《Hydrological process》杂志刊登“米切尔河巨型沉积扇上水文地貌对冲积冲沟侵蚀的影响”

作者： J. G. Shellberg, A. P. Brooks, J. Spencer, D. Ward

刊物：《Hydrological process》，2013年，27卷第7期，1086–1104页

关键词：冲积沟壑侵蚀；降雨侵蚀；超渗产流；抗蚀性；放牧管理

摘要：位于澳大利亚的米切尔河河流巨型冲积扇，地处热带，横跨昆士兰州。研究从多个时间和空间尺度评估了影响冲积冲沟侵蚀的水文地貌过程。运用水位标尺数据，当地水位记录以及基于激光雷达地形数据的HEC-RAS（美国工程兵团WES编制的河道水面线计算程序）模型对河漫滩淹没的纵向变化进行了量化，运用每日延时摄影和年度GPS观测对年内和年际的沟崖退移速率进行了测量。针对在整个河漫滩周期区不同的水源和相关的侵蚀过程，包括直接降雨，超渗产流，土壤渗水，河流回水和漫滩洪水淹没，对侵蚀进行了分析。冲积沟渠洪水淹没的频率由于河流的下切和约束而发生纵向变化。在冲积扇的顶部附近，大河道中洪水重现期达到百年一遇，但仍有部分河流回水淹没相邻的沟壑并侵蚀更新世冲积层。在全新世下游冲积平原，冲积沟渠淹没的重现期超过2到5年以上，并对年侵蚀总量产生很大的影响。然而，在所有站点大多数的沟崖退移是受直接降雨和超渗产流驱动的，因为24小时降雨总量是最容易预测的变量。其余的可变性可以解释为季节性的植被状况，复杂的土壤湿润和干燥的周期，张力裂缝的发展，近表面的孔隙水压力，土块剥落破坏和漫流，以及土壤属性的异质性。放牧管理的影响体现在土壤表面和多年生草本植物生长条件上，包括影响直接降雨侵蚀、水入渗、径流流量、沿河道的水浓度，以及高度分散型土壤的阻力或在强烈的热带降雨下的蔓延。

The hydrogeomorphic influences on alluvial gully erosion along the Mitchell River fluvial megafan

Authors：J. G. Shellberg, A. P. Brooks, J. Spencer, D. Ward

Journal：Hydrological Processes，Volume 27, Issue 7, pages 1086–1104, 30 March 2013

Keywords: alluvial gully erosion; rainfall erosion; infiltration-excess runoff; erosion resistance; grazing management

Abstract：Hydrogeomorphic processes influencing alluvial gully erosion were evaluated at multiple spatial and temporal scales across the Mitchell River fluvial megafan in tropical Queensland, Australia. Longitudinal changes in floodplain inundation were quantified using river gauge data, local stage recorders and HEC-RAS modelling based on LiDAR topographic data. Intra- and interannual gully scarp retreat rates were measured using daily time-lapse photographs and annual GPS surveys. Erosion was analysed in response to different water sources and associated erosion processes across the floodplain perirheic zone, including direct rainfall, infiltration-excess runoff, soil-water seepage, river backwater and overbank flood inundation. The frequency of river flood inundation of alluvial gullies changed longitudinally according to river incision and confinement. Near the top of the megafan, flood water was contained within the macrochannel up to the 100-year recurrence interval, but river backwater still partially inundated adjacent gullies eroding into Pleistocene alluvium. In downstream Holocene floodplains, inundation of alluvial gullies occurred beyond the 2- to 5-year recurrence interval and contributed significantly to total annual erosion. However, most gully scarp retreat at all sites was driven by direct rainfall and infiltration-excess runoff, with the 24-h rainfall total being the most predictive variable. The remaining variability can be explained by seasonal vegetative conditions, complex cycles of soil wetting and drying, tension crack development, near-surface pore-water pressure, soil block undermining from spalling and overland flow, and soil property heterogeneity. Implications for grazing management impacts on soil surface and perennial grass conditions include effects on direct rainfall erosion, water infiltration, runoff volume, water concentration along tracks, and the resistance of highly dispersible soils to gully initiation or propagation under intense tropical rainfall.

原文链接：http://onlinelibrary.wiley.com/doi/10.1002/hyp.9240/abstract