Beach Slopes From Satellite‐Derived Shorelines

TLDR

The steepness of the beach face is a fundamental parameter for coastal morphodynamic research, yet reliable large‑scale estimates are difficult to obtain. This letter introduces a novel method to estimate beach‑face slope from time‑series of satellite‑derived shoreline positions. The technique applies frequency‑domain analysis to identify the slope that minimizes high‑frequency tidal fluctuations relative to lower‑frequency erosion/accretion signals. Across eight test sites, the method shows strong agreement with field measurements (R² = 0.93) and, when applied to thousands of beaches in eastern Australia and California, reveals comparable regional distributions and offers new global‑scale insights into beach‑face slope variability.

Abstract

Abstract The steepness of the beach face is a fundamental parameter for coastal morphodynamic research. Despite its importance, it remains extremely difficult to obtain reliable estimates of the beach‐face slope over large spatial scales (thousands of km of coastline). In this letter, a novel approach to estimate this slope from time series of satellite‐derived shoreline positions is presented. This new technique uses a frequency domain analysis to find the optimum slope that minimizes high‐frequency tidal fluctuations relative to lower‐frequency erosion/accretion signals. A detailed assessment of this new approach at eight locations spanning a range of tidal regimes, wave climates, and sediment grain sizes shows strong agreement ( R 2 = 0.93) with field measurements. The automated technique is then applied across thousands of beaches in eastern Australia and California, USA, revealing similar regional‐scale distributions along these two contrasting coastlines and highlights the potential for new global‐scale insight to beach‐face slope spatial distribution, variability, and trends.