NOAA Office for Coastal Management (OCM) Lake Level Data: Mapping Confidence

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 depict the mapping confidence of the associated lake water level data for the water level amounts of -6 feet through +6 feet. The mapping

process is designed to give the most accurate picture of water extent possible, but inherent data errors introduce some uncertainty in the exact water

extents. The presentation of data confidence only represents the known error in the elevation data and not uncertainty associated with the natural evolution

of the coastal landforms (e.g., erosion or bluff failure) or future climate change impacts on lake levels.

To access the associated data to be used with this data:

NOAA Office for Coastal Management Lake Level Data: -6 Feet to +6 Feet Water Level Change data may be downloaded at:

https://coast.noaa.gov/llv

The NOAA Office for Coastal Management has tentatively adopted an 80 percent rank (as either inundated or not inundated) as the zone of relative confidence.

The use of 80 percent has no special significance but is a commonly used rule of thumb measure to describe economic systems (Epstein and Axtell, 1996). The

method used to determine the confidence data only includes the uncertainty in the lidar derived elevation data (root mean square error, or RMSE). This

confidence data shows that the water level depicted in the -6 feet to +6 feet water level change data is not really a hard line, but rather a zone with greater

and lesser chances of being wet or dry. Areas that have a high level of confidence that they will be wet, means that there is an 80 percent or greater

likelihood that these areas will be covered with water. Conversely, there is a 20 percent or less likelihood that the area will be dry. Areas mapped as wet

(inundation) with a high confidence (or low uncertainty) are coded as 2. Areas that have a high level of confidence that they will be dry, means that there is

an 80 percent or greater likelihood that these areas will be dry. Conversely, there is a 20 percent or less likelihood that the area will be wet. Areas mapped

as dry (no inundation) with a high confidence (or low uncertainty) are coded as 0. Areas that have a low level of confidence, means that there is a 21 - 79

percent likelihood of wet or dry conditions. Note that 60 percent of the time, the land-water interface will be within this zone. Areas mapped as dry or wet

with a low confidence (or high uncertainty) are coded as 1.

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. For a detailed description of the

confidence level and its computation, please see the Mapping Inundation Uncertainty document available at:

http://www.jcronline.org/doi/abs/10.2112/JCOASTRES-D-13-00118.1

The purpose of these data is to show the level of confidence in the water level data based on the uncertainty in the source lidar elevation data.

10959

A detailed methodology for producing these data can be found via the following url:

http://www.jcronline.org/doi/abs/10.2112/JCOASTRES-D-13-00118.1

Spatial_Reference_Information:

Horizontal_Coordinate_System_Definition:

Planar:

Map_Projection:

Map_Projection_Name: NAD 1983 Great Lakes and St Lawrence Albers

Albers_Conical_Equal_Area:

Standard_Parallel: 42.122774

Standard_Parallel: 49.01518

Longitude_of_Central_Meridian: -83.248627

Latitude_of_Projection_Origin: 45.568977

False_Easting: 1000000.0

False_Northing: 1000000.0

Planar_Coordinate_Information:

Planar_Coordinate_Encoding_Method: coordinate pair

Coordinate_Representation:

Abscissa_Resolution: 0.000000003398570314061545

Ordinate_Resolution: 0.000000003398570314061545

Planar_Distance_Units: meter

Geodetic_Model:

Horizontal_Datum_Name: D North American 1983

Ellipsoid_Name: GRS 1980

Semi-major_Axis: 6378137.0

Denominator_of_Flattening_Ratio: 298.257222101

These data illustrate the scale of potential water level decrease and increase, not the exact location, and do not account for erosion,

subsidence, or future construction. Water level is shown as it would appear based on each lake's long term average water level over the period of record

(excludes wind driven effects) with one foot increments of water level decrease or increase. These data should be used only as a screening-level tool

for management decisions. As with all remotely sensed data, all features should be verified with a site visit. The data set is provided as is, without

warranty to its performance, merchantable state, or fitness for any particular purpose. The entire risk associated with the results and performance of

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

purposes. Any conclusions drawn from the analysis of this information are not the responsibility of the Office for Coastal Management (OCM) or its

partners.

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

None

These data illustrate the scale of potential water level decrease and increase, not the exact location, and do not account for erosion, subsidence,

or future construction. Water level is shown as it would appear based on each lake's long term average water level over the period of record (excludes wind

driven effects) with one foot increments of water level decrease or increase. These data should be used only as a screening-level tool for management

decisions. As with all remotely sensed data, all features should be verified with a site visit. The data set is provided as is, without warranty to its

performance, merchantable state, or fitness for any particular purpose. The entire risk associated with the results and performance of this data set is

assumed by the user. This data set should be used strictly as a planning reference and not for navigation, permitting, or other legal purposes.

These data are complete. Gaps may exist, but these are due to a lack of available elevation data at the time of data set creation.

The data were reviewed for consistency and anomalies.