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

粤公网安备44010502000017号 William E.迪特里希 该项目集中于两个基本问题：1）如何通过一个低地洪泛平原系统的流量和沉积物路由缓和的短期和长期变化的沉积物输送到近海沉积环境？2）是什么控制了河流沉积在洪泛区的泥沙比例？据推测，在全新世海平面上升期间，洪泛区的净泥沙流失量最高，在海平面接近稳定后，沉积在 河漫滩已逐步下降。这两个基本问题正在解决的流量和泥沙路由过程，以及在中部飞和较低的斯特里克兰河的河漫滩泥沙流失的比例进行比较。从历史上看，斯特里克兰河的负荷大约是蝇河的7倍，据推测，这种较大的负荷导致了更大的河道动力学，更陡的斜坡，更粗糙的河床，更高的洪泛区，可能比蝇河的捕集效率更低。正在开发的数值模型是足够的机械，它可以解决的问题，阻尼和捕获效率的事件和季节尺度，但足够简化，它也可以模拟共同发展的床粒度，渠道坡度和河漫滩地形，理解捕获效率的时间演变的一个关键能力。虽然雄心勃勃，但模型的许多部分已经在以前的研究中组装。水动力学模型考虑了洪泛区形态和水文的影响。泥沙演算包括河道迁移的影响，并考虑泥沙的沉积和侵蚀的粒度。一个现场程序正在进行，以记录洪水波阻尼率，斯特里克兰和飞河的泥沙截留效率，并参数化的数值模型。正在通过地形测量和遥感图像分析对洪泛区形态进行量化。密集的调查的速度和悬浮泥沙场被用来激励和参数化的水力学和泥沙输运模型。短期和长期（不到100年）的河漫滩沉积率正在记录从浅芯。Ok Tedi矿业有限公司和Porgera合资企业正在提供广泛的水流和沉积物监测数据。以前的研究飞河使研究重点放在斯特里克兰河。

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.