Geomorphic Process from Topographic FormData & Models

The repeat topographic datasets used here are digital surface models (DSMs) derived using automated photogrammetry from photographs captured via aerial overflights during May 2002, 2009, and 2013. During overflights, discharge from Glen Canyon dam was held steady at 226 m3/s, and all subsequent analyses presented here apply to stages above this constant low flow discharge. DSMs are unique from traditional digital elevation models (DEMs) in that DSMs are not processed to remove vegetation. To compute geomorphic change during the inter-survey period, we used the Geomorphic Change Detection 6 software (http://gcd.joewheaton.org; see Wheaton et al., 2010). We assessed elevation uncertainty in the DSMs and found that uncertainty was spatially variable and significantly influenced by both surface slope and roughness, and thus employed a fuzzy inference system (FIS) to estimate DSM uncertainty on a pixel-by-pixel basis. Full details on the theory and implementation of FIS error modeling can be found in Wheaton et al., 2010, 2013, Kasprak et al., 2015, and Bangen et al., 2016. These data and models are associated with the journal manuscript: Kasprak A., Caster J., Bangen S., and Sankey J., 2017, Geomorphic process from topographic form: automating the interpretation of repeat survey data in river valleys: Earth Surface Processes and Landforms v. (online), doi: 10.1002/esp.4143, https://dx.doi.org/10.1002/esp.4143.本研究采用的重复地形观测数据集，为2002年5月、2009年5月及2013年5月通过航空航拍获取的影像，经自动化摄影测量技术生成的数字表面模型（Digital Surface Model, DSM）。本次航空航拍期间，格伦峡谷大坝（Glen Canyon Dam）的下泄流量稳定维持在226立方米每秒；本文后续所有分析均针对高于该恒定低流量的水位条件展开。数字表面模型（DSM）与传统数字高程模型（Digital Elevation Model, DEM）的核心差异在于，其未经过植被剔除处理流程。为计算两次测量间隔期内的地貌变化量，本研究采用了地貌变化检测6（Geomorphic Change Detection 6, GCD6）软件（访问地址：http://gcd.joewheaton.org；详细方法参见Wheaton等，2010）。本研究对DSM的高程不确定性开展评估，发现不确定性具有空间异质性，且显著受地表坡度与粗糙度的影响；因此采用模糊推理系统（Fuzzy Inference System, FIS）逐像素估算DSM的不确定性。关于模糊推理系统误差建模的理论框架与实现细节，可参阅Wheaton等（2010、2013）、Kasprak等（2015）以及Bangen等（2016）的相关研究。本数据集与相关模型关联的已发表期刊论文信息如下：Kasprak A.、Caster J.、Bangen S.与Sankey J.，2017年，《基于地形形态的地貌过程：自动化解译河谷重复测量数据》，《地球表面过程与地貌》（Earth Surface Processes and Landforms）在线版，DOI: 10.1002/esp.4143，访问链接：https://dx.doi.org/10.1002/esp.4143。