EAR-PF: Impact of flooding intensity on levee development and dynamics

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。埃里克·赤脚获得了NSF EAR博士后奖学金，将在印第安纳大学开展研究和教育计划。赤脚博士将研究洪水，这是一种严重的自然灾害，威胁着美国和世界各地的关键基础设施和社区。沿着河流走廊修建人工堤防(或堤防)通常是为了减少洪水危害，这些工程项目往往利用泛滥平原上的天然堤坝。当河水泛滥，泥沙向外扩散时，河堤就形成在河道旁边。由于堤防形成与河流属性的相关性较差，因此预测堤防形成的地点和时间仍然具有挑战性。这个项目试图验证一个新的假设：洪水的强度是堤坝形成的关键控制因素。通过结合对印第安纳州泛滥平原的分析和对密西西比河下游的监测，该项目将确定洪水强度对堤坝形成的重要性。赤脚博士还将确定洪水期间河流泛滥平原上泥沙的输送过程。这些研究成果将与一项教育推广计划相结合，该计划的重点是让公立学校的教育工作者编制以印第安纳州洪水灾害和可持续性为重点的新课程。此外，该项目将通过本地实地研究机会，支持LGBTQ+本科生参与STEM。天然堤防的形成和发展是在河水漫滩时形成的，当时含沙的水从河水中排出，并与河道相邻的沉积物形成。泥沙淤积模式受淹没泛滥平原的水面坡度控制。假定水面梯度的方向和性质取决于洪水强度；在操作上，这里定义为流量变异系数(CVQ)。然而，洪水强度对漫滩沉积的影响很少受到限制，因为对共同演变的漫滩地形和淹没水力学的直接观测很少。该项目将量化洪水强度对滩地淹没模式的影响，并分析由此产生的水面梯度如何影响堤防的形成和发展。这项研究将把重复的激光雷达数据集与对美国印第安纳州泛滥平原的实地调查和沉积学观测相结合，以比较不同历史洪水强度范围内的堤坝形态和组成。为了将洪水强度和泥沙扩散联系在一个机械框架内，将在以低洪水强度为典型的末端成员地区进行补充案例研究。在密西西比河的一个工程河段，在每年越岸条件下的水面高度和速度的现场测量将与重复的激光雷达地形测量相结合，以将淹没水力与地形演变相结合。来自该项目的新见解将满足一个关键的研究需求，因为当代气候变化导致的洪水加剧威胁到河流走廊的可持续性。科学成果将为土地管理战略提供参考，同时也推动沉积学和地貌学的根本进步。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Dr. Eric Barefoot has been granted an NSF EAR Postdoctoral Fellowship to carry out research and education plans at Indiana University. Dr. Barefoot will study flooding, a significant natural hazard that threatens critical infrastructure and communities in the US and across the world. Artificial embankments (or dikes) along river corridors are often constructed to reduce flooding hazards and these engineering projects often take advantage of natural levees on the floodplain. Levees form next to a river channel when the river floods and sediment spreads out away from the river. Because levee formation correlates poorly with river attributes, it remains challenging to predict where and when levees will form. This project seeks to test a new hypothesis: that the intensity of floods is a key control on levee formation. By combining analysis of floodplains across the State of Indiana with monitoring on the Lower Mississippi River, this project will determine the importance of flood intensity for levee formation. Dr. Barefoot will also identify processes by which sediment is transported on river floodplains during floods. These research outcomes will be coupled with an educational outreach plan that focuses on engaging public-school educators to produce new curriculum focused on flood hazards and sustainability in Indiana. Additionally, this project will bolster STEM engagement for LGBTQ+ undergraduate students through local field-based research opportunities. Natural levees form and develop during overbank flow, when sediment-laden water decants from the river, and deposits adjacent to the channel. The pattern of sediment deposition is controlled by water surface gradients across the inundated floodplain. The orientation and mag- nitude of water surface gradients are hypothesized to depend on flooding intensity; operationally defined here as the coefficient of variation of discharge (CVQ). However, the impact of flooding intensity on floodplain deposition is poorly constrained because direct observations of co-evolving floodplain topography and inundation hydraulics are scarce. This project will quantify the impact of flooding intensity on floodplain inundation patterns and analyze how resulting water surface gradients influence levee formation and development. This research will combine repeat lidar datasets with field surveys and sedimentological observations on floodplains in Indiana, USA, to compare levee morphology and composition spanning a range of historical flooding intensities. To link flooding intensity and sediment dispersal in a mechanistic framework, a complementary case study will be conducted in an end-member locality typified by low flooding intensity. In-situ measurements of water surface elevation and velocity during annual overbank conditions in an engineered section of the Mississippi River will be paired with repeat lidar topography surveys to couple inundation hydraulics with topographic evolution. New insights from this project will fill a critical research need because intensified flooding due to contemporary climate change threatens sustainability of river corridors. The scientific outcomes will inform land management strategies while also driving fundamental advances in sedimentology and geomorphology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.