Catchment-scale network analysis of functional sediment connectivity during an extreme rainfall event in the Grastal catchment, Austrian Central Alps

IF 3.1 2区 地球科学 Q2 GEOGRAPHY, PHYSICAL
Toni Himmelstoss, Florian Haas, Michael Becht, Tobias Heckmann
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引用次数: 0

Abstract

Global warming significantly impacts sediment dynamics in glaciated catchments, affecting water resource operations, water quality, recreational activities, and ecological systems. The propagation of climate-change-induced geomorphic changes and the catchment's sediment yield are moderated by sediment connectivity, defined as the degree to which a geomorphic system facilitates sediment transfer. Quantifying functional sediment connectivity at the catchment scale remains a challenge. To address this, we propose a novel approach combining graph theory with the morphological method. This approach is exemplified through a detailed case study of a 2022 thunderstorm event in the Grastal valley, Tyrol, Austria. First, a graph of potential sediment cascades is constructed using a geomorphological map, a digital elevation model and a flow routing algorithm. A short-term Digital Elevation Model of Difference (DoD) from consecutive ALS surveys is then used to infer sediment fluxes and calculate the Sediment Delivery Ratio (SDR) for each landform. The primary sediment mobilising processes were debris flows and fluvial erosion, with a significant proportion of debris flow material being deposited on slopes, not reaching the fluvial corridor. Strong fluvial erosion was observed in the proglacial area, but the propagation of these geomorphic changes is halted by an alluvial fan and a lake. Most landforms can be clearly categorised as connecting or disconnecting features based on their SDR. In total, a maximum of 12 % of mobilised sediments exited the catchment. Our findings demonstrate that (i) short-term, catchment-wide DoDs are valuable for assessing functional connectivity at an event temporal scale, (ii) using landforms as fundamental spatial units allows for the identification and in-depth analysis of critical sediment sinks and sources, and (iii) graph analysis facilitates the catchment-wide calculation of sediment delivery ratios between meaningful fundamental units and the delineation of significant sediment cascades.

奥地利中阿尔卑斯山格拉斯塔尔集水区极端降雨事件期间沉积物功能连通性的集水区尺度网络分析
全球变暖会严重影响冰川集水区的沉积物动力学,从而影响水资源运行、水质、娱乐活动和生态系统。气候变化引起的地貌变化的传播和集水区的沉积物产量受沉积物连通性的影响,沉积物连通性的定义是地貌系统促进沉积物转移的程度。在流域尺度上量化功能性沉积物连通性仍然是一项挑战。为此,我们提出了一种将图论与形态学方法相结合的新方法。我们通过对奥地利蒂罗尔州格拉斯塔尔山谷 2022 年一次雷暴事件的详细案例研究来说明这种方法。首先,利用地貌图、数字高程模型和水流路径算法构建了潜在沉积物级联图。然后,利用连续 ALS 勘测的短期数字高差模型(DoD)来推断沉积物通量,并计算出每种地貌的沉积物输送比(SDR)。主要的沉积物移动过程是泥石流和河道侵蚀,其中很大一部分泥石流物质沉积在斜坡上,没有进入河道走廊。在早冰期地区观察到强烈的河流侵蚀,但这些地貌变化的传播被冲积扇和湖泊阻断。大多数地貌可根据其 SDR 清晰地分为连接地貌和断开地貌。总之,最多有 12% 的移动沉积物流出了集水区。我们的研究结果表明:(i) 短期的、整个集水区范围内的 DoDs 对于评估事件时间尺度上的功能连通性很有价值;(ii) 使用地貌作为基本空间单元可以识别并深入分析关键的沉积物汇和源;(iii) 图形分析有助于计算整个集水区范围内有意义的基本单元之间的沉积物输送比,并划分重要的沉积物级联。
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来源期刊
Geomorphology
Geomorphology 地学-地球科学综合
CiteScore
8.00
自引率
10.30%
发文量
309
审稿时长
3.4 months
期刊介绍: Our journal''s scope includes geomorphic themes of: tectonics and regional structure; glacial processes and landforms; fluvial sequences, Quaternary environmental change and dating; fluvial processes and landforms; mass movement, slopes and periglacial processes; hillslopes and soil erosion; weathering, karst and soils; aeolian processes and landforms, coastal dunes and arid environments; coastal and marine processes, estuaries and lakes; modelling, theoretical and quantitative geomorphology; DEM, GIS and remote sensing methods and applications; hazards, applied and planetary geomorphology; and volcanics.
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