Sediment Volume Research Articles

Influence of different skew angles of the submerged vane on pressure flushing performance

Siltation significantly threatens a reservoir’s original storage capacity and lifespan. Pressure flushing is an effective measure against siltation through the partial drawdown of the reservoir water level with limited flushed cone volumes in front of the bottom outlet. In this study, a novel configuration with submerged vanes has been proposed and tested experimentally to increase the flushed sediment volume during pressure flushing. In the new configuration, submerged vanes aligned with ten skew angles (θ) of 10°, 20°, 30°, 45°, 70°, 110°, 135°, 150°, 160°, and 170° to the flow direction in noncohesive sediment bed materials were used. The results showed that increasing the skew angle at 45° ≤ θ ≤ 160° increased the flushing cone geometry. The minimum and maximum flushing cone dimensions and volume occurred at skew angles of θ = 45° and 135° ≤ θ ≤ 160° around the bottom outlet. The sediment flushing volume in the presence of submerged vanes at 135° ≤ θ ≤ 160° increased 25 times compared to tests without submerged vanes. Eventually, nonlinear regression analysis yielded an equation for estimating flushing cone volumes. The developed equation was tested in real case studies of a target reservoir, and an acceptable correlation between the calculated and experimental results was obtained.

Synthesis of water soluble ionic liquid copolymers based on acrylamide and investigation of their properties in flocculating of clay suspensions

To overcome water absorption and swelling by clay mineral layers, it is very important to develop stabilizing additives for water-based drilling fluids, where organic polymers are used as raw materials. Acrylamide copolymers, acting as flocculating agents, have the potential to separate minerals such as montmorillonite. In this study, three water-soluble copolymers containing acrylamide-amphoter, acrylamide-amphoter-anion, and acrylamide-amphoter-cation were synthesized and characterized using various analytical techniques, including Fourier-transform infrared spectroscopy, nuclear magnetic resonance, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, and derivative thermal gravimetric techniques. These copolymers were employed as flocculants to treat water suspensions containing montmorillonite particles, and a range of analytical methods, such as sedimentation volume measurement, scanning electron microscopy analysis, X-ray diffraction analysis, and contact angle measurement, were employed to identify the relationship between inhibitive performance. The flocculation of montmorillonite plates was attributed to the electrostatic attractions between montmorillonite and the synthesized copolymers. High molecular weight copolymers offer greater thermal stability and better flocculation characteristics for water-based drilling fluids. Among the tested copolymers, the acrylamide-amphoter-anion sample, with the highest molecular weight, exhibited the best performance as a coagulant when compared to the other copolymers.

EXTENDING THE SHELF-LIFE OF WHEAT BREAD USING PENTOSANES EXTRACTED FROM BARLEY

This research was aimed to delay the staling of wheat bread as one of the most used products globally by adding barley pentosanes, which is neglected and not taken into consideration despite their unique and multiple functional properties and their optimum storage temperature. Water-soluble pentosanes (WSP) and water-insoluble pentosanes (WIP)was extracted from barley (Hordeum vulgare) and added to wheat flour at different percentages. Five treatments were prepared: (T1) from flour only, (T2 and T3) adding WSP at levels of (1 and 2%), (T4 and T5) adding WIP at the same levels respectively. All treatments were stored at (20, 4 and -18 °C), for 72 h. The results indicated that the addition of pentosans (WSP and WIP) delayed the staling of bread, especially at the level of addition (2%) for both, when was stored at freezing temperature (-18°C). The results of the control treatment (T1) and the treatments that included the highest addition level (2%) ( T3 and T5) and after 72 hours of storage at (-18°C) were as follows: The moisture content of bread crumbs decreased to (39.44, 43.32 and 43.91%) respectively. While the moisture in the bread crust increased to (31.61, 33.98, 34.28%), respectively. The swelling power of the bread crumbs and the sediment volume also decreased to (0.74, 1.18, and 1.03%) and (23, 32 and 33%), respectively, which indicates the potency of pentosans and freezing temperature to delay the staling of wheat bread during the storage period.

Long-term slope instability induced by the reactivation of mass transport complexes: An underestimated geohazard on the Norwegian continental margin

Submarine landslides are significant geohazards, capable of displacing large volumes of sediment from continental margins to deposit mass transport complexes (MTCs) and generate offshore tsunamis. However, the reactivation of MTCs after their initial failure has long been overlooked. By analyzing high-quality three-dimensional seismic reflection data and seismic attribute maps, as well as comparing the geometry of different MTCs, we investigate the development of long-term slope instability and its hazardous consequences on the northwest flank of the Storegga Slide on the Norwegian margin. Our results demonstrate that the reactivation of MTCs can deform both their inner structure and overlying strata, promoting the formation of sinuous channels and local slope failures on the seafloor. These findings further reveal the MTCs that are underconsolidated or comprise slide blocks may remain unstable for a long time after their initial failure, particularly when affected by slope undercutting and a corresponding reduction in lateral support. This study shows that MTC-prone sequences are more likely to comprise regions of continental slopes with long-term instability and recurring marine geohazards.

Dominant morphodynamic processes of a macrotidal beach of the eastern tropical Pacific and its relationships with climate variability

In this study, the influence of different coastal processes, including ocean-atmospheric processes of regional scale, on the spatiotemporal variability of the morphodynamic from the emerged zone of a beach in the Colombian eastern tropical Pacific, specifically in the macrotidal regime's Playa La Bocana, was analyzed during 2014–2019. The linear dependence of the sediment volume on the tide, rainfall, and winds was quantified using Pearson correlations and with large-scale oceanic and climatic relationships, that could be related to sediment volume anomalies. The highest correlation sediment volume monthly mean values are presented with the tide on an intra-annual scale. On an inter-annual scale, the sea surface temperature and sea level pressure composites were consistent with the El Niño-Southern Oscillation patterns. Thus, a cooling (warming) of the tropical Pacific is associated with a higher (lower) sediment volume onshore at Playa La Bocana. Furthermore, it was found that increase (decrease) on Swell (Mean Wave Period and Significant Wave Height) decreased (increased) the volume of sediments. These results show that the tide is the main modulator of beach sediment volume changes under the macrotidal regime, on the intra-annual scale, and that on the inter-annual scale, sediment volume responds to the combined effect of the tide and changes in swell intensity modulated by ENSO conditions.

Comparative environmental and economic life cycle assessment of phytoremediation of dredged sediment using Arundo Donax, integrated with biomass to bioenergy valorization chain

The economic and environmental life cycle assessment (LCA) was integrated into a laboratory-based experiment to evaluate the feasibility and sustainability of phytoremediation of chloride-rich marine dredged sediment, using perennial reed Arundo Donax along with biomass valorization. As a prerequisite for life cycle assessments, a baseline mathematical model was developed to estimate the yields of biomass to bioenergy valorization chain including the estimation of biomass yield per m3 sediment, bioenergy yields from valorization schemes, expected green electricity yield, and the phytoremediation time frame. This mathematical model was applied to develop a parametric life cycle inventory for two scenarios of sediment phytoremediation separately or integrated with biomass valorization, for LCA and further sensitivity and uncertainty analysis. Comparative LCA unveiled that the cost and environmental impacts of annual phytoremediation of 1m3 sediment alone or integrated with biomass valorization are much inferior to the corresponding sediment landfill as the inevitable alternative approach for sediment management. With the chloride bioaccumulation capacity of 9940 mg per kg dry biomass of A. donax, the phytoremediation of sediment with chloride concentration higher than 1650 mg/kg may not be achievable in a realistic time frame. Due to the importance of considering sediment depth and the effectiveness of the plant rooting system in estimating the performance of phytoremediation and the time frame, the volume of sediment (1m3) is a more appropriate functional unit than the surface area (ha) for LCA studies of phytoremediation. In addition, considering the volume of sediment as a functional unit retains comparability to other valorization scenarios such as sediment incorporation in cementitious matrices and management scenarios such as landfill, which are generally expressed on a volume or mass basis. Integrating biomass-derived bioenergy production into phytoremediation could offer local and global benefits in terms of economy and environment mainly due to carbon sequestration and avoiding fossil-based fuels.

Analysis of The Predicted Volume of Domestic Household Waste in the Communities of Das Bila and Its Impact on The Siltation of Lake Tempe

The substantial waste production in the Bila watershed poses a severe threat to the area. This not only negatively affects the environment but also leads to sediment buildup in Lake Tempe. Managing the lake's health entails not solely addressing the lake itself, but also evaluating the impact within the encompassing river basin. This research examines the anticipated waste volume that could potentially contribute to sedimentation in Lake Tempe. The approach taken employs spatial analysis, utilizing a 20-meter buffer surrounding the water body. This buffer represents the zone within which the population is assumed to dispose of waste into the river. The accuracy of the findings was verified through interviews with residents residing within this 20-meter radius. The predominant source of the waste responsible for sedimentation is inorganic in nature, as it doesn't undergo natural decomposition. The study's projection suggests that by 2031, the cumulative volume of waste-triggered sedimentation will reach 1408.63 cubic meters. Addressing the burgeoning waste issue in the Bila watershed is paramount to preserving the integrity of Lake Tempe. By adopting a comprehensive perspective that encompasses both the lake and its surrounding river basin, effective strategies can be devised to mitigate sedimentation and ensure the longevity of this crucial ecosystem.

Mud retention in hydrologically closed basins promoted pre-vegetation meandering: evidence from the Neoproterozoic Diabaig Formation, Scotland

Abstract Fluvial point-bar deposits are described from the c. 1 Ga Diabaig Formation, representing some of the most compelling architectural evidence of planform sinuosity recognized in pre-vegetation sedimentary strata to date. The stratigraphical architecture of the deposits indicates different planform transformations in response to meander-bend expansion and downstream migration. Point-bar architectural motifs are locally abundant in the unit and this is attributed to elevated amounts of mud-calibre cohesive sediment. Mud afforded landscape stability that, together with limited stream power, was sufficient to corral sediment into single-thread, sinuous channels. Significant volumes of fine-grained sediment were encouraged to accumulate by the local basin setting of several topographically confined endorheic depressions. These conditions ceased once the hydrologically closed valleys were filled, with the overlying sandstone-dominated Applecross Formation subsequently deposited by low-sinuosity, braided rivers that bypassed fine-grained sediment oceanward. Other endorheic basins conducive to the formation of depositional meanders should be expected to have been relatively widespread on pre-vegetation Earth, though many individually limited in size, confined by their inherited topographies. Depositional architectures representative of sinuous channel planforms remain scarce within more extensive, externally drained basins.

Quantifying the contribution of bank erosion to a suspended sediment budget using boat‐mounted LiDAR and high‐frequency suspended sediment monitoring

AbstractUnderstanding the physical processes as well as the hydrological and morphological factors that influence channel bank erosion is important for river restoration and the management of the floodplain and associated ecosystems. In this study, we introduced an innovative approach to quantify river bank erosion and its contribution to a reach fine sediment budget by combining repeat bank erosion surveys using a jetboat‐mounted LiDAR scanner with concurrent high‐frequency suspended sediment load measurements into and out of the surveyed reach. Using this information, we established a sediment budget for a 5.5‐km‐long study reach of the lower Ōreti River, Southland, New Zealand. A total of three surveys were conducted along the study reach to understand changes in the bank erosion contribution to suspended sediment load at different time scales. The first two surveys were separated by a short period of 8 weeks, and the third survey followed 2.5 years later. The measured volumes of fine sediment rendered from bank erosion equated to 25% and 29% of the measured outflowing suspended load over these two inter‐survey epochs, respectively. By comparison, the net contribution of measured bank erosion and derived fine sediment deposition on the riverbed to the outflowing suspended load was 12% over the first, shorter epoch and 25% for the second, 2.5‐year epoch. These results highlight the important role of in‐channel sediment deposition in the variability of net suspended sediment exports from channel reaches experiencing bank erosion. The approach used in this study has a unique capability to accurately monitor bank erosion and obtain high‐resolution topography data capturing changes in river banks over different time periods.

Sediment routing in an incised valley during Hurricane Harvey (2017) in Houston, Texas, USA: Implications for modern sedimentation

Abstract Southeastern Texas (United States) recorded one of the largest flooding events in U.S. history during Hurricane Harvey (25–31 August 2017), mobilizing millions of cubic meters of sediment in Houston fluvial-estuarine systems. We conducted an integrated quantitative analysis to determine the net minimum volume of sediment transported during the storm using subaerial elevation change, satellite and ground-based images, and sediment dredging reports along major waterways. The 12 fluvial-estuarine streams and two controlled reservoir drainages in the Houston area transported a minimum of ~2.723 × 107 m3 of sediment. This volume is ~6–51 times larger than the average annual volume of sediment delivered to Galveston Bay in modern times (in the past 200 yr), and ~30–118 times larger when compared to Holocene rates. Nearly ~26% of the measured volume was deposited in Addicks and Barker reservoirs, decreasing holding capacities by ~1.2% and ~1.6%, respectively. In the stream drainages, sediment was mobilized from west-northwest of Houston and pulsed toward Galveston Bay, highlighting the extreme short-term variability in sediment delivery. Sediment flux through the Houston region during Harvey is an example of sediment storage followed by a pulsed delivery of high sediment volume rather than continuous delivery of sediment. Comparison of sediment volumes transported through natural and modified drainages through Houston demonstrates that channel modification resulted in significant bypass of sediment downstream. Urban watershed management is more effective when continual updates are implemented based on regional circumstances rather than based on historical fluxes.

Himalayan valley-floor widths controlled by tectonically driven exhumation

Himalayan rivers transport around a gigaton of sediment annually to ocean basins. Mountain valleys are an important component of this routing system: storage in these valleys acts to buffer climatic and tectonic signals recorded by downstream sedimentary systems. Despite a critical need to understand the spatial distribution, volume and longevity of these valley fills, controls on valley location and geometry are unknown, and estimates of sediment volumes are based on assumptions of valley-widening processes. Here we extract over 1.5 million valley-floor width measurements across the Himalaya to determine the dominant controls on valley-floor morphology and to assess sediment-storage processes. Using random forest regression, we show that channel steepness, a proxy for rock uplift, is a first-order control on valley-floor width. On the basis of a dataset of 1,148 exhumation rates, we find that valley-floor width decreases as exhumation rate increases. Our results suggest that valley-floor width is controlled by long-term tectonically driven exhumation rather than by water discharge or bedrock erodibility and that valley widening predominantly results from sediment deposition along low-gradient valley floors rather than lateral bedrock erosion.

Analisis Volume Sedimen Terhadap Pendangkalan Di Dalam Saluran Primer Jaringan Irigasi (Studi Kasus: D.I. Cipicung Subang)

Research conducted in the primary canal of D.I Cipicung, Subang Regency, experienced damage to the irrigation network. Damage to the D.I Cipicung irrigation canal network in the primary canal, so that research is needed to find out how much silting volume is caused by sediment deposition in the irrigation canal. The method in this study uses a mathematical method to determine the volume of sediment deposition in the channel. The results show that the volume of sediment in the primary canal in the Cipicung D.I irrigation network is Vq Primary = 16.24 m3 (difference in depth 0.64 m) or 0.16% of the length per section 50.5 m of the total length of the primary canal 300 m and the change in the cross section of the primary channel is A = 1.25 m2 or 27.11%. So that the results of these calculations, it is necessary to resolve by repairing the right side of the canal lining with construction, the entrance channel from the river to the primary canal needs to be built a gate, dredging of sediment is required in the primary canal, and maintenance is required so that the canal is routinely once a week or once a month so that the strong channel is not quickly damaged.
 Keywords: Sediment Siltation, Primary Canal, Irrigation Network Damage.

Formulation and Evaluation of Ornidazole Oral Re-Constitutable Suspension

Large numbers of drugs are available in the market in form of dry syrup, where reconstitution has to be done by patient. Ornidazole is an antibiotic used to treat some protozoan infections. It has also been investigated for use in Crohn's disease after bowel resection. In the present investigation the drug Ornidazole was selected for the design of oral reconstitutable suspension for improving its stability and palatability by using various techniques like physical mixing, solvent evaporation and co-grinding method with different suspending agents like Xanthan gum, SCMC, Guar gum and sodium alginate. The reconstitutable suspensions were evaluated for flow properties, particle size, pH, viscosity, sedimentation volume, redispersibility and drug release by in-vitro dissolution studies. Formulated OFS reconstitutable suspension has acceptable sedimentation properties. The drug excipients interactions and crystal morphology of optimized reconstitutable suspension were evaluated by Fourier transform infrared spectroscopy (FTIR), differential scanning Calorimetry (DSC), analysis. The results indicated that the release of the Ornidazole was rapid from all formulations than the pure drug. The drug release from the suspensions followed first order kinetics. From the results it is concluded that effective taste masking of Ornidazole was achieved using SCMC and successfully evaluated in reconstitutable suspension.

Gluten subfractions of wheat storage proteins are affected by high night temperature during grain formation

AbstractGluten (gliadin + glutenin) protein in wheat flour is affected by high temperature (day and/or night) resulting in undesirable consequences on dough quality. A study was conducted with early and late‐maturing wheat genotypes, to assess the spatial (superior‐ central and inferior‐ apical and basal spikelets) variation in the composition of gluten subfractions in the developing ear under high night temperature (HNT). We hypothesised that protein content in the superior and inferior grains may show a differential quantitative and qualitative response to HNT. HNT resulted in a significant increase in protein content which exhibited a strong (r = −0.44*) negative correlation with sedimentation volume (SV) that determines baking quality. The late‐maturity genotypes were more responsive to HNT with changes in ω‐5 and γ gliadin subfractions of both superior and inferior spikelets, though a consistent trend was not established. The proportion of high molecular weight (HMW) glutenins increased, whereas low molecular weight (LMW) glutenins reduced in most of the genotypes under HNT. Both HMW and LMW glutenins revealed significant positive (r = 0.43* and r = 0.81***, respectively) correlation with SV. The expression analysis of genes for gluten subfractions showed a significant decrease in transcript abundance of α, ω‐5, γ, HMW, and LMW fractions under HNT.

Multitemporal Analysis of Slow-Moving Landslides and Channel Dynamics through Integrated Remote Sensing and In Situ Techniques

The relationships between hillslope and fluvial processes were studied in a mountainous area of the Northern Apennines (Italy) where intermittent landslide activity has interacted for a long time with river morphodynamics. The aim of the study was to analyse such relationships in two study sites of the Scoltenna catchment. The sites were analysed in detail and monitored through time. A long-term analysis was carried out based on multitemporal photointerpretation of aerial photos. Slope morphological changes and land use modifications since 1954 were detected and compared with the evolution of the channel morphology. A short-term analysis was also performed based on two monitoring campaigns accomplished in 2021 and 2022 in order to detect possible slope displacements and channel-bed-level changes. The techniques used are global navigation satellite systems and drone photogrammetry accompanied by geomorphological surveys and mapping. The multitemporal data collected allowed us to characterise slope surface deformations and quantify morphological changes. The combination of various techniques of remote and proximal sensing proved to be a useful tool for the analysis of the surface deformations and for the investigation of the interaction between slope and fluvial dynamics, showing the important role of fluvial processes in the remobilisation of the landslide toe causing the displacement of a significant volume of sediment into the stream.

RATES OF MODERN DENUDATION OF A SMALL CATCHMENT IN THE MIDDLE MOUNTAIN BELT OF THE GREATER CAUCASUS (CASE STUDY OF THE GITCHE-GIZHGIT CATCHMENT)

The volumes of loose-clastic material moved by modern earth surface processes were quantified for a small mid-mountain catchment area ( F = 1,86 km2), located in the Baksan River basin using a number of independent methods (modeling of erosion and geomorphologic mapping). The total volume of removed material was estimated through the assessment of the thickness of bottom sediments accumulated in a reservoir located in the outlet section of the catchment area. The rates of linear and rill erosion have been found using the results of repeated UAV surveys and the pin method. The rates of rockfall processes are estimated on the basis of repeated ground-based laser scanning. Additionally, published data on the rates of earth surface processes in the mountains were used. Based on the results of field mapping and interpretation of space images, a map of the spatial pattern of leading earth surface processes was compiled. A digital terrain model of the catchment was constructed on the basis of detailed UAV survey. The volume of loose clastic material delivered to the reservoir was estimated using data on the average annual rates of leading earth surface processes, a map of their distribution over the catchment area, and the connectivity index. It has been established that the average annual denudation rate within the catchment area is 0,16 mm/year. At the same time, only about 3-10% of the products of denudation are delivered to the reservoir. The sediment yield, calculated on the basis of the volume of sediments in the reservoir, is 514 t/km2 per year. It is comparable to the sediment yield of small rivers draining the mid-mountain belt of the Alps with similar bedrock lithology, which was calculated using the results of long-term observations of water and sediment discharge at gauging stations.

Discussion: A Fuzzy Classification Process for Swelling Soils [Transp. Infrastruct. Geotechnol. 10(3), 474–487]

This communication article presents a discussion of various fundamental points pertaining to the Toksöz Hozatlıoğlu and Yılmaz (2023) (the Authors) investigation [published in Transp. Infrastruct. Geotechnol. 10(3), 474–487], specifically scrutinizing the practical ramifications of employing the liquid limit (LL) parameter (by itself) to infer soil expansivity. Based on previous experimental investigations and their own independent analyses presented in this article, the Discussers demonstrate that without proper consideration of soil mineralogical activity, the sole reliance on the LL parameter (as adopted in the Authors’ investigation) is often not a reliable basis for performing soil expansivity assessments. Accordingly, the LL-based fuzzy classification approach reported by the Authors, despite addressing potential uncertainties arising from LL determinations by the Casagrande percussion-cup method, would, in itself, not lead to significantly more reliable soil expansivity assessments. As a way forward, a practical and more realistic classification framework for expansive soils based on equilibrium sediment volume measurements is presented and compared to the LL-based scheme adopted in the Authors’ investigation. Through this endeavor, it is demonstrated that the sole reliance on the LL parameter generally produces overly conservative soil expansivity rankings.

Optimizing Solution in Decision Supporting System for River Basin Management Consisting of a Reservoir System

Decision support systems tackle problems and require systematic planning. They consider physical data, hydrological data, and sediment levels to achieve efficiency and adaptability in various situations. Therefore, this research aims to identify alternative engineering choices for the management of a river basin with a single reservoir system. Optimization techniques, including marine predator algorithm (MPA), genetic algorithm (GA), genetic programming (GP), tabu search (TS), and flower pollination algorithm (FPA), were applied to find the optimal reservoir rule curves using a reservoir simulation model. The study focused on the Ubolratana Reservoir in Thailand’s Khon Kaen Province, considering historic inflow data, water demand, hydrologic and physical data, and sedimentation volume. Four scenarios were considered: normal water scarcity, high water scarcity, normal excess water, and high excess water. The optimal rule curves derived from the reservoir simulation model, incorporating sedimentation and hedging rule (HR) criteria, were found to be the best engineering choices. In the normal and high water scarcity scenarios, they minimized the average water shortage to 95.558 MCM/year, with the lowest maximum water shortage 693.000 MCM/year. Similarly, in the normal and high excess water scenarios, the optimal rule curves minimized the average excess water, resulting in a minimum overflow of 1087.810 MCM/year and the lowest maximum overflow 4105.660 MCM/year. These findings highlight the effectiveness of integrating optimization techniques and a reservoir simulation model to obtain the optimal rule curves. By considering sedimentation and incorporating HR criteria, the selected engineering alternatives demonstrated their ability to minimize water shortage and excess water. This contributes to improved water resource management and decision-making in situations of scarcity and excess.

Assessing the short-term inter-annual growth of the largest documented gully network in South Africa using UAV and SfM methodology

ABSTRACT This research explores intra-gully sediment volume changes of a massive gully network (42 ha) located in the Eastern Cape, RSA, in response to high rainfall events during a three-year study period (2017–2020). Unmanned aerial vehicles (UAVs) and photogrammetric processing were used to generate high resolution digital surface models (DSMs). Volumetric calculations were run to estimate the extent of gully expansion within the system to determine intra-gully changes and sediment erosion over the study period. The gully was categorised into four zones based on predominant structure and processes. These are the Extension Zone, Expansion Zone, Transport/Deposition Zone and the Side Branches. Rainfall data from a rainfall station (10 km away) was used to investigate the correlation between rainfall depth, rainfall intensity, and flow accumulation over two wetter years and one drier year with gully expansion experienced during these periods. The gully network encountered a total gully sediment volume erosion of 104,489 m3 (6.01%) over the study period. Nineteen high to extreme intensity (>20 mm per day) rainfall events produced the runoff necessary for gully expansion during the 2017 and 2018 hydrological years. Notably, lower gully growth was recorded in the Expansion and Transport/Deposition Zones during the subsequent below average hydrological year in 2019–2020.

Morphosedimentary characteristics and formation mechanisms of new beaches generated after the Tajogaite volcano eruption of 2021 (La Palma, Spain)

Only in very special circumstances can new beaches develop due to natural processes in areas where they did not exist before. One such circumstance is related to volcanic eruptions, when a lava flow reaches the ocean. The sudden formation of new beaches is examined in this paper. Following the Tajogaite volcano eruption in September 2021, two lava deltas formed after the arrival of several lava flows to the coast. Attached to the flanks and front of these lava deltas, thirteen gravel beaches formed in just a few months. Detailed topographic and sedimentologic information was collected both on the beaches and adjacent submarine areas. The volume of sediments accumulated on these beaches was obtained after comparison of the actual topography with a previous one, yielding a total net accumulation of about 79,000 m3 of volcanoclastic pebbles and cobbles. This material comes from two major source areas: extensive offshore deposits of volcanic clasts within the depth of closure which are moved onshore by low steepness swell waves, and rock fragments derived from erosion of the lava delta front by high energy waves. Two types of beaches were identified. Beaches that already existed prior to the eruption showed significant increases in cross-shore length and height, with a net accumulation of 67,000 m3. In contrast, the dismantling of the lava delta front led to the formation of totally new beaches in certain locations, accounting for about 12,000 m3 of sediments. Several features, such as a steep foreshore slope, a well-developed storm berm and the presence of wood debris in many of these beaches at several meters height and tens of meters inland, are examined conjointly with the sediment characteristics, showing how textural maturity can change in response to the forcing agents acting in the different parts of the beach profile. The future evolution of these beaches is also considered. This study can enrich the knowledge regarding how new gravel beaches can form in volcanic settings.