Southern and central Lake Michigan coastal features and geomorphic change measurements (2012 to 2020)

Repository structure and contents This repository contains geospatial data identifying the position of coastal geomorphic features and measurements of coastal change along the southern and central Lake Michigan coast generated using National Oceanic and Atmospheric Administration (NOAA) digital elevation models (DEMs) acquired in 2012 and 2020, spanning a rapid rise in lake levels. The data reach from Pentwater, Michigan to the Sturgeon Bay Canal in Wisconsin. The repository is organized as follows: raster elevation_change.zip - Tiled DEMs of difference between the 2012 and 2020 NOAA DEMs elevation_change_probability.zip - Tiled probability of elevation difference representing real change following the methodology of Wernette and others, 2020 uncertainty_2012.zip - Tiled 2012 DEM vertical uncertainty uncertainty_2020.zip - Tiled 2020 DEM vertical uncertainty vector lines bluff_transects_segment_a.gpkg - shore-perpendicular transects spaced 5-m apart alongshore attributed with bluff information spanning from approximately Winthrop Harbor to Manitowoc bluff_transects_segment_b.gpkg - shore-perpendicular transects spaced 5-m apart alongshore attributed with bluff information outside of the reach spanning from approximately Winthrop Harbor to Manitowoc shoreline_transects.gpkg - shore-perpendicular transects spaced 5-m apart alongshore attributed with shoreline and nearshore bar information simplified_shoreline.gpkg - simplified shoreline used to generate the "segment_b" transects and the alongshore segments used for data aggregation points cliff_features segment_a cliff_base_2012_segment_a.gpkg - 2012 cliff base points identified along segment A transects cliff_base_2020_segment_a.gpkg- 2020cliff base points identified along segment A transects cliff_top_2012_segment_a.gpkg- 2012 cliff top points identified along segment A transects cliff_top_2020_segment_a.gpkg- 2020 cliff top points identified along segment A transects landward_extent_segment_a.gpkg- Auxiliary landward extent of coastal change points identified along segment A transects used to constrain the landward extent of volume computations segment_b cliff_base_2012_segment_b.gpkg - 2012 cliff base points identified along segment B transects cliff_base_2020_segment_b.gpkg- 2020cliff base points identified along segment B transects cliff_top_2012_segment_b.gpkg- 2012 cliff top points identified along segment B transects cliff_top_2020_segment_b.gpkg- 2020 cliff top points identified along segment B transects landward_extent_segment_b.gpkg- Auxiliary landward extent of coastal change points identified along segment B transects used to constrain the landward extent of volume computations nearshore_bars bar_peaks_2012.gpkg - alongshore bar peaks identified from the 2012 DEM bar_peaks_2020.gpkg - alongshore bar peaks identified from the 2020 DEM bar_troughs_2012.gpkg - alongshore bar troughs identified from the 2012 DEM bar_troughs_2020.gpkg - alongshore bar troughs identified from the 2020 DEM shorelines inundation_shoreline_points_2012_elevation_177_31.gpkg - points along the shoreline transects representing the datum-based inundation shoreline position shoreline_points_2012_elevation_175_92.gpkg - points along the shoreline transects representing the datum-based 2012 shoreline position shoreline_points_2020_elevation_177_31.gpkg- points along the shoreline transects representing the datum-based 2020 shoreline position polygons alongshore_segments lake_michigan_coastal_change_500_meter_alongshore_segments.gpkg - alongshore polygons roughly 500 meters in length attributed with aggregated bluff morphometry, shoreline morphometry, volumetric change, and additional information based on the ~100 shore-perpendicular transects intersecting each segment cross_shore_zone_polygons beach_zone_polygon.gpkg - polygon representing the beach cross-shore zone bluff_zone_polygon.gpkg- polygon representing the bluff cross-shore zone nearshore_zone_polygon.gpkg- polygon representing the nearshore cross-shore zone overall_zone_polygon.gpkg- polygon representing the overall, or entire, cross-shore zone metadata - metadata files with detailed descriptions of data attributes and processing Dataset generation overview This dataset used overlapping DEMs collected in 2012 and 2020 to generate elevation change rasters and measure coastal morphometry along Lake Michigan from Pentwater, Michigan to the Sturgeon Bay Canal in Wisconsin. The DEMs were resampled to an identical grid using blinear interpolation Shore-perpendicular transects were cast every 5-meters alongshore and elevation profiles were extracted along these transects from the 2012 and 2020 DEMs. These elevation profiles were used to extract datum-based shoreline positions, bluff crest and toe positions, and the locations of nearshore bar peaks and troughs. "Inundation" shorelines were identified based on the position of the time 2 (higher) datum-based shoreline on the time 1 elevation profile. The elevation and positions of these morphometric features was then used to compute attributes such as bluff height, bluff slope, beach width, and the retreat rates and distances of bluff crests, toes, shorelines, as well as the depths and movement distances of inner and outer nearshore bar peaks. Total shoreline retreat was partitioned into an inundation and erosion component. Cross-shore zone polygons representing the bluff, beach, nearshore, and overall (or combined) zone were generated using concave hulls of the morphometry points to examine the partitioning of sediment transport within these respective process domains. Volumetric change was computed within the cross-shore zones using the elevation change rasters. Alongshore segment polygons 500-m in length were generated to facilitate data aggregation (approximately 100 transects in each polygon) and volumetric change computation. The cross-shore zone polygons were intersected with each segment and volumetric change computed within the resulting intersected polygon. A change probability threshold of 0.9 was used as the central estimate of volumetric change, and probabilities of 0.75 and 0.95 were used estimate the uncertainty in volumetric change computations. Segments were attributed with the median, mean, minimum, maximum, and standard deviation of many of the attributes aggregated from the intersecting transects, such as bluff and shoreline retreat. Additionally, a simplified shoreline classification was generated, classifying each transect and segment into sandy, armored, and bluff categories to facilitate easier comparison of coastal change measurement results across broad scales. Finally, to inform interpretation of the coastal change results, transects and segments were attributed with information from several outside data sources including the Wisconsin shoreline inventory, the Michigan historical shoreline retreat dataset, and wave information from the United States Army Corps of Engineers Wave Information Studies. Please review the detailed metadata for each file for a more complete description of dataset processing methodology and attribute definitions.