CAREER: The role of organic particulates in controlling the growth of river deltas: a field, experimental, and numerical modeling study

对该项目的非技术性描述，解释了该项目的意义和重要性海平面上升和地面沉降的综合影响造成的沿海土地流失是21世纪世纪的一个主要问题。水坝后上游沉积物的滞留和堤坝对主要河流的限制，导致向沿海地区输送的沉积物减少，加剧了地面沉降问题。沿着美国墨西哥湾沿岸，通过对密西西比河进行工程改道，将沉积物输送到三角洲平原的更大部分，可以减少土地的流失。模拟模型是规划这种改道和评估不同管理方案对海岸沉积和侵蚀速率的影响的重要工具。然而，在知识的不同过程中的差距，有助于沿海沉积物预算可能会导致这些速率的不准确的模型预测。这些未知的过程之一是沿海植被的茎和叶直接捕获颗粒，这在三角洲沼泽中可能大大增加总的沉积速率。这项研究将量化植被捕获对海岸沉积预算的重要性，从而改善对海岸生长或淹没的预测。该项目的技术说明该项目涉及记录细沉积物在海岸土地建设过程中的作用的三个突出主题：（i）它建立了水动力特性、生物膜和植被特性之间的定量关系，以及通过植被的直接捕获进行沉积。(ii)它测试的假设，即植被阵列内的生物膜的存在大大增加了沉积速率。(iii)它改进了三角洲陆地动力学模型中植被颗粒捕获的代表性，并使用该模型来评估颗粒捕获在大尺度三角洲演化中的整体意义。实验室和现场实验和数值模拟的组合将被用来阐明这些主题。在生物地貌研究和教学（BRAT）水槽实验室实验将测试新兴理论的流动条件，颗粒特性和植被冠层结构之间的功能关系。水槽内培养的生物膜将能够测试不同表面特性对沉积的影响。这些结果将在现场进行测试，在原位水槽周围的蜡湖三角洲，路易斯安那州海岸的一个积极增长的部分完整的植被群落。在现场和实验室水槽开发的功能关系将被纳入三角洲沉积动力学的德尔夫特三维模型。敏感性分析进行的模型将评估大规模三角洲生长的精细沉积物-植被相互作用的重要性。该项目的教育部分包括利用BRAT水槽开发经验课程单元，在国家地球动力学中心开发关于细沉积物-植被相互作用的夏季短期课程，以及为旧金山弗朗西斯科探索馆开发关于沿海沼泽在土地形成过程中的作用的展览。三角洲建模工作将与沿海资源管理人员合作开发，并广泛传播路易斯安那州沿海沼泽恢复规划。

A non-technical description of the project, which explains the project's significance and importanceCoastal land loss through the combined effects of sea-level rise and land subsidence is a major concern of the 21st century. The retention of sediment upstream behind dams and confinement of major rivers by levees have resulted in diminished sediment delivery to coastal regions, exacerbating problems of land subsidence. Along the US Gulf Coast this loss of land may be lessened through engineered diversions of the Mississippi River that would deliver sediment to a larger portion of the delta plain. Simulation modeling is an essential tool for planning such diversions and evaluating impacts of different management scenarios on rates of coastal sedimentation and erosion. However, a gap in knowledge of the different processes contributing to coastal sediment budgets could lead to inaccurate model predictions of these rates. One of these unknown processes is the direct capture of particles by the stems and leaves of coastal vegetation, which in deltaic marshes might add substantially to overall sedimentation rates. This research will quantify the importance of vegetation capture for coastal sedimentation budgets, leading to improved prediction of coastal growth or submersion.A technical description of the projectThis project addresses three outstanding topics in documenting the role of fine sediment in coastal land building processes: (i) It develops a quantitative relationship between hydrodynamic properties, biofilm and vegetation properties, and sedimentation through direct capture by vegetation. (ii) It tests the hypothesis that the presence of biofilm within vegetation arrays substantially increases sedimentation rates. (iii) It improves the representation of particle capture by vegetation in models of delta land dynamics and uses the model to evaluate the overall significance of particle capture in large-scale delta evolution. A combination of laboratory and field experimentation and numerical modeling will be used to elucidate these topics. Laboratory experiments in the Biogeomorphology Research and Teaching (BRAT) flume will test emerging theory about the functional relationship between flow conditions, particle characteristics, and vegetation canopy structure. Biofilms cultivated within the flume will enable testing of the effects of different surficial properties on sedimentation. These results will be tested in the field, within in situ flumes constructed around intact vegetation communities in the Wax Lake Delta, an actively growing portion of the Louisiana coast. Functional relationships developed in the field and laboratory flumes will be incorporated into a Delft 3D model of delta sedimentation dynamics. Sensitivity analyses conducted with the model will evaluate the importance of fine sediment-vegetation interactions for large-scale delta growth. Educational components of the project include development of experiential course modules that use the BRAT flume, development of a summer short course on fine sediment-vegetation interactions at the National Center for Earth Dynamics, and development of an exhibit for the San Francisco Exploratorium on the role of coastal marshes in land building processes. Delta modeling efforts will be developed in collaboration with coastal resource managers and disseminated broadly for Louisiana coastal marsh restoration planning.