Garcia-Castellanos Daniel, O'Connor Jim E
Instituto de Ciencias de la Tierra Jaume Almera, ICTJA-CSIC, Solé i Sabarís s/n, 08028, Barcelona, Spain.
U.S. Geological Survey, 2130 SW Fifth Ave., Portland, OR, 97201, USA.
Sci Rep. 2018 Jul 12;8(1):10573. doi: 10.1038/s41598-018-28981-y.
Most current models for the landscape evolution over geological timescales are based on semi-empirical laws that consider riverbed incision proportional to rock erodability (dependent on lithology) and to the work performed by water flow (stream power). However, the erodability values obtained from these models are entangled with poorly known conditions of past climate and streamflow. Here we use the erosion reported for 82 outburst floods triggered by overtopping lakes as a way to estimate the outlet erodability. This avoids the common assumptions regarding past hydrology because water discharge from overtopping floods is often well constrained from geomorphological evidence along the spillway. This novel methodology yields values of erodability that show a quantitative relation to lithology similar to previous river erosion analyses, expanding the range of hydrological and temporal scales of fluvial incision models and suggesting some consistency between the mathematical formulations of long-term and catastrophic erosional mechanisms. Our results also clarify conditions leading to the runaway erosion responsible for outburst floods triggered by overtopping lakes.
当前大多数关于地质时间尺度上地貌演化的模型是基于半经验定律，这些定律认为河床下切与岩石可蚀性（取决于岩性）以及水流做功（河流功率）成正比。然而，从这些模型中获得的可蚀性值与过去气候和水流状况的未知条件相互交织。在这里，我们将82次因湖泊溢流引发的突发洪水所报告的侵蚀情况作为一种估算出水口可蚀性的方法。这避免了关于过去水文状况的常见假设，因为溢流洪水的流量通常可以根据溢洪道沿线的地貌证据得到很好的限制。这种新颖的方法得出的可蚀性值显示出与岩性的定量关系，类似于先前的河流侵蚀分析，扩展了河流下切模型的水文和时间尺度范围，并表明长期和灾难性侵蚀机制的数学公式之间存在一定的一致性。我们的结果还阐明了导致湖泊溢流引发突发洪水的失控侵蚀的条件。
