Supplementary file 1_Composite shoreline-retreat workflow (CoShReW): a case study on the Andalusian coast.zip

Current models for long-term shoreline response to sea-level rise (SLR), such as the Bruun Rule, have significant limitations as they fail to account for site−specific processes and often misrepresent the influence of dunes, rocky platforms, or estuarine sediment sources and sinks. Here we integrate four previously published formulations into the Composite Shoreline−Retreat Workflow (CoShReW), a compound sequence that can be adapted or expanded according to data availability. The workflow needs several topo−bathymetric variables and shoreline data to calculate the expected shoreline retreat. It is distributed as open source code (GitHub) to guarantee reproducibility. As a first study-case, CoShReW is applied to 1281 cross-shore profiles along the highly heterogeneous Andalusian coast (SW Spain). To capture this coastal variability, we conduct a detailed characterization along the study area using Principal Component Analysis (PCA) of significant wave height, peak period, tidal range and sediment grain size, defining four different profile types. Resulting shoreline retreat projections differ by more than an order of magnitude among these classes, with dune elevation and estuary capacity emerging as dominant controls in dissipative sectors, and historical erosion rates prevailing on reflective or cliff−backed shores. Sensitivity analysis quantifies the relative importance of the governing variables for each profile type, indicating where local data collection would most improve forecast confidence. The present study findings reveal that local geomorphology can equal or exceed SLR as a driver of shoreline change in some habitats, emphasizing the need to consider and integrate site-specific adaptation measures in long-term shoreline retreat assessments for complex coastal environments.

当前针对海平面上升（Sea-Level Rise, SLR）的长期岸线响应模型（如布鲁恩法则（Bruun Rule））均存在显著局限：既无法考量局地特异性过程，也常误判沙丘、岩质平台或河口沉积物源汇的影响。本研究将四种已发表的公式整合至复合岸线后退工作流（Composite Shoreline-Retreat Workflow，CoShReW）中，该复合流程可依据数据可获得性进行调整或拓展。该工作流需依托多组地形-水深变量与岸线数据，以计算预期的岸线后退量。其以开源代码形式发布于GitHub平台，以确保研究可复现性。作为首个研究案例，我们将CoShReW应用于西班牙西南部安达卢西亚沿岸的1281条跨岸剖面，该沿岸区域具有高度异质性。为刻画该沿岸区域的变异性，我们基于有效波高、峰值周期、潮差与沉积物粒径数据开展主成分分析（Principal Component Analysis，PCA），对研究区进行详细特征分类，最终界定出四种不同的剖面类型。不同剖面类型的岸线后退预测结果差异可达一个数量级以上：在消散型岸段，沙丘高程与河口容纳能力成为主导控制因素；而在反射型岸段或崖壁依托岸段，历史侵蚀速率则占据主导地位。敏感性分析量化了各剖面类型的主控变量相对重要性，明确了在哪些区域补充局地数据可最大程度提升预测置信度。本研究结果表明，在部分生境中，局地地貌对岸线变化的驱动作用可等同于甚至超过SLR，这凸显了在复杂海岸环境的长期岸线后退评估中，需考虑并整合局地特异性适应措施的必要性。