Hydrological thresholds and basin control over paleoflood records in lakes
Hydrological thresholds and basin control over paleoflood records in lakes
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DOI：
10.1130/g37261.1
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发表时间：
2016
期刊：
影响因子：
5.8
通讯作者：
D. Schillereff;R. Chiverrell;N. Macdonald;J. Hooke
中科院分区：
文献类型：
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作者：
D. Schillereff;R. Chiverrell;N. Macdonald;J. Hooke
长期水文数据的缺乏阻碍了可靠地确定在变暖的世界中洪水变得更加频繁和/或强烈的可能性。湖泊沉积物保留了特征事件层，为形成广泛分布且独特的历史洪水年表提供了潜力。推断洪水强度仍然是一个更大的挑战，之前通过分析陡峭的极地或高山序列部分克服了这一挑战。在这里，我们演示了一种从未开发的资源中获取洪水频率和强度数据的方法，这些资源是大多数温带湖泊的典型视觉均匀有机沉积物。 Brotherswater（英格兰西北部）沉积物圈闭的地球化学成分和端元模型以及邻近的短核心颗粒尺寸数据区分了季节性和长期同生（冬季流量和沉积物供应增加）和自生（夏季生产力、热混合）沉积过程中罕见的粗粒洪水沉积物的特征。将古洪水重建与当地河流流量进行比较表明，水文阈值审查了事件特征的保存，在三角洲近端沉积物中可检测到的复发间隔为 4 年，在湖中心则下降到 9 年。事件阈值（流量）和过程特征是从沉积物档案中辨别洪水强度的重要前提。在全球普遍存在的温带湖泊中实施我们的方法，为水文学家、气候建模者、工程师和政策制定者应对未来洪水风险提供了一个巨大、独特的长期水文数据存储库。
The scarcity of long-term hydrological data is a barrier to reliably determining the likelihood of floods becoming more frequent and/or intense in a warmer world. Lake sediments preserve characteristic event layers, offering the potential to develop widely distributed and unique chronologies of historical floods. Inferring flood magnitude remains a greater challenge, previously overcome in part by analyzing sharply laminated polar or alpine sequences. Here we demonstrate an approach to obtain flood frequency and magnitude data from an unexploited resource, the largely visually homogeneous, organic sediments that typify most temperate lakes. The geochemical composition and end-member modeling of sediment trap and adjacent short core particle size data for Brotherswater (northwest England) discriminates the signature of infrequent, coarse-grained flood deposits from seasonal and longer term allogenic (enhanced discharge and sediment supply during winter) and autogenic (summer productivity, thermal mixing) depositional processes. Comparing the paleoflood reconstruction to local river discharges shows that hydrological thresholds censor event signature preservation, with 4 yr recurrence intervals detectable in delta-proximal sediments declining to 9 yr in the lake center. Event threshold (discharge) and process characterization are essential precursors to discerning flood magnitude from sediment archives. Implementation of our approach in globally prevalent temperate lakes offers a vast, unique repository of long-term hydrological data for hydrologists, climate modelers, engineers, and policy makers addressing future flood risks.