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Comparison of digital terrain and field-based channel derivation methods in a subalpine catchment, Front Range, Colorado.

机译：在科罗拉多州Front Range的亚高山流域，数字地形和基于实地的渠道推导方法的比较。

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摘要

Understanding the reliability of digitally derived channel networks for mountainous headwater catchments is important to many water resource and land-use management applications. Digital elevation models (DEMs) have become an essential tool for an increasing array of mountain runoff analyses. The purpose of this study is to investigate the influence of digitally-derived topographic variables on channel network formation for a high-elevation glaciated watershed. To accomplish this, our objectives were to (1) test how differences in gridded DEM resolution affect spatially distributed topographic parameters of local slope (tan beta), specific contributing area (alphas), and topographic wetness index (TWI) derived from both eight and infinite directional flow algorithms, (2) map the actual stream channel network at Loch Vale and examine the influence of surface variables on channel initiation, and (3) evaluate the performance of common methods for deriving channel networks from gridded topographic data by comparing to the observed network.;We found that coarser DEM resolution leads to a loss of detail in spatial patterns of topographic parameters and an increase in the calculated mean values of ln(alphas) and TWI. Grid cell sizes above 1m result in a substantial shift in the overall cumulative frequency distributions of ln(alphas) and TWI towards higher values. A field survey at Loch Vale revealed a complex and disjointed channel network, with 242 channelized points and 30 channel heads. We found no predictable relationships between channel head locations and geomorphic process domains. Analysis of variance (ANOVA) showed no statistically significant difference in mean ln(alphas) and TWI for channel head locations grouped by elevation, aspect, slope, formation process or upslope land cover type. For most DEM resolutions and flow partitioning algorithms, deriving channel networks with spatially constant flow accumulation and TWI thresholds provides poor network representation. The publicly available National Hydrography Dataset (NHD) layer oversimplifies the channel network by neglecting almost all first and second order channels. Many of the DEM-derived channel networks that use spatially constant flow accumulation and TWI thresholds also do not reproduce the locations of low order channels in the observed channel network well. Assumptions of topographic control on channel initiation are not shown to be valid at Loch Vale, likely due to their inability to capture subsurface processes and geologic features important to channel formation.;However, if using these topographically dependent threshold methods to delineate channel networks, we suggest the use of field-based survey data to identify appropriate thresholds. With appropriate thresholds, both 1m and 10m DEMs can produce channel networks with similar drainage densities to the observed network, even if locations of low order channels are not predicted accurately. Performance degrades for 30m DEMs, so we suggest that DEMs with resolutions coarser than 10m should be avoided for channel network delineation.
机译：了解山区上游水源地的数字化渠道网络的可靠性对于许多水资源和土地利用管理应用至关重要。数字高程模型（DEM）已成为增加山区径流分析阵列的重要工具。这项研究的目的是调查高海拔冰川分水岭的数字化地形变量对河道网络形成的影响。为了实现这一目标，我们的目标是（1）测试网格DEM分辨率的差异如何影响由8个和2个国家和地区得出的局部斜率（tan beta），比贡献面积（alpha）和地形湿度指数（TWI）的空间分布地形参数。无限方向流算法，（2）映射尼斯湖的实际河道网络，检查表面变量对河道启动的影响，（3）通过与网格地形数据进行比较，评估从网格化地形数据推导河道网络的常用方法的性能。我们发现，较粗的DEM分辨率会导致地形参数空间模式的细节丢失，并导致ln（alphas）和TWI的计算平均值增加。大于1m的网格单元大小会导致ln（alpha）和TWI的整体累积频率分布朝着更高的值大幅偏移。尼斯湖的现场调查显示，渠道网络复杂且不相连，有242个通道化点和30个通道头。我们发现通道头位置和地貌过程域之间没有可预测的关系。方差分析（ANOVA）显示，按高程，坡向，坡度，形成过程或上坡土地覆盖类型分组的通道头位置，平均ln（alpha）和TWI均无统计学显着差异。对于大多数DEM分辨率和流分配算法，派生具有空间恒定流累积和TWI阈值的通道网络将提供较差的网络表示。公开可用的国家水文数据集（NHD）层几乎忽略了所有一阶和二阶通道，从而过分简化了通道网络。许多使用空间恒定流量累积和TWI阈值的DEM派生的通道网络也无法很好地重现观察到的通道网络中低阶通道的位置。在河谷地区，对渠道启动进行地形控制的假设并未显示出有效，这可能是由于它们无法捕获对渠道形成至关重要的地下过程和地质特征。但是，如果使用这些依赖地形的阈值方法来描绘渠道网络，我们建议使用基于实地的调查数据来确定适当的阈值。通过适当的阈值，即使无法准确预测低阶通道的位置，1m和10m的DEM都可以产生与观测网络具有相似排水密度的通道网络。对于3000万个DEM，性能会下降，因此我们建议避免使用分辨率大于10m的DEM进行信道网络划分。

著录项

  • 作者

    Hastings, Blaine.;

  • 作者单位

    Colorado State University.;

  • 授予单位 Colorado State University.;
  • 学科 Geodesy.;Geomorphology.;Hydrology.
  • 学位 M.S.
  • 年度 2012
  • 页码 119 p.
  • 总页数 119
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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