Lower Barataria Bay and Lower Breton Sound soil texture model

Wetlands in the Mississippi River Delta Plain (MRDP) have been suffering from a high rate of land loss. Sediment cores have been drilled into the wetlands to understand their growth and degradation, and to provide subsurface information for the coastal protection and restoration projects. However, few three-dimensional (3-D) stratigraphy models have been developed for the wetlands on a regional scale, due to difficulties in correlating large amount of spatial scattered subsurface data and integrated visualization of stratigraphic features and topobathymetric features. In this study, a 3-D model was constructed in the Lower Barataria Bay (LBB) and the Lower Breton Sound (LBS), covering an area of 190 km2 and extending from 0.5 m to -4 m in elevation. Sediment composition (sand%, silt% and clay%) was spatially interpolated, using a compositional kriging method, extended from ordinary kriging by a log-ratio transformation. Instead of visualizing three composition components independently, sediment composition was translated into sediment texture to be visualized as sediment types. Modeling results intuitively show spatial distribution of stratigraphic features and their spatial relationships with topobathymetric features such as marsh surface, river channel and dredging channels. Results show a silty depositional package, which consists of crevasse splays and periodic overbank flooding deposits, made up the largest portion of the wetlands. A clayey blanket is observed to cover most part of the LBB and landward side of the LBS. A large area of clayey blanket in the seaward part of the LBS has apparently been eroded away, which is likely caused by coastal reworking processes.

密西西比河三角洲平原（MRDP）的湿地正遭受着严重的土地流失。为探究其生长与退化，并为其海岸防护与恢复工程提供地下信息，已对湿地进行沉积岩芯钻探。然而，由于在区域尺度上关联大量空间散布的地下数据以及综合展示地层特征与地形水文学特征的困难，针对湿地的三维（3-D）地层学模型开发甚少。在本研究中，于下巴塔里亚湾（LBB）和下布伦顿湾（LBS）构建了三维模型，覆盖面积达190平方公里，海拔高度从0.5米至-4米不等。采用成分克里金法对沉积物组成（沙含量%、粉含量%和黏含量%）进行空间插值，该方法通过对数比变换扩展了普通克里金法。而非独立可视化三个成分，沉积物组成被转化为沉积物纹理，以沉积物类型进行可视化。建模结果直观地展示了地层特征的时空分布及其与地形水文学特征（如湿地表面、河流通道和疏浚通道）的时空关系。结果显示，由裂缝扩张和周期性溢洪沉积物组成的粉质沉积物构成了湿地最大的部分。在一巴塔里亚湾的大部分区域和下布伦顿湾陆向一侧观察到黏土层。而下布伦顿湾海向部分的大面积黏土层显然已被侵蚀，这可能是海岸重塑过程所致。