Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 52 for “"Bedforms"”.
-
Bedforms and Gravity Underflows in Marine Environments
… can develop long-wavelength, upstream-migrating bedforms is presented for the first time. Additional experimental evidence of the coexistence of upstream-migrating antidunes and small-scale downstream-migrating ripples created by both supercritical saline density currents and turbidity currents …
-
Flow, sediment transport and bedforms under combined flows
… in natural environments and generates a range of bedforms on sandy beds. Combined-flow bedforms are abundant in coastal and lacustrine environments, as well as in their ancient counterparts in the rock record. However, few experimental studies have focused on the relationship between the …
-
The drumlin problem : streamlined subglacial bedforms in southern Sweden
This thesis investigates stream-lined subglacial bedforms (often referred to as drumlins) in southern Sweden. The broad aim of this is to contribute to the solution of the ‘drumlin problem’. The term drumlin has come to be applied to a wide range of features whose internal architecture (core) and …
-
Flutes, megaflutes and erosional bedforms: a reappraisal of their dynamics
Erosional bedforms in deep-sea environments record the passage of highly erosive turbidity currents that are often voluminous and fully bypassing. This investigation focuses upon a subset of erosional bedforms that are elliptical in shape, and utilises a multidisciplinary approach to reappraise the …
-
A method for synthesizing sedimentary structures generated by migrating bedforms
Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1978.
-
Measurements and dynamics of multiple scale bedforms in tidally energetic environments
The presence of superimposed bedforms, where smaller bedforms exist on larger bedforms, is ubiquitous to energetic tidal environments. Due to their wide range in scale, it is difficult to simultaneously observe these features over tidal timescales. This thesis examines the morphological response of …
-
Measurements and dynamics of multiple scale bedforms in tidally energetic environments
The presence of superimposed bedforms, where smaller bedforms exist on larger bedforms, is ubiquitous to energetic tidal environments. Due to their wide range in scale, it is difficult to simultaneously observe these features over tidal timescales. This thesis examines the morphological response of …
-
The influence of channel-skewed bedforms on flow structure in a high-amplitude meandering channel
… The influence of these channel-skewed bedforms on bend flow structure is poorly understood. These forms are of particular interest as they may prevent shoaling over point bars and promote erosion on the outer bank (similar to engineered bendway weirs). In addition, the geometry of these …
-
Turbulence and macro-turbulence in the bottom boundary layer downstream of large-scale bedforms; implications for sediment transport
… flow structures, generated downstream of the bedforms; these are characterised by alternating modules of lower and higher streamwise speeds than the mean flow. These structures modify the suspended sediment transport, generating high turbidity levels within macro-scale features of low flow …
-
The sedimentology of bedforms to barforms within tidally-influenced fluvial zones (TIFZx): lower Columbia River, OR/WA, USA, and the lower Chehalis River, WA, USA
… and internal sedimentary architecture of the bedforms and barforms in these systems. These results will be used to further the current understanding, and sedimentological models, of single- and multi- threaded TIFZs. New data are presented defining the large-scale TIFZ hydraulic environments …
-
Hydrodynamics and sedimentary structures of antidunes in gravel and sand mixtures
… the current literature available on antidune bedforms and their hydrodynamic environment, alongside recent studies of the turbulence environments associated with bedforms in unidirectional flow. Based on this understanding, three suites of experiments were designed and conducted to elucidate …
-
The effects of groundwater seepage on stream regimen : a laboratory study
… and monitored. </p><p> In the absence of bedforms, upward (positive) seepage has little effect on stream competence or transport rate, even when quicksand conditions are reached. The decrease in effective grain density brought about by uptward seepage might possibly be compensated entirely …
-
Observations and modeling of sand transport in a wave dominated environment
Observations of bedforms, suspended sediment and water velocities were used to examine sediment transport processes at the sandy LE0-15 site located off the New Jersey coast. The bedforms were observed during storms using a rotary sidescan sonar and were found to be wave orbital scale ripples. The …
-
Vertical Velocity Distributions in Sand -Bed Alluvial Rivers
… average percent error of 22.2% when the smaller bedforms were used as the geometry in the Nelson-Smith method.
-
Burial of Short Cylinders Induced by Local Scour and Bedform Migration Under Waves Plus Currents
… of geometric and migrating characteristics of bedforms under combined flows was conducted. Under certain hydraulic conditions, ripples with different geometric characteristics may coexist at different locations over the larger bottom features like sandwaves. Superposition of bedforms play and …
-
Three-dimensional eolian bounding surface architecture of the Entrada sandstone, Utah: expanding our understanding of reservoir heterogeneity in wet eolian systems
… located between climbing sinuous transverse bedforms or patches of bedforms. The Entrada Sandstone at RBM is interpreted to have been deposited primarily within a central portion of a wet eolian system that experienced a long-term trend of available sediment supply increase. The erg was …
-
Hydrodynamic variability and bedform dynamics at an inner shelf artificial reef
… stressors (e.g. Trembanis et al., 2004), sorted bedforms (e.g. Green et al., 2004) and object scour (e.g. Quinn, 2006), but our understanding of bedform morphodynamics is still incomplete. Consequently, this study examines the specific hydrodynamic and bedform morphodynamics occurring over an …
-
Bed Morphology and Sediment Transport Under Oscillatory Flow
… restrict the three-dimensional development of bedforms. For the case of the long water excursion experiments, the ripple size was found to initially decrease as the maximum orbital velocity was increased, as it has been reported by other authors. However, as the maximum orbital velocity was …
-
Modelling fine sediment transport over an immobile gravel bed
… the sediment starved bedform or fewer isolated bedforms. Bedform types that are typically associated with partial mobility condition are: sand ribbons, barchanoid dunes, isolated dunes and sediment starved dunes, bedload sheets and low-relif bedforms. The state of knowledge suggests that there …
-
Bedform and Flow Relationships, Little Missouri River Near Medora, North Dakota
<p>Data concerning flow conditions over known bedforms in the Little Missouri River were used to seek relationships between the two. The flow parameters that were measured included: current velocity, depth, water temperature, and suspended-load concentration. A bedload sample was also taken at each …
Page 1 of 3