Journal ArticleDOI
Characterization of the structure of river-bed gravels using two-dimensional fractal analysis
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TLDR
In this paper, the authors used two-dimensional variogram surfaces to derive directionally dependent estimates of fractal dimension and found that fractal dimensions were greater in the downstream direction than in other directions suggesting that the effects of water working are to alter the level of surface organisation by increasing surface irregularity and hence roughness.Abstract:
This paper is concerned with the application of fractal analysis to understand the structure of water-worked gravel-bed river surfaces. High resolution digital elevation models, acquired using digital photogrammetric methods, allowed the application of two-dimensional fractal methods. Previous gravel-bed river studies have been based upon sampled profiles and hence one-dimensional fractal characterisation. After basic testing that bed elevation increments are Gaussian, the paper uses two-dimensional variogram surfaces to derive directionally dependent estimates of fractal dimension. The results identify mixed fractal behavior with two characteristic fractal bands, one associated with the subgrain scale and one associated with the grain scale. The subgrain scale characteristics were isotropic and sensitive to decisions made during the data collection process. Thus, it was difficult to differentiate whether these characteristics were real facets of the surfaces studied. The second band was anisotropic and not sensitive to data collection issues. Fractal dimensions were greater in the downstream direction than in other directions suggesting that the effects of water working are to alter the level of surface organisation, by increasing surface irregularity and hence roughness. This is an important observation as it means that water-worked surfaces may have a distinct anisotropic signal, revealed when using a fractal type analysis.read more
Citations
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Journal ArticleDOI
Topographic structure from motion: a new development in photogrammetric measurement
Mark A. Fonstad,James T. Dietrich,Brittany C. Courville,Jennifer L. R. Jensen,Patrice Carbonneau +4 more
TL;DR: This test shows that SfM and low-altitude platforms can produce point clouds with point densities comparable with airborne LiDAR, with horizontal and vertical precision in the centimeter range, and with very low capital and labor costs and low expertise levels.
Journal ArticleDOI
Accurate 3D comparison of complex topography with terrestrial laser scanner: Application to the Rangitikei canyon (N-Z)
TL;DR: In this article, a 3D point cloud comparison method is proposed to measure surface changes via 3D surface estimation and orientation in 3D at a scale consistent with the local surface roughness.
Journal ArticleDOI
Estimation of erosion and deposition volumes in a large, gravel‐bed, braided river using synoptic remote sensing
TL;DR: In this article, the authors developed a methodology for channel change detection, coupled with the use of synoptic remote sensing, for erosion and deposition estimation, and applied it to a wide, braided, gravel-bed river.
Journal ArticleDOI
Simple spatially-distributed models for predicting flood inundation: A review
TL;DR: In this paper, the authors review the theoretical basis for modelling floodplain flow with simplified hydraulic treatments based on a dimensional analysis of the one-dimensional shallow water equations and then review how such schemes can be applied in practice and consider issues of space discretization, time discretisation and model parameterisation, before going on to consider model assessment procedures.
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Optical remote mapping of rivers at sub-meter resolutions and watershed extents
W. Andrew Marcus,Mark A. Fonstad +1 more
TL;DR: In this paper, optical remote sensing of rivers is proposed to generate accurate and continuous maps of in-stream habitats, depths, algae, wood, stream power and other features at sub-meter resolutions across entire watersheds so long as the water is clear and the aerial view is unobstructed.
References
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Book
The Fractal Geometry of Nature
TL;DR: This book is a blend of erudition, popularization, and exposition, and the illustrations include many superb examples of computer graphics that are works of art in their own right.
Journal ArticleDOI
Fractional Brownian Motions, Fractional Noises and Applications
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Fluvial Processes in Geomorphology
Book
Fractals: Form, Chance and Dimension
TL;DR: Fractals as mentioned in this paper is a new field of mathematics that models the most interdisciplinary grab-bag of naturally occurring forms, such as coastlines and clouds, crystals, snowflakes and cosmological structures.