How does grid-resolution modulate the topographic expression of geomorphic processes?

Abstract

Abstract. In many locations, our ability to study the processes which shape the Earth are greatly enhanced through the use of high-resolution digital topographic data. However, although the availability of such datasets has markedly increased in recent years, many locations of significant geomorphic interest still do not have highresolution topographic data available. Here, we aim to constrain how well we can understand surface processes through topographic analysis performed on lower-resolution data. We generate digital elevation models from point clouds at a range of grid resolutions from 1 to 30 m, which covers the range of widely used data resolutions available globally, at three locations in the United States. Using these data, the relationship between curvature and grid resolution is explored, alongside the estimation of the hillslope sediment transport coefficient (D, in m 2 yr −1 ) for each landscape. Curvature, and consequently D, values are shown to be generally insensitive to grid resolution, particularly in landscapes with broad hilltops and valleys. Curvature distributions, however, become increasingly condensed around the mean, and theoretical considerations suggest caution should be used when extracting curvature from landscapes with sharp ridges. The sensitivity of curvature and topographic gradient to grid resolution are also explored through analysis of one-dimensional approximations of curvature and gradient, providing a theoretical basis for the results generated using two-dimensional topographic data. Two methods of extracting channels from topographic data are tested. A geometric method of channel extraction that finds channels by detecting threshold values of planform curvature is shown to perform well at resolutions up to 30 m in all three landscapes. The landscape parameters of hillslope length and relief are both successfully extracted at the same range of resolutions. These parameters can be used to detect landscape transience and our results suggest that such work need not be confined to high-resolution topographic data. A synthesis of the results presented in this work indicates that although high-resolution (e.g., 1 m) topographic data do yield exciting possibilities for geomorphic research, many key parameters can be understood in lower-resolution data, given careful consideration of how analyses are performed.

Supervised classification of landforms in Arctic mountains

“…58 By limiting ourselves to available >20-m-resolution topography, we are working at the limit of most process-based methods for topographic analysis. 59 We experimented with the inclusion of hydrologic parameters within our classifications, and found the extensive summit plateaus and planar side slopes in our field area led to anomalous positioning of channels relative to mapped channels. Alternatively, simple landform classifications using a small number of parameters have been used generically to distinguish areas by shape (rather than process).…”

Effects of gradient, distance, curvature and aspect on steep burned and unburned hillslope soil erosion and deposition

“…Both our hillslope gradient measurements (inclinometer and 10 m DEM) are flawed at representing topographic gradient accurately (e.g. Nonetheless, recent analysis by Grieve et al (2016) shows that when carefully considered and constrained, 10 m DEMs can provide gradient and curvature measures appropriate for geomorphic analysis. Moreover, we may not be quantifying gradient or curvature at the most relevant spatial scale.…”

“…Thus, the correct spatial scale to capture gradient may be somewhere between or even finer than these two measures, or could vary depending on the dominant transport process. Nonetheless, recent analysis by Grieve et al (2016) shows that when carefully considered and constrained, 10 m DEMs can provide gradient and curvature measures appropriate for geomorphic analysis.…”

Spatio-Temporal Mapping of Plate Boundary Faults in California Using Geodetic Imaging

“…Critical breaks in landscape length scale depend on surface process types and rates, degree of soil mantle and rock outcrop, etc. While hillslope lengths and drainage density may be sufficiently resolved at dekameter length scales (see review [123]), some sensitive elements are much finer (e.g., places like Carrizo Plain). These include hilltop curvature (e.g., [124]), channel head locations and shallow landslide behavior ( [90] for example).…”