screening-level tool that uses nationally consistent data sets and analyses to help users examine

multiple scenarios and prioritize actions. The Lake Level Viewer may be accessed at https://coast.noaa.gov/llv.

These data consist of 13 water extent polygons and 13 water depth rasters (3 m resolution, depth values in meters) that show the potential water level when

the water level is decreased from 0 feet to -6 feet (resulting in potential land exposure) and when water level is increased from 0 to +6 feet (resulting

in potential flooding). These data are based on the each lake's long term average water level over the period of record (1913-2008). More information on

the long term average water level can be found at https://www.glerl.noaa.gov//pubs/fulltext/2013/20130021.pdf,

https://www.glerl.noaa.gov//pubs/fulltext/2013/20130022.pdf, and the Great Lakes Water Level Dashboard (https://www.glerl.noaa.gov/data/dashboard/GLWLD.html).

The process used to produce the data can be described as a bathtub approach. The process uses two source data sets to derive the final water extent polygons

and water depth rasters for each iteration of water level decrease or increase: the Digital Elevation Model (DEM) of the area and each lake's long term

average water level over the period of record (1918-2017) at the time of data set creation. Data can be downloaded at https://coast.noaa.gov/llv.

The model used to produce these data does not account for erosion, subsidence, or any future construction. Water levels are as they would appear during calm

conditions (excludes wind-driven effects). As with all remotely sensed data, all features should be verified with a site visit. The data are provided as is,

without warranty to their performance, merchantable state, or fitness for any particular purpose. The entire risk associated with the results and

performance of these data is assumed by the user. This data should be used strictly as a planning reference and not for navigation, permitting, or other

legal purposes.

Process Steps:

• 2017-01-01 00:00:00 - The process to derive the rasters and polygons is as follows: 1. A water level surface is generated for each lake using each lake's long term average water level over the period of record (1918-2003). Each 1 foot iteration (from -6 feet to + 6 feet) of water level was either subtracted or added to this base water level surface and subsequently used for mapping. 2. Using the DEM and the water level surface (for each 1 foot iteration of drop or rise), raster calculations are made using ArcGIS Spatial Analyst Raster Calculation tool to generate multiple rasters, one 32-bit floating point raster representing the depth of water level and one 8-bit single value raster representing the extent of water level.

This data may be downloaded at https://coast.noaa.gov/llv;