Aeolian dune fields form some of the most striking patterns on Earth and Mars. These patterns reflect the internal dune dynamics of self-organization within boundary conditions, which are the unique set of environmental variables within which each dune field evolves. Dune-field pattern self-organization occurs because of interactions between the dunes themselves and the rich diversity of dune-field patterns arises because boundary conditions alter the type and frequency of dune interactions. These hypotheses are explored in three parts. First, source-area geometry and areal limits are two newly recognized boundary conditions. Measurements of crest length and spacing from satellite images of dune patterns with point and line source-area geometries show an increase in crest length and spacing over distance, whereas crest length and spacing in plane-sourced patterns emerge equally across the dune field. The areal limit boundary condition is the size and shape of the dune field itself. Empirical measurements from ten dune fields ranging over four orders of magnitude in area show that spacing increases and defect density decreases as the area of the dune field increases. A simple analytical model indicates that dune fields that are five times longer in the dune migration direction can achieve the greatest spacing for a given area. Second, time-series aerial photographs and airborne LiDAR show that fully developed, crescentic aeolian dunes at White Sands, New Mexico, interact and the dune pattern organizes in systematically similar ways as wind ripples and subaqueous dunes and ripples. Interaction type, classified as constructive, regenerative or neutral in terms of pattern development, changes spatially with the pattern because of the imposition of the line-source area and sediment availability boundary conditions. Upwind dominance by constructive interactions at the field line-source yields to neutral and regenerative interactions in the sediment availability-limited field center. Third, the dune-field pattern in the Olympia Undae Dune Field on Mars is comprised of two generations of dunes. This scenario of pattern reformation with a new wind regime shows that the emergence of the younger pattern is controlled by the boundary condition of the antecedent dune topography imposed upon the interaction between the younger and older patterns. / text

Typescript (photocopy). / Digitized by Kansas State University Libraries / Department: Geology.

Les dunes marines sont de grandes structures sédimentaires qui, ensemble, couvrent de larges zones appelées champs de dunes. Des dunes ont été découvertes dans tous les océans, de la côte jusqu'aux talus continentaux. Leur forme et mobilité sont des témoins du lien étroit qui existe entre le transport sédimentaire, l'hydrodynamique (courants marins) et la topographie du fond. L'étude des dunes est intéressante scientifiquement parlant, mais elle est également motivée par des enjeux économiques et environnementaux. Les dunes peuvent être étudiées de deux manières : La modélisation et l'analyse de données de terrain (granulométrie, courantométrie, données sismiques, données bathymétriques). Ces deux approches sont très différentes mais complémentaires. Avec l'amélioration des données Sondeur Multi-Faisceaux (SMF), il est maintenant possible de visualiser la morphologie des dunes et de suivre leur évolution de manière plus détaillée. Plusieurs méthodes automatiques d'analyse de la morphologie et de la dynamique des dunes ont été développées pour analyser les Modèles Numériques de Terrain (MNTs) construits à partir de ces données SMF. Pourtant, aucun ne permet d'estimer les valeurs de descripteurs morphologiques et dynamiques pour chaque dune. L'analyse et l'évaluation de ces descripteurs restent régionales avec le découpage des MNTs en régions rectangulaires. Seul un traitement manuel permet d'estimer ces descripteurs pour chaque dune. L'objectif de cette thèse est de développer des algorithmes automatiques permettant de quanti er la morphologie et la dynamique de chaque dune. Pour ce faire, une représentation des données SMF sous forme d'une tessellation triangulaire a été préférée au classique MNT régulier. Tout d'abord, les dunes doivent être extraites de la topographie du fond marin. Un algorithme par accroissement de régions avec adaptation de l'échelle d'analyse, issu de la géomorphométrie est proposé. Les crêtes de dunes sont d'abord extraites en combinant un algorithme de simplification de tessellations avec un algorithme d'extraction de lignes de crête. La résolution de la tessellation est adaptée par l'algorithme de simplification afin de faciliter l'extraction des lignes de crête. Les lignes de crête sont des objets bien définis en géométrie différentielle. Leur extraction s'appuie sur l'interprétation de cette définition appliquée à des modèles discrets du fond (tessellations). Les crêtes servent d'embryons à l'algorithme d'extraction des dunes. L'estimation des paramètres morphologiques des dunes (longueur, largeur, hauteur, etc.) découle de l'extraction automatique des dunes. L'utilisation d'une méthode de recalage non rigide (isométrique) pour la quantification de la dynamique est discutée. Des tessellations représentant la topographie d'un même champ de dunes à différents moments sont analysées par l'algorithme d'extraction des dunes. Ensuite, une dune est associée à une dune d'une autre tessellation qui lui correspond (même dune à un autre instant). La dynamique de chaque dune est quantifiée à partir des résultats de l'algorithme de recalage : les transformations permettant d'aligner différentes représentations d'une dune. / Marine dunes are large sedimentary mounds often organized in dunefields. Theyhave been discovered in oceans all around the globe, from continental rises to nearshore areas. These mobile seafloor structures reflect the unique and complex relationship between the sediment, the seafloor topography and the hydrodynamics (currents). Dunes are not only interesting at a scientific level. In fact, their study is also motivated by economic, safety and environmental reasons. The study of dunes can be divided into two complementary approaches: Modelling and analysis of in situ data (granulometry, current, bathymetric data).The increased quality of MultiBeam EchoSounder (MBES) data allows scientists to monitor and visualize the complexity of, both, dune morphology and dynamics. Au-tomatic methods to characterize dune morphology and dynamics using Digital TerrainModels (DTMs) have already been proposed. But, none does it at the dune scale. Mor-phological and dynamical descriptors are estimated for patches of the dunefield. Today, the evaluation of such descriptors for each dune can only be achieved manually.The objective of this thesis is to design automatic algorithms for the quantification of dune morphology and dynamics. A representation of MBES data as triangular meshes has been preferred to the usual gridded DTMs. The first stage consists of delineating dunes in the seafloor. A scale adaptative, region growing algorithm based on geomorphometry is proposed. The combination of mesh implification and crest extraction algorithms enables to accurately recover dune crest lines. The mesh simplification facilitates the crest extraction by adapting the mesh resolution. Crest extraction is based on the discrete interpretation of the definition of crest lines in differential geometry. The crests are, then, used as seed regions by the dune extraction algorithm.

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Sargassum fluitans and natans, types of brown algae, wash up on Galveston Island, Texas annually from May to August. Sargassum smells bad, hurts tourism and impairs sea turtle hatchings. Coastal managers are confronted with the difficult choice of cleaning Sargassum off the beach or leaving it alone. The current beach management practice is to rake the algae with tractors and deposit it at the base of the dunes. The environmental impacts of raking and ecological benefits of Sargassum are unknown. The Galveston Island Park Board of Trustees (GIPBT) used to rake all beaches under their management before Hurricane Alicia in 1983. Then, citizens started to complain that raking was causing erosion. Now, there are people who argue for both raking and leaving the beach alone. Environmental policies require complex decisions that take into consideration social, economical, ecological, and cultural values. The GIPBT initiated the Sargassum Policy Committee to gain knowledge of different stakeholder values and scientific research to develop beach management. The first study analyzed elevation changes over a year period on raked and unraked beaches on both the West and East end of Galveston Island. The Analysis ofVariance results indicated that there is not a difference in elevation changes between the raked and unraked beaches over a year.The second study analyzed the effects of Sargassum on the dune plant Panicum amarum. Plants were asexually grown in a greenhouse in sand without (control) and with Sargassum. The effects of small versus large amounts, top versus mixed with sand and washed versus unwashed Sargassum were tested. The results indicated that the addition of Sargassum increased plant growth. The treatments with large amounts of Sargassum and unwashed treatments showed significant growth changes at the 95% confidence level. The last component analyzed the collaborative potential of the Sargassum Policy Committee through observations of meetings and surveys of the members. Daniel and Walker’s Progressive Triangle was used to assess the relationship, procedural and substance dimensions of collaborative learning. Then, suggestions were made for increasing collaboration. The combination of scientific research and stakeholder values has resulted in the creation of sound beach management.

Sargassum fluitans and natans, types of brown algae, wash up on Galveston Island, Texas annually from May to August. Sargassum smells bad, hurts tourism and impairs sea turtle hatchings. Coastal managers are confronted with the difficult choice of cleaning Sargassum off the beach or leaving it alone. The current beach management practice is to rake the algae with tractors and deposit it at the base of the dunes. The environmental impacts of raking and ecological benefits of Sargassum are unknown. The Galveston Island Park Board of Trustees (GIPBT) used to rake all beaches under their management before Hurricane Alicia in 1983. Then, citizens started to complain that raking was causing erosion. Now, there are people who argue for both raking and leaving the beach alone. Environmental policies require complex decisions that take into consideration social, economical, ecological, and cultural values. The GIPBT initiated the Sargassum Policy Committee to gain knowledge of different stakeholder values and scientific research to develop beach management. The first study analyzed elevation changes over a year period on raked and unraked beaches on both the West and East end of Galveston Island. The Analysis ofVariance results indicated that there is not a difference in elevation changes between the raked and unraked beaches over a year.The second study analyzed the effects of Sargassum on the dune plant Panicum amarum. Plants were asexually grown in a greenhouse in sand without (control) and with Sargassum. The effects of small versus large amounts, top versus mixed with sand and washed versus unwashed Sargassum were tested. The results indicated that the addition of Sargassum increased plant growth. The treatments with large amounts of Sargassum and unwashed treatments showed significant growth changes at the 95% confidence level. The last component analyzed the collaborative potential of the Sargassum Policy Committee through observations of meetings and surveys of the members. Daniel and Walker’s Progressive Triangle was used to assess the relationship, procedural and substance dimensions of collaborative learning. Then, suggestions were made for increasing collaboration. The combination of scientific research and stakeholder values has resulted in the creation of sound beach management.

The primary objective of this study is to investigate the suitability of utilizing dune sand as a paving construction material in hot desert-like areas of the world, where regions of sand dunes exist. The high availability, low cost, and excellent physical properties of the current surplus of elemental sulfur and the benefits given to asphaltic binders by sulfur raises the possibility of using sulfur in asphalt mixes to produce stable mixtures with locally obtainable dune sand. Characterization of various sulfur-asphalt-dune sand mixtures for highway construction were made. The materials used in this investigation were elemental sulfur, AR-4000 (60-70 pen.) asphalt, and dune sand from Yuma, Arizona. The main variables include (a)proportion of sulfur and asphalt in the binder, (b)amount of binder in the mixture, (c)curing temperature, (d)test temperature, and (e)mixing techniques. The various mixtures were prepared by the one-wet mixing cycle technique. Similar dune sand mixtures with asphalt only were evaluated for comparison purposes. The different mixes were evaluated by the Marshall method, tensile strength tests (double punch), compression tests (standard and immersion), flexural tests (standard), dynamic modulus tests (double punch), and microscopic examinations of sulfur-asphalt binders and sulfur-asphalt-dune sand mixtures (thin sections). Preliminary characterizations of the various mixes were made on the basis of their Marshall stability, flow, density, and air void contents. Other engineering properties such as tensile strength, compressive strength, modulus of rupture, dynamic modulus, and microscopic studies were determined for selected mixes. The results consistently indicated that the sulfur-asphalt-dune sand mixes exhibited superior engineering characteristics and performance as compared to similar mixes without sulfur. The overall conclusion drawn from this study is that the dune sand which is not normally accepted for use as aggregate in asphaltic mixtures, can be used with the utilization of sulfur-asphalt binder systems to produce paving mixtures with compatible or better engineering properties in comparison to conventional asphaltic concretes.

In unsteady flows, dune dimensions may vary considerably from fully-developed dimensions produced from a flat bed under a steady and uniform flow. Specifically, dune height and length are observed to lag discharge when the flow is non-steady, resulting in dimensions that are out of phase with the prevailing flow. This research attempts to provide some insight into the behaviour of dunes when the flow is suddenly changed, as well as the time-scale of the related dune changes. Nineteen experimental runs were carried out in the 21-m long, 0.76-m wide Sediment Transport Flume at Queen’s University. In ten of these runs the flow depth, h, was suddenly increased (h2/h1 > 1) and in nine runs the flow depth was suddenly decreased (h2/h1 < 1). In all runs, the slope of free surface was kept equal to the slope of the bed such that the change in flow rate is represented by the change in the flow depth. Seven ratios of the two flow depths, h2/h1 (varying between 0.49 and 2.29), were performed for three slopes (S = 1/792, 1/534, 1/341). The bed material was a coarse, poorly-graded silica sand (D50 = 1.0 mm). Longitudinal bed profiles were taken along the centreline of the flume approximately every 6–8 minutes to determine the transient dune dimensions and the time at which the dunes acquired their new equilibrium dimensions. This time is termed the duration of dune development, Td. Through dimensional and physical considerations, Bielenberg (2006) established that the dimensionless counterpart of Td should be a function of the material number, relative flow depth, relative flow intensity, and ratio of the flow depths h2/h1. The present experiments were carried out to investigate the influence of the relative flow intensity and h2/h1 on the duration of dune development. Results indicate that equilibrium dune dimensions do not depend on the initial shape of the bed. After the period Td, the dunes tend to be similar to those produced from a flat bed. It is found that Td is strongly dependent on h2/h1, and weakly dependent on the flow intensity. All other determining variables remaining the same, Td decreases with increasing values of flow intensity. Semi-empirical relations for the dimensionless duration of dune development are presented. / Thesis (Master, Civil Engineering) -- Queen's University, 2007-09-24 09:45:13.624

The purpose of this study was to develop management guidelines to ensure the long term ecological sustainability of the beach and sand dune area of Grand Beach Provincial Park. A qualitative approach was taken including interviews of individuals who use Grand Beach. A literature review was completed describing the history of use at Grand Beach Provincial Park, ecological processes specific to the park, and management guidelines in other jurisdictions in Canada with similar natural features. Aerial imagery provided a temporal look at intensely used areas in the park. Recommendations include: 1) completion of a biophysical study of the park including an inventory of flora and fauna species 2) development of a monitoring plan incorporating the natural environment with the human dimension of the park 3) engagement of park visitors through signage, education and awareness, and 4) engage the scientific community to form partnerships for further research studies in the park.

The purpose of this study was to develop management guidelines to ensure the long term ecological sustainability of the beach and sand dune area of Grand Beach Provincial Park. A qualitative approach was taken including interviews of individuals who use Grand Beach. A literature review was completed describing the history of use at Grand Beach Provincial Park, ecological processes specific to the park, and management guidelines in other jurisdictions in Canada with similar natural features. Aerial imagery provided a temporal look at intensely used areas in the park. Recommendations include: 1) completion of a biophysical study of the park including an inventory of flora and fauna species 2) development of a monitoring plan incorporating the natural environment with the human dimension of the park 3) engagement of park visitors through signage, education and awareness, and 4) engage the scientific community to form partnerships for further research studies in the park.