Temporal and spatial adjustments of channel migration and planform geometry: responses to ENSO driven climate anomalies on the tropical freely‐meandering Aguapeí River, São Paulo, Brazil
Temporal and spatial adjustments of channel migration and planform geometry: responses to ENSO driven climate anomalies on the tropical freely‐meandering Aguapeí River, São Paulo, Brazil
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河道迁移和平面几何的时空调整：对巴西圣保罗热带自由蜿蜒的阿瓜佩伊河 ENSO 驱动的气候异常的响应
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发表时间：
2018
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通讯作者：
G. Nanson
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作者：
Tainá Medeiros Suizu;G. Nanson
对巴西圣保罗州西部巴拉那河左岸支流阿瓜佩河的两个河段进行了研究，目的是评估弯曲曲率在该湿热带系统中对河道迁移的作用，并检查近半个世纪来土地利用变化或厄尔尼诺南方涛动（ENSO）驱动的气候异常是否改变了迁移行为和平面几何形状。测量了曲流-弯曲迁移率和形态测量参数，包括曲流-弯曲曲率、弯曲度、曲流波长和河道宽度，并分析了弯曲截止频率，以确定到2010年的48年间河道调整的变化率。结果表明，最大的平均通道迁移率发生在弯曲的曲率约2-3 RC/W，类似于其他以前研究的温带和亚北极自由蜿蜒的河流，虽然不明显，并倾向于更紧密的曲率。从1962年到2010年，Aguapeí河的弯曲度显著降低，从紧密弯曲转变为更开放的弯曲，河道迁移率总体下降，颈部截止频率相应降低，河道宽度总体增加。由于大部分流域（96%）在1962年已被砍伐，与对邻近河流系统的解释不同，河道形态和过程变化不是由于土地利用的改变，而是由于ENSO驱动的自1972年以来峰值流量的急剧增加约32%。总之，这项研究表明，最近的气候和相关的流态变化对这里调查的Aguapeí河的河道行为有明显的影响。版权所有© 2018约翰威利父子有限公司
Two reaches of Aguapeí River, a left‐bank tributary of the Paraná River in western São Paulo state, Brazil, were studied with the objective of assessing the role of bend curvature on channel migration in this wet‐tropical system and examining if land‐use changes or ENSO (El Niño Southern Oscillation) driven climate anomalies over nearly half a century have changed migration behaviour and planform geometry. Meander‐bend migration rates and morphometric parameters including meander‐bend curvature, sinuosity, meander wavelength and channel width, were measured and the frequency of bend cutoffs was analysed in order to determine the rate of change of channel adjustment over a 48 year period to 2010. Results show that maximum average channel migration rates occur in bends with curvatures of about 2–3 rc/w, similar to other previously studied temperate and subarctic freely meandering rivers although not as pronounced and with a tendency to favour tighter curvature. From 1962 to 2010 the Aguapeí River has undergone a significant reduction in sinuosity, a shift from tightly curving to more open bends, an overall decline in channel migration rates, an associated decrease in the frequency of neck‐cutoffs and an overall increase in channel width. As the majority of the drainage basin (96%) was already deforested in 1962, channel form and process changes were, unlike an interpretation for an adjacent river system, not attributed to altered land‐use but rather to a sharp ENSO‐driven increase in the magnitude of peak flow‐discharges of some 32% since 1972. In summary, this research revealed that recent climate and associated flow regime changes are having a pronounced effect on river channel behaviour in the Aguapeí River investigated here. Copyright © 2018 John Wiley & Sons, Ltd.