Wood recruitment and retention: The fate of eroded trees on a braided river explored using a combination of field and remotely-sensed data sources
Wood recruitment and retention: The fate of eroded trees on a braided river explored using a combination of field and remotely-sensed data sources
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木材补充和保留：结合实地和遥感数据源探索辫状河上被侵蚀树木的命运
DOI：
10.1016/j.geomorph.2012.10.003
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发表时间：
2013
期刊：
影响因子：
3.9
通讯作者：
M. Welber
中科院分区：
文献类型：
--
作者：
W. Bertoldi;A. Gurnell;M. Welber
本文研究了大型砾石床辫状河（意大利塔利亚门托河）中的木材补充和沉积动态。我们结合了现场测量、自动重复地面图像和遥感调查来量化河岸侵蚀和相关下游沉积造成的木材输入。对洪水造成岛屿边缘植被侵蚀的两个地点进行了调查。侵蚀事件之前的激光雷达调查提供了有关侵蚀区域的形态和植被结构的数据，从而可以估计被连根拔起的树木数量。自动获取的地面图像序列（并由现场测量支持）显示了沉积树木的时间、数量和位置。结果表明，辫状河的复杂形态导致了特定的沉积模式。我们观察到砾石栏上木材分布广泛，堵塞的特点是少量原木（平均 2-3 根），并且在许多情况下只有一根原木。大部分被侵蚀的树木（高达 40%）沉积在最近的下游坝上。这说明在补充地点附近保留了大量木材，而剩余木材则广泛分布在下游。观察到的当地木材滞留水平的差异与侵蚀地点与主河道的接近程度有关，并且还观察到洪水事件的峰值和落肢之间的滞留差异，证实水深和可能的流速是控制木材沉积的关键参数。
This paper investigates wood recruitment and deposition dynamics in a large gravel-bed, braided river (Tagliamento River, Italy). We used a combination of field measurements, automatically repeated ground images, and remotely sensed surveys to quantify wood input through bank erosion and associated downstream deposition. Two sites were investigated where floods caused the erosion of vegetated island edges. A lidar survey preceding the erosion events provided data on the morphology and vegetation structure of the eroded areas, allowing estimation of the number of trees that were uprooted. Sequences of ground-based images acquired automatically (and supported by field measurements) showed the time, number, and location of deposited trees. Results show that the complex morphology of braided rivers induces specific deposition patterns. We observed wide dispersal of wood on gravel bars, with jams characterised by a small number of logs (on average 2–3) and, in many cases, only a single log. A large proportion of the eroded trees (up to 40%) were deposited on the nearest downstream bar. This illustrates significant wood retention close to the recruitment site, with the remaining wood dispersed widely downstream. Differences in the observed level of local wood retention were associated with the proximity of the erosion site to the main channel and differences were also observed in retention between the peak and the falling limb of flood events, confirming that water depth and probably flow velocity are the crucial parameters controlling wood deposition.