Linking the Surface and Subsurface in River Deltas—Part 1: Relating Surface and Subsurface Geometries
Linking the Surface and Subsurface in River Deltas—Part 1: Relating Surface and Subsurface Geometries
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DOI：
10.1029/2020wr029282
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发表时间：
2021-08
影响因子：
5.4
通讯作者：
J. Hariharan;Zhongyuan Xu;H. Michael;C. Paola;E. Steel;P. Passalacqua
中科院分区：
文献类型：
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作者：
J. Hariharan;Zhongyuan Xu;H. Michael;C. Paola;E. Steel;P. Passalacqua
河流三角洲是世界上人口密集的地区，地下水储量脆弱。由于人类活动和气候变化，咸水侵入和污染物迁移对这些地下含水层造成的污染日益严重。已知地下沉积物的排列和组成对含水层污染有重大影响;然而，对地下沉积物进行精确测量具有挑战性。在这项工作中，我们探索表面和地下属性之间的关系，并确定最敏感的指标不同的强迫条件。为此，我们用基于规则的数值模型DeltaRCM模拟了河流三角洲的演变，并测试了输入泥沙含量和稳定海平面上升（SLR）对三角洲演变的影响。从模型输出中，我们测量了各种表面和地下指标，这些指标是根据它们对图像和建模结果的适用性选择的。然后使用Kullback-Leibler（KL）分歧来定量衡量哪些指标最能指示所施加的强迫。定性观测和KL分歧分析表明，地下连通性的估计可以使用表面信息进行约束。特别是，更可变的海岸线粗糙度值和更高的表面润湿分数值对应于增加的地下连通性。这些发现补充了传统的估计河流主导的三角洲系统地下结构的方法，并代表了识别地表观测和地下形态之间直接联系的一步。
River deltas are densely populated regions of the world with vulnerable groundwater reserves. Contamination of these groundwater aquifers via saline water intrusion and pollutant transport is a growing threat due to both anthropogenic and climate changes. The arrangement and composition of subsurface sediment is known to have a significant impact on aquifer contamination; however, developing accurate depictions of the subsurface is challenging. In this work, we explore the relationship between surface and subsurface properties and identify the metrics most sensitive to different forcing conditions. To do so, we simulate river delta evolution with the rule‐based numerical model, DeltaRCM, and test the influence of input sand fraction and steady sea level rise (SLR) on delta evolution. From the model outputs, we measure a variety of surface and subsurface metrics chosen based on their applicability to imagery and modeling results. The Kullback‐Leibler (KL) divergence is then used to quantitatively gauge which metrics are most indicative of the imposed forcings. Both qualitative observations and the KL divergence analysis suggest that estimates of subsurface connectivity can be constrained using surface information. In particular, more variable shoreline roughness values and higher surface wetted fraction values correspond to increased subsurface connectivity. These findings complement traditional methods of estimating subsurface structure in river‐dominated delta systems and represent a step toward the identification of a direct link between surface observations and subsurface form.