Collaborative Research: Investigating Human and Climate Influences on Delta Evolution Using Fluvial Discharge and Coastal Evolution Models

三角洲受陆地和海洋共同作用的影响，是陆海界面上重要的沉积地貌，提供了过去环境变化的记录。目前，世界各地的三角洲正受到人类活动的严重改变，尤其是河流筑坝，这减少了到达海岸的沉积物数量。虽然大型水坝是最近才出现的现象，但自农业出现和扩张以来，人类对景观的改变一直在进行。结合野外数据收集、河流模型和海岸演化模型，本研究将探讨人类活动是否对西班牙地中海沿岸现代埃布罗三角洲的形成产生了重大影响。具体地说，埃布罗三角洲的增长可以归因于罗马时代为农业目的而大规模砍伐森林。实地研究将通过收集和分析三角洲平原上的沉积物岩心来记录埃布罗三角洲近3000年来的演变。气候驱动的水文模型HydroTrend将用于计算这段时间内河流向海岸的沉积物排放量，包括可能归因于气候变化和可能由人类对埃布罗河流域的改变引起的沉积物排放量的变化。一个能够结合长时间尺度的海岸线演变的数值模型将被应用于检查三角洲形状的原因，并评估河流流量的变化在被海浪重新加工后将如何影响海岸。河流和海岸数值模型的耦合是群落表面动力学模拟系统（CSDMS）概念验证的重要目标。随着海平面的上升，三角洲的泥沙负荷继续被内陆的水坝隔离，了解三角洲的历史和未来的形态变化变得越来越重要。三角洲通常人口密集，为社会提供了许多重要的自然资源，特别是沿着多岩石的西班牙地中海海岸，靠近海平面的土地很少。在受人类文明影响的地区，三角洲可以作为大流域气候和土地利用变化的记录。西班牙埃布罗三角洲以其独特的平面形状，在过去的两千年里经历了重大的形态变化；这些变化可能归因于埃布罗流域的人类活动。该研究结果将广泛适用于揭示世界三角洲的历史（如尼罗河，波河，多瑙河，印度河，密西西比河）。如果人类活动在很大程度上造成了世界三角洲的形状，这将为理解人类在未来几个世纪将如何管理这些资源提供一个重要的背景，特别是在气候变化和人类继续改变这些地貌的情况下。

Influenced by both terrestrial and marine processes, deltas are critical sedimentary landforms at the land-sea interface that provide records of past environmental changes. Deltas worldwide are currently being severely altered by human activities, in particular river damming, which has reduced the amount of sediment reaching the coast. Although large dams are relatively recent phenomena, human alteration of landscapes has been ongoing since the advent and expansion of agriculture. Combining field data collection, fluvial modeling, and coastal evolution modeling, this research will examine whether human activities have significantly influenced the formation of the modern Ebro Delta, on the Mediterranean coast of Spain. Specifically, it is hypothersized that the growth of the Ebro Delta can be attributed to massive deforestation for agricultural purposes initiated in Roman times. Field research will document the evolution of the Ebro Delta over approximately the last 3,000 years by collecting and analyzing sediment cores from along the delta plain. The climate-driven hydrological model HydroTrend will be used to compute riverine sediment discharge to the coast over this time period, incorporating changes to sediment delivery that could be attributable to climatic changes and those that could be caused by human alterations to the Ebro River watershed. A numerical model of shoreline evolution capable of incorporating long timescales will be applied to examine the causes of the delta's shape and to evaluate how changes to riverine discharge would affect the coast after being reworked by waves. Coupling of the fluvial and coastal numerical models serves an important goal as proof-of-concept of the Community Surface Dynamics Modeling System (CSDMS).Understanding the historic and future morphologic change of deltas has become increasingly important as sea levels rise and sediment loads feeding deltas continue to be sequestered behind dams in the hinterland. Deltas are often densely populated and provide many importantt natural resources to society, particularly along the rocky Spanish Mediterranean coast with scant land near sea level. In regions that have been affected by human civilization, deltas can serve as a record of climate and land-use changes across large watersheds. The Ebro Delta, Spain, with its distinctive plan-view shape, has experienced significant morphologic changes over the last two millennia; changes that may be attributable to human activities in the Ebro watershed. The results of this research will have wide applicability to unraveling the history of deltas worldwide (e.g., Nile, Po, Danube, Indus, Mississippi). If human activities are largely responsible for the shape of the world's deltas, this would provide an important context for understanding how humankind will manage these resources over the coming centuries, particularly as climate changes and humans continue to alter these landforms.