Coastal Dune Development Research Articles

Modeling Multi‐Fraction Coastal Aeolian Sediment Transport With Horizontal and Vertical Grain‐Size Variability

AbstractGrain size affects the rates of aeolian sediment transport on beaches. Sediment in coastal environments typically consists of multiple grain‐size fractions and exhibits spatiotemporal variations. Still, conceptual and numerical aeolian transport models are simplified and often only include a single fraction that is constant over the model domain. It is unclear to what extent this simplification is valid and if the inclusion of multi‐fraction transport and spatial grain‐size variations affects aeolian sediment transport simulations and predictions of coastal dune development. This study applies the numerical aeolian sediment transport model AeoLiS to compare single‐fraction to multi‐fraction approaches for a range of grain‐size distributions and spatial grain‐size scenarios. The results show that on timescales of days to years, single‐fraction simulations with the median grain size, D50, often give similar results to multi‐fraction simulations, provided the wind is able to mobilize all fractions within that time frame. On these timescales, vertical variability in grain size has a limited effect on total transport rates, but it does influence the simulation results on minute timescales. Horizontal grain‐size variability influences both the total transport rates and the downwind bed grain‐size composition. The results provide new insights into the influence of beach sediment composition and spatial variability on total transport rates toward the dunes. The findings of this study can guide the implementation of grain‐size variability in numerical aeolian sediment transport models.

Intra- and Inter-site variability of the beach dune profile and vegetation line: Is there a scale-invariant profile?

The response and recovery of foredunes to storms is an important control on barrier response to sea level rise. While field studies suggest that dune height is site-specific and dependent to varying degrees on sediment supply and transport potential, the process-based Coastal Dune Model (CDM) predicts that dune height depends on the distance of the vegetation line to the shoreline (Lveg) and that the beach-dune profile is scale-invariant. This study examines the intra- and inter-site variability of the beach-dune profile in relation to Lveg along the north shore of Prince Edward Island (PEI), Canada. A combination of LiDAR and UAV surveys of >19,000 beach-dune profiles suggest that the ratio of dune crest elevation (Cy) and distance from the shoreline above AMSL (Sx) to the Crest (Cx), is inversely related to cross-shore distance of Lveg. The tallest dunes have the steepest seaward slopes (Cy/(Cx-Sx)→0.45) and small Lveg distances controlled by the variability of the beach-dune envelope, while the shortest dunes are associated with beaches with relatively gentle slopes (Cy/(Cx-Sx)→0.01) and large Lveg distances controlled by tide and storm inundation. Comparison to previously published beach-dune profiles reveals a similar relationship between the profile and Lveg, suggesting that the morphology of the beach-dune system along the north shore of PEI and at other sites globally are reflective of their respective histories of storm activity, and do not trend towards the scale-invariant form assumed in the CDM. Further study of the contingent (or local) controls on coastal dune development and morphology are necessary to predict the evolution of coastal barriers to sea level rise and changes in storm activity.

Late Pleistocene evolution of Robe Range, southern Australia – The timing and carbonate source dynamics of coastal dune development

Robe Range is a coastal barrier that extends for over 155 km along the modern coastline of the Coorong Coastal Plain in southern Australia, a region renowned as preserving one of the world's longest records of Quaternary eolian dune deposition. Previous research has shown that the late Pleistocene dune development in this barrier structure is linked with sea-level highstands, particularly warm interstadials of marine isotope stage (MIS) 5. To better understand the principal depositional phases and sediment provenance of the dune successions of Robe Range, we use a combination of amino acid racemization analyses on the foraminifer Lamellodiscorbis dimidiatus and optically stimulated luminescence dating of associated quartz sand. The new and previously published optical dating results indicate that phases of dune formation correlate with MIS 5c–a (ca. 105–75 ka) and early in MIS 3 (ca. 61–53 ka). More importantly, the distribution of the extent of amino acid racemization on single-foraminifers reveals that the overall barrier successions have complex sources of carbonate sediment, principally derived from contemporaneous inner shelf temperate carbonate factories and reworked skeletal grains from the erosion of older marginal marine successions. The regional narrowing of the Bonney Shelf restricted the degree of lateral changes of the shoreline in response to the glacial–interglacial cycles, in contrast to the wider Lacepede Shelf to the north. The characteristics of offshore shelf topography allow wind-driven onshore transport and delivery of bioclastic sand from mixed-age carbonate sources to onshore coastal dunes during lower sea levels, particularly in association with the intensified wind regime of early MIS 3. This points to other factors influencing coastal dune emplacement besides simply glacio–eustatic sea-level changes, and relates to the availability of biogenic particles and the delicate balance between shelf topography and wind regimes during the interstadials of the late Pleistocene.

High resolution luminescence chronology of coastal dune deposits near Chumphon, Western Gulf of Thailand

The development of coastal dunes is linked to environmental controls such as sea-level variability, climatic conditions, and coastal morphology. Understanding the spatial and temporal variations of dunes is crucial for predicting how coastal landscapes may react to future climate changes and sea-level rise. However, there are very few detailed studies on the longer time-scale evolution (centennial to millennial) of coastal dunes from subtropical and tropical regions. Here, we combine a high-resolution luminescence chronology with sedimentological analyses to study the depositional history of a transverse coastal dune located within the Bang Berd dune field, Western Gulf of Thailand. While luminescence dating of uniform aeolian deposits is normally straight forward, we observe strong variations in the natural dose rate which are likely explained by the enrichment of accessory minerals in some laminae. Deposition of the dune started at least around 3000 years ago and coincides with a regional sea level drop. Sedimentary structures indicate deposition occurring predominantly in relation to the northeasterly winter monsoon. As the sea-level rise and increased storm intensity in the future may lead to stronger erosion along the coast, this study is highlighting the importance of the Bang Berd dune system as natural protection against coastal inundation.

Sea level rise outpaced by vertical dune toe translation on prograding coasts

Sea level is rising due to climate change and is expected to influence the development and dynamics of coastal dunes. However, the anticipated changes to coastal dunes have not yet been demonstrated using field data. Here, we provide evidence of dune translation that is characterized by a linear increase of the dune toe elevation on the order of 13–15 mm/year during recent decades along the Dutch coast. This rate of increase is a remarkable 7–8 times greater than the measured sea level rise. The observed vertical dune toe translation coincides with seaward movement of the dune toe (i.e., progradation), which shows similarities to prograding coasts in the Holocene both along the Dutch coast and elsewhere. Thus, we suspect that other locations besides the Dutch coast might also show such large ratios between sea level rise and dune toe elevation increase. This phenomenon might significantly influence the expected impact of sea level rise and climate change adaptation measures.

The main periods and environmental controls of coastal dune development along the west coast of the Korean Peninsula during the mid to late Holocene

This study traces coastal sand dune development processes in East Asia during the Holocene to understand climate and environmental changes. We used optically stimulated luminescence (OSL) dating to examine periods of activation and stabilization of dunes along the western coast of the Korean Peninsula. The results from the Taean Chollipo, Seocheon Dasari, and Gochang Sabanri dunes were then compared with those from previous studies to establish a broad understanding of coastal dune development in this region. Sedimentation rates were calculated for the three dunes, and their development periods were classified through statistical analysis that included data from previous studies. We defined five main periods of late Holocene dune development (<0.1 ka, 0.2–0.5 ka, 1.2–2.0 ka, 2.5–3.2 ka, and 5.5–6.5 ka). These correlated to periods of sea level decrease and global cooling determined by ice rafted debris records. We concluded that the development of coastal dunes in western Korea was influenced by sea level decreases, and global cooling events were enhanced by the East Asian winter monsoon. In addition, human activity increases also contributed to the development of the dunes. This study showed how coastal sand dunes can be evaluated as important indicators of global climate change. These results improved our understanding of how paleoclimate changes affected environmental conditions in East Asia and how coastal dune development periods can be used to reconstruct paleo-environmental conditions.

Long-Term Observations of Beach Variability at Hasaki, Japan

Long-term beach observation data for several decades are essential to validate beach morphodynamic models that are used to predict coastal responses to sea-level rise and wave climate changes. At the Hasaki coast, Japan, the beach profile has been measured for 34 years at a daily to weekly time interval. This beach morphological dataset is one of the longest and most high-frequency measurements of the beach morphological change worldwide. The profile data, with more than 6800 records, reflect short- to long-term beach morphological change, showing coastal dune development, foreshore morphological change and longshore bar movement. We investigated the temporal beach variability from the decadal and monthly variations in elevation. Extremely high waves and tidal anomalies from an extratropical cyclone caused a significant change in the long-term bar behavior and foreshore slope. The berm and bar variability were also affected by seasonal wave and water level variations. The variabilities identified here from the long-term observations contribute to our understanding of various coastal phenomena.

백령도 가을리에 분포하는 고(古)해안사구층의 특성과 형성 시기

The Baengnyeongdo-island, located at the northernmost point of the west coast, has developed several coastal landforms. Although the coastal landforms of Baengnyeongdo-island are widely used as a tourism resource, a lot of academic research has not been conducted. In this study, particle size analysis, XRF, and OSL age dating were performed on the BR sandy deposits to find out the formation of coastal sand dunes on Baengnyeongdo-island. Based on the physicochemical properties, the BR section was divided into three parts; BR-A, BR-B and BR-C. First, about 56ka, which corresponds to the MIS 3, fine sand was deposited and forms the BR-C section. Second, the BR-B which located middle part of BR section, showed reversed age stratigraphy. The BR-B was interpreted as reworked sediments based on sedimentary facies and chemical weathering intensity. And, the BR-A composed of fine and medium sands was formed in middle Holocene. This research has significance in that it finds out the paleo sand dunes formed in Pleistocene. This study can contribute to understanding coastal sand dune development on the west coast.

Storm-induced sediment supply to coastal dunes on sand flats

Abstract. Growth of coastal dunes requires a marine supply of sediment. Processes that control the sediment transfer between the subtidal and the supratidal zone are not fully understood, especially in sand flats close to inlets. It is hypothesised that storm surge events induce sediment deposition on sand flats, providing fresh material for aeolian transport and dune growth. The objective of this study is to identify which processes cause deposition on the sand flat during storm surge conditions and discuss the relationship between the supratidal deposition and sediment supply to the dunes. We use the island of Texel (NL) as a case study, of which multiannual topographic and hydrographic datasets are available. Additionally, we use the numerical model XBeach to simulate the most frequent storm surge events for the area. Results show that supratidal shore-parallel deposition of sand occurs in both the numerical model and the topographic data. The amount of sand deposited is directly proportional to surge level and can account for more than a quarter of the volume deposited at the dunes yearly. Furthermore, storm surges are also capable of remobilising the top layer of sediment of the sand flat, making fresh sediment available for aeolian transport. Therefore, in a sand flat setting, storm surges have the potential of reworking significant amounts of sand for aeolian transport in periods after the storm and as such can also play a constructive role in coastal dune development.

An 800 kyr record of dune emplacement in relationship to high sea level forcing, Cooloola Sand Mass, Queensland, Australia

The Cooloola Sand Mass is a large coastal dune field situated in southeast Queensland, Australia and is part of a much larger system of coastal dune fields, including the world's largest sand Island, Fraser Island, as well as Moreton Island and Stradbroke Island. Cooloola is characterised by a sequence of onlapping, parabolic dune units that have been emplaced episodically over the Pleistocene and Holocene. The tectonically stable coastline of SE Queensland is an ideal area to study the driving mechanisms of coastal dune development, as sea level variability is driven primarily by glacial eustasy. Geomorphic and chronostratigraphic analyses have identified seven major periods of dune activity with the earliest phase of deposition occurring ca. 800 ka. Subsequent periods of dune emplacement date to about ca. 150 ka, 110 ka, 10–6 ka, 5–3.5 ka, ca. 2 ka and 0.4–0.2 ka.The Holocene dune activity coincides with the last stages of post-glacial marine transgression and suggests these large parabolic dunes formed in response to rising sea levels. It is likely that this pattern is consistent through the Pleistocene, and the MIS 5 interglacial period is also recorded. For earlier events the large absolute errors on the ages make interpretation difficult. There is a notable absence of OSL ages dating to the Last Glacial Maximum and no ages that are unambiguously associated with lowstand periods. This is most likely because the coast would have been 60 km offshore of its current position during lowstands, limiting sediment supply and wind energy at the modern coast. These results provide strong evidence that coastal dune fields in SE Australia are predominantly emplaced during sea-level rise, as originally proposed in the Cooper-Thom model.

Factors Responsible for Rapid Diminishing of Endangered Grass Plant Elymus farctus subsp. boreoatlanticus in Phytocoenoses on Dunes Coast of Baltic Sea

Sand couch-grass Elymus farctus (Viv.) Runemark ex Melderis subsp. boreoatlanticus (Simonet & Guin.) Melderis is a species of psammophytic perennial grass which grows on low embryo dunes, less frequently on white dunes, on a sandy substrate which is rich in chlorides, with a neutral or alkaline pH. The occurrence of E. farctus subsp. boreoatlanticus was confirmed on the Polish Baltic coast only in six stands out of 20 quoted in the 19th century and at the beginning of the 20th century, and the species is classified as critically endangered (CR). One of the largest populations of that species is situated on the Wolin Island (the Baltic Sea, west coast of Poland). The population of this species was monitored between 2015-2017 in the habitat of initial white coastal dunes (Nature 2000 site, code 2110), where the sand couch-grass is a characteristic species of Honckenyo-Agropyretum juncei R.Tx. 1955 plant association. The results of the conducted research show that the main reason for the rapid decline of the population of Elymus farctus subsp. boreoatlanticus on the western coast of Poland is recreational use of beaches, which is growing in an uncontrollable manner and puts pressure on this habitat, followed by complete destruction of psammophilous and halophilous vegetation. In addition, impact from marine abrasion inhibits the development of white coastal dunes where E. farctus subsp. boreoatlanticus occurs, and intensive aeolian sand accumulation hinder the regenerative ability of shoots and significantly limit vegetative reproduction.

The effects of beach width variability on coastal dune development at decadal scales

A cellular automata model is used to evaluate, over decadal time spans, the effect of beach width changes on the development of coastal dune systems. The model includes the effects of aeolian transport, hydrodynamic erosion and accretion, groundwater and vegetation growth. Simulations using fixed and mobile beach widths scenarios were carried out for a 90-year period. Unlimited and limited sediment supply conditions were regulated by groundwater depth. The final topographies were compared based on morphological characteristics such as dunefoot position and volume increase. Results show that there is a preferential cross-shore position where the foredune tends to be built which is a function of beach width and sediment supply. For narrow beaches, foredunes tend to develop at higher elevations than for wide beaches due to differences in wave dissipation, whereas dune volume is controlled by hydrodynamic erosion and dune recovery potential by sediment supply. Furthermore, if sediment supply is limited, the effect of beach width on dune volume only appears for beach widths greater than 300 m, suggesting that limitation in supply can dominate dune growth on regular beaches whereas on wide systems, such as sand flats and spits, beach width size dominates. These results suggest that for a decadal scale, beach width controls the space available for dune formation, thus the position of the most seaward dune, but the effect of beach width on dune volume can be overruled by other supply limiting conditions such as groundwater depth.

The influence of groundwater depth on coastal dune development at sand flats close to inlets

A cellular automata model is used to analyze the effects of groundwater levels and sediment supply on aeolian dune development occurring on sand flats close to inlets. The model considers, in a schematized and probabilistic way, aeolian transport processes, groundwater influence, vegetation development, and combined effects of waves and tides that can both erode and accrete the sand flat. Next to three idealized cases, a sand flat adjoining the barrier island of Texel, the Netherlands, was chosen as a case study. Elevation data from 18 annual LIDAR surveys was used to characterize sand flat and dune development. Additionally, a field survey was carried out to map the spatial variation in capillary fringe depth across the sand flat. Results show that for high groundwater situations, sediment supply became limited inducing formation of Coppice-like dunes, even though aeolian losses were regularly replenished by marine import during sand flat flooding. Long dune rows developed for high sediment supply scenarios which occurred for deep groundwater levels. Furthermore, a threshold depth appears to exist at which the groundwater level starts to affect dune development on the inlet sand flat. The threshold can vary spatially depending on external conditions such as topography. On sand flats close to inlets, groundwater is capable of introducing spatial variability in dune growth, which is consistent with dune development patterns found on the Texel sand flat.

Exploring the contributions of vegetation and dune size to early dune development using unmanned aerial vehicle (UAV) imaging

Abstract. Dune development along highly dynamic land–sea boundaries is the result of interaction between vegetation and dune size with sedimentation and erosion processes. Disentangling the contribution of vegetation characteristics from that of dune size would improve predictions of nebkha dune development under a changing climate, but has proven difficult due to the scarcity of spatially continuous monitoring data. This study explored the contributions of vegetation and dune size to dune development for locations differing in shelter from the sea. We monitored a natural nebkha dune field of 8 ha, along the coast of the island Texel, the Netherlands, for 1 year using an unmanned aerial vehicle (UAV) with camera. After constructing a digital surface model and orthomosaic we derived for each dune (1) vegetation characteristics (species composition, vegetation density, and maximum vegetation height), (2) dune size (dune volume, area, and maximum height), (3) degree of shelter (proximity to other nebkha dunes and the sheltering by the foredune). Changes in dune volume over summer and winter were related to vegetation, dune size and degree of shelter. We found that a positive change in dune volume (dune growth) was linearly related to initial dune volume over summer but not over winter. Big dunes accumulated more sand than small dunes due to their larger surface area. Exposed dunes increased more in volume (0.81 % per dune per week) than sheltered dunes (0.2 % per dune per week) over summer, while the opposite occurred over winter. Vegetation characteristics did not significantly affect dune growth in summer, but did significantly affect dune growth in winter. Over winter, dunes dominated by Ammophila arenaria, a grass species with high vegetation density throughout the year, increased more in volume than dunes dominated by Elytrigia juncea, a grass species with lower vegetation density (0.43 vs. 0.42 (m3 m−3) week−1). The effect of species was irrespective of dune size or distance to the sea. Our results show that dune growth in summer is mainly determined by dune size, whereas in winter dune growth was determined by vegetation type. In our study area the growth of exposed dunes was likely restricted by storm erosion, whereas growth of sheltered dunes was restricted by sand supply. Our results can be used to improve models predicting coastal dune development.

UAV-imaging to model growth response of marram grass to sand burial: Implications for coastal dune development

Abstract Vegetated coastal dunes have the capacity to keep up with sea-level rise by accumulating and stabilizing wind-blown sand. In Europe, this is attributed to marram grass (Ammophila arenaria), a coastal grass species that combines two unique advantages for dune-building: (1) a very high tolerance to burial by wind-blown sand, and (2) more vigorous growth due to positive feedback to sand burial. However, while these vegetation characteristics have been demonstrated, observational data has not been used to model a function to describe the growth response of Ammophila to sand burial. Studies that model coastal dune development by incorporating positive feedback, as a result, may be hampered by growth functions that are unvalidated against field data. Therefore, this study aims to parameterize an empirical relationship to model the growth response of Ammophila to burial by wind-blown sand. A coastal foredune along a nourished beach in the Netherlands was monitored from April 2015 to April 2016. High-resolution geospatial data was acquired using an Unmanned Aerial Vehicle (UAV). Growth response of Ammophila, expressed by changes in Normalized Difference Vegetation Index ( Δ NDVI) and vegetation cover ( Δ Cover), is related to a sand burial gradient by fitting a Gaussian function using nonlinear quantile regression. The regression curves indicate an optimal burial rate for Ammophila of 0.31 m of sand per growing season, and suggest (by extrapolation of the data) a maximum burial tolerance for Ammophila between 0.78 (for Δ Cover) and 0.96 m (for Δ NDVI) of sand per growing season. These findings are advantageous to coastal management: maximizing the potential of Ammophila to develop dunes maximizes the potential of coastal dunes to provide coastal safety.

Late Holocene cliff-top dune evolution in the Hengchun Peninsula of Taiwan: Implications for palaeoenvironmental reconstruction

The Fung-Chuei-Sha (FCS) cliff-top dunes, the only coastal cliff-top dunes known in Taiwan, are situated on a 70m high, tectonically uplifted Quaternary marine terrace surface in the Hengchun Peninsula of southern Taiwan. The development of the FCS dune and its relationship with palaeoenvironmental changes are still unknown. The optically stimulated luminescence (OSL) dating approach utilizing a pIRIR150 (post infrared, infrared stimulated luminescence at 150°C) single aliquot regenerative (SAR) dose protocol for K-rich feldspar, in combination with radiocarbon dates and high resolution sedimentological analyzes, have proven to be a powerful tool for reconstructing the depositional history of the FCS dune and the related palaeoenvironmental conditions during the late Holocene. This study identified three major aeolian sediment accumulation periods at ∼4ka to ∼2.3ka, ∼1.8ka to ∼1.1ka, and ∼0.7ka to ∼0.4ka, which are consistent with the cold/cooling periods identified from the palaeoclimate record of the Dongyuan Lake in southern Taiwan. Two palaeosurfaces and two short interruptions of sand accumulation indicate periods of surface stabilization at the FCS site. The OSL ages and radiocarbon ages from the dune, and the palaeoclimate data from Dongyuan Lake suggest that these surfaces developed at ∼4.3ka, ∼2ka, ∼1ka and ∼0.3ka. The palaeoclimatic conditions inferred from the FCS dunes are largely consistent with those reconstructed for the coastal dunes of the Fulong Beach area in northeastern Taiwan. This may indicate an over-regional pattern of dune formation primarily driven by strong winds of the Asian Winter Monsoon as the primary forcing factor for coastal dune development in Taiwan during the late Holocene.

Lateral vegetation growth rates exert control on coastal foredune hummockiness and coalescing time

Abstract. Coastal foredunes form along sandy, low-sloped coastlines and range in shape from continuous dune ridges to hummocky features, which are characterized by alongshore-variable dune crest elevations. Initially scattered dune-building plants and species that grow slowly in the lateral direction have been implicated as a cause of foredune hummockiness. Our goal in this work is to explore how the initial configuration of vegetation and vegetation growth characteristics control the development of hummocky coastal dunes including the maximum hummockiness of a given dune field. We find that given sufficient time and absent external forcing, hummocky foredunes coalesce to form continuous dune ridges. Model results yield a predictive rule for the timescale of coalescing and the height of the coalesced dune that depends on initial plant dispersal and two parameters that control the lateral and vertical growth of vegetation, respectively. Our findings agree with previous observational and conceptual work – whether or not hummockiness will be maintained depends on the timescale of coalescing relative to the recurrence interval of high-water events that reset dune building in low areas between hummocks. Additionally, our model reproduces the observed tendency for foredunes to be hummocky along the southeast coast of the US where lateral vegetation growth rates are slower and thus coalescing times are likely longer.

Coastal dune development and morphological changes along the littorals of Garigliano, Italy, and Elis, Greece, during the Holocene

Geomorphological and sedimentological studies were carried out along the Garigliano and Elis littorals with the aim to highlight if similar geoenvironmental features are controlled by same coastal processes. Actually, both sites are in Mediterranean climate regions very far each other, modeled by western winds and storms, characterized by wide sandy coastal dunes parallel to the present shoreline, with abundant pumices, and locally anthropized. The Garigliano littoral is characterized by Holocene dune and Pleistocene aeolian deposits. The beach is bounded landwards by a dune system emplaced during the Holocene. Geoarchaeological surveys highlighted the presence of a Roman road which cut the dune, with age older than Graeco-Roman Period. Since the end of the 1950’s, strong littoral retreat affected the beach-dune system, partly due to human activity. The coastland of Elis is characterized by Quaternary marine deposits. Three significant morphogenetic phases occurred during the Holocene. During the last phase, from Graeco-Roman Period to current, shoreline retreat and deposition of aeolian sands occurred. Geoarchaeological evidences suggest that this phase is related to a sea-level lowstand followed by a slow sea-level rise up to the present position, and by humid-temperate climate. Geomorphological surveys of the dunes of Garigliano and Elis, each other compared, suggest that the main phases of their development are related to the effects of climatic conditions, sea-level changes, and secondly to the recent anthropization. The coarse pumices found on both beaches of Campania and Peloponnese regions show the same mineralogical and petrographic features, so we assumed that they likely originated from the Aeolian Arc, southern Italy, which have same composition. These pumices reached the studied coasts by flotation, under the influence of winds and marine surface currents from the southwest-southeast and northwest-west respectively, participating to local coastal processes and representing a good geoindicator of long-distance drift. Precisely for these morphologically converging aspects, such distant sites have been selected and compared.

W. S. Cooper As I Knew Him: Teacher, Mentor and Friend

W. S. Cooper As I Knew Him: Teacher, Mentor and Friend

Measuring and modeling the effect of surface moisture on the spectral reflectance of coastal beach sand.

Surface moisture is an important supply limiting factor for aeolian sand transport, which is the primary driver of coastal dune development. As such, it is critical to account for the control of surface moisture on available sand for dune building. Optical remote sensing has the potential to measure surface moisture at a high spatio-temporal resolution. It is based on the principle that wet sand appears darker than dry sand: it is less reflective. The goals of this study are (1) to measure and model reflectance under controlled laboratory conditions as function of wavelength () and surface moisture () over the optical domain of 350–2500 nm, and (2) to explore the implications of our laboratory findings for accurately mapping the distribution of surface moisture under natural conditions. A laboratory spectroscopy experiment was conducted to measure spectral reflectance (1 nm interval) under different surface moisture conditions using beach sand. A non-linear increase of reflectance upon drying was observed over the full range of wavelengths. Two models were developed and tested. The first model is grounded in optics and describes the proportional contribution of scattering and absorption of light by pore water in an unsaturated sand matrix. The second model is grounded in soil physics and links the hydraulic behaviour of pore water in an unsaturated sand matrix to its optical properties. The optical model performed well for volumetric moisture content 24% ( 0.97), but underestimated reflectance for between 24–30% ( 0.92), most notable around the 1940 nm water absorption peak. The soil-physical model performed very well ( 0.99) but is limited to 4% 24%. Results from a field experiment show that a short-wave infrared terrestrial laser scanner ( = 1550 nm) can accurately relate surface moisture to reflectance (standard error 2.6%), demonstrating its potential to derive spatially extensive surface moisture maps of a natural coastal beach.