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

对项目的非技术描述，解释了项目的意义和重要性海平面上升和地面沉降的综合影响导致的沿海土地流失是21世纪的一个主要问题。上游的泥沙被水坝截留，主要河流被堤防围堵，导致向沿海地区输送的泥沙减少，加剧了地面沉降问题。在美国墨西哥湾沿岸，通过工程改造密西西比河改道，将沉积物输送到三角洲平原的大部分地区，可能会减少土地的流失。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，由于对影响海岸沉积物收支的不同过程缺乏了解，可能导致模型对这些速率的预测不准确。其中一个未知的过程是沿海植被的茎叶直接捕获颗粒，这在三角洲沼泽中可能会大大增加总体沉积速率。这项研究将量化植被捕获对海岸沉积预算的重要性，从而改进海岸生长或淹没的预测。该项目的技术描述该项目涉及三个突出的主题，即记录细沉积物在沿海土地建设过程中的作用：(i)通过植被直接捕获，在水动力特性、生物膜和植被特性以及沉积之间建立定量关系。㈡它检验了植被阵列内生物膜的存在大大增加沉积速率的假设。（iii）改进了三角洲陆地动力学模型中植被颗粒捕获的表征，并利用该模型评价了大尺度三角洲演化中颗粒捕获的总体意义。结合实验室和现场实验和数值模拟将用来阐明这些主题。生物地貌学研究与教学（BRAT）水槽的实验室实验将测试有关流动条件，颗粒特征和植被冠层结构之间功能关系的新兴理论。在水槽内培养的生物膜将能够测试不同表面特性对沉降的影响。这些结果将在现场进行测试，在蜡湖三角洲完整植被群落周围建造的原位水槽中进行测试，这是路易斯安那州海岸一个活跃的生长部分。在现场和实验室水槽中开发的功能关系将被纳入三角洲沉积动力学的代尔夫特3D模型。利用该模型进行的敏感性分析将评估细沉积物-植被相互作用对大规模三角洲生长的重要性。该项目的教育部分包括开发使用BRAT水槽的体验课程模块，在国家地球动力学中心开发一个关于细沉积物-植被相互作用的夏季短期课程，以及为旧金山探索博物馆开发一个关于沿海沼泽在土地建设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展，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.