Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, TX 78758, USA.
Department of Geological and Environmental Sciences, Western Michigan University, MI 49008, USA; Division of Geological Applications and Mineral Resources, National Authority for Remote Sensing and Space Sciences, Cairo 1564, Egypt.
Sci Total Environ. 2020 Aug 10;729:138868. doi: 10.1016/j.scitotenv.2020.138868. Epub 2020 Apr 23.
The Nile Delta is home to half of Egypt's population and has ample agricultural, industrial, and cultural resources, yet the land subsides in response to many natural and anthropogenic impacts. We report the recent subsidence rate and patterns in the Nile Delta using the synthetic aperture radar Sentinel-1 data of 144 images obtained between 2015 and 2019, based on coherence small baseline subset interferometry of ~2900 interferograms. We distinguished three patterns of deformation due to three different physical mechanisms: 1) The land subsides with rates ranging from -12 to -20 mm/year in major cities (such as Zagazig, Mit Ghamr, Tanta, Mansoura and Mahla) due to urban-induced loading; 2) A subsidence rate ranges between -3 and -8 mm/year along the coastal margins due to natural sediment dewatering and compaction. This rate is consistent with the global positioning system rate of -3.5 mm/year and 3) A subsidence rate ranges from -20 to -16 mm/year and -6 to -12 mm/year in newly reclaimed lands on the west and east of the delta's flood plains, respectively, due to groundwater overexploitation. Our findings, in contrast with results from previous studies of regional deformation mainly felt to be controlled by natural processes, demonstrate a localized subsidence and predominant anthropogenic control on the land deformation and call for revisiting sea level rise-related flooding models in the Nile Delta. In light of the new findings, the authorities should take necessary measures to reduce the ongoing land subsidence through enforcement of urban planning policies in the delta's flood plain and development of a sustainable management strategy for groundwater extraction.
尼罗河三角洲是埃及一半人口的家园，拥有丰富的农业、工业和文化资源，但由于许多自然和人为影响，该地区土地正在下沉。我们使用 2015 年至 2019 年期间获得的 144 幅合成孔径雷达 Sentinel-1 数据，基于约 2900 个干涉图的相干小基线子集干涉测量，报告了尼罗河三角洲最近的沉降速率和模式。我们区分了三种变形模式，这是由于三种不同的物理机制造成的：1）由于城市诱发的荷载作用，主要城市（如 Zagazig、Mit Ghamr、Tanta、Mansoura 和 Mahla）的土地沉降速率在-12 至-20mm/年之间；2）由于自然沉积物脱水和压实，沿海边缘的沉降速率在-3 至-8mm/年之间。这一速率与全球定位系统的速率-3.5mm/年一致；3）在三角洲洪泛平原的西部和东部新开垦土地上，沉降速率分别为-20 至-16mm/年和-6 至-12mm/年，这是由于地下水过度开采造成的。与以前主要受自然过程控制的区域变形研究结果相比，我们的发现表明存在局部沉降，并且土地变形主要受人为因素控制，这就需要重新审视尼罗河三角洲与海平面上升相关的洪水模型。鉴于新的发现，当局应采取必要措施，通过在三角洲洪泛区执行城市规划政策以及制定地下水开采可持续管理战略，减少正在发生的土地沉降。
