=== versions === python 3.12.0 | pystac-client 0.9.0 | planetary-computer 1.0.0 | rasterio 1.5.2 | scikit-image 0.26.0 | utide 0.4.0 | numpy 2.5.4 | pandas 3.0.6 === East Riding erosion profiles (PDF table) === 108 profiles parsed; dropped 2 with a typing error in the coordinates: [10, 71] study stretch: profiles 22-89, 64 profiles, 64 with a 1989-2026 rate council cliff-top erosion rate 1989-2026: median 1.85 m/yr, range 0.07-3.28 m/yr profile location rate_1989_2026 loss_last_year 22 North Boundary of North Caravan Park, Skipsea 1.50 1.60 23 South end of Seaside Caravan Park, Ulrome 1.11 0.77 24 Between defences opposite Southfield Lane, Ulrome 1.09 1.02 25 North end of Green Lane, Skipsea 1.22 0.45 26 South of Green Lane, Skipsea 0.95 0.00 27 Opposite Skipsea village 1.12 0.90 28 Opposite bungalows to south of Skipsea 1.30 0.95 29 To south of Withow Gap, Skipsea 1.40 0.00 === tide gauge readings (Environment Agency, 15-minute) === readings first last days gauge Bridlington 3552 2025-11-01 00:00:00+00:00 2026-10-19 15:15:00+00:00 41 Spurn Point 3897 2025-11-01 00:00:00+00:00 2026-10-19 15:15:00+00:00 41 dropped 345 Bridlington readings sitting on the dry-harbour floor (-1.61 m) === harmonic tide model (utide) === Bridlington 16 constituents; largest amplitudes (m): M2 1.82, S2 0.63, N2 0.33, K2 0.19, O1 0.18 Spurn Point 16 constituents; largest amplitudes (m): M2 2.09, S2 0.73, N2 0.38, O1 0.20, K2 0.19 hold-out days, predicted minus observed (m): rmse bias gauge Bridlington Spurn Point Bridlington Spurn Point day 2026-01-01 0.58 0.65 -0.54 -0.57 2026-04-01 0.22 0.23 0.18 0.18 2026-07-01 0.15 0.15 0.09 0.08 === Sentinel-2 search === 751 scenes of tile 30UXE with tile cloud cover < 80%, 2017-01-02 to 2026-10-17 137 384 37 367 === analysis mosaic === 14 blocks of 512 x 512 pixels at 10 m; mosaic 2048 x 3584 pixels (20.5 x 35.8 km), EPSG:32630 === reference shoreline === median MNDWI of the 20 least cloudy scenes; Otsu threshold 0.163 reference shoreline 33.3 km long, Skipsea to Withernsea 332 transects, 100 m apart, 250 m landward and 350 m seaward of the reference line === shoreline extraction === 751 scenes processed in 1 s: 551 with a shoreline, 200 with less than 20% of the shore zone clear Otsu MNDWI thresholds: median 0.174, 5th-95th percentile 0.052 to 0.275 === shoreline positions on transects === 69,486 shoreline positions from 545 scenes (2017-01-02 to 2026-10-17) positions per transect: median 208, min 156 overpass time 11:06 to 11:25 UTC; predicted tide at overpass -3.29 to +1.99 m (median -0.58 m) === tide correction === tide coefficient k (m of shoreline shift per m of tide): median -27.2, equivalent beach slope 1:27 (5th-95th pct 1:17 to 1:36) scatter about the trend: median 41.6 m without tide correction, 21.1 m with it outliers removed: 2,423 of 69,486 positions (3.5%) === shoreline change rates (negative = landward retreat) === LRR, tide-corrected: median -1.01 m/yr, IQR -1.75 to -0.23 LRR, no tide correct: median -0.72 m/yr EPR (first vs last 12 months): median -0.32 m/yr median 95% CI half-width of LRR: 1.01 m/yr tide-corrected, 2.01 m/yr uncorrected transects with significant retreat (CI excludes 0): 164 of 332 trend in predicted tide at overpass time: -0.4 cm/yr; times the median k that is a spurious +0.11 m/yr of apparent seaward shoreline motion === comparison with East Riding of Yorkshire Council cliff-top rates === 62 council profiles matched to transects council 1989-2026 cliff-top retreat: median 1.87 m/yr council Mar 2025-Mar 2026 cliff loss: median 0.68 m Sentinel-2 2017-2026 waterline retreat (tide-corrected LRR): median 1.08 m/yr Sentinel-2 without tide correction: median 0.78 m/yr Spearman rank correlation, council rate vs Sentinel-2 retreat: 0.60 (p = 0.000) difference (Sentinel-2 minus council): median -0.81 m/yr, MAD 0.37 profiles council_1989_2026 s2_retreat s2_no_tide section Skipsea-Atwick (22-32) 10 1.17 0.71 1.52 Atwick-Hornsea (33-46) 11 0.96 1.14 0.89 Hornsea-Mappleton (47-59) 13 2.53 1.88 1.48 Aldbrough (60-74) 14 2.18 1.41 0.40 Aldbrough-Withernsea (75-89) 14 1.88 0.92 -0.48 example scene S2C_MSIL2A_20260813T110621_R137_T30UXE_20260813T143310 (2026-08-13 11:06 UTC), 100% of shore zone clear, Otsu threshold 0.187 predicted tide: median -0.11 m over all hours, -0.62 m at overpasses; 5th-95th pct -2.37/+2.07 vs -2.64/+1.38 m example transect 203 (20.4 km): LRR -2.96 ± 0.99 m/yr (uncorrected -2.32), k -22.4, scatter 37 -> 20 m figures and CSV files written to output\