Ian J Walker | University of California, Santa Barbara (original) (raw)

Papers by Ian J Walker

Sandy Beach Morphodynamics, 2020

Abstract Wind is a highly capable geological agent on many sandy beaches above, and sometimes bel... more Abstract Wind is a highly capable geological agent on many sandy beaches above, and sometimes below, the high-tide limit where sand can become dry and mobilised by aeolian (wind-blown) processes. This chapter reviews current understanding of the measurement and modelling of aeolian sand transport over beaches. The fundamentals of boundary layer airflow dynamics and aeolian sand transport are explained and key aeolian transport models are classified and critiqued with respect to their application on beaches. In particular, a suite of key environmental controls that affect aeolian sand transport on beaches are reviewed, namely wind climate, beach morphology: width, slope and fetch, moisture, salt and biological crusts, roughness elements and vegetation. For each, influences on aeolian sand transport mechanics and modelling are discussed and implications for back beach morphodynamics are explored. This chapter focuses primarily on empirical field and wind-tunnel research findings and identifies key advances and current challenges for aeolian research in coastal settings.

Boreas, 2017

After retreat of the Cordilleran Ice Sheet (CIS) and subsequent glacio-isostatic adjustment of th... more After retreat of the Cordilleran Ice Sheet (CIS) and subsequent glacio-isostatic adjustment of the central coast of British Columbia (BC), Canada, a complex coastline emerged as relative sea level rapidly reached equilibrium and maintained stability over the end of the Late Pleistocene and Holocene. This study provides a late Quaternary reconstruction of the landscape evolution of a geographically distinct location on the central BC coast, northwest Calvert Island, which experienced a re-advance of the CIS near the end of the Late Pleistocene and minimal subsequent relative sea-level change. Geomorphological observations from LiDAR imagery, sedimentological and palaeoecological evidence from exposures, cores and shovel pits, and a robust luminescence and 14 C-based chronology spanning the last 15 000 years are used to reconstruct the landscape of northwest Calvert Island following CIS retreat. A singlealiquot regenerative dose protocol that was developed specifically for luminescence dating of the sediments on Calvert Islandwas utilized in this study. Localized proglacial sedimentation was linked to the glacial re-advance experienced at the end of the Late Pleistocene. Extensive coastal reconfiguration (e.g. rapid shoreline progradation of >1 m a À1) occurred in the absence of extensive RSL change, which was the main driver of coastal change elsewhere along the BC coast. Changes in climate, small magnitude changes in RSL, and fire all probably played a role in isolated aeolian landform development and stabilization in the study area. An important contribution of this study is the documentation of the multidisciplinary approach for reconstructing palaeogeography, using multiple geochronological methods, micro-and macro-sedimentology, the palaeoecology inferred from both macro and microfossils (e.g. diatoms and foraminifers), stratigraphy, field mapping and remote sensing. In addition, these findings inform our understanding of the drivers of coastal sedimentary processes, particularly in the temperate coastal rainforest region of BC, and the role that fire may play in those processes. Coastal palaeogeography studies in the region will become increasingly important as discoveries of Late Pleistocene human habitation along the coastal migration route continue to be documented.

Geomorphology, 2019

Sediment transport pathways and resulting erosion-deposition patterns across beach-foredune syste... more Sediment transport pathways and resulting erosion-deposition patterns across beach-foredune systems can be complex. Although a great deal is known about the effects of wind fetch, surface moisture, topographic forcing, and vegetation cover, the role of large woody debris (LWD) as a control on sediment redistribution across beaches is relatively understudied. Pieces of LWD act as non-porous roughness elements that induce secondary flow circulation, thereby creating unique sedimentation patterns that differ markedly from those over a flat beach. Large accumulations of LWD collectively have a bulk porosity that provides substantial sand trapping

Quaternary Research, 2017

Descriptions of the Cordilleran Ice Sheet retreat after the last glacial maximum have included sh... more Descriptions of the Cordilleran Ice Sheet retreat after the last glacial maximum have included short-lived readvances occurring during the Older and Younger Dryas stadial periods and into the Holocene, but identification of these events has been largely limited to southwest and central British Columbia and northwest Washington State. We present evidence of a late Pleistocene readvance of Cordilleran ice occurring on the central coast of British Columbia on Calvert Island, between northern Vancouver Island and Haida Gwaii. Evidence is provided by sedimentological and paleoecological information contained in a sedimentary sequence combined with geomorphic mapping of glacial features in the region. Results indicate that a cold climate existed between 15.1 and 14.3 cal ka BP and that ice advanced to, and then retreated from, the western edge of the island between 14.2 and 13.8 cal ka BP. These data provide the first evidence of a major fluctuation in the retreating ice sheet margin in t...

Journal of Coastal Research, 2016

The Province Lands dunefield at Cape Cod is characterised by large parabolic dunes on which have ... more The Province Lands dunefield at Cape Cod is characterised by large parabolic dunes on which have developed very significant numbers of active saucer and bowl blowouts. Blowouts occur across the entire dune landscape but many are initiated on the high lee margins of large erosional ridges and bowl blowouts within the larger parabolic dune landscape. Evolution of these blowouts is characterised by multiple stages. The first few evolutionary stages are described. In addition, the aerodynamics and flow structure within a trough blowout and former saucer blowout developed within a high ridge crest is elucidated from 2D sonic anemometer data, smoke bombs and videography. The flow is characterised by decreasing then increasing flow up the blowout centreline, and marked, highly turbulent opposed flow separation immediately inside and around the marginal entrance walls of the blowout.

World Geomorphological Landscapes, 2016

The archipelago of Haida Gwaii, formerly known as the Queen Charlotte Islands, is one of the most... more The archipelago of Haida Gwaii, formerly known as the Queen Charlotte Islands, is one of the most dynamic geomorphic environments in Canada. Climatic and geophysical forces have combined to shape the unique landscape of the archipelago. Strong cyclonic storms from the Pacific Ocean are frequent and are accompanied by heavy rainfall. The two strongest earthquakes in Canadian history happened on the Queen Charlotte Fault just west of the archipelago in the Pacific Ocean. Coastal landscapes on the west coast are rugged and rocky, whereas the north and east coasts are formed in thick glacial sediments that are being rapidly eroded by waves. The mountainous spine that runs the length of Haida Gwaii is susceptible to landslides and other mass wasting processes. Slope failures are the primary agent of natural disturbance in these mountains and occur at rates that are among the highest in Canada. They are triggered by heavy rainfall, forestry activities, and earthquakes.

Earth Surface Processes and Landforms, 2016

The results from three years of surveying and monitoring a dynamic foredune and dunefield restora... more The results from three years of surveying and monitoring a dynamic foredune and dunefield restoration effort on Vancouver Island, Canada is presented. Complete removal of foredune vegetation occurred in three phases spaced a year apart in an effort to control invasive Ammophila spp. The collection of airborne LiDAR, orthophotographs, and bimonthly topographic surveys provided a means to quantify and examine sediment budgets and geomorphic responses. Three survey swaths, corresponding with each phase of vegetation removal, were established to provide detailed topographic coverage over the impacted beach, foredune, and dunefield landscape units. The swath corresponding with the first phase of removal recorded a positive sediment budget of 1•3 m 3 m À2 after three years. A control swath, with data collected for a year prior and two years following removal, exhibited a distinct pulse of sediment delivery into the dunefield unit with a maximum gain of 0•03 m 3 m À2 pre-removal compared to 0•11 m 3 m À2 post-removal. Vegetation analysis zones, associated with each of the three swaths, demonstrate a range of vegetation responses due to variation in the vegetation removal and subsequent re-invasion or removal methods employed. The first site to be cleared of vegetation, received ongoing invasive re-growth control, and three years following removal vegetation cover dropped from 57% in 2009 to 13% in 2012 (À44%). An adjacent site was cleared of vegetation two years later (only one year of recovery) but experienced rapid Ammophila re-invasion and percent cover changed from 61% in 2009 to 26% in 2012 (À35%). The data presented provides insights for improving the application of sediment budget monitoring in dynamic restorations and discusses the potential for detailed spatial-temporal survey data to improve our understanding of meso-scale landscape morphodynamics following foredune disturbance. Overall, the vegetation removal treatments reduced the extent of invasive grass and increased dunefield mobility and dynamic activity.

Geomorphology, 2015

This paper examines the multi-decadal evolution of a foredune and backshore river complex on a wa... more This paper examines the multi-decadal evolution of a foredune and backshore river complex on a wavedominated, drift-aligned coast at Wickaninnish Bay on southwestern Vancouver Island, British Columbia, Canada. Local shoreline positions are generally prograding seaward as fast as + 1.46 m a −1 in response to rapid regional tectonic uplift and positive onshore sediment budgets. The northern end of the foredune system has extended rapidly alongshore in response to net northward littoral drift. Despite these net accretional responses, the beach-dune system experiences relatively frequent (return interval~1.53 years) erosive events when total water levels exceed a local erosional threshold elevation of 5.5 m above regional chart datum. Geomorphic recovery of the beach-dune system from erosive events is usually rapid (i.e., within a year) by way of high onshore sand transport and aeolian delivery to the upper beach. This response is complicated locally, however, by the influence of a backshore river that alters spatial-temporal patterns of both intertidal and supratidal erosion and deposition. Historic landscape changes and rates of shoreline positional change are derived from several years of aerial photography (1973, 1996, 2007, 2009, 2012) using the USGS Digital Shoreline Analysis System (DSAS). Significant volumetric changes are also estimated from aerial LiDAR-derived DEMs in 2005, 2009 and 2012, and related morphodynamics are interpreted using a statistically constrained geomorphic change detection method. Results suggest that supratidal bar development, overwash deposition and aeolian deposition on a low-lying supratidal platform, combined with alongshore extension of the foredune complex, is forcing Sandhill Creek to migrate northward in the direction of beach drift. In response, the river actively erodes (−1.24 m a −1) a bluff system landward of the channel, which generates substantial sediment volumes (− 0.137 m 3 m −2 a −1) that feed a large intertidal braided channel and delta system. These local responses provide context for a conceptual model of the evolution of a wave-dominated, drift-aligned beach-foredune system that interacts with a backshore river. This model may provide useful information to local park managers as erosion and sedimentation hazards threaten visitor safety and park infrastructure.

Temporal and spatial scale of aeolian flux on a vegetated foredune during a high energy event R. ... more Temporal and spatial scale of aeolian flux on a vegetated foredune during a high energy event R. Davidson‐Arnott, B.O. Bauer, I.J. Walker, P.A. Hesp, J. Ollerhead, C. Chapman In the past two decades the advent of high frequency acoustic and piezo‐electric sensors has advanced our understanding of the temporal pattern of aeolian transport on beaches primarily at a single point above the bed. Recently, the deployment of laser particle counters has permitted the collection of data from a vertical array making it possible to examine temporal fluctuations in the vertical concentration profile. A vertical array of Wenglor laser particle counters deployed on the crest of a large, vegetated foredune on the north coast of Prince Edward Island yielded 1Hz data during a storm event in May, 2010 on transport intensity (grain counts) measured at six levels above the sand surface (between 1.4 cm and 47.2 cm) with coincident measurements of 3D wind vectors. Additional particle counters were deploy...

Treatise on Geomorphology, 2013

Airflow dynamics over dunes differ significantly from those over flat terrain due to topographica... more Airflow dynamics over dunes differ significantly from those over flat terrain due to topographically generated pressure fields that cause deviations in flow behavior (e.g., streamline compression, expansion and/or curvature, flow separation and/or reversal). Recent research using ultrasonic anemometry, modeling of computational fluid dynamics (CFD), wind tunnel simulations, and detailed field experiments have enhanced our understanding of boundary layer flow over dunes and, thus, advanced recent efforts to model the interactions between dune geomorphology, airflow dynamics, and sand transport. This chapter reviews principally the fundamentals of airflow over and in the lee of transverse dunes and discusses several key advances and limitations in measurement and modeling of flow dynamics. Although progress in our understanding has been made mostly via study of transverse desert dunes, due to their relatively simple shape and surface roughness characteristics (i.e., no vegetation), research advances from other dune settings (e.g., coastal foredunes) are also reviewed briefly. Though covered more extensively in other chapters, implications for sediment transport and dune morphodynamics are also discussed. Areas for further research are identified based on gaps in knowledge on the implications of flow dynamics for mesoscale (i.e., landform to landscape scale) dune sediment budgets, migration and morphological evolution.

Treatise on Geomorphology, 2013

This chapter provides a companion chapter to Hesp (2012) in which the initiation, dynamics, morph... more This chapter provides a companion chapter to Hesp (2012) in which the initiation, dynamics, morphology, and evolution of the principal coastal dune types are examined. Those dune types are foredunes, blowouts, parabolic dunes, and transgressive dune fields. This chapter presents an accompanying overview of those dunes in the form of a photoessay which attempts to show the morpho-ecological diversity of, and within the various dune types. The initiation, morphological types and stages, and evolutionary patterns of the various dune types are examined, and the photographs and diagrams attempt to provide a visual explanation of some of the diverse range of dune types, ages, and stages possible.

Geomorphology, 2015

This paper explores historical evolution of blowouts at Cape Cod National Seashore (CCNS), USAa s... more This paper explores historical evolution of blowouts at Cape Cod National Seashore (CCNS), USAa site that hosts one of the world's highest densities of active and stabilized blowouts. The Spatial-Temporal Analysis of Moving Polygons (STAMP) method is applied to a multi-decadal dataset of aerial photography and LiDAR to extract patterns of two-dimensional movement and morphometric changes in erosional deflation basins and depositional lobes. Blowout development in CCNS is characterized by several geometric (overlap) and movement (proximity) responses, including: i) generation and disappearance, ii) extension and contraction, iii) union or division, iv) clustering and v) divergence by stabilization. Other possible movement events include migration, amalgamation and proximal stabilization, but they were not observed in this study. Generation events were more frequent than disappearance events; the former were highest between 1985 and 1994, while the latter were highest between 2000 and 2005. High rates of areal change in erosional basins occurred between 1998 and 2000 (+3932 m 2 a −1), the lowest rate (+333 m 2 a −1) between 2005 and 2009, and the maximum rate (+4589 m 2 a −1) between 2009 and 2011. Union events occurred mostly in recent years (2000-2012), while only one division was observed earlier (1985-1994). Net areal changes of lobes showed gradual growth from a period of contraction (−1119 m 2 a −1) between 1998 and 2000 to rapid extension (+2030 m 2 a −1) by 2010, which is roughly concurrent with rapid growth of erosional basins between 2005 and 2009. Blowouts extended radially in this multi-modal wind regime and, despite odd shapes initially, they became simpler in form (more circular) and larger over time. Net extension of erosional basins was toward ESE (109°) while depositional lobes extended SSE (147°). Lobes were aligned with the strongest (winter) sand drift vector although their magnitude of areal extension was only 33% that of the basins. These differences in extension responses likely result from more complex and evolving flow-form interactions inside erosional basins. Historical photographs and CCNS documents suggest that blowout evolution may be influenced by land-use changes, such as revegetation campaigns in 1985 that were followed by high blowout generation. High magnitude regional storm events (e.g., hurricanes) also play a role. The analytical framework presented provides a systematic means for twodimensional geomorphic change detection and pattern analysis that can be applied to other landscapes.

Geomorphology, 2012

Recent research on quasi-instantaneous turbulent kinematic Reynolds stresses (RS, − u′w′) and dec... more Recent research on quasi-instantaneous turbulent kinematic Reynolds stresses (RS, − u′w′) and decomposed quadrant event activity (e.g., ejections and sweeps) over dunes in fluvial settings and in wind tunnels has shown that turbulent stresses at the toe of a dune often exceed time-averaged, streamwise shear stress (ρ u * 2) estimates. It is believed that semi-coherent turbulent structures are conveyed toward the bed along concave streamlines in this region and that impact of these structures cause fluctuations in local surface stresses that assist in grain entrainment. This has been hypothesized to explain how sand is supplied to the windward slope through a region of flow stagnation. Toward the crest, surface stress increases and becomes dominated by streamwise accelerations resulting from streamline compression and convexity that suppress vertical motions. High-frequency (32 Hz) measurements of turbulent wind flow from 3-D ultrasonic anemometers are analyzed for oblique onshore flow over a vegetated coastal foredune in Prince Edward Island, Canada. Reynolds stress and quadrant activity distributions varied with height (0.60 m and 1.66 m) and location over the dune. In general, quadrant 2 ejection (u′ b 0, w′ > 0) and quadrant 4 sweep activity (u′ >0, w′ b 0) dominated momentum transfer and RS generation over quadrant 1 outward interaction (u′ >0, w′ > 0) and quadrant 3 inward interaction (u′ b 0, w′ b 0) activity. On the lower stoss slope, significant ejection and sweep event activity was most frequent (85 to 92%, ejections plus sweeps), whereas, at the upper crest, significant ejection and sweep activity became less frequent while significant outward and inward interactions increased in frequency (25 to 36%). An 'exuberance effect' (i.e., changing shape of quadrant frequency distribution skewed toward ejection and sweep activity) is observed whereby streamline compression and convexity effects inhibit vertical fluctuations in flow and, thus, reduce the frequency of ejections and sweep activity toward the crest. In separated flow in the lee of the crest, quadrant distributions were more symmetrical as a result of more mixed, multi-directional flow. These trends in turbulent event distributions and Reynolds stress have implications for sediment transport dynamics across the dune and may help to explain sand transport potential and dune maintenance. For example, areas with a high frequency of ejection and sweep activity may have higher rates of sediment entrainment and transport, whereas areas with lower ejection and sweep activity and an increase in outward and inward interactions, which contribute negatively to Reynolds stress generation, may experience a greater potential for deposition. Further research on associations between quadrant event activity and coincident sand transport is required to confirm this hypothesis and the resultant significance of the flow exuberance effect in aeolian dune morphodynamics.

Journal of Arid Environments, 2021

This research investigated spatial and temporal environmental changes associated with climatic va... more This research investigated spatial and temporal environmental changes associated with climatic variability and off-highway vehicle (OHV) activity in the Algodones Dunes, California, using time-series analysis of Moderate Resolution Imaging Spectroradiometer imagery from 2001 to 2016. We compared changes in land cover, surface albedo, and surface temperatures between the Imperial Sand Dunes Recreation Area (ISDRA) and areas with no OHV activity in the North Algodones Dunes Wilderness area (NADW). Both areas showed a decreasing normalized difference vegetation index (NDVI) and an increasing albedo from 2001 to 2016; however, ISDRA had a lower NDVI value and higher albedo compared to the adjacent NADW. Transects across these adjoining areas revealed substantial differences in daytime and nighttime land surface temperatures. ISDRA had an appreciably higher mean daytime temperature and a lower mean nighttime temperature compared to those within NADW. Results suggest direct association between increasing OHV activity and reduced vegetation cover, increased soil exposure, and higher daytime temperatures in the Algodones Dunes. We recommend enhanced monitoring of ecosystem and land use changes coupled with enhanced land use management to reduce the contributions of recreational OHV activity on land degradation and to maintain habitat for key species and ecosystems of interest in the dune field.

33 Measurements of lee-side airflow response from an extensive array of meteorological instrument... more 33 Measurements of lee-side airflow response from an extensive array of meteorological instruments 34 combined with smoke and flow streamer visualization is used to examine the development and 35 morphodynamic significance of the lee-side separation vortex over closely spaced transverse dune 36 ridges. A differential deflection mechanism is presented that explains the three-dimensional pattern 37 of lee-side airflow structure for a variety of incident flow angles. These flow patterns produce 38 reversed, along-dune and deflected surface sand transport in the lee that result in a net ‘lateral 39 diversion’ of sand mass transport over one dune wavelength for incident angles as small as 10° 40 from crest-transverse (i.e., 80° from the crest line). This lateral displacement in fluid mass transport 41 increases markedly with incident flow angle, when expressed as the absolute value of the total 42 deflection in degrees. Reversed flow and multidirectional sand transport occur for incident...

Geological Society of America Abstracts with Programs, 2017

: Sand dunes are large coastal features typically formed when windblown sand is trapped and stabi... more : Sand dunes are large coastal features typically formed when windblown sand is trapped and stabilized by vegetation. Located between the back beach and inland features, they are an essential component of the coastal sediment budget and a primary control on the backshore ecosystem. In this role, coastal dunes provide essential ecosystem services, including habitat for endangered species such as piping plovers,sites of high tourism value, groundwater recharge zones, and protection of coastal infrastructure and properties from wave erosion and storm surge flooding.

Remote Sensing, 2021

Uncrewed aerial systems (UAS) provide an effective method to examine geomorphic and vegetation ch... more Uncrewed aerial systems (UAS) provide an effective method to examine geomorphic and vegetation change in restored coastal dune ecosystems. Coupling structure-from-motion (SfM) photogrammetry with RGB orthomosaic imagery allows researchers to characterize spatial-temporal geomorphic responses associated with differences in vegetation cover. Such approaches provide quantitative data on landscape morphodynamics and sediment erosion and deposition responses that allow scientists and land managers to assess the efficacy of dynamic restoration efforts and, in turn, make informed decisions for future restoration projects. Two different restored coastal foredune sites in Humboldt County, California were monitored between 2016–20 with UAS (quadcopter and fixed-wing), kite aerial photogrammetry (KAP), and terrestrial laser scanning (TLS) platforms. We compared our KAP- and UAS-SfM elevation models to concurrently collected TLS bare earth models for five of our fifteen collections. The goal of...

Sandy Beach Morphodynamics, 2020

Boreas, 2017

Geomorphology, 2019

Quaternary Research, 2017

Journal of Coastal Research, 2016

World Geomorphological Landscapes, 2016

Earth Surface Processes and Landforms, 2016

Geomorphology, 2015

Treatise on Geomorphology, 2013

Geomorphology, 2015

Geomorphology, 2012

Journal of Arid Environments, 2021

Geological Society of America Abstracts with Programs, 2017

Remote Sensing, 2021

Climate change is increasingly affecting British Columbia’s landscapes, communities and economic ... more Climate change is increasingly affecting British Columbia’s landscapes, communities and economic activities. Future projections show that climate change will continue and suggest that direct and indirect impacts will become more pervasive. The following are some of the key risks and adaptation opportunities associated with climate change in BC: Many regions and sectors of British Columbia will experience increasing water shortages. Smaller glaciers, declining snowpack, shifts in timing and amount of precipitation, and prolonged drought will increasingly limit water supply during periods of peak demand. Competition amongst water uses will increase and have implications for transborder agreements. Ongoing adaptive measures include the incorporation of climate change impacts into some official water management plans, upgrades to reservoir capacity and various demand management initiatives. Hydroelectric power generation, especially during (increasing) peak energy demands in summer, is ...

From Impacts to Adaptation: Canada in a Changing Climate. Government of Canada, Ottawa., 2008

Equilibrium concepts are widespread in aeolian geomorphology, especially those incorporating time... more Equilibrium concepts are widespread in aeolian geomorphology, especially those incorporating time-averaged parameterizations of fluid flow and sediment transport. The main objective of this chapter is to reflect critically on whether a new paradigm based on coherent flow structures (CFS) is emerging as a viable alternative to the traditional steady-state perspective on aeolian processes. A survey of recent research addressing the existence and nature of CFS in aeolian systems indicates that: (i) there is as yet no convincing evidence in support of the classic bursting process or of any discrete flow structure with a characteristic topology (e.g., hairpin vortex) for the case of near-surface boundary layer flow over flat sandy surfaces (with or without saltation); (ii) there are instances in which near-surface vortices of varying geometry are found in association with small obstacles (e.g., logs, pebbles, vegetation clumps) on sandy surfaces, but it is not always apparent what the pattern of erosion or deposition in the vicinity of the obstacle will be, given that there are additional controls that involve surface hardness and sediment delivery from upwind; (iii) flow over aeolian dunes is generally well understood and very similar to flow over fluvial dunes with characteristic zonation, including flow acceleration and streamline compression on the stoss slope and a recirculation eddy and wake region in the lee; and (iv) the importance of these dune-related flow zones to sediment transport response is more reliably understood through examination of a range of turbulence parameters (e.g., Reynolds stress, turbulent kinetic energy) in addition to the time-averaged flow quantities alone. In order to advance our understanding of CFS in aeolian geomorphology, it will be essential to develop better technologies for high-frequency monitoring of wind and sediment flux, to focus attention on sediment transport events with specific topologies (e.g., streamers) rather than attempt to capture flow events and hope that there is an accompanying transport signal, to move beyond simple quadrant analysis and adopt analytical methods that elucidate the time-history of event signatures, and to reformulate existing time-averaged parameterizations of sediment flux to incorporate event-based information.

Ocean Sciences Meeting, 2018

This paper compares and contrasts UAS-based Structure from Motion (SfM) and TLS survey methods as... more This paper compares and contrasts UAS-based Structure from Motion (SfM) and TLS survey methods as applied to evaluate the impacts of, and recovery from, the extreme El Niño 2015-16 on the seasonal geomorphic and sediment budget responses of an embayed, high-energy beach-dune system on the central coast of British Columbia, Canada. TLS and UAS mapping campaigns over a two-year period provided seasonal bare-earth digital terrain models (DTMs) and orthophoto mosaics. Spatial-temporal change detection methods were used to quantify volumes of significant erosion and deposition within the beach-dune system. The frequency and magnitude of erosive events and aeolian activity were also estimated from oblique, time-lapse photography.
During the 2015-16 El Niño season, elevated water levels and storm waves eroded the foredune and lowered the beach surface by ~ 1m. Erosion was greatest in the middle of the beach with dune scarping of over 2m where wave energy was focused. Minor accretion occurred during the summer of 2016 on the upper beach, and ramp rebuilding was observed mostly from slumping and avalanching of existing dune sands. The following winter 2017 storm season led to minor erosion on the beach and extensive incipient dune development and sand ramp recovery fronting the foredune to an extent close to pre-El Niño elevations.

Comparison of change surfaces between methods revealed limitations in the SfM method, namely due to vegetation effects on DTM generation, which limit its ability to detect change in the coastal environment. The costs, time, logistics, and accuracy for both SfM and TLS survey methodologies for coastal geomorphic change detection analysis is also evaluated. Combined, the UAS and SfM workflow provides a competitive solution to more expensive and time-consuming survey methods, such as TLS and aerial LiDAR, but its utility and accuracy is highly dependent on research objectives and post-processing techniques.