Storm Profile Research Articles

Interaction of global electron content with the Sun and solar wind during intense geomagnetic storms

Assessment of solar and solar wind parameters driving the ionosphere model is essential for prediction of the ionospheric weather. In the present paper impact of the different solar, interplanetary and geomagnetic parameters on the global electron content (GEC) during intense space weather storms is investigated. Hourly GEC values are calculated from JPL global maps of total electron content GIM-TEC from 1995 to 2023. The sample comprises 90 intense storms from 1995 to 2023 associated with monthly peak of the weighted accumulation of the geomagnetic Apo(τ, t) index exceeding 90 nT. The 27 day weighted accumulation of the solar sunspot numbers SSN2(τ), solar radio flux F10.7(τ), the solar hydrogen emission Lyman_α(τ) and the composite magnesium MgII(τ) indices are explored as precursors of GEC enhancements. As distinct from the positive ionosphere storm, the solar wind speed Vsw, the solar wind electric field Ey, merging electric field Em and Apo(τ, t) indices proved to be effective as potential drivers of the negative GEC depletion. The positive and negative dGEC deviations from hourly GEC are produced by subtracting a quiet reference GECav averaged during 24h prior the storm normalized by GECav. The hourly storm profiles Vsw(t), Em(t), Ey(t), Apo(τ, t), Dst(t), GEC(t) and dGEC(t) were reduced by method of superposed epochs. The zero epoch t0 = 0 was taken at the peak Apo*(τ, t0) and the storm time lasted for 48h from −12h prior t0 and 35h afterwards. The best correlation of the positive storm dGECp amplitude is obtained with MgII(τ) and the negative storm dGECn with Em* and Apo*(τ, t0) which are used to derive characteristics of five key points of storm-time dGEC(t) model: 1 – onset of the storm profile t1 = t(dGECp); 2 – the amplitude dGECpmax and its time t2(dGECpmax); 3 – the time of transition t3(dGEC = 0) from the positive to negative (±) GEC storm; 4 – minimum negative disturbance dGECnmin and its time t4(dGECnmin), 5 – the end of the storm profile t5(dGECn). Analytical model of dGEC(t) is derived with Epstein step functions fitting 5 key points. Deviations dGEC(t) are inverted to GEC(t) using quiet reference pre-storm GECav. The model is validated for three intense storms on 26–28 February, 23–25 March and 23–25 April 2023. The results show improvement of dGEC forecast with RMS error reduced from 45 to 80% compared to results produced by the international reference ionosphere−plasmasphere model IRI-Plas.

Analysis of a Dust Storm Profile: A Case Study in Iraq

In recent years, many academics have investigated various aspects of dust storms as one of the environmental challenges. In this study, a Battelle laser photometer coupled to a portable computer was used to monitor, analyze, and correlate the particle size distribution to wind speed across a 24-hour period that included the dust storm from January 18–19, 2020. These were connected with wind speed data obtained from an automated weather station (F.A. 511, Wilh Lambrecht). They also examined how the ratio of fibers to particles varied when the wind speed changed during a dust storm within the same period as the aforementioned. The results show that, during storms, a rise in the number of particles occurs as a consequence of high wind speeds, local near-ground turbulence, and strong wind, which work together to effectively lift up heavier particles. Also, it demonstrates a perfect relationship between the profiles of dust particles and fibers with a time lag in relation to wind speed, and an inversion in the order of the individual particle size profiles corresponding to a critical wind speed was noticed. A time lag of around five hours relative to the wind speed profile is also observed. Despite the similar shapes and the trend of the profiles, the ratio of fiber to particle is not constant.

Urban Flood Modelling under Extreme Rainfall Conditions for Building-Level Flood Exposure Analysis

The expansion of urban areas and the increasing frequency and magnitude of intense rainfall events are anticipated to contribute to the widespread escalation of urban flood risk across the globe. To effectively mitigate future flood risks, it is crucial to combine a comprehensive examination of intense rainfall events in urban areas with the utilization of detailed hydrodynamic models. This study combines extreme value analysis techniques applied to rainfall data ranging from sub-hourly to daily durations with a high-resolution flood modelling analysis at the building level in the centre of Thessaloniki, Greece. A scaling procedure is employed to rainfall return levels assessed by applying the generalised extreme value (GEV) distribution to annual maximum fine-temporal-scale data, and these scaling laws are then applied to more reliable daily rainfall return levels estimated by means of the generalised Pareto distribution (GPD), in order to develop storm profiles with durations of 1 h and 2 h. The advanced flood model, CityCAT, is then used for the simulation of pluvial flooding, providing reliable assessments of building-level exposure to flooding hazards. The results of the analysis conducted provide insights into flood depths and water flowpaths in the city centre of Thessaloniki, identifying major flowpaths along certain main streets resulting in localised flooding, and identifying around 165 and 186 buildings highly exposed to inundation risk in the study area for 50-year storm events with durations of 1 h and 2 h, respectively. For the first time in this study area, a detailed analysis of extreme rainfall events is combined with a high-resolution Digital Terrain Model (DTM), used as an input into the advanced and fully featured CityCAT hydrodynamic model, to assess critical flowpaths and buildings at high flood risk. The results of this study can aid in the planning and design of resilient solutions to combat urban flash floods, as well as contribute to targeted flood damage mitigation and flood risk reduction.

Development of design typhoon profile for offshore wind turbine foundation design in Southern China

For offshore wind development in Southern China, typhoon represents the extreme environmental loading condition to be considered in the design of the turbine structures. For the geotechnical design of the foundations, it is specified by the design code that the effect of cyclic loading on the soil strength and stiffness must be considered. This necessitates the complete time history of loads on the foundation experienced during a design typhoon. Idealised storm profiles with staged mean wind speeds and significant wave heights are commonly used as input to time-domain simulations to generate the foundation load history. However, no such design typhoon profile is provided in the Chinese design standard which creates considerable difficulty and uncertainty in the design process. In this paper, the methodology and the rationale that were applied to derive the design typhoon profiles for an offshore wind project in Guangdong province are presented. The wind and wave characteristics generated by typhoon are described in detail and the implications for the foundation design are discussed. To demonstrate application of the proposed typhoon profile, a case study for the ULS design of a suction bucket jacket is presented.

Malaria and COVID-19 coinfection in a non-malaria-endemic area in Brazil

Differential diagnosis of coronavirus disease 2019 (COVID-19) from other febrile diseases is one of several challenges imposed by the pandemic. We present a case of severe malaria and COVID-19 coinfection in a non-malaria-endemic region. A 44-year-old female with malaise, fever, hypotension, jaundice, and enlarged liver and spleen was admitted to the intensive care unit. Reverse transcription-quantitative PCR results for severe acute respiratory syndrome coronavirus 2 were positive. Rapid tests, microscopy, and quantitative PCR were positive for Plasmodium vivax. Cytokine storm profiles were identified. We could not determine whether the severe vivax malaria in our patient was triggered by COVID-19 coinfection.

Wildfire effect on forest rainfall infiltration and runoff: a cellular automata-based simulation

A storm event-based simulation system is developed to reproduce the effects of wildfire on a predefined forest area's rainfall infiltration and runoff. The simulation system reproduces individual surface cell slope, infiltration capacity, and hydrophobicity. A cellular automaton represents space and time. The Horton equation reproduces infiltration capacity evolution. Different equation parameters account for precipitation intensity variations. Infiltration volume and runoff velocity are computed at the cell level. A Digital Elevation Model reproduces the topography. A real rainfall event is reproduced for a section of La Primavera Forest in Jalisco, Mexico. For a subwatershed within the area of interest, wildfire effects are shown on infiltration, overland flow and outlet discharge throughout the rainfall event. It is shown that rainfall infiltration for wildfire affected terrain is lower and that overland flow and outlet discharge is higher. Infiltration and runoff dynamics at a surface cell depend on storm profile, cell slope, cell soil texture, and overall topography. Water dynamics on the area of interest are shown with a movie effect. It is concluded that a cellular automaton-based model can reproduce infiltration and runoff for different soil texture, topographic and rain conditions. This simulation system is geared for an optimisation system to pinpoint the locations of a series of forest land remediation controls that or maximise infiltration or minimise runoff.

Multi-Condition QSAR Model for the Virtual Design of Chemicals with Dual Pan-Antiviral and Anti-Cytokine Storm Profiles.

Respiratory viruses are infectious agents, which can cause pandemics. Although nowadays the danger associated with respiratory viruses continues to be evidenced by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as the virus responsible for the current COVID-19 pandemic, other viruses such as SARS-CoV-1, the influenza A and B viruses (IAV and IBV, respectively), and the respiratory syncytial virus (RSV) can lead to globally spread viral diseases. Also, from a biological point of view, most of these viruses can cause an organ-damaging hyperinflammatory response known as the cytokine storm (CS). Computational approaches constitute an essential component of modern drug development campaigns, and therefore, they have the potential to accelerate the discovery of chemicals able to simultaneously inhibit multiple molecular and nonmolecular targets. We report here the first multicondition model based on quantitative structure–activity relationships and an artificial neural network (mtc-QSAR-ANN) for the virtual design and prediction of molecules with dual pan-antiviral and anti-CS profiles. Our mtc-QSAR-ANN model exhibited an accuracy higher than 80%. By interpreting the different descriptors present in the mtc-QSAR-ANN model, we could retrieve several molecular fragments whose assembly led to new molecules with drug-like properties and predicted pan-antiviral and anti-CS activities.

Mapping storm spatial profiles for flood impact assessments

Synthetic design storms are often used to plan new drainage systems or assess flood impacts on infrastructure. To simulate extreme rainfall events under climate change, design storms can be modified to match a different return frequency of extreme rainfall events as well as a modified temporal distribution of rainfall intensities. However, the same magnitude of change to the rainfall intensities is often applied in space. Several hydrological applications are limited by this. Climate change impacts on urban pluvial floods, for example, require the use of 2D design storms (rainfall fields) at sub-kilometer and sub-hourly scales. Recent kilometer scale climate models, also known as convection-permitting climate models (CPM), provide rainfall outputs at a high spatial resolution, although rainfall simulations are still restricted to a limited number of climate scenarios and time periods. We nevertheless explored the potential use of rainfall data obtained from these models for hydrological flood impact studies by introducing a method of spatial quantile mapping (SQM). To demonstrate the new methodology, we extracted high-resolution rainfall simulations from a CPM for four domains representing different urban areas in Switzerland. Extreme storms that are plausible under the present climate conditions were simulated with a 2D stochastic rainfall model. Based on the CPM-informed stochastically generated rainfall fields, we modified the design storms to fit the future climate scenario using three different methods: the SQM, a uniform quantile mapping, and a uniform adjustment based on a rainfall–temperature relationship. Throughout all storms, the temporal distribution of rainfall was the same. Using a flood model, we assessed the impact of different rainfall adjustment methods on urban flooding. Significant differences were found in the flood water depths and areas between the three methods. In general, the SQM method results in a higher flood impact than the storms that were modified otherwise. The results suggest that spatial storm profiles may need to be re-adjusted when assessing flood impacts.

Estimating unprecedented extremes in UK summer daily rainfall

The UNSEEN (unprecedented simulated extremes using ensemble) method involves using a large ensemble of climate model simulations to increase the sample size of rare events. Here we extend UNSEEN to focus on intense summertime daily rainfall, estimating plausible rainfall extremes in the current climate. To address modelling limitations simulations from two climate models were used; an initialised 25 km global model that uses parameterised convection, and a dynamically downscaled 2.2 km model that uses explicit convection. In terms of the statistical characteristics that govern very rare return periods, the models are not significantly different from the observations across much of the UK. Our analysis provides more precise estimates of 1000 year return levels for extreme daily rainfall, reducing sampling uncertainty by 70%–90% compared to using observations alone. This framework enables observed daily storm profiles to be adjusted to more statistically robust estimates of extreme rainfall. For a damaging storm in July 2007 which led to surface water flooding, we estimate physically plausible increases in the total daily rainfall of 50%–100%. For much of the UK the annual chance of record-breaking daily summertime rainfall is estimated to be around 1% per year in the present-day climate. Analysis of the dynamical states in our UNSEEN events indicates that heavy daily rainfall is associated with a southward displaced and meandering North Atlantic jet stream, increasing the advection of warm moist air from across Southern Europe and the Mediterranean, and intensifying extratropical storms. This work represents an advancement in the use of climate modelling for estimating present-day climate hazards and outlines a framework for applying UNSEEN at higher spatial and temporal resolutions.

Using high-resolution climate change information in water management: a decision-makers' perspective.

The UK Climate Change Act requires the Environment Agency to report the risks it faces from climate change and actions taken to address these. Derived information from projections is critical to understanding likely impacts in water management. In 2019, the UK published an ensemble of high-resolution model simulations. The UKCP Local (2.2 km) projections can resolve smaller scale physical processes that determine rainfall and other variables at subdaily time-scales with the potential to provide new insights into extreme events, storm runoff and drainage management. However, simulations also need to inform adaptation. The challenge ahead is to identify and provide derived products without the need for further analysis by decision-makers. These include a wider evaluation of uncertainty, narratives about rainfall change across the projections and bias-corrected datasets. Future flood maps, peak rainfall estimates, uplift factors and future design storm profiles also need detailed guidance to support their use. Central government support is justified in the provision of up-to-date impacts information to inform flood risk management, given the large risks and exposure of all sectors. The further development of projections would benefit from greater focus and earlier scoping with industry representatives, operational tool developers and end users. This article is part of a discussion meeting issue 'Intensification of short-duration rainfall extremes and implications for flash flood risks'.

Storm types in India: linking rainfall duration, spatial extent and intensity.

We examine wet events (WEs) defined from an hourly rainfall dataset based on 64 gauged observations across India (1969-2016). More than 90% of the WEs (accounting for nearly 60% of total rainfall) are found to last less than or equal to 5 h. WEs are then clustered into six canonical local-scale storm profiles (CanWE). The most frequent canonical type (CanWE#1 and #2) are associated with very short and nominal rainfall. The remaining canonical WEs can be grouped into two broad families: (i) CanWE#3 and #5 with short (usually less than or equal to 3-4 h), but very intense rainfall strongly phase-locked onto the diurnal cycle (initiation peaks in mid-afternoon) and probably related to isolated thunderstorms or small mesoscale convective clusters (MCS), and (ii) CanWE#4 and #6 with longer and lighter rainfall in mean (but not necessarily for their maximum) and more independent of the diurnal cycle, thus probably related to larger MCSs or tropical lows. The spatial extent of the total rainfall received during each CanWE, as shown by IMERG gridded rainfall, is indeed smaller for CanWE#3 and #5 than for CanWE#4 and especially #6. Most of the annual maximum 1 hour rainfalls occur during CanWE#5. Long-term trend analysis of the June-September canonical WEs across boreal monsoonal India reveals an increase in the relative frequency of the convective storm types CanWE#3 and #5 in recent years, as expected from global warming and thermodynamic considerations. This article is part of a discussion meeting issue 'Intensification of short-duration rainfall extremes and implications for flash flood risks'.

A parameterization of DNV-GL storm profile for the calculation of design wave of marine structures

This paper proposes a parameterization of the Det Norske Veritas and Germanischer Lloyd (DNV GL) storm profile for the development of analytical solution for the calculation of the associated return period. This solution allows the possibility of calculating the design wave for marine structures by means of a very simple approach. The basic concept is to substitute the sequence of actual storms at a given site with a sequence of trapezoidal storms (TS) defined on the basis of the DNV GL storm temporal evolution and derive analytically the return period referring to the TSs sequence. The DNV GL storm is represented by a trapezium which may be totally defined by means of three parameters: the trapezium height related to the storm intensity, and its minor and major bases, which represent two durations Dp, D* pertaining to the maximum significant wave height Hsmax and to 50% of Hsmax, respectively. It is assumed that the parameters Dp, D* are uncorrelated to the storm intensity and are the same for all the storms. With this assumption, the return period is obtained in a closed form as a function of the ratio n between Dp and D*, D* itself, and of the exceedance probability distribution of significant wave height. The model is validated by comparison with Equivalent Triangular Storm (ETS) model by processing buoys data at four locations representative of different wave climates: Haltenbanken in North Sea, Alghero in Mediterranean Sea, stations 41001 and 46006 in Atlantic and Pacific Oceans, respectively. Results reveal that although its significant simplicity, the TS model provides reliable estimate of return values which are in agreement with those achieved by ETS model. Further, the employment of TS model with the values of parameters n and D* corresponding to the DNV GL profile is suitable for any location.

Statistical study on interplanetary drivers behind intense geomagnetic storms and substorms

Geomagnetic storms and substorms play a central role in both the daily life of mankind and in academic space physics. The profiles of storms, especially their initial phase morphology and the intensity of their substorms under different interplanetary conditions, have usually been ignored in previous studies. In this study, 97 intense geomagnetic storms (Dstmin ≤ –100 nT) between 1998 and 2018 were studied statistically using the double superposed epoch analysis (DSEA) and normalized superposed epoch analysis (NSEA) methods. These storms are categorized into two types according to different interplanetary magnetic field (IMF) Bz orientations: geomagnetic storms whose IMF is northward, both upstream and downstream relative to the interplanetary shock, and geomagnetic storms whose upstream and downstream IMF is consistently southward. We further divide these two types into two subsets, by different geomagnetic storm profiles: Type I/Type II — one/two-step geomagnetic storms with northward IMF both upstream and downstream of the interplanetary shock; Type III/TypeIV — one/two-step geomagnetic storms with southward IMF both upstream and downstream of the interplanetary shock. The results show that: (1) geomagnetic storms with northward IMF both upstream and downstream of the interplanetary shock have a clear initial phase; geomagnetic storms with southward IMF in both upstream and downstream of the interplanetary shock do not; (2) the IMF is an important controlling factor in affecting the intensity characteristics of substorms. When Bz is positive before and after the interplanetary shock arrival, the Auroral Electrojet (AE) index changes gently during the initial phase of geomagnetic storms, the median value of AE index is maintained at 500–1000 nT; (3) when Bz is negative before and after the interplanetary shock arrival, the AE index rises rapidly and reaches its maxmum value about one hour after storm sudden commencements (SSC), although the time is scaled between reference points and the maximum value of AE is usually greater than 1,000 nT, representing intense substorms; (4) for most cases, the Dst0 usually reaches its minimum at least one hour after Bz. These results are useful in improving contemporary space weather models, especially for those that address geomagnetic storms and substorms.

LARGE SCALE TESTS ON FORESHORE EVOLUTION DURING STORM SEQUENCES AND THE PERFORMANCE OF A NEARLY VERTICAL STRUCTURE

This work presents the results of an experimental investigation on the effects of a sequence of storms on wave overtopping at a nearly vertical battered seawall at the back of a sandy foreshore. The experiments were carried out in the Large Wave Flume (GWK) at Leibniz Universität Hannover (Germany), as part of the research project ICODEP (Impact of Changing fOreshore on flood DEfence Performance), within the European Union programme Hydralab+. The layout consisted of a 10/1 battered seawall and a natural sandy foreshore with an initial 1:15 slope. The beach sand had a nominal diameter of 0.30 mm. Three storm sequences were simulated, where each consisted of three individual storms. Each storm was divided into six steps in which the wave conditions and still water level were varied to represent the peak of an actual storm. The six sea states were based on a JONSWAP spectral shape, with wave heights roughly between 0.6 m and 0.8 m. Two still water levels were tested. For the central two steps the level was such that the freeboard was only 0.14 m and almost all waves were overtopping. In the remaining steps low still water levels were employed, leaving a narrow swash zone. Two storm profiles were considered, the first one with a lower level of energy and the second one with a higher one. These were combined in the three different sequences. All the tested wave conditions were designed to be erosive for the beach, with no recovery in between. Each sequence started from a plain beach configuration and the beach was not restored in between storms. The measurements included waves, pressure and forces, sediment concentrations and flow velocity together with overtopping. The profile of the beach was measured after each sea state tested.

Development of design storm hyetographs in hyper-arid and arid regions: case study of Sultanate of Oman

The temporal distribution of the design storm is an important input in hydrological models. This research aims to develop design storm profiles representative of arid and hyper-arid areas based on actual storm recordings. Two hundred thirty-six rainfall storms were collected from seventeen rainfall gauges that cover the coastal zone of Oman for the period from 1993 to 2007. Storms were classified into four categories according to their total durations. Design storm hyetographs were derived from raw rainfall records for all four categories using the Alternating Block Method (ABM) and were also computed by ABM applied on the Intensity-Duration-Frequency (IDF) curves. Both design storm profiles were compared and it was found that the ABM_IDF storm profiles were equivalent to the four ABM_Storms profiles from a practical point of view as they produce similar peak discharges. The storm profiles developed in the current research were also compared to the commonly used Soil Conservation Service (SCS) dimensionless distributions and the UK50 storm profiles. The results showed that the most conservative commonly used SCS type II and the UK50 summer profiles are not safe to be used in design purposes in arid and hyper arid regions, despite their wide utilization in many codes of practice in these regions. The study recommends using the newly developed dimensionless storm profiles derived from the actual records.

Mechanisms controlling the complete accretionary beach state sequence

AbstractAccretionary downstate beach sequence is a key element of observed nearshore morphological variability along sandy coasts. We present and analyze the first numerical simulation of such a sequence using a process‐based morphodynamic model that solves the coupling between waves, depth‐integrated currents, and sediment transport. The simulation evolves from an alongshore uniform barred beach (storm profile) to an almost featureless shore‐welded terrace (summer profile) through the highly alongshore variable detached crescentic bar and transverse bar/rip system states. A global analysis of the full sequence allows determining the varying contributions of the different hydro‐sedimentary processes. Sediment transport driven by orbital velocity skewness is critical to the overall onshore sandbar migration, while gravitational downslope sediment transport acts as a damping term inhibiting further channel growth enforced by rip flow circulation. Accurate morphological diffusivity and inclusion of orbital velocity skewness opens new perspectives in terms of morphodynamic modeling of real beaches.

A new equivalent exponential storm model for long-term statistics of ocean waves

The paper proposes a new solution, in the context of equivalent storm models, for long-term statistics of ocean storms. These models are essentially based on the concept of equivalent sea which consists of substituting the actual storms at a given location with a sequence of equivalent storms, achieved from a statistical perspective.Firstly the Equivalent Triangular Storm (ETS) was proposed in which triangular storms were considered. The model was then generalized assuming a power law for a more realistic description of the storm history in time domain. The two models were developed following the same logic and assuming the equivalent storm symmetric with respect to its peak. In both cases the solution for the calculation of return period of a sea storm whose maximum significant wave height is greater than a given threshold is achieved, but only for ETSs it has a closed form and for all the others shapes it requires a numerical calculation.The main focus of the present work is to combine in a unique model the main advantages of the two previous ones, that is to obtain an optimized shape (as for EPS) and closed from solutions for the long-term statistics (as for ETS). An exponential law is introduced, taking into account asymmetry in storm profile. The long-term statistics of ocean storms is then investigated via this new Equivalent Exponential Storm (EES) model, by analyzing the effects of asymmetry between the growth and decay phases of each storm. Data from National Data buoy Center (NDBC) are processed for the new EES model validation and comparison with previous ETS and EPS. The results show that the assumption of asymmetric storm profile does not lead to significant changes of the long-term statistics, but could be very useful in other kinds of application as it enables a more realistic representation of storm history. Finally, in comparison with ETS and EPS, it has been seen that EES provides a better representation of actual storm duration.

LAND COVER EFFECT ON DUNE EROSION AND OVERWASH

In this study, a numerical morphodynamic model eXtreme Beach behaviour (XBeach) was used to simulate the effects of land cover on the shape of the post storm profile s at two test sites on barrier islands at Outer Banks, North Carolina. The simulations included dune erosion and overwash regimes and were carried out with and without the inclusion of land cover effects. The model results were assessed by comparing post storm profiles extracted from XBeach and Light Detection And Ranging (LiDAR) data. The simulations showed that the morphological response of the profiles was sensitive to land cover and inclusion of these effects improved the model results.

Signatures of strong geomagnetic storms in the equatorial latitude

Ionosonde data from two equatorial stations in the African sector have been used to study the signatures of four strong geomagnetic storms on the height – electron density profiles of the equatorial ionosphere with the objective of investigating the effects and extent of the effects on the three layers of the equatorial ionosphere. The results showed that strong geomagnetic storms produced effects of varying degrees on the three layers of the ionosphere. Effect of strong geomagnetic storms on the lower layers of the equatorial ionosphere can be significant when compared with effect at the F2-layer. Fluctuations in the height of ionization within the E-layer were as much as 0% to +20.7% compared to −12.5% to +8.3% for the F2-layer. The 2007 version of the International Reference Ionosphere, IRI-07 storm-time model reproduced responses at the E-layer but overestimated the observed storm profiles for the F1- and F2-layers.

Storm-driven cyclic beach morphodynamics of a mixed sand and gravel beach along the Mid-Atlantic Coast, USA

The morphodynamics of a mixed sand and gravel beach in Delaware were investigated based on 18 almost monthly beach-profile surveys at 46 locations from 2009 to 2011, 60 sediment cores, and 550 surface sediment samples collected at various alongshore and cross-shore transects. Three different atmospheric disturbances occurred within a 3-month window during the study period: 1) a distal hurricane, 2) an energetic winter storm, and 3) “Nor'Ida”, a long-lasting and extremely energetic event resulting from the collision of a hurricane and winter storm. The storm-induced beach changes and post-storm recovery following each of the three storms are evaluated. A distinctive beach cycle was identified consisting of a built-up berm profile and depleted nearly-planar storm profile. The time-scale of the beach cycle relates to the frequency and intensity of storm impact and duration of inter-storm recovery instead of simple seasonality. The initiation of post-storm recovery occurs during the subsiding phase of the storm, attributable to the reduction in wave height and steepness transitioning to accretionary swells. The sediment characteristics of the storm deposit associated with Nor'Ida demonstrated substantial cross-shore variation ranging from sandy-gravel and gravelly-sand within the storm swash zone (near the pre-storm dune edge) to well-sorted medium to coarse sand seaward of the storm swash zone. Storm deposits along mixed sand and gravel beaches demonstrate a variety of sedimentological characteristics. In addition, the studied beaches lacked a sandbar under all wave conditions. A new beach cycle model is proposed for the non-barred mixed sand and gravel beach. • Sedimentological characteristics of the Nor'Ida storm deposit showed cross-shore variation. • Storm deposits of mixed sand and gravel beaches cannot be based solely on a layer of poorly-sorted coarse sediment. • A sandbar did not form under all wave conditions encountered during this study. • A modified beach cycle model is developed for the mixed sand and gravel Delaware coast. • The model consists of a storm-driven time-scale and planar non-barred post-storm beach.