Imaging the Physical Controls on Rock Debris Surface Properties With a Novel 3D Reconstruction Method
Abstract
The technical objective of the proposed effort is to determine the relative roles of rockfall dynamics and post-depositional processes in controlling rock debris surface characteristics. The proposed effort seeks to achieve the stated technical objective using a combined approach involving (1) photo-based three-dimensional reconstructions, (2) computational analysis and (3) surface exposure dating. Research will be conducted along a 20-km-long escarpment that varies continuously in height along its length, where rockfall is sourced from similar rocks, and where it is possible to identify and quantify a range of deposit ages. High-resolution digital topography and imagery will be generated from the study area using structure-from-motion photogrammetry to classify surface types and debris size distributions. This 3D reconstruction method uses computer image-processing techniques to extract 3D point clouds and corresponding high resolution orthrectifed color images from a set of digital photographs of a scene acquired from varying angles. Computational routines will be used to automatically classify model points as either debris or bare bedrock. The resulting classification will form the basis for algorithms that will extract coverage area and grain size information for the rockfall debris fields. The approach will combine conventional image-based classification algorithms with Fourier analysis and spectral filtering of the topographic data itself to isolate terrain features at certain wavelengths. Next, using the high-resolution terrain model, a 3D numerical rockfall model, such as the Rockfall Analyst extension for ArcGIS, will be used to quantify energy losses during rockfall and model the spatial distribution and grain size sorting of rockfall deposits, thereby constraining the kinetic energy of rockfall and allowing prediction of patterns of debris deposition. Finally, cosmogenic exposure-age dating using the ^36Cl system and field measurements of physical and mechanical properties will be performed on talus boulders and exposed bedrock to constrain debris longevity and rates of production. Using these combined methods, two hypotheses will be tested: (1) grain size distribution on talus slopes below a cliff depends primarily on escarpment height and (2) in a desert environment, talus tends to weather in place rather than being transported downslope.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 12, 2017
- Source ID
- W911NF1510392
Entities
People
- Dylan Ward
Organizations
- Army Contracting Command
- United States Army
- University of Cincinnati