Total Water Level Research Articles

Evaluation of a global total water level model in the presence of radiational S[formula omitted] tide

The development of a computationally efficient scheme for predicting the global distribution of total water level (TWL) is discussed. The ocean model is barotropic, has a horizontal grid spacing of 1/12°, and is based on the NEMO modeling framework. It is forced by the gravitational potential and hourly atmospheric fields for 2008. Hourly time spacing was required to resolve the S2 tide in global air pressure and wind. The predicted tide in water deeper than 400 m was nudged to TPXO8 “observations” of tidal elevation or current using a scheme called tidal nudging (Kodaira et al., 2019). The benefit of nudging horizontal velocity in the momentum equation, compared to sea level in the continuity equation, is discussed. Tidal nudging is shown to improve tidal predictions of sea level at the coast, particularly at the S2 tidal frequency. The predicted radiational S2 tide in sea level forced solely by the S2 tide in global air pressure reaches amplitudes exceeding 80 cm. Decreasing the time spacing of the air pressure forcing from 1 h to 3 h reduces the S2 amplitude in air pressure by a factor of 0.82, consistent with expectations based on Fourier analysis. This highlights the importance of using hourly atmospheric forcing when predicting the global sea level response to atmospheric forcing. The radiational S2 tide in sea level is subject to strong nonlinear interaction with the gravitational tide, leading to a pronounced attenuation of the radiational S2 tide. The attenuation is explained by an increase in effective bottom friction at the S2 frequency due to the presence of the gravitational tide. Four schemes for predicting TWL are evaluated to quantify the impact of tidal nudging and nonlinear interaction of tide and surge. Using TWLs observed by 304 coastal tide gauges, we show it is necessary to include both tidal nudging and nonlinear interaction. Plans for the further development of an operational flood forecast system for the Canadian coast, based on the above model, are discussed.

Effects of Electrolyte Supplements on Body Water Homeostasis and Exercise Performance during Exhaustive Exercise

This study aimed to compare the physiologic effects of regular water consumption to those of electrolyte drink consumption in exercise capacity and recovery after exhaustive exercise. The participants were 10 healthy young men who exercised on a treadmill before and after receiving regular water and an electrolyte drink (3RINK) four weeks later. A 250-mL fluid volume was ingested 30 min before exercise and immediately after. Body composition, water metabolizing hormones, and body electrolytes were analyzed at rest (R), immediately after exercise (P0), and 1 h after exercise (P1). Moreover, serum lactic acid levels were measured to determine recovery. Total body water, intracellular, and extracellular water levels were higher after consuming 3RINK at P0 than at R. There was no interaction effect between the types of fluids and antidiuretic hormone, aldosterone, and renin levels. Hematocrit levels showed an interaction effect between the type of fluid and period. Sodium levels were significantly different between the different types of fluids at P0 and P1. Finally, an interaction effect was noted between each type of fluid and serum lactate levels. Thus, 3RINK intake before and after exhaustive exercise increased body capacity to retain water, improved exercise ability, and reduced exercise-related fatigue.

The Effects of Different Concentrations of Bay Leaf Extract on Shelf Life of Preserved Scad Fish

Scad fish (Decapterus kurroides) is the most productive fish species. To provide the added value, fishermen can process scad fish into various forms of processed products, such as preserved fish, which extend the shelf life. In order to extend the shelf life of canned fish, natural preservatives could be used that contain antimicrobial agents, such as bay leaves. The present study aimed to determine the effects of bay leaf extract in different concentrations on the shelf life of preserved scad fish. In the present study, the completely randomized design was used as an experimental research method. The treatments given differed in terms of the concentration of the bay leaf extract. The groups were treated as the scad fish without bay leaf extract (A), scad fish soaked in 6% of bay leaf extract (B), scad fish soaked in 7% of bay leaf extract (C), scad fish soaked in 8% of bay leaf extract (D), and scad fish soaked in 9% of bay leaf extract (E). The analyzed parameters included the total plate count, pH, and water level test using Analysis of Variance (ANOVA). The supportive parameters observed included an organoleptic test. The results indicated that the lowest total bacterial count from the beginning to the end of the experiment (18 hours) occurred on treatment C (7% of bay leaf extract addition), which was 1.54 × 103 to 5.85 × 106. Regarding the water level test from the beginning to the end of the experiment, treatment A (control) was not significantly different from other treatments. The difference in the concentration of bay leaf extract on scad fish effectively inhibited the growth of bacterial colonies. In conclusion, adding bay leaf extract to scad fish could inhibit bacteria for up to 12 hours. Treatment C (7% of bay leaf extract) gave the best results since this concentration level could inhibit the bacteria on scad fish.

Efficient estimation of distributional properties of extreme seas from a hierarchical description applied to calculation of un-manning and other weather-related operational windows

Methods of computational statistics allow efficient estimation of extreme ocean environments, and facilitate optimal operational decision making. We describe estimation of extreme quantiles of total water level and related quantities from a non-stationary hierarchical model for ocean storms. The model incorporates a directional–seasonal extreme value model for occurrences of storm peak significant wave height, a conditional directional model for within-storm evolution of sea states relative to storm peak, a conditional model for the maximum crest within a sea state, and models for total water level. Importance sampling is used for efficient computation of marginal total water level characteristics. We use the model to estimate an optimal un-manning procedure for a notional North Sea offshore structure in severe conditions.

Estimation of the non-exceedance probability of extreme storm surges in South Korea using tidal-gauge data

Abstract. Global warming, one of the most serious aspects of climate change, can be expected to cause rising sea levels. These have in turn been linked to unprecedentedly large typhoons that can cause flooding of low-lying land, coastal invasion, seawater flows into rivers and groundwater, rising river levels, and aberrant tides. To prevent typhoon-related loss of life and property damage, it is crucial to accurately estimate storm-surge risk. This study therefore develops a statistical model for estimating such surges' probability based on surge data pertaining to Typhoon Maemi, which struck South Korea in 2003. Specifically, estimation of non-exceedance probability models of the typhoon-related storm surge was achieved via clustered separated peaks-over-threshold simulation, while various distribution models were fitted to the empirical data for investigating the risk of storm surges reaching particular heights. To explore the non-exceedance probability of extreme storm surges caused by typhoons, a threshold algorithm with clustering methodology was applied. To enhance the accuracy of such non-exceedance probability, the surge data were separated into three different components: predicted water level, observed water level, and surge. Sea-level data from when Typhoon Maemi struck were collected from a tidal-gauge station in the city of Busan, which is vulnerable to typhoon-related disasters due to its geographical characteristics. Fréchet, gamma, log-normal, generalized Pareto, and Weibull distributions were fitted to the empirical surge data, and the researchers compared each one's performance at explaining the non-exceedance probability. This established that Weibull distribution was better than any of the other distributions for modelling Typhoon Maemi's peak total water level. Although this research was limited to one city on the Korean Peninsula and one extreme weather event, its approach could be used to reliably estimate non-exceedance probabilities in other regions where tidal-gauge data are available. In practical terms, the findings of this study and future ones adopting its methodology will provide a useful reference for designers of coastal infrastructure.

Modeling surface waves and tide–surge interactions leading to enhanced total water levels in a macrotidal bay

ABSTRACT Large waves and storm surge generated by powerful storms can have detrimental impacts on coastal areas. The Gulf of Maine and Bay of Fundy system in the Atlantic Ocean is a particularly dynamic environment where storm surge can synergistically combine with the large tides to yield serious impacts on low-lying coastal areas. In this study, impacts from Hurricane Arthur in 2014 were investigated with observations and numerical simulations using a coupled hydrodynamic-wave model. The results indicate that the storm generated significant wave heights up to 5 m in the Gulf of Maine and a storm surge of over 0.5 m in coastal areas in the Upper Bay of Fundy, however this surge occurred during the neap tide with no associated flooding. Additional simulations, including a historically important event called the Saxby Gale of 1869, were also simulated. This powerful storm occurred during a perigean spring tide, and the model results indicate wave heights of over 10 m and storm surge of over 0.7 m that caused significant flooding. The results indicate that a well-timed tropical cyclone during a high spring tide has the potential to create a storm surge that could overtop existing dyke systems, causing extensive flooding and damage.

The relative role of constructive and destructive processes in dune evolution on Cape Lookout National Seashore, North Carolina, USA

AbstractCoastal dunes are dynamic features that are continuously evolving due to constructive (e.g., wind‐ and wave‐driven sediment transport) and destructive (e.g., elevated total water levels during storm events) processes. However, the relative importance of these processes in determining dune evolution is often poorly understood. In this study, ten lidar datasets from 1997 to 2016 are used to determine the relative role of erosion and accretion processes driving foredune change on the coast of Cape Lookout National Seashore, North Carolina, USA. Beach and dune morphometrics reveal that dune toe locations have generally retreated since 1997, while dune crest heights accreted by 0.01–0.02 m/year. We develop three univariate metrics that represent (1) the potential for erosion, i.e., total water level impact hours per year, (2) accretion, i.e., dune building hours per year, and (3) the relative net effect of foredune accretion and erosion processes, i.e., constructive–destructive dune forcing (CDDF) ratio, and test the correlative power of these metrics in explaining changes in foredune morphology. The total water level impact hours per year metric explained as much as 66% and 67% of the variance in dune crest and toe elevations, respectively, across the nearly two decades of dune evolution. The greatest number of dune building hours per year and largest dunes within the study site co‐occurred at locations exposed to the dominant cross‐shore wind direction as a result of varying shoreline orientation. The CDDF ratio was positively correlated to changes in the dune toe elevation in approximately 70% of dunes within the study site, outperforming the impact and dune building hours per year metrics. Our results show that these three metrics can provide first‐order estimates of dune morphometric change across multiple spatial and temporal scales, which may be particularly useful at sites where lidar acquisition is intermittent.

The performance of the copulas in estimating the joint probability of extreme waves and surges along east coasts of the mainland China

In designing coastal and nearshore structures, the joint probability of the wave heights and storm surges is essential in determining the possible highest total water level. The key elements to accurately estimate the joint probability are the appropriate sampling of the extreme values and selection of probability functions for the analysis. This study is to provide a full assessment of the performance of the different methods employed in the joint probability analysis. The bivariate extreme wave height and surge samples are analysed using 2 different probability distributions and the performance of 4 copulas, namely: Gumbel–Hougaard copula, Clayton copula, Frank copula and Galambos copula, is assessed. The possible highest total water levels for 100-year return period along the coastline of the mainland China are estimated by the joint probability method with the Gumbel–Hougaard copula. The results show that the wave heights and surges are highly correlated in the areas of dense typhoon paths. The distributions of the possible highest total water levels show a higher value in the southeast coast and lower value in the north. The results also indicate that at the locations where the sea states are energetic, the joint probability approach can improve the accuracy of design.

Nonstationary Extreme Value Analysis of Nearshore Sea-State Parameters under the Effects of Climate Change: Application to the Greek Coastal Zone and Port Structures

In the present work, a methodological framework, based on nonstationary extreme value analysis of nearshore sea-state parameters, is proposed for the identification of climate change impacts on coastal zone and port defense structures. The applications refer to the estimation of coastal hazards on characteristic Mediterranean microtidal littoral zones and the calculation of failure probabilities of typical rubble mound breakwaters in Greek ports. The proposed methodology hinges on the extraction of extreme wave characteristics and sea levels due to storm events affecting the coast, a nonstationary extreme value analysis of sea-state parameters and coastal responses using moving time windows, a fitting of parametric trends to nonstationary parameter estimates of the extreme value models, and an assessment of nonstationary failure probabilities on engineered port protection. The analysis includes estimation of extreme total water level (TWL) on several Greek coasts to approximate the projected coastal flooding hazard under climate change conditions in the 21st century. The TWL calculation considers the wave characteristics, sea level height due to storm surges, mean sea level (MSL) rise, and astronomical tidal ranges of the study areas. Moreover, the failure probabilities of a typical coastal defense structure are assessed for several failure mechanisms, considering variations in MSL, extreme wave climates, and storm surges in the vicinity of ports, within the framework of reliability analysis based on the nonstationary generalized extreme value (GEV) distribution. The methodology supports the investigation of future safety levels and possible periods of increased vulnerability of the studied structure to different ultimate limit states under extreme marine weather conditions associated with climate change, aiming at the development of appropriate upgrading solutions. The analysis suggests that the assumption of stationarity might underestimate the total failure probability of coastal structures under future extreme marine conditions.

Inter‐Model Comparison of Delft3D‐FM and 2D HEC‐RAS for Total Water Level Prediction in Coastal to Inland Transition Zones

AbstractHydrodynamic models play a key role in simulating total water level (TWL), that is, a combination of river flow, tide, surge, wind and wave‐induced water level, and representing flood inundation dynamics in coastal areas. An appropriate selection of two‐dimensional (2D) models that integrate riverine and estuarine interactions with ocean dynamics is crucial to generate accurate TWL predictions and assist stakeholders and federal agencies in decision making and flood emergency responses. In this study, we compare the performance of two widely used hydrodynamic models (e.g., 2D HEC‐RAS and Delft3D‐Flexible Mesh [FM]) with respect to their ability of predicting TWL in Delaware Bay, United States. Based on a previously established model configuration, we simulate Hurricane Sandy and Isabel that affected the Bay and led to considerable damages and economic losses. We then evaluate model capabilities with tidal analysis, compare observed vs. simulated TWL and analyze spatiotemporal variations of TWL through scenario‐based simulations. Our results suggest that atmospheric forcing input in Delft3D‐FM significantly improves TWL predictions as compared to those of 2D HEC‐RAS. Furthermore, model simulations with Delft3D‐FM can be faster than 2D HEC‐RAS by a factor of 6–10. Despite these advantages, 2D HEC‐RAS (version 5.07) is a noncommercial software easier to implement and can be a simpler alternative for modeling extreme events when atmospheric forcing is not relevant in the model domain.

МОРФОЛОГІЧНІ ОСОБЛИВОСТІ ТА АЕРОБНА ПРОДУКТИВНІСТЬ У ФУТБОЛІСТІВ З ГІПЕРМОБІЛЬНІСТЮ СУГЛОБІВ

Інтенсифікація фізичних навантажень у сучасному футболі вимагає від спортсменів розвитку високого рівня загальної, швидкісної і спеціальної витривалості. При побудові тренувально-змагальних навантажень у футболі особливий інтерес з боку тренерів та лікарів викликають спортсмени з ознаками дисплазії сполучної тканини, одним з частих проявів якої є гіпермобільність суглобів. Системність залучення сполучної тканини у диспластичний процес при гіпермобільності суглобів може вплинути на розвиток фізичних якостей, фізичної підготовленості, рівень функціонального стану та аеробної продуктивності і може бути причиною негативного спортивного результату. Не врахування особливостей таких спортсменів може бути причиною виникнення гострого фізичного перенапруження. Метою даної роботи було встановлення морфологічних особливостей та рівня аеробної продуктивності у футболістів з ознаками гіпермобільності суглобів. Для виконання поставленої мети було проведено аналіз даних 46 футболістів високого класу збірної Азербайджану з футболу віком від 16 до 34 років. Визначення морфометричних показників проводилось антропометрією, склад тіла оцінювався імпедансометрією, клінічні ознаки гіпермобільності суглобів діагностувались за критеріями Р. Beighton, оцінка аеробної продуктивності проводилась прямим газоаналізом дозованого фізичного навантаження на велоергометрі. За результатами дослідження рівня гіпермобільності суглобів було встановлено, що 56,5% футболістів мали нормальну рухливість , 30,4% – помірну та 13,0% – значну гіпермобільність. У футболістів із значною гіпермобільністю суглобів рівень аеробної продуктивності був найменшим і становив 53,3±2,5 мл/хв/кг і найбільшим (59,5±1,2 мл/хв/кг)- у групі з нормальною рухливістю суглобів . Досліджуючи динаміку величини максимального споживання кисню в групах було встановлено статистично значиме зменшення її величини зі збільшенням ступеню гіпермобільності (р<0,05). Так, у групі з нормальною рухливістю приріст VO2 max становив 5,3±0,2 мл/хв/кг, в групі з помірною гіпермобільністю – 3,7±0,2 мл/хв/кг та в групі зі значною гіпермобільністю – 1,7±0,2 мл/хв/кг. Дослідження складу тіла в групах, розподілених за рівнем гіпермобільності суглобів, встановило, що найнижчим рівень загальної води був в групі з вираженою гіпермобільністю (р<0,05). Така динаміка відбувалась за рахунок зменшення рівня зовнішньоклітинної рідини, що може свідчити про порушення процесів обміну саме у міжклітинному матриксі. Встановлено статистично значиме зменшення рівня максимального споживання кисню зі збільшенням ступеню гіпермобільності суглобів. Доведено різницю у відповіді функціональних систем організму футболістів під час тренування загальної витривалості. Встановлення зв’язків між показниками складу тіла та величиною максимального споживання кисню може бути основою для регулювання тренувально-змагальних навантажень та для спортивного відбору.

An early warning system for wave-driven coastal flooding at Imperial Beach, CA

Waves overtop berms and seawalls along the shoreline of Imperial Beach (IB), CA when energetic winter swell and high tide coincide. These intermittent, few-hour long events flood low-lying areas and pose a growing inundation risk as sea levels rise. To support city flood response and management, an IB flood warning system was developed. Total water level (TWL) forecasts combine predictions of tides and sea-level anomalies with wave runup estimates based on incident wave forecasts and the nonlinear wave model SWASH. In contrast to widely used empirical runup formulas that rely on significant wave height and peak period, and use only a foreshore slope for bathymetry, the SWASH model incorporates spectral incident wave forcing and uses the cross-shore depth profile. TWL forecasts using a SWASH emulator demonstrate skill several days in advance. Observations set TWL thresholds for minor and moderate flooding. The specific wave and water level conditions that lead to flooding, and key contributors to TWL uncertainty, are identified. TWL forecast skill is reduced by errors in the incident wave forecast and the one-dimensional runup model, and lack of information of variable beach morphology (e.g., protective sand berms can erode during storms). Model errors are largest for the most extreme events. Without mitigation, projected sea-level rise will substantially increase the duration and severity of street flooding. Application of the warning system approach to other locations requires incident wave hindcasts and forecasts, numerical simulation of the runup associated with local storms and beach morphology, and model calibration with flood observations.

Quantifying the precision of retracked Jason-2 sea level data in the 0–5 km Australian coastal zone

This paper aims to quantify the precision of retracked Jason-2 altimeter sea level data (2008–2016) in the 0–5 km Australian coastal zone. A new retracking strategy has been developed to achieve the highest possible precision of coastal sea-level data. Coastal waveforms were classified into four groups according to the adaptability of dedicated coastal retrackers, from which each group was reprocessed using an optimal retracker. A modified Brown model was introduced to reprocess the quasi-specular waveforms over calm waters. A seamless transition of sea surface heights from different retrackers was achieved by estimating and removing the significant wave height dependent height differences. In order to generate the 20-Hz sea level anomaly (SLA) and total water level envelope (TWLE) at the coast, the regional along-track mean sea surface (MSS) with a high spatial resolution (~300 m) was estimated. Compared to the global MSS model, the use of the along-track MSS has dramatically reduced the SLA variance by 140 cm2 in the 0–15 km coastal strip.The results from the evaluation of data precision for Jason-2 ground tracks and the validation against tide gauges show that this new retracking strategy can retrieve more reliable sea level data nearshore. The precision of 20-Hz sea level data in the 0–5 km Australian coastal strip ranges typically from 5 cm to 6 cm in most coastal areas, which is only ~1 cm lower than that beyond 5 km off the coastline. However, in Northwest Australian and some coastal regions, the data precision drops to ≥7 cm due partly to the specific coastal sea states and topography. In addition, it is found that the altimeter and tide gauge TWLE time series have a high correlation (>0.8) in the 0–5 km distance band, indicating that coastal sea-level data are useful for applications such as estimation of river plumes, long-term variation of water level in lakes and rivers, and the analysis of storm surges.

A hierarchical Bayesian model of storm surge and total water levels across the Great Lakes shoreline – Lake Ontario

This study presents a novel approach to determine the distribution of compound flood events composed of storm surge and static water levels along the Great Lakes shoreline. A mixture distribution of the bulk (Student-t) and tail (GPD-negative binomial) components of storm surge is estimated in a hierarchical Bayesian modeling framework. Parameters are modeled across the entire shoreline using Gaussian processes and hourly gauged data, with priors for spatial autocorrelation informed by numerical output from a lake hydrodynamic model. The distribution of total water levels is obtained through Monte Carlo sampling that combines the estimated distribution of surge with stochastic traces of static lake levels that account for water level management, seasonality, and plausible variability in water supplies. The approach can therefore support coastal flood risk assessments in cases when the distribution of static water levels changes are due to altered water level management or climate change. The model is applied in a case study on Lake Ontario. Results suggest that spatial variability in parameter estimates varies significantly by month and mixture distribution component. Evaluations of performance indicate the model is able to capture adequately storm surge behavior at gauges across the lakeshore, even under cross-validation. A frequency analysis of total water levels at two ungauged sites is presented, with specific attention given to the implications of model assumptions on uncertainty in design events. The paper concludes with a discussion of model limitations and avenues for future work.

Satellite-derived shoreline detection at a high-energy meso-macrotidal beach

Publicly available satellite imagery can now provide multi-decadal time series of shoreline data from local to global scale, enabling analysis of sandy beach shoreline variability across a spectrum of temporal scales. Such data can, however, be associated with large uncertainties, particularly for beaches experiencing a large tidal range (>2 m) and energetic incident waves. We use a decade of bi-monthly topographic surveys at the high-energy meso-macrotidal beach of Truc Vert, southwest France, and concurrent wave and water-level hindcast to investigate the uncertainties associated with satellite-derived time series of the shoreline position. We show that consideration of the water level and wave runup elevation is critical for accurately estimating waterline position and, in turn, shoreline position. At Truc Vert, including non-tidal water level residuals (e.g. wind-driven surge) and accounting for time- and elevation-varying beach slope for horizontal correction did not improve satellite-derived shoreline position. A new total water level threshold is proposed to maximize the number of usable images while minimizing errors. Accounting for wave runup and the new water level threshold at Truc Vert, the number of usable satellite images is doubled and shoreline position errors are at least halved compared to previous work at this site. Using the 1984–2019 reconstructed shoreline, we also show that the satellite-derived shoreline trends and interannual variability are in better agreement with field measurements. Although the approach proposed here needs to be tested on other sites in different tidal/wave forcing environments with different morphological and sediment characteristics, we anticipate that it will improve the temporal and spatial description of shoreline change on most surf tidal beaches where accurate continuous water level and wave hindcasts and/or observations are available.

Morphodynamic Evolution of Post-Nourishment Beach Scarps in Low-Energy and Micro-Tidal Environment

Beach scarps are commonly associated with nourishment. Large and persistent beach scarps not only affect the performance of beach nourishment, but also are safety hazards to tourists. In this study, the morphological evolution of beach scarps was examined at a nourished beach in a low-energy and micro-tidal environment. Topographic surveys of nine beach profiles were carried out every 3–6 months after nourishment, lasting for nearly 4.5 years, combined with observed and simulated hydrodynamic data. The results showed that beach scarps were extensively developed after nourishment and migrated landward gradually. The formation of beach scarps was attributed to the higher designed berm, while the migration was possibly initiated by the subsequent higher total water level connected with the irregular tides. However, scarps were completely removed by the first post-nourishment severe storm and had been long absent ever since although two other energetic storms approached. This was different from the result of previous studies, which could be attributed to the much gentler upper beach slope. These results highlighted that the first post-nourishment storm played a key role in the evolution of beach scarps at low-energy and micro-tidal nourished beaches. This study also proposed two methods of determining berm elevation in beach nourishment according to China’s experiences, which would be helpful for other countries’ beach nourishment projects.

Characterisation of wet and dry spells and associated atmospheric dynamics at the Pra River catchment of Ghana, West Africa

Study regionThe Pra river catchment in Ghana, West Africa. Study focusKnowledge of the spatio-temporal distribution of wet and dry spells are crucial for rain-fed agriculture at the Pra River catchment. This study characterised spells and their associated atmospheric dynamics at the Pra river catchment. Specifically, the variability of historical and future wet and dry spells and atmospheric dynamics on the rainfall and spell patterns at the catchment were studied. New hydrological insightsShort duration spells have a higher occurrence at the catchment as compared to long duration spells. Seasonally, short duration dry spells are most common in December–February, whereas wet spells are expected in March–May. Future scenarios show an increase in both wet and dry spells. Composites of the atmospheric dynamics for 2–3 day dry spells show moisture convergence over the entire catchment, with lower total column water levels. However, there is a dipole of moisture convergence and divergence for wet spell composites, with higher than normal total column water. An anticyclonic circulation, inducing a ridge at 500 hPa, coupled with low-level southerlies at 850 hPa act to support wet spell occurrences in JJA. The findings contribute to sub-seasonal and seasonal forecasting, and hence will improve agricultural practices in the catchment in support of food security.

Flood management challenges in transitional environments: Assessing the effects of sea-level rise on compound flooding in the 21st century

One of the main challenges facing decision-makers, particularly in highly modified transitional systems (i.e., coastal and inland waters, estuaries, river mouths, deltas, and coastal lagoons), is to determine whether current flood defenses will be sufficient throughout the 21st century. In case they are not, address the questions of where and when flood defenses will fail and how much. The methodology presented in this paper addresses the effects of the mean sea-level rise on flooding failures caused by the occurrence of multiple concomitants (compatible and simultaneous) forcing agents in channelized transitional systems throughout the 21st century. It analyzes the spatial and temporal evolution of overflowing failures and compares the crest height of flood defenses with the extreme total water level events expressed as a function of the return periods. The presented procedure then characterizes the mechanism responsible for flooding and identifies the channelized transitional system areas that should be protected at different temporal horizons. The results are converted into management maps, where the spatio-temporal variability and uncertainty of the results are analyzed to facilitate knowledge-based decision making and long-term adaptation planning. The application of the proposed method to the Guadalete estuary, a highly modified estuary representative of the coasts of southern Europe, indicates that: (1) the middle part of the estuary is the most sensitive to flooding due to the sea-level rise; (2) if no actions for mitigation are taken, the number of overflowing failures by the end-century will increase by a 2000% in the middle estuary as a consequence of the combination of the extremes of the astronomical tide and river discharge with the mean sea-level rise; (3) the extreme total water level events of 50-year return period in 2050 will be 1.8 m higher than the current crest height of the levees with a 95% confidence. Therefore, it is recommended that reliable methodologies such as the one proposed here be incorporated into the recommendations for the cost-optimization of the construction and maintenance of protection structures against sea-level rise, such as the Spanish Recommendations of Maritime Works (ROM Program).

Satellite-based drought analysis in the Zambezi River Basin: Was the 2019 drought the most extreme in several decades as locally perceived?

Study regionThe study area is the river basin upstream of the Kariba dam located in the Zambezi River at the border of Zambia and Zimbabwe. Study focusDuring the dry season of 2019 in Sub-Saharan Africa, extremely low water levels occurred in the Zambezi. According to news media, locals perceived this drought as the worst in several decades. We analyzed the 2019 drought in the Zambezi River Basin upstream of the Kariba dam to determine whether it indeed was the longest, most intense, and severe drought, in terms of precipitation, total water storage and reservoir water level observations over recent decades. New hydrological insights for the regionData analysis indicates that the 2019 drought indeed had the lowest basin-averaged annual rainfall, most severe local rainfall deficit in the north of the basin, and lowest reservoir level since 1995. However, the rainfall deficit was more severe in 2002, both basin-wide and locally in the south of the basin. The total storage deficit was more severe in 2004, both basin-wide and locally in the central part of the basin. However, as the available storage data did not cover the entire deficit for 2019, its final duration and severity remain unknown. Therefore, it depends on the drought characteristic, hydrological variable, and location within the basin, whether the 2019 drought was indeed the most extreme over recent decades.

Enhancing Flood Hazard Assessments in Coastal Louisiana Through Coupled Hydrologic and Surge Processes

Traditional coastal flood hazard studies do not typically account for rainfall-runoff processes in quantifying flood hazard and related cascading risks. This study addresses the potential impacts of antecedent rainfall-runoff, tropical cyclone (TC)-driven rainfall, and TC-driven surge on total water levels and its influence in delineating a coastal flood transition zone for two distinct coastal basins in southeastern Louisiana (Barataria and Lake Maurepas watersheds). Rainfall-runoff from antecedent and TC-driven rainfall along with storm surge was simulated using a new rain-on-mesh module incorporated into the ADCIRC code. Antecedent rainfall conditions were obtained for 21 landfalling TC events spanning 1948–2008 via rain stations. A parametric, TC-driven, rainfall model was used for precipitation associated with the TC. Twelve synthetic storms of varying meteorological intensity (low, medium, and high) and total rainfall were utilized for each watershed and provided model forcing for coastal inundation simulations. First, it was found that antecedent rainfall (pre-TC landfall) is influential up to 3 days pre-landfall. Second, results show that antecedent and TC-driven rainfall increase simulated peak water levels within each basin, with antecedent rainfall dominating inundation across the basin's upper portions. Third, the delineated flood zones of coastal, transition, and hydrologic show stark differences between the two basins.