scholarly journals Evaluating the influence of erosion and tectonic processes on California’s topography by measuring its fractal dimension and anisotropy across scales

2021 ◽  
Author(s):  
Hervé Guillon ◽  
Belize Lane ◽  
Colin F. Byrne ◽  
Gregory B. Pasternack ◽  
Samuel Sandoval Solis
Keyword(s):  
Fractal Dimension ◽  
Spatial Scales ◽  
Bedload Transport ◽  
Friction Laws ◽  
Erosion Processes ◽  
Bed Elevation ◽  
Tectonic Processes ◽  
Auto Correlation ◽  
River Bed ◽  
End Members

<p>Roughness is paramount in Earth sciences, and landscapes, laboratory alluvial fans, river bed elevation, bedload transport and the friction laws of fluid mechanics all exhibit a fractal behavior described by a scale-persistent roughness. Yet, for a given landscape, the exact meaning of statistical roughness, or fractal dimension, remains unclear. The fractal dimension of topography is mainly understood as two end-members: at large spatial scales, it describes tectonic processes; at small spatial scales it describes erosion processes. In this study, we nuance this description by identifying the spatial scale at which erosion processes are inadequately described by fractal dimension and provide quantitative bounds on the meaning of the statistical roughness of topography at scales from 0.25 km to 100 km using three lines of evidence. First, we leverage spatial statistics to evaluate the auto-correlation structure of topographic statistical roughness across the physiographically diverse state of California, USA. Second, we identify the down-slope and across-slope directions using two-dimensional Fourier analysis, and measure the anisotropy of topography by evaluating statistical roughness in each direction. Third, we perform a spatial correlation analysis between statistical roughness and the Péclet number which describes the balance between diffusion and incision processes. Our preliminary results indicate that correlation between statistical roughness and Péclet number fades at scales greater than 4.6 km. In addition, auto-correlation saturation occurs for statistical roughness at scales greater than 16.5 km. Hence our analysis provides a more nuanced description of the statistical roughness of topography: it represents erosion processes at scales up to 4.6 km while being dominated by tectonics at scales greater than 16.5 km.</p>

Using fractal geometry to make rapid field measurements of riverbed topography at ecologically useful spatial scales

2002 ◽  
Vol 53 (6) ◽  
pp. 999 ◽  
Author(s):  
B. J. Robson ◽  
E. T. Chester ◽  
L. A. Barmuta
Keyword(s):  
Fractal Dimension ◽  
Fractal Geometry ◽  
Random Sampling ◽  
Spatial Scales ◽  
Field Measurements ◽  
Habitat Types ◽  
River Bed ◽  
Bed Roughness ◽  
Rolling Balls

A method is described for making rapid in situ field measurements of riverbed topography over spatial scales of ≅1–10 m. This method uses rolling balls to make quick, accurate measurements of river-bed roughness at several spatial scales. Random sampling and replication generate multiple estimates of the fractal dimension (d) that can be used to test for significant differences in the complexity of riverbed architecture between habitat types and spatial scales.

scholarly journals A low-cost technique to measure bank erosion proces ses along middle-size river reaches

2018 ◽  
Author(s):  
Gonzalo Duró ◽  
Alessandra Crosato ◽  
Maarten G. Kleinhans ◽  
Wim S. J. Uijttewaal
Keyword(s):  
Laser Scanning ◽  
Spatial Scales ◽  
Low Cost ◽  
Bank Erosion ◽  
Water Levels ◽  
Small Scale ◽  
Observation Distance ◽  
River Bank ◽  
Erosion Processes ◽  
Rtk Gps

Abstract. Diverse methods are currently available to measure river bank erosion at broad-ranging temporal and spatial scales. Yet, no technique provides low-cost and high-resolution to survey small-scale bank processes along a river reach. We investigate the capabilities of Structure-from-Motion photogrammetry applied with imagery from an Unmanned Aerial Vehicle (UAV) to describe the evolution of riverbank profiles in middle-size rivers. The bank erosion cycle is used as a reference to assess the applicability of different techniques. We surveyed 1.2 km of a restored bank of the Meuse River eight times within a year, combining different photograph perspectives and overlaps to identify an efficient UAV flight to monitor banks. The accuracy of the Digital Surface Models (DSMs) was evaluated compared with RTK GPS points and an Airborne Laser Scanning (ALS) of the whole reach. An oblique perspective with eight photo overlaps was sufficient to achieve the highest relative precision to observation distance of ~1:1400, with 10 cm error range. A complementary nadiral view increased coverage behind bank toe vegetation. The DSM and ALS had comparable accuracies except on banks, where the latter overestimates elevations. Sequential DSMs captured signatures of the erosion cycle such as mass failures, slump-block deposition, and bank undermining. Although this technique requires low water levels and banks without dense vegetation, it is a low-cost method to survey reach-scale riverbanks in sufficient resolution to quantify bank retreat and identify morphological features of the bank failure and erosion processes.

A compass without a map: tortuosity and orientation of eastern painted turtles (Chrysemys picta picta) released in unfamiliar territory

2006 ◽  
Vol 84 (8) ◽  
pp. 1129-1137 ◽  
Author(s):  
I.R. Caldwell ◽  
V.O. Nams
Keyword(s):  
Fractal Dimension ◽  
Random Walk ◽  
Spatial Scales ◽  
Chrysemys Picta ◽  
Reference Stimulus ◽  
Correlated Random Walk ◽  
Specific Mechanism ◽  
Minimal Time ◽  
Painted Turtles

Orientation mechanisms allow animals to spend minimal time in hostile areas while reaching needed resources. Identification of the specific mechanism used by an animal can be difficult, but examining an animal's path in familiar and unfamiliar areas can provide clues to the type of mechanism in use. Semiaquatic turtles are known to use a homing mechanism in familiar territory to locate their home lake while on land, but little is known about their ability to locate habitat in unfamiliar territory. We tested the tortuosity and orientation of 60 eastern painted turtles ( Chrysemys picta picta (Schneider, 1783)). We released turtles at 20 release points located at five distances and in two directions from two unfamiliar lakes. Turtle trails were quite straight (fractal dimension between 1.1 and 1.025) but were not oriented towards water from any distance (V-test; u < 0.72; P > 0.1). Turtles maintained their initially chosen direction but either could not detect water or were not motivated to reach it. Furthermore, paths were straighter at larger spatial scales than at smaller spatial scales, which could not have occurred if the turtles had been using a correlated random walk. Turtles must therefore be using a reference stimulus for navigation even in unfamiliar areas.

A multi-decade assessment of the impact of large fire events on sediment redistribution using LAPSUS - the Águeda catchment, north-central Portugal

2021 ◽  
Author(s):  
Dante Föllmi ◽  
Jantiene Baartman ◽  
João Pedro Nunes ◽  
Akli Benali
Keyword(s):  
Soil Depth ◽  
Spatial Scales ◽  
Fire Severity ◽  
Sediment Dynamics ◽  
Land Uses ◽  
Erosion Rates ◽  
Erosion Processes ◽  
Sediment Redistribution ◽  
Central Portugal ◽  
The Impact

&lt;p&gt;&lt;strong&gt;Abstract&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Wildfires have become an increasing threat for Mediterranean ecosystems, due to increasing climate change induced wildfire activity and changing land management practices. Apart from the initial risk, fire can alter the soil in various ways depending on different fire severities and thus post-fire erosion processes are an important component in assessing wildfires&amp;#8217; negative effects. Recent post-fire erosion (modelling) studies often focus on a short time window and lack the attention for sediment dynamics at larger spatial scales. Yet, these large spatial and temporal scales are fundamental for a better understanding of catchment sediment dynamics and long-term destructive effects of multiple fires on post-fire erosion processes. In this study the landscape evolution model LAPSUS was used to simulate erosion and deposition in the 404 km&lt;sup&gt;2&lt;/sup&gt; &amp;#193;gueda catchment in northern-central Portugal over a 41 year (1979-2020) timespan. To include variation in fire severity and its impact on the soil four burnt severity classes, represented by the difference Normalized Burn Ratio (dNBR), were parameterized. Although model calibration was difficult due to lack of spatial and temporal measured data, the results show that average post-fire net erosion rates were significantly higher in the wildfire scenarios (5.95 ton ha&lt;sup&gt;-1&lt;/sup&gt; yr&lt;sup&gt;-1&lt;/sup&gt;) compared to those of a non-wildfire scenario (0.58 ton ha&lt;sup&gt;-1&lt;/sup&gt; yr&lt;sup&gt;-1&lt;/sup&gt;). Furthermore, erosion values increased with a higher level of burnt severity and multiple fires increased the overall sediment build-up in the catchment, fostering an increase in background sediment yield. Simulated erosion patterns showed great spatial variability with large deposition and erosion rates inside streams. Due to this variability, it was difficult to identify land uses that were most sensitive for post-fire erosion, because some land-uses were located in more erosion-sensitive areas (e.g. streams, gullies) or were more affected by high burnt severity levels than others. Despite these limitations, LAPSUS performed well on addressing spatial sediment processes and has the ability to contribute to pre-fire management strategies. For instance, the percentage soil loss map (i.e. comparison of erosion and soil depth maps) could identify locations at risk.&lt;/p&gt;

Critical Zone Observatories: Building a network to advance interdisciplinary study of Earth surface processes

2008 ◽  
Vol 72 (1) ◽  
pp. 7-10 ◽  
Author(s):  
S. P. Anderson ◽  
R. C. Bales ◽  
C. J. Duffy
Keyword(s):  
Fluid Transport ◽  
Spatial Scales ◽  
Critical Zone ◽  
Watershed Scale ◽  
Spatial And Temporal Scales ◽  
Complex Interactions ◽  
Tectonic Processes ◽  
Interdisciplinary Approaches ◽  
Dynamic Interface ◽  
Interdisciplinary Study

AbstractWe live at the dynamic interface between the solid Earth and its outer fluid envelopes. This interface, extending from the outer vegetation canopy to the base of active groundwater, was recently named the Critical Zone because it supports life and is increasingly impacted by human actions. Understanding the complex interactions between processes that operate in and shape the Critical Zone requires interdisciplinary approaches that span wide spatial and temporal scales. Tectonic processes, weathering, fluid transport, and biological processes control the function and structure of the Critical Zone. Three Critical Zone Observatories recently established by the U.S. National Science Foundation are designed to integrate studies of process interactions up to the watershed scale. A goal of the program is to build the three independently conceived observatories into a network from which broader understanding — larger spatial scales but also deeper insight — can emerge.

The role of erosion in the morphometry of composite volcanoes

2021 ◽  
Author(s):  
Roos van Wees ◽  
Pierre-Yves Tournigand ◽  
Daniel O’Hara ◽  
Pablo Grosse ◽  
Gabor Kereszturi ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Age Determination ◽  
Morphometric Parameters ◽  
Physical Weathering ◽  
Erosion Rates ◽  
Erosion Processes ◽  
Digital Elevation ◽  
Shape Complexity ◽  
Geochronological Constraints ◽  
Natural Composite

&lt;p&gt;Volcanoes are extremely dynamic landforms. They grow by the accumulation of eruptive products and intrusions and degrade by a range of erosion processes such as superficial runoff, chemical and physical weathering, fluvial and glacial incision, and mass movements. In this study, we aim at documenting and quantifying the morphology of natural composite volcanoes using a range of morphometric indices, to better understand the factors that control erosion rates and patterns.&lt;/p&gt;&lt;p&gt;In addition to standard morphometric indices, including edifice ellipticity and irregularity, computed by the MORVOLC algorithm, a fractal dimension tool is developed to quantitatively report the shape complexity of stratovolcanoes. A convex hull approach is used to derive minimal erosion volumes and estimate erosion rates, considering available geochronological constraints. Morphometric parameters are derived from digital elevation models (DEMs) for a few exemplary stratovolcanoes of contrasted ages from the same volcanic region. To analyse the potential bias induced by the selected DEMs and the identification of the volcanic edifice outline, we also conduct a sensitivity analysis. The morphometric parameters are similarly extracted using the freely and globally available ALOS 30m (AW3D30), SRTM 30m (SRTMGL1), and ASTER 30m (GDEM 003), and compared to values obtained with the TanDEM-X 12m. The subjective user-drawn edifice outlines are compared to outlines generated by available algorithms, i.e. NETVOLC and MBOA, and their impact on the accuracy of morphometric indexes is quantified. &amp;#160;&lt;/p&gt;&lt;p&gt;Our results highlight that erosion increases edifice irregularity and fractal dimension. Preliminary trends between volcano fractal dimension, eroded volume, and age suggest that fractal analysis has the potential to be used as a relative age determination tool. The proposed morphometric characterisation paves the way for a comparison between natural volcanoes and controlled lab experiments reproducing the degradation of pristine volcanic cones by surface runoff to be developed later in our project. &amp;#160;&lt;/p&gt;

Weathering, Soils, and Slope Processes

2009 ◽  
Author(s):  
John Wainwright
Keyword(s):  
Chemical Weathering ◽  
Life Support ◽  
Spatial Scales ◽  
Chemical Processes ◽  
Earth Systems ◽  
Erosion Processes ◽  
The North ◽  
In Situ Modification ◽  
Dry Conditions ◽  
The Mediterranean

Hillslopes are the dominant landform features of the Earth’s surface. They make up the interface between the atmosphere and Earth systems, providing a substrate that supports life and thus the basis for human activities within the Mediterranean. Their location at this interface means that hillslopes evolve through a complex interaction of different processes, operating at a range of different time and spatial scales. At longer timescales, processes of weathering convert rock and other parent materials into soils. Soils allow the growth of vegetation and thus further feedbacks between atmospheric and surface processes; in some cases these feedbacks can be seen to provide relative stability, while in others the system can become more fragile (Chapter 20). The latter case often arises as a result of erosion processes of various types. Water erosion and mass movements are a significant element of Mediterranean landscape evolution, occurring in parallel with (in response to, and affecting) tectonic processes that have moulded the configuration of the Earth’s crust (see Chapter 1), producing the unique combination of environmental characteristics of the region. Since the Late Pleistocene, depending on location, human activity has led to an acceleration of many of these processes, with important consequences for the basic ‘life-support system’ of the region and for global environmental cycles. The in situ modification of near-surface materials is typically considered to take place along a continuum relating to the dominance of mechanical or chemical processes (e.g. Birkeland 1999). The simplest control may be considered to be climatic, with mechanical breakdown of particles dominating in cold, dry conditions, and chemical processes dominating in warm, wet conditions. Comparing this model to the present day climate of the Mediterranean suggests, as with other processes, something of a north–south divide in terms of the dominant weathering process. The northern part of the basin (together with the Levant and the north-facing uplands of the Maghreb) would seem to be dominated by moderate chemical weathering; exceptions being the arid areas of south-east Spain, southern Sicily, eastern Cyprus, and parts of the Anatolian plateau as well as areas where low average temperatures would also reduce rates, such as in the Alps and parts of Slovenia and Croatia.

scholarly journals THE FRACTAL DIMENSION OF STAR-FORMING REGIONS AT DIFFERENT SPATIAL SCALES IN M33

2010 ◽  
Vol 720 (1) ◽  
pp. 541-547 ◽  
Author(s):  
Néstor Sánchez ◽  
Neyda Añez ◽  
Emilio J. Alfaro ◽  
Mary Crone Odekon
Keyword(s):  
Fractal Dimension ◽  
Spatial Scales ◽  
Star Forming ◽  
Star Forming Regions
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