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During the past decades, the systematic investigation of the morphodynamics of meandering rivers mostly involved the theoreticalanalytical methodology. The development of analytical models enabled the definition of equilibrium conditions, stability and evolution of river meanders and to investigate the interaction between planform and bedform processes and mechanisms. In recent years the new branch of remote sensing applied to river morphodynamics has been constantly developing simultaneously to the rapid increase of computational and satellite resources. The remote sensing analysis xiii is nowadays employed in a wide range fields in geophysics; for this reason, the past years have seen the prolific development of numerous algorithms for remote sensing analysis. However, remote sensing of meandering river morphodynamics has not been consistently integrated with morphodynamic modelling so far. There is a lack of sophisticated algorithms for the extraction of extensive morphodynamic information from the available remotely sensed data; this gap prevented researchers from seeking systematic validation of analytical models to define their range of applicability, and to exploit their potential for improved insight on observations in real world meandering rivers. The evolutionary dynamics of the channel width, at local and bend scale, as well as the dynamics of bars in meandering rivers represent two major unsettled issues in our present understanding of river meandering dynamics. In this thesis I first provide a systematic methodology for the automated extraction of meandering river morphodynamic information from multitemporal, multispectral remotely sensed data, coded in the PyRIS software. Moreover, I develop an analytical model to investigate the long-term planform evolution of periodic sequences of meander bends incorporating spatio-temporal variations of channel curvature, width and slope. A first model component predicts the temporal evolution of the channel width and slope based on a novel treatment of the sediment continuity at the reach scale. A second model component is a fully analytical, evolutionary model of periodic meanders with spatially and temporally oscillating width accounting for nonlinear feedbacks in flow and sediment transport by means of a twoparameters perturbation approach. Application of the PyRIS software to several long reaches of freeflowing meandering rivers allows me to develop a consistent set of observations on the temporal and spatial evolution of channel width and curvature with unprecedented level of detail. Furthermore, model outcomes indicate that meander-averaged width and slope invariably decrease during meander development, and that the temporal adjustment of the hydraulic geometry is controlled by the ratio between the evolutionary timescales of planform and riverbed, quantified from the analyzed meandering rivers dataset. The nonlinear perturbation model indicates that width and curvature co-evolve according to a hysteretic behavior in time and predicts that the meander belt width dramatically decreases when the meander resonance threshold is crossed. The modelling approach predicts wider-at-bend meanders when the bank pull is dominant with respect to bar push, which in turn promotes meander bends that are wider at inflections. Analytical modeling and remote sensing analysis are mostly integrated through a statistical approach; bend-scale evolutionary analysis xiv of planform descriptors such as channel width, width oscillations and curvature in large pristine meandering rivers exhibit good agreement with the outcomes of the proposed analytical models. Finally, the integration between analytical modeling and remote sensing analysis allows me to identify the key processes controlling the interaction between migrating sediment bars and planform-driven steady point bars. The conditions for the formation of migrating bars in meandering rivers are mostly related to the production of sediment supply by the basin, contrarily to the widespread idea that meandering rivers exhibiting migrating bars typically display lower values of the channel curvature.

Conventional morphodynamic models are typically based on a coupled system of hydrodynamic equations, a bed-update equation, and a sediment-transport equation. However, the sediment-transport equation is almost invariably empirical, with numerous options available in the literature. Bed morphological evolution predicted by a conventional model can be very sensitive to the choice of sediment-transport formula. This thesis presents a physics-based model, where the shallow water-sediment-mixture flow is idealised as being divided into two layers of variable (in time and space) densities: the lower layer concerned with bedload transport, and the upper layer representing sediment in suspension. The model is referred to as a Quasi-2-Layer (Q2L) model in order to distinguish it from typical 2-Layer models representing stratified flow by two layers of different but constant and uniform densities. The present model, which does not require the selection of a particular empirical formula for sediment transport rates, is satisfactorily validated against widely used empirical expressions for bedload and total transport rates. Analytical solutions to the model are derived for steady uniform flow over an erodible bed. Case studies show that the Q2L model, in contrast to conventional morphodynamic approaches, yields more realistic results by inherently including the influence of the bed slope on the sediment transport. This conclusion is validated against experimental data from a steep sloping duct. An analytical study using the Q2L model investigates the influence of bed-slope on bedload transport; the resulting expressions are in turn used to modify empirical sediment transport formulae (derived for horizontal beds) in order to render them applicable to arbitrary stream-wise slopes. The Q2L model provides an alternative approach to studying sediment-transport phenomena, whose adequate analysis cannot be undertaken following coniv ventional approaches without further increasing their degree of empiricism. The Q2L model can also lead to the enhancement of conventional morphodynamic models. For coarse sediments and/or relatively low flow velocities, bedload transport is usually responsible for most sediment transport. Bedload transport consists of a combination of particles rolling, sliding and saltating (hopping) along the bed. Hence, saltation models provide considerable insight into near-bed sediment transport. This thesis also presents an analysis of the statistics and mechanics of a saltating particle model. For this purpose, a mathematically simple, computationally efficient, stochastic Lagrangian model has been derived. This model is validated satisfactorily against previously published experimental data on saltation. The model is then employed to derive two criteria aimed at ensuring that statistically convergent results are achieved when similar saltation models are employed. According to the first criterion, 103 hops should be simulated, whilst 104 hops ought to be considered according to the second criterion. This finding is relevant given that previous studies report results after only a few hundred, or less, particle hops have been simulated. The model also investigates sensitivity to the lift force formula, the friction coefficient, and the collision line level. A method is proposed by which to estimate the bedload sediment concentration and transport rate from particle saltation characteristics. This method yields very satisfactory results when compared against widely used empirical expressions for bedload transport, especially when contrasted against previously published saltation-based expressions.

Tidal inlets on sandy shorelines separate barrier islands and serve as a conduit for transport of sand and water between embayments and oceans, seas, or other tidally influenced waterbodies. Tides and waves induce currents along the coastline that transport sediment across-shore and alongshore. Coastal managers must optimize barrier-inlet system stability while conserving limited sediment resources, and often base management decisions and engineering design upon geomorphic and numerical models that predict the morphological behavior of tidal inlets on short-to-medium timescales (years to decades). The overall goal of this study was threefold. First, to provide science-based practical guidance for regional sediment management in the vicinity of tidal inlets. Secondly, to enhance the understanding of the temporal and spatial scales of sediment pathways in these regions through numerical simulation of traced sediment transport. And, third, to combine these lessons learned in both regional sediment management and analysis of morphodynamic and sediment bypassing pathways with application to a common practical management practice of inlet shoal mining and adjacent beach placement. The temporal and spatial scales controlling the morphodynamics of barrier-inlet systems were reviewed within a regional sediment management context. Next, the application of regional sediment management methods to case studies of multiple barrier-inlet systems in West-Central Florida led to the development of a decision-support tool for regional sediment management (RSM) as applied to barrier-inlet systems. Connecting multiple barrier islands and inlets at appropriate spatio-temporal scales is critical in developing an appropriately scoped sediment management plan for a barrier-inlet system. Evaluating sediment bypassing capacity and overall inlet morphodynamics can better inform regional sand sharing along barrier-inlet coastlines; particularly where sediment resources are scarce and a close coupling between inlet dredging and beach placement is vital to long-term sustainable management. Continued sea-level rise and anthropogenic activities may intensify the need for investigating longer-term processes and expanding regional planning at a centennial timescale, and are acknowledged as challenging tasks for RSM studies going forward. A regionally focused, multi-inlet study was necessary to improve the management plans for the case study inlets (from north to south): John’s Pass, Blind Pass, Pass-a-Grille Inlet, and Bunces Pass. Key recommendations based on the case studies include: 1) allow the natural sediment bypassing to be re-established at Blind Pass inlet through reduced ebb-tidal delta mining, 2) reduce the interruption to sediment bypassing at John’s Pass and Pass-a-Grille inlets through an improved design of the dredged mining areas located along sediment bypassing pathways, 3) allow for continued natural sediment bypassing at Bunces Pass, and, 4) incorporate the cyclic sediment bypassing through swash-bar attachment into the management plan at Bunces Pass and adjacent barrier-islands. Similar systems in other regions may benefit from the lessons derived in this case study of an adaptively managed multi-inlet system. A numerical model that computes hydrodynamics, sediment transport, and morphodynamics including bed layering was incorporated in this study to analyze sediment transport pathways between littoral sources from adjacent beaches and the geomorphic features of an idealized tidal inlet designed to imitate the John’s Pass tidal inlet in West-central Florida, USA. This study developed a methodology to numerically trace sediment transport, deposition and erosion. This method was applied to investigate sediment-bypassing pathways under varying temporal and spatial scales. The analyses of the adjacent beach’s contribution to tidal inlet sediment bypassing demonstrated variable temporal scales on sediment transport and exchange. High-energy wave events dominated the temporal scale for sand to be transported from the updrift beach to the ebb-tidal delta, whereas cyclical tidal processes had a significant influence on the spatial pattern of exchange between the shoals and channel features of the tidal inlet. The ability to simulate burial and erosion of tracers allowed identification of offshore sedimentation hotspots such as terminal lobe as well as zones of deposition and active transport in shallow water, such as the updrift channel margin linear bar and the downdrift platform of the ebb-tidal delta. The general sediment-bypassing pathway reflected a tidal-driven redistribution following event-driven pulses of wave-induced sediment mobilization. Sediment was transported along the beach during these energetic wave events. Flood- and ebb-tidal currents transported the sediment mobilized by high waves into the inlet channels. This was followed by subsequent gradual redistribution of the deposited channel sediments over the ebb-tidal delta features during fair-weather conditions. The modeling methods were then applied to investigate the sediment pathways and bypassing processes for three validated numerical models of coastal tidal inlets that span a range of forcing conditions. The processes that influence sediment transport along various pathways between the several morphological features of each inlet and its adjacent beaches were examined. The sediment tracing methodology employed in this study allowed for an evaluation of the sediment transport pathways between the various morphologic features of a tidal inlet, as well as their respective processes that drive the exchange of sediments. Characterizing and correlating the sediment pathways between tidal inlet morphologic features can improve the inlet reservoir model, which is a predictive model of inlet shoal volumes based on empirical formulae. The results of this study illustrate the value of including sediment-tracking techniques in simulating sediment bypassing and the potential of this application to inform coastal engineering and design modifications to sediment reservoirs of tidal inlets. And, finally, the spatial patterns of transport and erosion and deposition of traced, littoral source sediment, were investigated using the same modeling framework to evaluate the design of ebb-tidal delta mining on sediment bypassing dynamics of a tidal inlet system based on an idealized model of John’s Pass, Florida. Seven mining areas were simulated with traced sediment sources from the updrift beach, downdrift beach, and adjacent shoals. The tracers’ migration pattern and mining area infilling were analyzed to depict the sediment bypassing pathways and their contributions to mining area infilling. Mining area recovery rates were highest along the channel margin linear bar, and decrease offshore and downdrift. Updrift sand sources contributed more to mining area infilling than downdrift sand sources. The position of the mining area in relation to the updrift or downdrift morphological features dictates whether it will receive primarily updrift- or downdrift-originating littoral sediment from the beach. The source of sedimentation within the mining areas is a combination of inlet-ward transport of beach sediment and nearby shoal sediment. Proximity to the inlet channel determined the degree to which sedimentation had originated from longshore transported beach sediment. This methodology can improve confidence in management decisions concerned with the sand-sharing capacity of barrier-inlet systems in a local and regional context.

Seagrasses are ecosystem engineers, forming extensive meadows that provide critical habitat and modulate local morphodynamics. Their canopies induce drag on flow to attenuate mean flow and reduce near-bed flow velocities, which can shield the bed from erosion and sediment suspension. Alternatively, seagrass loss can enhance erosion and sediment suspension, which can be initiated through short-lived extreme events, or chronic long-term disturbances. Physical process and disturbances can govern the evolution of seagrass meadow ecosystems. In two separate chapters, this research examined 1) the influence of climate variability and storms on seagrass loss and erosion at a high spatial resolution, and 2) how flow attenuation by seagrass varies across tidal cycles and at different locations in the Choked Passage meadow, on the Central Coast of British Columbia. We used high resolution multibeam echosounder (MBES) bathymetry and backscatter data from 2018 to 2021, drone mapped seagrass delineations from 2014 to 2021, and wind and wave data from 2014 to 2021. Flow data (i.e. velocity magnitude, velocity direction, and acoustic backscatter) above the seagrass canopy was collected with an Acoustic Doppler Current Profiler (ADCP) along transects and moored to the seafloor over a tidal cycle. Sediment samples were collected from the bed to estimate critical shear stress and verify sediment classes from an acoustic backscatter analysis. From 2018 to 2021, the meadow experienced significant erosion (net surface lowering of -18,768 m3) and loss of seagrass (10% reduction), which we attribute to the preceding winter storm activity driven by moderate La Niña conditions. The spatial patterns of erosion and seagrass loss was non-uniform across the meadow. Coupled erosion and seagrass loss resulted in the generation and/or expansion of blowouts. We observed a trend of a reduction in seagrass coverage following winters with a high number of storm events and/or high recorded storm intensity from 2014 to 2021. We believe the Choked Passage seagrass meadow undergoes cyclic behaviour with reduction in seagrass coverage during energetic ENSO years, followed by a recovery period during weak years. The ADCP was used to detect the seagrass canopy height, measure flow, and estimate shear stress. Overall, flow is fastest in the northern section of the main meadow, particularly in the north-west corner where the meadow is patchy. Moreover, flow appears to accelerate through the meadow interior, which suggests that topographic steering and the strength of incoming currents exceeds the ability of seagrass to dampen flow velocity. During the transition from peak flood to ebb, flow velocity remained heightened for longer above the southern meadow and lagged the other sections. Shear stress results indicate that sediment can be transported as bedload and in suspension under peak flow velocities at some of the sites examined within the meadow. Shear stress is largest in the meadow center and lower towards the southern margin of the main meadow. Based on our results, when sediment transport is initiated under peak tidal and/or extreme conditions, sediment is likely primarily transported as bedload, creating the observed sand wave and blowout bedforms. This research demonstrated linkages between extreme storms (during ENSO years), seabed morphology, and seagrass coverage, and examined the variability in the interaction between flow, seagrass, and sediment transport. Geomorphic processes and disturbances have an important influence on ecosystem structure and function over time, therefore, it is important to understand how these processes operate and are modified by external drivers. The results of this study have significant implications on seagrass conservation, restoration, and the evolution of coastal landscapes. / Graduate

Philosophiae Doctor - PhD / River systems are by nature complex and dynamic systems, which vary in structure and therefore function, and are closely connected to their landscapes. The primary aim of this thesis was to develop a systems operational understanding of how river patterns and processes (geomorphology and hydrology) link to aquatic and riparian systems and biodiversity (ecology) in a framework of evolving land cover/use and management. This illustrated the hydrogeomorphic controls regulating the structure and functioning of rivers in the provision of goods and services that vegetation, especially riparian vegetation, perform as ecological infrastructure, with a focus on the Duiwe River catchment. This study used a combination of desktop and field analysis. The desktop analysis followed the spatial and temporal historical land use change detection of river sub-catchments to assess the influence on water quality and river flow. It included historical water quality, flow records, rainfall data and aerial photograph time series analysis for trend detection, which were linked to changes in land use activities. The field surveys included cross-section surveys, physical and chemical sediment analysis, vegetation distribution, ground-water depth surveys and instream biological surveys of aquatic bioindicators. The study illustrated a correlation between land cover/use, water quality and river ecological integrity. When spatial heterogeneity of the catchments was altered by human or natural events, it was reflected by changes in the water quality. The linkages between the land cover/use and ecological integrity were examined using macroinvertebrates and algae. Macroinvertebrates were indicative of habitat integrity and river condition, while the benthic filamentous algae were indicative of increased nutrients and alkalinity. Results indicated that the full consortium of algae and macroinvertebrates be used as bioindicators for ecological integrity assessments in these short, coastal rivers. The influence of riparian vegetation and its effectiveness in providing regulating (retaining sediment and nutrients) and provisioning (good water quality for humans and the aquatic environment) services was examined by relating contrasting land uses, riparian vegetation, nutrient dynamics and water quality. The land covers generated different runoff volumes, water quality parameter concentrations and associated nutrient loads. Agriculture and alien Acacia mearnsii trees had the greatest impact on nutrient loads. However, a decreasing trend in nutrient concentrations was observed in the cross-section from the pastures to the riparian zones to the river at all sites. The key findings from this study were formulated into a conceptual framework flow-chain model demonstrating the linkages between river pattern, processes and ecology in the provision of ecosystem services. This interdisciplinary investigation demonstrated strong links between climate, topography, hydrogeomorphology, land cover/use, human activities and their influence on ecological river integrity. The developed framework provides a hierarchical model to link the different disciplines. It illustrates the top-down constraints provided by the system controllers and habitat drivers, coupled with the anthropogenic impacts as controllers to determine the response of biological entities (riparian vegetation and aquatic biota) at different scales, to ultimately provide ecosystem services. It provides the basis for an understanding of the linkages, processes and interactions that allows, prevents or alters ecosystem service provision by river ecosystems and in the study context, by riparian buffer zones.

The recent emergence of Structure-from-Motion Photogrammetry (SfM) has created a cost-effective alternative to conventional laser scanning for the production of high-resolution topographic datasets. There has been an explosion of applications of SfM within the geomorphological community in recent years, however, the focus of these has largely been small-scale (102 - 103 m2), building on innovations in low altitude Unmanned Aircraft Systems (UAS). This thesis examines the potential to extend the scope of SfM photogrammetry in order to quantify of landscape scale processes. This is examined through repeat surveys of a ~35 km2 reach of the Dart River, New Zealand. An initial SfM survey of this reach was conducted in April 2014, following a large landslide at the Slipstream debris fan. Validation of the resulting digital elevation models using Independent Control Point's (ICPs) suggested encouraging results, however benchmarking the survey against a long-range laser scanned surface indicated the presence of significant systematic errors associated with inaccurate estimation of the SfM bundle adjustment. Using a combination of scaled laboratory field experiments, this research aimed to develop and test photogrammetric data collection and modelling strategies to enhance modelling of 3D scene structure using limited constraints. A repeat survey in 2015 provided an opportunity to evaluate a new survey strategy, incorporating a convergent camera network and a priori measurement of camera pose. This resulted in halving of mean checkpoint residuals and a reduction in systematic error. The models produced for both 2014 and 2015 were compared using a DEM differencing (DoD) methodology to assess the applicability of wide-area SfM models for the analysis of geomorphic change detection. The systematic errors within the 2014 model confound reliable change detection, although strategies to correlate the two surveys and measure the residual change show promise. The future use of SfM over broad landscape scales has significant potential, however, this will require robust data collection and modelling strategies and improved error modelling to increase user confidence.

Blind Pass, a heavily structured wave-dominated tidal inlet on the west central coast of Florida, has undergone substantial morphologic changes in the past 150 years. Initially Blind Pass was a mixed-energy inlet. In 1848 a hurricane opened a new inlet to the north called Johns Pass, which captured a large portion of the tidal prism of Blind Pass. Since then Blind Pass migrated southward until it was structurally stabilized in 1937. The decreasing tidal prism resulted in significant inlet channel filling. The channel has been dredged 12 times since 1937. The present inlet is stabilized by two jetties and a series of seawalls. Detailed time-series field measurements of bathymetry and tidal flows were conducted between 2001 and 2004, after the last channel dredging in the summer of 2000. The measured depositional rate in the inlet channel approximately equals the net southward longshore transport rate. This suggests that the inlet has served as a trap for the southward longshore transport allowing negligible bypassing to the eroding downdrift beach. Most of the active sedimentation occurs on the northern side of the inlet. The sediment in the thalweg is largely coarse shell lag, indicating adequate sediment flushing by the ebbing tide. The cross-channel flow measurements revealed that ebb flow was approximately twice as high in the channel thalweg as compared with the rest of the channel. The flood flow was largely uniform across the entire inlet and dominated over the northern portion of the inlet due to the weak ebb flow there. This cross-channel flow pattern is crucial to the understanding of the sedimentation patterns in the Blind Pass channel. Two years after the last dredging the mouth has become shallow enough to induce wave breaking across the shoal area. Distinctive seasonal patterns of sedimentation were measured thereafter in the inlet channel, influenced by seasonal wave climate. The sedimentation is event driven from passage of cold fronts bringing elevated wave energy that accelerates the southward longshore transport. During normal conditions the sediment deposited in the mouth area is redistributed further into the inlet by the flood current combined with wave-driven current.

<p>My doctoral work stems from an original motivation to understand more closely why some areas of sandy coastlines erode and others accrete<—>an intriguing fundamental question and one of societal relevance wherever human coastal infrastructure exists. What are the physical processes driving shoreline change, and over what spatial and temporal scales are they manifest? If forces driving the littoral system change, how does the shoreline respond? Can we attribute observed patterns of shoreline change to a particular process?</p><p>Recent novel numerical shoreline-evolution modeling demonstrated that wave-driven gradients in alongshore sediment transport could produce self-organized, emergent features on spatial scales from sand waves to large-scale capes [<italic>Ashton et al.</italic>, 2001], introducing a new theoretical perspective to the cross-shore-oriented considerations of the coastal scientific community. The unexpected model results inspired fresh hypotheses about shoreline pattern formation and the forcing mechanisms behind them.</p><p>One overarching hypothesis was that under regimes of high- and low-angle deep-water incident waves, alongshore shoreline perturbations grow or diffuse away, respectively. To test the hypothesis we looked for a correlation between shoreline curvature (showing perturbations to a nearly straight coastline) and shoreline change in observed measurements. High-resolution topographic lidar surveys of the North Carolina Outer Banks from 1996<–>2006 allowed robust, quantitative comparisons between shoreline surveys spanning tens of kms. In Chapter 1 [<italic>Lazarus and Murray</italic>, 2007] we report that over the last decade, at multi-km scales along the barrier islands, convex-seaward promontories tended to erode and concave-seaward embayments accrete<—>a pattern of diffusion consistent with the smoothing effects of alongshore-transport gradients driven by a low-angle wave climate. Why then, after a decade or more of smoothing, do plan-view bumps in the shoreline still persist? In Chapter 2 [<italic>Lazarus et al.</italic>, in review] we compile evidence suggesting that (a) a framework of paleochannels may control the areas of persistent multi-km-scale shoreline convexity that (b) in turn drive decadal-term transient changes in shoreline morphology by (c) affecting gradients in wave-driven alongshore sediment transport.</p><p>In Chapter 3, a third investigation of large-scale coastal behavior, we explore an existing premise that shoreline change on a sandy coast is a self-affine signal wherein patterns of changes are scale-invariant, perhaps suggesting that a single process operates across the scales. Applying wavelet analysis<—>a mathematical technique involving scaled filter transforms<—>we confirm that a power law fits the average variance of shoreline change at alongshore scales spanning approximately three orders of magnitude (5<–>5000 m). The power law itself does not necessarily indicate a single dominant driver; beach changes across those scales likely result from a variety of cross-shore and alongshore hydrodynamic processes. A paired modeling experiment supports the conclusion that the power relationship is not an obvious function of wave-driven alongshore sediment transport alone.</p><p>Our tests of theory against field observations are middle steps in pattern-to-process attribution; they fit into a larger body of coastal morphodynamic research that in time may enable shoreline-change prediction. Present hydrodynamic models are still too limited in spatial and temporal scope to accommodate the extended scales at which large morphological changes occur, but more integrated quantitative models linking bathymetry, wave fields, and geologic substrate are underway and will set the next course of questions for the discipline.</p> / Dissertation

This thesis presents results from spatial-temporal and volumetric change analysis of blowouts on the Cape Cod National Seashore (CCNS) landscape in Massachusetts, USA. The purpose of this study is to use methods of analysing areal and volumetric changes in coastal dunes, specifically blowouts, and to detect patterns of change in order to contribute to the knowledge and literature on blowout evolution. In Chapter 2.0, the quantitative analysis of blowout change patterns in CCNS was examined at a landscape scale using Spatial-Temporal Analysis of Moving Polygons (STAMP). STAMP runs as an ArcGIS plugin and uses neighbouring year polygon layers of our digitized blowouts from sequential air photo and LiDAR data (1985, 1994, 2000, 2005, 2009, 2011, and 2012 for 30 erosional features, and 1998, 2000, 2007, and 2010 for 10 depositional features). The results from STAMP and the additional computations provided the following information on the evolution of blowouts: (1) both geometric and movement events occur on CCNS; (2) generation of blowouts in CCNS is greatest in 1985 and is potentially related to vegetation planting campaigns by the Park; (3) features are expanding towards dominant winds from the North West and the South West; (5) the erosional and depositional features are becoming more circular as they develop, (6) the evolution of CCNS blowouts follows a similar pattern to Gares and Nordstrom’s (1995) model with two additional stages: merging or dividing, and re-activation. In Chapter 3.0, the quantitative analysis of volumetric and areal change of 10 blowouts in CCNS at a landscape scale is examined using airborne LiDAR and air photos. The DEMs of neighbouring years (1998, 2000, 2007, and 2010) were differenced using Geomorphic Change Detection (GCD) software. Areal change was detected by differencing the area of polygons that were manually digitized in ArcGIS. The changes in wind data and vegetation cover were also examined. The results from the GCD and areal change analysis provide the following information on blowout evolution: (1) blowouts generate/initiate; (2) multiple blowouts can merge into an often larger blowout; (3) and blowouts can experience volumetric change with minimal aerial change and vice versa. From the analyzes of hourly Provincetown wind data (1998-2010), it was evident that blowouts developed within all three time intervals. The percentages of comparable winds (above 9.6 m s-1) were highest in 1998, 1999, 2007 and 2010. It is speculated that tropical storms and nor'easters are important drivers in the development of CCNS blowouts. In addition, supervised classifications were run on sequential air photos (1985 to 2009) to analyze vegetation cover. The results indicated an increase in vegetation cover and decrease of active sands over time. Two potential explanations that link increased vegetation to blowout development are: (1) sparse vegetation creates a more conducive environment for the initiation of blowouts by providing stability for the lateral walls, and (2) high wind events (e.g. hurricanes and nor'easters) could cause vegetation removal, allowing for areas of exposed sand for blowout initiation and development. / Graduate / 0799 / 0368 / kimia.abhar@gmail.com