DEM Elevation Uncertainty due to Sentinel-2 Water Mask Resolution

Description This repository contains the datasets and intermediate products used to quantify the vertical uncertainty introduced by the 10 m spatial resolution of the Sentinel-2 water mask in the DEM-based estimation of water surface elevation (WSE). Because the indirect WSE validation relies on NDWI-derived water masks, the finite 10 m pixel size of Sentinel-2 can shift the detected shoreline position horizontally, especially in steep, confined valleys. To evaluate how such shifts could affect DEM-derived elevations, we quantified the vertical sensitivity of the DEM to a hypothetical ±10 m displacement of the water mask. A 1 m-resolution cross-valley slope raster (in percent) was generated from the DEM. For each date, the Sentinel-2 NDWI water mask was converted to vector format, and the shoreline polygon boundaries were extracted and sampled as points. At each shoreline point, the local slope value was extracted from the slope raster. Vertical sensitivity was then computed as: Δz = slope % / 10 which represents the change in elevation (in meters) associated with a 10 m horizontal shift, equivalent to one Sentinel-2 pixel. The resulting Δz values describe the point-wise DEM elevation uncertainty attributable exclusively to the spatial resolution of the Sentinel-2 water mask. Summary statistics (minimum, maximum, mean, median, and standard deviation) were computed for each date to characterize uncertainty along the study reach. Contents 1. Excel files (one per date) Contain point shoreline samples with the following fields: `raste_val` : Local slope at shoreline (percent) `delta_z` : Estimated vertical sensitivity (slope% / 10) Files included: `Slope_values_delaz_2024-07-11.xlsx` `Slope_values_delaz_2024-08-12.xlsx` `Slope_values_delaz_2024-09-09.xlsx` 2. Raster file Slope raster (percent) derived from the 1 m LiDAR DEM, accessed via LiDAR Download Portal 3. Vector files Shoreline points shapefile, including extracted slope and Δz values for each date NDWI-derived water mask raster used to delineate shoreline boundaries Purpose These datasets support the uncertainty analysis presented in the manuscript and allow reproducibility of the DEM-based WSE sensitivity assessment relative to Sentinel-2 water-mask resolution.