Abstract The Nam Dinh Coast is a constituent part of the dynamic coastline, belonging to the Red River Delta. It is bounded to the north and south by the Red and Day Rivers, with Ninh Co and So Rivers located in the middle. This coast has been undergoing severe erosion during the last hundred years. Over this period, vital agricultural area along the coastline has vanished into the sea and families have been forced to abandon their houses due to the erosive action of waves. Numerous studies were conducted to identify the major causes governing the erosion problems, and several hypotheses have been proposed. In the present work, remote sensing data analysis techniques with both optical and synthetic aperture radar (SAR) were employed to examine the hypothesis that land subsidence is contributing to the erosion along the Nam Dinh Coast. The results revealed that the high lateral erosion rates observed at sandy beaches between estuaries are approximately -6 m/yr in the south and -10 m/yr in the north of the So River. Meanwhile, sediments transported from the rivers accumulate mainly around the estuaries, leading to rapid accretions of approximately +93, +4, and +46 m/yr for Day, Ha Lan (So River), and Ba Lat (Red River), respectively. Simultaneously, land is sinking and uplifting at highly uneven rates, with a few sections subsiding 10 times faster than the overall spatial average. Uplifting observed in southern areas ranges from +1.2 to +1.9 mm/yr. In contrast, subsidence was identified in the northern parts, with mean rates varying from -0.1 to -12.3 mm/yr. Based on the Bruun Rule, the combined effects of land subsidence and relative sea level rise (SLR) could explain approximately 66% of the observed rate of erosion in the northern part of Ha Lan. Findings from surface deformation data contribute to a deeper insight into coastal erosion in Nam Dinh.

中文翻译：

---

南定海岸（越南）的地面沉降及其对海岸侵蚀的影响

摘要 南定海岸是动态海岸线的组成部分，属于红河三角洲。它的南北以红河和戴河为界，宁河和苏河位于中间。在过去的一百年里，这条海岸经历了严重的侵蚀。在此期间，海岸线上的重要农业区已消失在海中，由于海浪的侵蚀作用，家庭被迫放弃房屋。进行了大量研究以确定控制侵蚀问题的主要原因，并提出了几个假设。在目前的工作中，采用光学和合成孔径雷达 (SAR) 的遥感数据分析技术来检验地面沉降导致南定海岸侵蚀的假设。结果表明，在河口之间的沙滩上观察到的高侧蚀率在南部约为 -6 m/yr，在 So 河北部约为 -10 m/yr。同时，从河流输送的沉积物主要在河口周围堆积，导致 Day、Ha Lan（So 河）和 Ba Lat（红河）分别快速增加约 +93、+4 和 +46 m/yr . 同时，土地以极不均匀的速度下沉和隆升，一些部分的下沉速度比整体空间平均速度快 10 倍。在南部地区观察到的抬升范围为 +1.2 至 +1.9 毫米/年。相反，在北部地区发现了沉降，平均速率从 -0.1 到 -12.3 毫米/年不等。根据布鲁恩法则，地面沉降和相对海平面上升 (SLR) 的综合影响可以解释哈兰北部观测到的侵蚀率的大约 66%。地表变形数据的发现有助于更深入地了解南定的海岸侵蚀。