Department of Physical Geography, Utrecht University, Utrecht, The Netherlands; Department of Subsurface and Groundwater Systems, Deltares Research Institute, Utrecht, The Netherlands.
Department of Physical Geography, Utrecht University, Utrecht, The Netherlands.
Sci Total Environ. 2018 Sep 1;634:715-726. doi: 10.1016/j.scitotenv.2018.03.372. Epub 2018 Apr 9.
The Vietnamese Mekong delta is subsiding due to a combination of natural and human-induced causes. Over the past several decades, large-scale anthropogenic land-use changes have taken place as a result of increased agricultural production, population growth and urbanization in the delta. Land-use changes can alter the hydrological system or increase loading of the delta surface, amplifying natural subsidence processes or creating new anthropogenic subsidence. The relationships between land use histories and current rates of land subsidence have so far not been studied in the Mekong delta. We quantified InSAR-derived subsidence rates for the various land-use classes and past land-use changes using a new, optical remote sensing-based, 20-year time series of land use. Lowest mean subsidence rates were found for undeveloped land-use classes, like marshland and wetland forest (6-7mmyr), and highest rates for areas with mixed-crop agriculture and cities (18-20mmyr). We assessed the relationship strength between current land use, land-use history and subsidence by predicting subsidence rates during the measurement period solely based on land-use history. After initial training of all land-use sequences with InSAR-derived subsidence rates, the land-use-based approach predicted 65-92% of the spatially varying subsidence rates within the measurement error range of the InSAR observations (RMSE=5.8mm). As a result, the spatial patterns visible in the observed subsidence can largely be explained by land use. We discuss in detail the dominant land-use change pathways and their indirect, causal relationships with subsidence. Our spatially explicit evaluation of these pathways provides valuable insights for policymakers concerned with land-use planning in both subsiding and currently stable areas of the Mekong delta and similar systems.
越南湄公河三角洲由于自然和人为因素的综合作用而正在下沉。在过去几十年中，由于三角洲地区农业生产、人口增长和城市化的发展，大规模的人为土地利用变化已经发生。土地利用变化可以改变水文系统或增加三角洲表面的负荷，从而放大自然沉降过程或产生新的人为沉降。到目前为止，湄公河三角洲还没有研究土地利用历史与当前地面沉降速率之间的关系。我们利用新的基于光学遥感的 20 年土地利用时间序列，对各种土地利用类型的 InSAR 衍生沉降速率和过去土地利用变化进行了量化。未开发的土地利用类型（如沼泽地和湿地森林）的平均沉降速率最低（约 6-7mmyr），而混合作物农业和城市地区的沉降速率最高（约 18-20mmyr）。我们通过仅根据土地利用历史预测测量期间的沉降速率，评估了当前土地利用、土地利用历史和沉降之间的关系强度。在使用 InSAR 衍生沉降速率对所有土地利用序列进行初始训练之后，基于土地利用的方法预测了测量误差范围内的空间变化沉降速率的 65-92％（RMSE=5.8mm）。因此，在观测沉降中可见的空间模式在很大程度上可以用土地利用来解释。我们详细讨论了主要的土地利用变化途径及其与沉降的间接因果关系。我们对这些途径的空间明确评估为湄公河三角洲和类似系统中关注土地利用规划的政策制定者提供了有价值的见解，这些系统包括沉降区和当前稳定区。
