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Man-induced regime shifts in small estuaries—II: a comparison of rivers

机译：小河口中人为引起的政权转移——II：河流的比较

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This is Part II of two papers on man-induced regime shifts in small, narrow, and converging estuaries, with focus on the interaction between effective hydraulic drag, fine sediment import, and tidal amplification, induced by river engineering works, e.g., narrowing and deepening. Paper I describes a simple linear analytical model for the tidal movement in narrow, converging estuaries and a conceptual model on the response of tidal rivers to river engineering works. It is argued that such engineering works may set in motion a snowball effect bringing the river into an alternative steady state. Part II analyses the historic development in tidal range in four rivers, e.g., the Elbe, Ems, Loire, and Scheldt, all in northwest Europe; data are available for many decades, up to a century. We use the analytical model derived in Part I, showing that the effective hydraulic drag in the Ems and Loire has decreased considerably over time, as anticipated in Part I. We did not find evidence that the Upper Sea Scheldt is close to its tipping point towards hyperturbid conditions, but risks have been identified. In the Elbe, tidal reflections against the profound step in bed level around Hamburg seem to have affected the tidal evolution in the last decades. It is emphasized that the conceptual picture sketched in these papers is still hypothetical and needs to be validated, for instance through hind-cast modeling of the evolution of these rivers. This will not be an easy task, as historical data for a proper calibration of the models required are scarce.
机译：这是两篇关于在狭窄，狭窄和汇聚河口中人为引起的政权转移的论文的第二部分，其重点是河流工程工作（例如，狭窄和狭窄）引起的有效水力阻力，细沙输入和潮汐放大之间的相互作用。加深。论文一描述了一个简单的线性分析模型，用于狭窄，汇聚河口的潮汐运动，以及一个关于潮汐河对河流工程响应的概念模型。有人认为，这样的工程可能会引发滚雪球效应，使河流进入另一种稳定状态。第二部分分析了西北欧洲四条河流的潮汐范围的历史发展；例如易北河，埃姆斯河，卢瓦尔河和斯海尔德河。数据可以使用长达数十年之久。我们使用第一部分中得出的分析模型，表明随着时间的推移，Ems和Loire中的有效水力阻力已随着第一部分中的预期而显着降低。我们没有找到证据表明上海斯海尔德河接近其临界点浑浊情况，但已确定风险。在易北河，潮汐对汉堡周围床位的大幅上升的反射似乎已经影响了过去几十年的潮汐变化。需要强调的是，这些论文中所描绘的概念图仍然是假设的，需要进行验证，例如，通过对这些河流的演变进行后播建模。这不是一件容易的事，因为缺乏对所需模型进行适当校准的历史数据。

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