Collaborative Research - Processes Controlling Depositional Signals of Environmental Change in the Fly River Sediment Dispersal system:Rates and Mechanisms of Floodplain Deposition

William E. Dietrich该项目主要关注两个基本问题：1)流经低地洪泛平原系统的水流和沉积物路线如何调节沉积物向近海沉积环境输送的短期和长期变化？2)是什么控制了沉积在河漫滩上的河流泥沙负荷的比例？全新世海平面上升期间，洪泛区净输沙量最大，海平面接近稳定后，洪泛区输沙量的比例逐渐下降。这两个基本问题正在通过比较水流和泥沙路线过程，以及在中游和下游斯特里克兰德河的洪泛平原上损失的泥沙比例来解决。从历史上看，Strickland的负荷是Fly的7倍，据推测，更大的负荷导致了更大的河道动力学，更陡峭的斜坡，更粗糙的河床，更高的洪泛区，可能比Fly的捕获效率更低。目前正在开发一个数值模型，该模型具有足够的机制，可以解决事件和季节尺度上的阻尼和捕获效率问题，但也足够简化，可以模拟共同演化的河床粒度、河道坡度和洪泛区地形，这是理解捕获效率时间演化的关键能力。尽管雄心勃勃，但该模型的许多部分已经在以前的研究中组装起来了。水动力模型考虑了河漫滩形态和水文的影响。泥沙运移包括河道迁移的影响，并以粒度来解释泥沙的沉积和侵蚀。目前正在进行一个实地项目，以记录洪水波衰减率，斯特里克兰河和弗莱河的沉积物捕获效率，并对数值模型进行参数化。目前正通过地形调查和遥感图像分析来量化洪泛区的形态。通过对速度场和悬沙场的深入调查，可以对水力学和输沙模型进行激励和参数化。从浅层岩心记录了冲积平原的短期和长期沉积速率（小于100年）。Ok Tedi Mining, Ltd.在Middle Fly和Porgera Joint Venture在Strickland提供了广泛的流量和沉积物监测数据。以往对Fly River的研究使研究重点集中在Strickland River上。

EAR-0203577 William E. Dietrich This project focuses on two fundamental questions: 1) How does flow and sediment routing through a lowland floodplain system moderate short and longer-term variations in sediment delivery towards offshore depositional environments? and 2) What controls the proportion of a river's sediment load that is deposited on its floodplain? It is hypothesized that net sediment loss to the floodplains was highest during Holocene sea-level rise and, after near stabilization of sea level, the proportion of the sediment load deposited in the floodplain has progressively declined.These two basic question are being addressed by comparing the flow and sediment routing processes, and the proportion of sediment lost to floodplains on the middle Fly and lower Strickland Rivers. Historically, the Strickland carried about 7 times the load of the Fly and it is hypothesize that this larger load has led to greater channel dynamics, steeper slopes, coarser bed, more elevated floodplain and possibly a lower trapping efficiency than the Fly. A numerical model is being developed that is sufficiently mechanistic that it can address the questions of damping and trapping efficiency on the event and seasonal scale, yet simplified enough that it can also model the co-evolving bed grain size, channel slope and floodplain topography, a crucial capability for understanding the time evolution of trapping efficiency. Though ambitious, many parts of the model have been assembled in previous research. The hydrodynamic model accounts for the effects of floodplain morphology and hydrology. The sediment routing includes effects of channel migration and accounts for the deposition and erosion of sediment by grain size.A field program is being conducted to document the flood wave damping rates, the sediment trapping efficiency of the Strickland and Fly Rivers, and to parameterize the numerical model. Quantification of floodplain morphology is being done through topographic surveys and analysis of remote sensing imagery. Intensive surveys of the velocity and suspended sediment fields are used to motivate and parameterize the hydraulics and sediment transport model. Short and longer-term (less than 100 years) rate of floodplain deposition is being documented from shallow cores. Extensive flow and sediment monitoring data are being provided by Ok Tedi Mining, Ltd. on the Middle Fly and by Porgera Joint Venture on the Strickland. Previous research on the Fly River enables the research focus to be on the Strickland River.