Roads versus flows in the Great Western Woodlands: surface-water insights into linear infrastructure effects

These datasets and spatial files are the data underlying the analyses presented in the paper 'Linear infrastructure impacts on landscape hydrology' published in the Journal of Environmental Management in 2018 (Volume 206, pp 446-457).

The extent of roads and other forms of linear infrastructure is burgeoning worldwide, but their impacts are inadequately understood and thus poorly mitigated. Previous studies have identified many potential impacts, including alterations to the hydrological functions and soil processes upon which ecosystems depend. However, these impacts have seldom been quantified at a regional level, particularly in arid and semi-arid systems where the gap in knowledge is the greatest, and impacts potentially the most severe.

To explore the effects of extensive track, road, and rail networks on surface hydrology at a regional level we assessed over 1000 km of linear infrastructure, including approx. 300 locations where ephemeral streams crossed linear infrastructure, in the largely intact landscapes of Australia’s Great Western Woodlands. We found a high level of association between linear infrastructure and altered surface hydrology, with erosion and pooling 5 and 6 times as likely to occur on-road than off-road on average (1.06 erosional and 0.69 pooling features km-1 on vehicle tracks, compared with 0.22 and 0.12 km-1, off-road, respectively). Erosion severity was greater in the presence of tracks, and 98% of crossings of ephemeral streamlines showed some evidence of impact on water movement (flow impedance (62%); diversion of flows (73%); flow concentration (76%); and/or channel initiation (31%)). Infrastructure type, pastoral land use, culvert presence, soil clay content and erodibility, mean annual rainfall, rainfall erosivity, topography and bare soil cover influenced the frequency and severity of these impacts.

We conclude that linear infrastructure frequently affects ephemeral stream flows and intercepts natural overland and near-surface flows, artificially changing site-scale moisture regimes, with some parts of the landscape becoming abnormally wet and other parts becoming water-starved. In addition, linear infrastructure frequently triggers or exacerbates erosion, leading to soil loss and degradation. Where linear infrastructure densities are high, their impacts on ecological processes are likely to be considerable. Linear infrastructure is widespread across much of this relatively intact region, but there remain areas with very low infrastructure densities that need to be protected from further impacts. There is substantial scope for mitigating the impacts of existing and planned infrastructure developments.

本数据集与空间文件为2018年发表于《环境管理期刊》（Journal of Environmental Management）第206卷第446-457页的论文《线性基础设施对景观水文的影响》（Linear infrastructure impacts on landscape hydrology）中各项分析的支撑数据。

全球范围内，道路与其他各类线性基础设施的覆盖范围正迅猛扩张，但其产生的影响却未得到充分认知，相应的减缓应对措施亦较为匮乏。过往研究已识别出诸多潜在影响，包括改变生态系统赖以维系的水文功能与土壤过程。然而，此类影响极少在区域尺度上得到量化，尤其是在知识缺口最大、影响潜在危害也最为严重的干旱与半干旱生态系统中。

为在区域尺度上探究大规模步道、道路与铁路网络对地表水文（surface hydrology）的影响，我们在澳大利亚大西部林地（Great Western Woodlands）这一整体保存较为完好的区域内，对总长超1000公里的线性基础设施展开了评估，其中涵盖约300处时令河（ephemeral stream）横穿线性基础设施的点位。研究发现，线性基础设施与地表水文改变之间存在显著关联：平均而言，道路范围内发生侵蚀与积水的概率分别是非道路区域的5倍与6倍（车辙道上每公里出现1.06处侵蚀地貌与0.69处积水特征，而非道路区域每公里仅为0.22处与0.12处）。存在步道的区域侵蚀程度更为严重，且98%的时令河横穿点位均表现出对水体运移产生影响的证据，具体包括：水流阻滞（占比62%）、水流改道（73%）、水流汇聚（76%）以及/或河道形成（31%）。基础设施类型、牧业用地类型、涵洞（culvert）设置情况、土壤黏土含量与可蚀性、年平均降雨量、降雨侵蚀力（rainfall erosivity）、地形条件以及裸土覆盖率，均会对上述影响的发生频率与严重程度产生影响。

我们的研究表明，线性基础设施常会干扰时令河的水流，并拦截自然坡面径流（overland flow）与近地表水流，人为改变局地尺度的水分状况，致使部分区域出现异常积水，而另一部分区域则面临缺水困境。此外，线性基础设施常会诱发或加剧侵蚀作用，进而导致土壤流失与土地退化。在线性基础设施密度较高的区域，其对生态过程的影响可能极为显著。尽管该相对完好的区域大部分区域已广泛分布线性基础设施，但仍存在部分基础设施密度极低的区域，需加以保护以避免遭受进一步的影响。现有及规划中的基础设施项目的影响仍存在较大的减缓空间。