InSAR-Derived Coastal Subsidence Reveals New Inundation Scenarios Over the Yellow River Delta.

Coastal subsidence exacerbates relative sea level rise (SLR) and increases the risk of coastal flooding. However, the contribution of local land subsidence (LLS) in the Yellow river delta (YRD) to the relative SLR remains unclear, leading to a gap in the understanding of future inundation scenarios. In this article, we firstly used five years of Sentinel-1 data to generate the high-accuracy coastal subsidence of the YRD. Radar interferometry (InSAR) results show that fast subsiding funnels larger than 50 mm/yr are mainly distributed in the brine mining clusters, and the maximum subsidence rate exceeds 300 mm/yr. We then proposed an inundation estimation method by combining extended seeded region growing model, InSAR-derived LLS and SLR. This method can effectively output the coastal inundation time series, quantify and characterize the changes of inundation area and depth without detailed hydrodynamic conditions. Moreover, we presented high spatiotemporal resolution inundation scenarios for the entire YRD, revealing that in the absence of control measures, annual subsidence of 19 mm/yr contributes at least three times more than that SLR to the increased flood risk in 2050 under the low greenhouse gas emissions scenario (SSP1-2.6). However, under the scenario of SSP5-8.5, 4611 km(2) of land would be inundated by 2100 and coastal dams are extremely likely to be damaged. This article is expected to provide a practical and cost-effective alternative to understanding the contribution of coastal subsidence to the relative SLR, and for choosing when and how to mitigate land subsidence to prevent future coastal flooding in the delta.