Rivers with alluvial bars store more wood than those without, supplied through channel shifting. However, wood dynamics (arrival or new deposits, departure or entrainment, and stable or immobile pieces) can vary substantially over time in response to critical hydrological drivers that are largely unknown. To evaluate them, we studied the dynamics of large wood pieces and logjams along a 12-km reach of the lower Allier River using six series of aerial images of variable resolution acquired between 2009 and 2020, during which maximum river discharge fluctuated around the dominant flood discharge (Q_1.5) that is potentially the bankfull discharge along this well-preserved not incised reach. Individual wood departure was best correlated with water levels exceeding dominant flood discharge. The duration of the highest magnitude flood was best correlated with wood depositions, with shorter floods resulting in a higher number of deposits. Finally, most of the wood remained stable when river discharge did not exceed 60% of Q_1.5 over a long period of time. Changes in inter-annual wood budget (reach-scale) depend on the duration over which discharge exceeded 60% of Q_1.5. Hydrological conditions driving jam build-up and removal were similar to those controlling individual wood piece dynamics. The results suggest that specific hydrological conditions influence the dynamics of large wood and log jams in the Allier River. Understanding the dynamics of large wood and its impact on river morphology is fundamental for successful river management and habitat restoration initiatives.

中文翻译：

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用于探索大型木材动态水文驱动因素的高分辨率年际框架

有冲积坝的河流比没有冲积坝的河流储存更多的木材，这些木材是通过河道移动提供的。然而，木材动态（到达或新沉积物、离开或夹带以及稳定或不动的碎片）可能会随着时间的推移而发生很大变化，以响应很大程度上未知的关键水文驱动因素。为了对其进行评估，我们使用 2009 年至 2020 年间获取的六组不同分辨率的航空图像，研究了阿列河下游 12 公里河段沿线的大木块和堵塞的动态，在此期间，最大河流流量在主要洪水周围波动。泄流（Q _1.5），这可能是沿着这个保存完好的非切割河段的满岸泄流。个别木材的离开与超过主要洪水流量的水位最相关。最高强度洪水的持续时间与木材沉积最相关，洪水越短，沉积物的数量就越多。最后，当河流流量长期不超过 Q _1.5的 60% 时，大部分木材保持稳定。年际木材预算（达到规模）的变化取决于排放量超过 Q _1.5 60% 的持续时间。驱动果酱形成和清除的水文条件与控制单个木块动态的水文条件相似。结果表明，特定的水文条件影响阿列河中大型木材和原木堵塞的动态。了解大型木材的动态及其对河流形态的影响是成功的河流管理和栖息地恢复举措的基础。