Preprints
Filtering by Subject: Geomorphology
The sustainability of beach nourishments: A review of nourishment and environmental monitoring practice
Published: 2020-06-10
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Environmental Engineering, Environmental Monitoring, Environmental Sciences, Geomorphology, Physical Sciences and Mathematics, Sustainability
Beach nourishments are a widely used method to mitigate erosion along flood-prone sandy shorelines. In contrast to hard coastal protection structures, nourishments are considered as soft engineering, although little is known about the cumulative, long-term environmental effects of both marine sediment extraction and nourishment activities. Recent endeavours to sustain the marine ecosystem and [...]
A systematic approach and software for the analysis of point patterns on river networks
Published: 2020-06-10
Subjects: Earth Sciences, Geomorphology, Physical Sciences and Mathematics
Many geomorphic phenomena such as bank failures, landslide dams, riffle-pool sequences and knickpoints can be modelled as spatial point processes. However, as the locations of these phenomena are constrained to lie on or alongside rivers, their analysis must account for the geometry and topology of river networks. Here, we introduce a new numeric class in TopoToolbox called Point Pattern on [...]
A novel rules-based shoreface translation model for predicting future coastal change: ShoreTrans
Published: 2020-06-04
Subjects: Earth Sciences, Engineering, Geomorphology, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Other Engineering, Physical Sciences and Mathematics
Predicting change to global shorelines presents an increasing challenge as sea-level rise (SLR) accelerates. Many shoreline prediction models use variations of the ‘Bruun-rule’, failing to account for relevant processes and morphologic complexity. To address this, we introduce a simple rules-based model (ShoreTrans) designed for complex, real-world profiles that predicts change across a wide [...]
Advective sorting of silt by currents: a laboratory study
Published: 2020-05-27
Subjects: Earth Sciences, Geomorphology, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Sedimentology
Accumulations of fine sediments along continental shelf and deep-sea bathymetric contours, known as contourite drifts, form a sedimentary record that is dependent on oceanographic processes such as ocean-basin-scale circulation. A tool used to aid in interpretation of such deposits is the sortable silt hypothesis, which suggests that the mean size of the sortable silt (silt from 10-63 µm) within [...]
Effect of Lateral Outflow on Three-Dimensional Flow Structure in a River Delta
Published: 2020-05-26
Subjects: Earth Sciences, Geomorphology, Hydrology, Physical Sciences and Mathematics
Spatial and temporal patterns in three-dimensional flow structure are linked to channel processes and morphology in many environments. However, there is not yet an understanding of how the flow structure is influenced by channelized and gradually distributed lateral outflows that are often prevalent in river deltas. This study presents an analysis of three-dimensional flow structure data [...]
Cave airflow patterns control calcite dissolution rates within a cave stream: Blowing Springs Cave, Arkansas, USA
Published: 2020-05-24
Subjects: Earth Sciences, Environmental Sciences, Geochemistry, Geomorphology, Hydrology, Physical Sciences and Mathematics
Erosion rates within streams vary dramatically over time, as differences in discharge and sediment load enhance or inhibit erosion processes. Within cave streams, and other bedrock channels incising soluble rocks, changes in water chemistry are an important factor in determining how erosion rates will vary in both time and space. Prior studies within surface streams, springs, and caves suggest [...]
The perpetual fragility of creeping hillslopes
Published: 2020-05-18
Subjects: Earth Sciences, Geomorphology, Physical Sciences and Mathematics
Soil-mantled hillslopes owe their smooth, convex shape to creep; the slow and persistent, gravity-driven motion of grains on slopes below the angle of repose. Existing models presume that soil creep occurs via mechanical displacement of grains by (bio)physical disturbances. Recent simulations, however, suggest that soil can creep without these disturbances, due to internal relaxation dynamics [...]
Macroscopic flow disequilibrium over aeolian dune fields
Published: 2020-05-08
Subjects: Atmospheric Sciences, Earth Sciences, Geomorphology, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Sedimentology
Aeolian dune fields are self-organized patterns formed by wind-blown sand. Dunes are topographic roughness elements that impose drag on the atmospheric boundary layer (ABL), creating a natural coupling between form and flow. While the steady-state influence of drag on the ABL is well studied, non-equilibrium effects due to roughness transitions are less understood. Here we examine the large-scale [...]
Projections of global delta land loss from sea-level rise in the 21st century
Published: 2020-05-06
Subjects: Earth Sciences, Geomorphology, Hydrology, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Sedimentology
River deltas will likely experience significant land loss because of relative sea-level rise (RSLR), but predictions have not been tested against observations. Here, we use global data of RSLR and river sediment supply to build a model of delta response to RSLR for 6,402 deltas, representing 86% of global delta land. We validate this model against delta land area change observations from [...]
Rock glaciers represent hidden water stores in the Himalaya
Published: 2020-05-06
Subjects: Earth Sciences, Geomorphology, Glaciology, Hydrology, Physical Sciences and Mathematics
In High Mountain Asia (HMA), ongoing glacier retreat affects human and ecological systems through reduced water availability. Rock glaciers are climatically more resilient than glaciers and likely contain potentially valuable water volume equivalents (WVEQ). In HMA knowledge of rock glaciers is extremely sparse and here we present the first systematic assessment of rock glaciers for the Himalaya, [...]
Modeling the spatial dynamics of marsh ponds in New England salt marshes
Published: 2020-04-27
Subjects: Earth Sciences, Geomorphology, Physical Sciences and Mathematics
Ponds are common features on salt marshes, yet it is unclear how they affect large-scale marsh evolution. We developed a spatially explicit model that combines cellular automata for pond formation, expansion, and drainage, and partial differential equations for elevation dynamics. We use the mesotidal Barnstable marsh (MA, USA) as a case study, for which we measured pond expansion rate by remote [...]
Runout of rock avalanches limited by basal friction but controlled by fragmentation
Published: 2020-04-22
Subjects: Earth Sciences, Geomorphology, Physical Sciences and Mathematics
Rock avalanches display exceptionally long runouts, which are found to correlate with their volume and attributed to size dependent dynamic lowering of the effective basal friction. However, even for similar volumes, runouts are seen to span several orders of magnitude suggesting additional controlling factors. Here, we document experiments with analogue models of rock avalanches aimed at testing [...]
A seismic monitoring approach to detect and quantify river sediment mobilisation by steelhead redd-building activity
Published: 2020-04-20
Subjects: Earth Sciences, Geomorphology, Physical Sciences and Mathematics
The role of spawning salmonids in altering river bed morphology and sediment transport is significant yet poorly understood. This is due, in large part, to limitations in monitoring the redd-building process in a continuous and spatially extended way. A complementary approach may be provided through the use of a small seismic sensor network analysing the ground motion signals generated by the [...]
Lateral variability in strain along a mass-transport deposit (MTD) toewall: a case study from the Makassar Strait, offshore Indonesia
Published: 2020-04-18
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics, Sedimentology
Contractional features characterise the toe domain of mass-transport deposits (MTDs). Their frontal geometry is typically classified as frontally-confined or frontally-emergent. However, it remains unclear how frontal emplacement style and contractional strain within an MTD can vary along strike. We use bathymetry and 3D seismic reflection data to investigate lateral variability of frontal [...]
Lateral variations in lower crustal strength control the temporal evolution of mountain ranges: examples from south-east Tibet
Published: 2020-04-17
Subjects: Earth Sciences, Geochemistry, Geomorphology, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Controversy surrounds the rheology of the continental lithosphere, and how it controls the evolution and behaviour of mountain ranges. In this study, we investigate the effect of lateral contrasts in the strength of the lower crust, such as those between cratonic continental interiors and weaker rocks in the adjacent deforming regions, on the evolution of topography. We combine numerical [...]