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Badass gully morphodynamics and sediment generation in Waipaoa Catchment, New Zealand
Earth Surface Processes and Landforms ( IF 3.3 ) Pub Date : 2020-09-30 , DOI: 10.1002/esp.5010
Ian C. Fuller 1 , Florian Strohmaier 2 , Samuel T. McColl 1 , Jon Tunnicliffe 3 , Michael Marden 4
Affiliation  

Large (>0.1 km2) gully–mass movement complexes (badass gullies) are significant contributors to the sediment cascade in New Zealand's steepland East Coast Region catchments. The scale of change taking place in these gully systems allows significant evolution in morphology and sediment dynamics to be tracked at annual to decadal timescales. Here we document changes in two adjacent badass gullies in Waipaoa catchment (Tarndale and Mangatu) to infer sediment generation processes and connectivity using a morphological budgeting approach. A baseline dataset for this study is provided by a LiDAR‐derived digital elevation model (DEM) in 2005. We produced new DEMs and orthophoto mosaics using photogrammetry in 2017, 2018, and 2019 to quantify gully morphodynamics and associated volumes of sediment erosion and deposition in both systems as they co‐evolved. Results indicate ongoing rapid development of both gully complexes. Severe erosion took place at the gully heads with lowering and migration (up to 25 m vertically and laterally) of the topographic divide separating the two gullies between 2005 and 2019. Over the same period, net lowering of each gully system was ~250 mm year−1. Key sediment‐generating processes included surface erosion, deep‐seated landslides, and debris flows. Longer term, the overall contribution of sediment from both badass gullies to the Waipaoa catchment has been declining. In the mid‐20th century, both gullies yielded in excess of 300 kt year−1. From 2005 to 2019, 80 kt year−1 was yielded from Tarndale and 110 kt year−1 from Mangatu. Our most recent surveys demonstrated considerable variability in sediment yield, ranging from 76 kt year−1 (2017–2018) to 291 kt year−1 (2018–2019). The annual variability observed reflects the complex morphodynamics of discrete hillslopes and tributary fans in these badass gully systems and underlines the importance of integrating decadal and annual surveys when assessing system trajectory. © 2020 John Wiley & Sons, Ltd.

中文翻译:

新西兰怀波阿集水区的ass流沟形态动力学和沉积物生成

大(> 0.1 km 2沟壑-质量运动复合体(badass沟壑)是新西兰陡峭的东海岸地区流域沉积物级联的重要贡献者。在这些沟壑系统中发生的变化的规模使得可以在每年到十年的时间尺度上追踪形态和沉积动力学的重大变化。在这里,我们记录了Waipaoa流域(Tarndale和Mangatu)两个相邻的坏蛋沟的变化,以使用形态预算方法推断沉积物的产生过程和连通性。这项研究的基准数据集由LiDAR衍生的数字高程模型(DEM)于2005年提供。我们在2017年,2018年和2019年使用摄影测量法制作了新的DEM和正射镶嵌图,以量化沟渠形态动力学以及相关的沉积物侵蚀和沉积量在两个系统中共同发展。结果表明两种沟渠复合体的持续快速发展。在2005年至2019年之间,沟壑头发生了严重侵蚀,使两个沟壑之间的地形分界线降低和迁移(垂直和横向方向高达25 m)。同一时期,每个沟壑系统的净降幅为〜250 mm年-1。关键的沉积物生成过程包括表面侵蚀,深层滑坡和泥石流。从长远来看,两个大ass沟的沉积物对怀波阿集水区的总体贡献一直在下降。在20世纪中叶,两个沟渠的产量都超过了300 kt年-1。从2005年到2019年,塔恩代尔产量为80 kt年-1,曼加图产量为110 kt年-1。我们最近的调查显示,沉积物产量存在很大差异,范围从76 kt年-1(2017-2018)到291 kt年-1(2018–2019)。观测到的年度变化反映了这些坏谷沟渠系统中离散的山坡和支流扇的复杂形态动力学,并强调了在评估系统轨迹时整合年代和年度调查的重要性。分级为4 +©2020 John Wiley&Sons,Ltd.
更新日期:2020-09-30
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