CAREER: Alluvial-river dynamics through watershed networks

河流及其支流形成了网络，将地球上遥远的地貌融为一体，将我们的家园、农场、城市和荒野地区连接起来。这些河流不断变化，有时几乎察觉不到，有时戏剧性地调整其形态，以携带降雨、冰雪融化和周围景观侵蚀所提供的水和沉积物。自然和人类活动都会改变进入河流的水和泥沙的平衡，导致当供水超过泥沙供应时，河流向下侵蚀到河床中，或者当泥沙供应增加到超出水所能携带的范围时，泥沙沉积并提高河床水位。威克特和他的团队将开发一种理论来预测这些河流系统的变化，并将其纳入一个包括降雨和径流、湖泊和湿地以及塑造河流的过程的计算机模型中。他们将使用美国明尼苏达州和阿根廷萨尔塔的河流数据来测试这一理论和模型。这些河流的河床高度在过去的冰川周期中变化了几十到数百米，在过去200年里变化了几米，以应对气候和土地利用的变化。圣安东尼瀑布实验室在小规模河流上进行的受控实验将补充这些基于现场的测试。这项工作的拟议成果是一个有效的、基于物理的预测模型，用于模拟河网随气候和土地利用变化而演变的情况。该项目将培养本科生、研究生和博士后学者。该团队将与Ojibwe人合作，扩大对科学的参与。Wickert和他的团队将开发和测试理论和模型，以模拟河网对水和泥沙供应变化的反应。他们将把河流支流网络编码成数学网络，另外还包括山谷、湖泊和周围的山坡。然后，他们将通过这些网络耦合和求解描述冲积河流动力学的方程，以预测河流对外部扰动的复杂反应。这些方程将成为一个新的数值模型的基础，该模型将根据现场和实验室数据进行测试，并由泥沙输入和水排放的记录和模拟驱动。该模型将使我们能够快速模拟冲积河流对地貌变化驱动因素的响应，从而提高我们重建过去的河流动态和预测未来环境变化对河流的影响的能力。该奖项反映了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。

Rivers and their tributaries form networks that integrate the far reaches of Earth's landscapes, linking our homes, farms, cities, and wilderness areas. These rivers are ever-changing, sometimes near-imperceptibly and sometimes dramatically adjusting their forms to carry the water and sediment supplied by rainfall, snow/ice melt, and erosion of the surrounding landscape. Both natural and human activities can alter the balance of water and sediment entering rivers, causing them to erode downwards into their beds when water supply outweighs sediment supply, or to deposit sediments and raise the level of their beds when sediment supply increases beyond what the water can carry. Wickert and his team will develop a theory to predict these river-system changes, and incorporate it into a computer model that includes rainfall and runoff, lakes and wetlands, and processes that shape rivers. They will test this theory and model using data from rivers in Minnesota, USA, and Salta, Argentina. These rivers' bed elevations have changed by tens to hundreds of meters during past glacial cycles and by several meters over the past 200 years in response to changing climate and land use. Controlled experiments on small-scale rivers conducted at the Saint Anthony Falls Laboratory will supplement these field-based tests. The proposed outcome of this work is an efficient, physics-based, predictive model to simulate river-network evolution in response to climate and land-use change. The project will train undergraduate students, graduate students, and postdoctoral scholars. The team will work with the Ojibwe people to broaden participation in science.Wickert and his group will develop and test theory and models to simulate river-network response to changes in water and sediment supply. They will codify river-tributary networks into mathematical networks that additionally incorporate valleys, lakes, and the surrounding hillslopes. They will then couple and solve equations describing alluvial-river dynamics across these networks to predict the complex response of rivers to external perturbations. These equations will underlie a new numerical model, to be tested against field and laboratory data and driven by records and simulations of sediment inputs and water discharge. This model will enable us to rapidly simulate alluvial-river response to drivers of geomorphic change, thereby improving our ability to both reconstruct past river dynamics and forecast the impacts of environmental change on rivers into the future.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.