The Role of River Discharge and Geometric Structure on Diurnal Tidal Dynamics, Alabama, USA.
The Role of River Discharge and Geometric Structure on Diurnal Tidal Dynamics, Alabama, USA.
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DOI：
10.1029/2021jc018007
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发表时间：
2022-03
影响因子：
3.6
通讯作者：
Torres, Raymond
中科院分区：
文献类型：
--
作者：
Dykstra, Steven L.;Dzwonkowski, Brian;Torres, Raymond
当潮汐向内陆传播时，它们会被河道几何形状和河流流量所扭曲。河流-海洋过渡中的潮汐动力学通常在具有相对稳定的河流条件的高能潮汐环境中观察到，使可变河流流量对潮汐和纵向变化的影响知之甚少。为了研究可变河流流量对潮汐-河流相互作用的影响，我们研究了河流流量范围为几个数量级的低能潮汐环境，即Tombigbee River-移动的Bay河流-海洋过渡的昼夜微潮，使用21个站点的水位和流速观测。结果表明，向海河段的宽度辐合和向陆回水河段的高度辐合减小了潮汐日衰减，通道辐合变化的位置在湾头内陆约40-50 km处，最大分叉处向海。河流事件放大了向海区域的潮汐，减弱了向陆区域的潮汐。这就形成了一个由河流引起的峰值振幅区域，该区域位于洪水极限的向海方向（即，双向-单向电流转换），允许更多的潮汐能传播到内陆。潮流衰减和延迟比水位河流流量，使相位滞后动态。河流对潮汐的影响被纵向描绘，并随着河流流量的增加而向海转移，范围高达180 km。结果表明，河流对潮汐的影响在冲积系统中的纵向移动可以解析地估计使用河流流量与潮汐流量的比值和系统的几何收敛。我们简单的分析理论为理解沿着日益动态的海岸的潮汐-河流-地貌平衡提供了一条途径。沿着河流-海洋过渡，河流流量衰减了向陆区域的潮汐，放大了向海区域的潮汐。随着河流流量的增加，双向潮汐流区域变为单向，使潮汐河流向海移动了180 km平面形状通道几何形状（例如，宽度收敛）可能不是潮汐-河流水动力学转变的可靠指标
As tides propagate inland, they become distorted by channel geometry and river discharge. Tidal dynamics in fluvial‐marine transitions are commonly observed in high‐energy tidal environments with relatively steady river conditions, leaving the effects of variable river discharge on tides and longitudinal changes poorly understood. To study the effects of variable river discharge on tide‐river interactions, we studied a low‐energy tidal environment where river discharge ranges several orders of magnitude, the diurnal microtidal Tombigbee River‐Mobile Bay fluvial‐marine transition, using water level and velocity observations from 21 stations. Results showed that diurnal tidal attenuation was reduced by the width convergence in seaward reaches and height convergence of the landward backwater reaches, with the channel convergence change location ∼40–50 km inland of the bayhead and seaward of the largest bifurcation. River events amplified tides in seaward regions and attenuated tides in landward regions. This created a region of river‐induced peak amplitude seaward of the flood limit (i.e., bidirectional‐unidirectional current transition), allowing more tidal energy to propagate inland. Tidal currents were attenuated and delayed more by river discharge than water levels, making the phase lag dynamic. The river impacts on the tides were delineated longitudinally and shifted seaward as river discharge increased, ranging up to ∼180 km. Results indicated the longitudinal shifts of river impacts on tides in alluvial systems can be estimated analytically using the ratio of river discharge to tidal discharge and the geometric convergence of the system. Our simple analytical theory provides a pathway for understanding the tide‐river‐geomorphic equilibrium along increasingly dynamic coasts. Along the fluvial‐marine transition, river discharge attenuated tides in landward regions and amplified tides in seaward regions Regions of bidirectional tidal flow became unidirectional as river discharge increased, shifting the tidal river ∼180 km seaward Planform channel geometry (e.g., width convergence) may not be a robust indicator of the transition in tide‐river hydrodynamics