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Sediment fingerprinting technology is widely used to differentiate sediment sources. However, despite its long-recognized benefits, there it has been seldom applied to assess the variability of sediment sources during storm events. In this study, sediment fingerprinting is used for four storm events to determine the dynamic changes in sediment sources throughout them in the black soil region in Northeast China. Three potential sediment sources—cultivated land, unpaved roads, and gullies—were effectively differentiated using four geochemical tracers (As, Be, Cs, and Cu), with an accuracy of 100%. The relative sediment contribution from each source was determined using linear and Bayesian mixing models. The mean absolute fit (MAF) values of the linear mixing model (MAFmean = 0.976–0.949) were higher than those of the Bayesian mixing model (MAFmean = 0.921–0.992), indicating that the first performed better. Cultivated land was the primary source of the sediment load, accounting for 59.03% of it (load-weighted mean = 68.29%), followed by the gullies (37.15%, load-weighted mean = 28.09%), and unpaved roads (3.90%, load-weighted mean = 3.69%) for the four storm events. In addition, a high variability in sediment source contribution was observed during the storm events. Cultivated land was the dominant sediment source during storm events with higher sediment concentrations (logarithmic function, r2 = 0.878, p

Study region: The Seohwa watershed, South Korea. Study focus: Agricultural practices and urbanization in watersheds increase nutrient loads (total nitrogen (TN), total phosphorus (TP), and nitrate-nitrogen (NO3--N)) in streams and deteriorate water quality. Between October 2017 and October 2018, water samples were collected from a small stream (MS), main tributary (TS), and sub-tributaries (ST) characterized by different land-use patterns. The objective of this study was to identify the sources that determine water quality in the respective streams and to estimate whether water quality was dependent on land-use patterns. New hydrological insights for the region: TN in MS progressively decreased downstream, whereas such spatial variation was not observed in TS and ST. For TP, TS and ST samples showed elevated concentrations during storm events, but not in MS. These observations resulted from TN and TP derived from natural and anthropogenic sources associated with land-use patterns. Interestingly, TN/TP ratios were strongly negatively correlated with the proportion of residential area (R2 = 0.92) rather than other land-use patterns such as agricultural area and forest. In addition, statistical analysis and dual isotopes of nitrate (NO3-) showed that the water quality in MS and the one in TS and ST were predominantly affected by natural sources and anthropogenic sources, respectively. Considering the effects of land-use patterns and rainfall on water quality, anthropogenic sources should be precisely identified to manage stream water in small watersheds more effectively.

Climate change is rapidly altering hydrological processes and consequently the structure and functioning of Arctic ecosystems. Predicting how these alterations will shape biogeochemical responses in rivers remains a major challenge. We measured [C]arbon and [N]itrogen concentrations continuously from two Arctic watersheds capturing a wide range of flow conditions to assess understudied event‐scale C and N concentration‐discharge (C‐Q) behavior and post‐event recovery of stoichiometric conditions. The watersheds represent low‐gradient, tundra landscapes typical of the eastern Brooks Range on the North Slope of Alaska and are part of the Arctic Long‐Term Ecological Research sites: the Kuparuk River and Oksrukuyik Creek. In both watersheds, we deployed high‐frequency optical sensors to measure dissolved organic carbon (DOC), nitrate (NO3− ${{\text{NO}}_{3}}^{-}$), and total dissolved nitrogen (TDN) for five consecutive thaw seasons (2017–2021). Our analyses revealed a lag in DOC:NO3− ${{\text{NO}}_{3}}^{-}$ stoichiometric recovery after a hydrologic perturbation: while DOC was consistently elevated after high flows, NO3− ${{\text{NO}}_{3}}^{-}$ diluted during rainfall events and consequently, recovery in post‐event concentration was delayed. Conversely, the co‐enrichment of TDN at high flows, even in watersheds with relatively high N‐demand, represents a potential "leak" of hydrologically available organic N to downstream ecosystems. Our use of high‐frequency, long‐term optical sensors provides an improved method to estimate carbon and nutrient budgets and stoichiometric recovery behavior across event and seasonal timescales, enabling new insights and conceptualizations of a changing Arctic, such as assessing ecosystem disturbance and recovery across multiple timescales. Plain Language Summary: The Arctic is one of the first regions to experience the impacts of climate change and is already experiencing rapid changes to the water cycle, seasonality, and permafrost state. These changes can be expressed in the chemistry observed in a river network, and ecosystem‐scale responses to change are integrated at a watershed outlet. With this study, we leveraged 5 years of high‐frequency data collected from two Arctic headwaters to observe how these watersheds respond to hydrologic disturbance. Overall, we found that at the event‐scale, Arctic rivers are responsive to precipitation events, where carbon (C) increases and reactive nitrogen (N) as nitrate (NO3− ${{\text{NO}}_{3}}^{-}$), is diluted in tandem when a storm event occurs. We also found that after the peak of the storm event, there is a difference in recovery rates for C and N that indicate storm events represent a hydrologic and biogeochemical disturbance. Overall, our findings are important for documenting hydrologic responses to a changing Arctic. Key Points: In both watersheds, we found consistent divergent responses of dissolved organic carbon (DOC) and nitrate to hydrologic disturbanceDOC:TDN responded convergently during storms, suggesting a large pool of hydrologically available organic matter in tundra landscapesThe use of high‐frequency optical sensor data provides an improved method to estimate carbon and nutrient behavior at the event timescale [ABSTRACT FROM AUTHOR]

Muddy sediments are the most prominent constituents of sedimentary successions in tide-dominated river deltas and have highly complex depositional mechanisms. In this study, we performed fine-grained (4–11 μm) quartz optically stimulated luminescence (OSL) dating on two sediment cores collected at a shipwreck site in the turbidity maximum zone (TMZ) of the modern Yangtze River mouth, China, which were compared with previously published dating results including 45–63 um quartz OSL dating, radionuclide dating, porcelain artifacts recovered from the wreck, macro-plastics, and the morphological history recorded in marine charts. We investigate the luminescence characteristics of muddy sediments trapped in the TMZ and discuss the implications of OSL ages in understanding depositional mechanisms in tide-dominated river mouths. The results indicate that most OSL ages of muddy sediments in the delta front setting are overestimated compared with other dating methods. We suggest that OSL age overestimation reflects the trapping of sediments from offshore in the TMZ imported by saltwater intrusions and storm events. The offshore inputs contain high percentages of residual luminescence and are also subjected to incomplete bleaching due to turbid water conditions and near-bed dispersal in the salt-wedge river mouth. We thus suggest that the reduced bleaching efficiency of muddy sediments in delta front settings needs to be accounted for in understanding sedimentary processes and distinguishing between different sedimentary facies in tide-dominated river mouths. Furthermore, we propose that differences in quartz OSL ages of fine- and medium-grained fractions may arise in response to extreme events.

Monitoring provides data and information necessary for water quality assessment, but often it is prohibitive, especially when frequent sampling is required. In this study, we explored feasible sampling intervals for improved efficiency of nonpoint source (NPS) pollution assessment. We compared NPS pollutant loads calculated with concentration samples collected at 1, 2, 3, 4, and 6-hour intervals for the first 24 hours of 13 storm events and investigated the effect of different sampling intervals on load estimation for three watersheds that have different land uses. When compared to load estimates made from concentrations sampled at the reference (1-hour) interval, differences in load estimates were less than 10% in the cases of the 2-hour and 3-hour intervals in the urbanized and agricultural watersheds, respectively, except in the case of suspended solids (SS). When it comes to the total load estimation, up to 3-hour interval sampling provided load estimates with acceptable accuracy, except for SS. Thus, the 3-hour sampling interval was considered feasible for long-term pollutant load assessment, while the 2-hour sampling interval was suggested for SS. Such findings are expected to facilitate NPS pollution assessment by providing information required to improve monitoring efficiency. HIGHLIGHTS The efficiency and accuracy of different water sampling intervals were assessed for improved feasibility of nonpoint source pollutant monitoring.; The sampling intervals of equal to or less than 3 hours could provide accurate and efficient pollutant load estimates in agricultural areas.; Urbanized areas required relatively frequent water sampling to satisfy the required accuracy.;

Dryland stream channels adjusting to urbanization are difficult to study without some indication of the extent and frequency of specific hydrological events. Investigations of changing channels in Fountain Hills, Arizona, urbanized since 1970, can benefit from knowledge gained from a storm event of over 55 mm rainfall in January 2016, equivalent to ~25% of annual precipitation. Morphological flow capacity was reached with this rainfall event, which had a recurrence interval of 1.4 years for a 24‐h period and 3.6 years for a 3‐day duration. This storm is typical of events that occur in less than half the years of record, occurring between zero and three times each year in the 26 years of record available. Analysis of this event assists in the calibration of measured cross‐sections, providing a useful benchmark for space‐time substitution in dryland environments where flow is ephemeral. Correspondence of the recurrence interval of the storm to somewhat frequent 'bankfull' channel‐forming events, despite signs of flashiness, suggests a tight coupling between rainfall and runoff and a tempered response to urbanization effects in Fountain Hills—achievable through decades of proactive planning and adaptive wash management in a master‐planned community. [ABSTRACT FROM AUTHOR]

Concentration–discharge (C‐Q) relationships are an effective tool for identifying watershed biogeochemical source and transport dynamics over short and long timescales. We examined stormflow C‐Q, hysteresis, and flushing patterns of total suspended sediment (TSS) and soluble reactive phosphorus (SRP) in two stream reaches of a severely impaired agricultural watershed in northeastern Wisconsin, USA. The upper watershed reach—draining a relatively flat, row crop‐dominated contributing area—showed predominantly anti‐clockwise TSS hysteresis during storms, suggesting that particulate materials were mobilized more from distal upland sources than near‐ and in‐channel areas. In contrast, the incised lower watershed reach produced strong TSS flushing responses on the rising limb of storm hydrographs and clockwise hysteresis, signalling rapid mobilization of near‐ and in‐channel materials with increasing event flows. C‐Q relationships for SRP showed complex patterns in both the upper and lower reaches, demonstrating largely non‐linear chemodynamic C‐Q behaviour during events. As with TSS, anti‐clockwise SRP hysteresis in the upper reach suggested a delay in the hydrologic connectivity between SRP sources and the stream, with highly variable SRP concentrations during some events. A broad range of clockwise, anti‐clockwise, and complex SRP hysteresis patterns occurred in the lower watershed, possibly influenced by in‐channel legacy P stores and connection to tile drainage networks in the lower watershed area. Total suspended sediment and SRP responses were also strongly related to precipitation event characteristics including antecedent precipitation, recovery period, and precipitation intensity, highlighting the complexity of stormflow sediment and phosphorus responses in this severely impaired agricultural stream. [ABSTRACT FROM AUTHOR]

Storm events can mobilize nitrogen species from landscapes into streams, exacerbating eutrophication and threatening aquatic ecosystems as well as human health. However, the transport pathways and storm responses of different nitrogen forms remain elusive. We used high-frequency chemical and isotopic sampling to partition sources of stormwater runoff and determine transport pathways of multiple nitrogen forms in an agricultural catchment. Bayesian mixing modeling reveals shallow subsurface water as the dominant source of stormwater runoff, contributing 74% of the water flux and 72, 71, and 79% of total nitrogen (TN), total dissolved nitrogen (TDN), and nitrate (NO 3 -N), respectively. Groundwater, by contrast, contributed 11% of stormwater runoff and 21, 22, and 17% of TN, TDN, and NO 3 -N, respectively. The remaining 14% of stormwater runoff can be attributed to rainwater, which contains much less TN, TDN, and NO 3 -N. Surprisingly, during storm events, the dominant nitrogen form was NO 3 -N rather than dissolved organic nitrogen. Antecedent conditions and runoff characteristics have an important influence on nitrogen loads during storm events. Our results provide insight into hydrological mechanisms driving nitrogen transport during storm events and may help in developing catchment management practices for reducing nitrogen pollution in aquatic ecosystems.

Low mode internal waves in the stratified ocean are partially generated by the wind field in the near‐inertial range and important for interior mixing and for the oceanic energy pathways. Long‐term observations of energy fluxes of internal waves are sparse. Here, we study the temporal variability of wind‐generated low mode near‐inertial internal waves inside an internal tide beam emanating from seamounts south of the Azores. We use 20 months of consecutive mooring observations to calculate the mode 1 and mode 2 near‐inertial energy flux as well as the near‐inertial kinetic and potential energy. The energy flux time series is not steady due to its intermittent forcing with modes 1 and 2 contributing in a similar way to the total. A peak in the energy flux time series that can be directly linked to a storm event allows us to split the time series into a background period and a storm event period. The relative contribution of mode 1 to mode 2 remains the same during a storm event and background period. This study provides new insights into the relative importance of single wind events for the near‐inertial energy flux and the opportunity to quantify the impact of an isolated strong wind event compared to a calm, tide‐dominated background state. Thus, an adequate representation of storm events in parameterizations used for mixing estimates by ocean general circulation models is needed, as they are potentially of similar importance as the internal tides. Plain Language Summary: Internal waves, which are dynamical perturbations of the background density and velocity fields propagating through the stratified ocean, can be generated among others, by the wind over the sea surface. These internal waves with a frequency close to the local Coriolis frequency are called near‐inertial internal waves. Understanding their generation dynamics is necessary to better understand their role for ocean mixing. In this study, we investigate 20 months of observations in a region south of the Azores Islands and are able to split the measured time series in a background and a wind event period. We find that single wind events are an important factor in generating energetic internal waves. This demonstrates the need for an adequate representation of these events in future ocean models. Key Points: A 20‐month mooring time series is used to determine the low mode near‐inertial internal wave energy flux and energy densityA peak in the energy flux is linked to hurricane Leslie, splitting the observations into a background and a storm event periodThe peak in the energy flux induced by a storm is equivalent to that of 150 days of background wind [ABSTRACT FROM AUTHOR]

Hydrological events transport large proportions of annual or seasonal dissolved organic carbon (DOC) loads from catchments to streams. The timing, magnitude and intensity of these events are very sensitive to changes in temperature and precipitation patterns, particularly across the boreal region where snowpacks are declining and summer droughts are increasing. It is important to understand how landscape characteristics modulate event‐scale DOC dynamics in order to scale up predictions from sites across regions, and to understand how climatic changes will influence DOC dynamics across the boreal forest. The goal of this study was to assess variability in DOC concentrations in boreal headwater streams across catchments with varying physiographic characteristics (e.g., size, proportion of wetland) during a range of hydrological events (e.g., spring snowmelt, summer/fall storm events). From 2016 to 2017, continuous discharge and sub‐daily chemistry grab samples were collected from three adjacent study catchments located at the International Institute for Sustainable Development‐Experimental Lakes Area in northwestern Ontario, Canada. Catchment differences were more apparent in summer and fall events and less apparent during early spring melt events. Hysteresis analysis suggested that DOC sources were proximal to the stream for all events at a catchment dominated by a large wetland near the outlet, but distal from the stream at the catchments that lacked significant wetland coverage during the summer and fall. Wetland coverage also influenced responses of DOC export to antecedent moisture; at the wetland‐dominated catchment, there were consistent negative relationships between DOC concentrations and antecedent moisture, while at the catchments without large wetlands, the relationships were positive or not significant. These results emphasize the utility of sub‐daily sampling for inferring catchment DOC transport processes, and the importance of considering catchment‐specific factors when predicting event‐scale DOC behaviour. [ABSTRACT FROM AUTHOR]

Storm events have a significant impact on coastal topography, which can subsequently lead to coastal erosion and ecological deterioration. Traditional field measurements are affected by environmental factors and consume substantial resources, making it difficult to conduct large-scale terrain, hydrodynamic and other monitoring tasks. Significant challenges still remain to identify the response of coastal processes to storm events due to the lack of field measured data. In this study, the response of coastal morphodynamical variations to extreme storm events was simulated by the coupled XBeach and FVCOM models and the storm-induced coastal evolution was evaluated in the China Yellow Sea. The costal morphodynamical variations under different wind conditions were also quantified. The results reveal that erosion dominated the supratidal zone while accretion mainly occurred in the subtidal zone. Comparing the coastal morphology before and after the storm, we found the alongshore currents were the primary factors influencing sediment transport. The degree of coastal erosion and accretion shift was positively correlated with the wind speed and direction. The present nested model may serve as a valuable tool for predicting future coastal erosion and accretion, contributing to more scientifically informed coastal management decisions. The study also provides a scientific basis for understanding the response mechanism of coastal morphodynamical process to extreme storm events and coastline evolution under global change. • Response of coastal morphodynamical variation to extratropical storm surges was simulated by a nested numerical XBeach and FVCOM models. • The alongshore currents induced by extratropical storm surges cause coastal erosion. • Coastal erosion occurs in the supratidal and intertidal zones, while accretion occurs in the subtidal zone during extratropical storm surges. [ABSTRACT FROM AUTHOR]

Seasonal turbidity patterns and event-level hysteresis analysis of turbidity verses discharge in four 1 km2 headwater catchments in California's Sierra Nevada indicate localized in-channel sediment sources and seasonal accumulation-depletion patterns of stream sediments. Turbidity signals were analyzed for three years in order to look at the relationships between seasonal turbidity trends, event turbidity patterns, and precipitation type to stream sediment production and transport. Seasonal patterns showed more turbidity events associated with fall and early to mid- winter events than with peak snow-melt. No significant turbidity patterns emerged for periods of snow melt vs. rain. Single event hysteresis loops showed clockwise patterns were dominant suggesting local sediment sources. In successive discharge events, the largest turbidity spike was often associated with the first but not necessarily the largest discharge event-indicating seasonal depletion of local sediment stores. In multi-peaked discharge events, hysteresis loops shifted from clockwise to linear or random patterns suggesting that localized sediment stores are being used up and sufficient flow energy must be reached to start entraining the more consolidated bank/bed sediment or that dominant sediment sources may be shifting to less localized areas such as hill slopes. A conceptual model with phases of accumulation and transport is proposed.

Storm events lead to agricultural and urban runoff, to mobilization of contaminated particulate matter, and to input from combined sewer overflows into rivers. We conducted time‐resolved sampling during a storm event at the Ammer River, southwest Germany, which is representative of small river systems in densely populated areas with a temperate climate. Suspended particulate matter (SPM) and water from 2 sampling sites were separately analyzed by a multi‐analyte liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for 97 environmentally relevant organic micropollutants and with 2 in vitro bioassays. Oxidative stress response (AREc32) may become activated by various stressors covering a broad range of physicochemical properties and induction of aryl hydrocarbon receptor–chemical‐activated luciferase gene expression (AhR‐CALUX) by hydrophobic compounds such as dioxins and dioxin‐like molecules. Compound numbers, concentrations, their mass fluxes, and associated effect fluxes increased substantially during the storm event. Micropollutants detected in water and on SPM pointed toward inputs from combined sewer overflow (e.g., caffeine, paracetamol), urban runoff (e.g., mecoprop, terbutryn), and agricultural areas (e.g., azoxystrobin, bentazone). Particle‐facilitated transport of triphenylphosphate and tris(1‐chloro‐2‐propyl) phosphate accounted for up to 34 and 33% of the total mass flux even though SPM concentrations were <1 g L–1. Effect fluxes attributed to SPM were similar or higher than in the water phase. The important role of SPM‐bound transport emphasizes the need to consider not only concentrations but also mass and effect fluxes for surface water quality assessment and wastewater/stormwater treatment options. Environ Toxicol Chem 2021;40:88–99. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

The project captured a subset of the hydrological cycle for the tropical island of O'ahu, linking precipitation to groundwater recharge and aquifer storage. We determined seasonal storm events contributed more to aquifer recharge than year‐round baseline orographic trade wind rainfall. Hydrogen and oxygen isotope values from an island‐wide rain collector network with 20 locations deployed for 16 months and sampled at 3‐month intervals were used to create the first local meteoric water line for O'ahu. Isotopic measurements were influenced by the amount effect, seasonality, storm type, and La Niña, though little elevation control was noted. Certain groundwater compositions from legacy data showed a strong similarity with collected precipitation from our stations. The majority of these significant relationships were between wet season precipitation and groundwater. A high number of moderate and heavy rainfall days during the dry season, large percentage of event‐based rainfall, and wind directions outside of the typical NE trade wind direction were characteristics of the 2017–2018 wet season. This indicates that the majority of wet season precipitation is from event‐based storms rather than typical trade wind weather. The deuterium‐excess values provided the strongest evidence of a relationship between groundwater and different precipitation sources, indicating that this may be a useful metric for determining the extent of recharge from different rain events and systems. [ABSTRACT FROM AUTHOR]

Coastal wetlands provided a favorable settling site for Neolithic people because of their highly exploitable biomass, but were vulnerable to marine hazards such as coastal flooding. The Chinese Hemudu culture persisted for ~2000 years (7200–5300 cal. year BP) in the Ningbo coastal lowland of East China. This study explores the Hemudu people's survival strategy using sedimentological and chronological records, and organic and acetic-acid-leachable alkaline-earth (Ca, Sr, and Ba) chemistry on a well-dated profile from the coastal Wuguishan site in the Ningbo Plain. Analyses of alkaline-earth elements in surficial sediments collected from present-day alluvial plain, tidal river, and saltmarsh/tidal flat environments in the Ningbo Plain were also undertaken to explain sedimentary environmental changes and their linkage to Hemudu activity at the Wuguishan site. Results indicate high sediment acetic-acid-leachable Ca and Sr contents with high Sr/Ba ratios, and high sediment total inorganic carbon contents at the site during 6300–6000 cal. year BP, which coincided with a marine incursion at the nearby Neolithic Yushan site. However, the increasing sediment total organic carbon contents and decreasing δ13C values suggest that the Wuguishan site evolved from an upper tidal flat to a saltmarsh environment, attracting settlement by the prehistoric Hemudu people after ~6200 cal. year BP. Sr and Ca contents and Sr/Ba ratios decreased after ~6000 cal. year BP, indicating that the site developed into a low-salinity marsh in the supratidal environment after rapid accumulation caused by a storm event at ~6020 cal. year BP. Furthermore, the high Sr and Ba contents in the layers of Hemudu Culture Period III indicate the Hemudu people's consumption of seafood and their adaption strategy for living in the vulnerable coastal wetland. [ABSTRACT FROM AUTHOR]

Sediment fingerprinting has been widely used to distinguish discrete sediment sources; however, application to intra‐storm sediment source variability has received relatively little focus despite the benefit being long recognized. In this investigation, sediment fingerprinting was applied to a 53‐hr storm event sampled hourly to determine sediment source dynamics throughout the event. Sediment sources were differentiated using 16 variables, and source contribution determined using Bayesian and Frequentist mixing models for comparison. Both models provided comparable source predictions for the dominant source estimates and the general temporal pattern. The Frequentist model appeared to exhibit some unreliable values coinciding with low GOF and attributed to inherent model structure. The Bayesian model showed higher uncertainty, likely due to the "process error" utilized associated with single sample mixtures. High variability in sediment source contribution was observed between hourly time steps; however, local smoothing reveals temporal trends during the event. A higher average proportion of mudstone is found in the falling limb (0.544) compared with the rising limb (0.464), and the reverse is observed for mountain range (0.218 vs. 0.283) and unconsolidated (0.073 vs. 0.055). In the initial hours of the storm, mudstone source contribution significantly drops, whereas mountain range and unconsolidated contributions peak. The SSC‐Q clockwise hysteresis indicates proximal sediment sources, suggesting the mudstone sediment is stored channel sediment and easily entrained. This sediment flushes through, coinciding with a drop as the distal mountain range and unconsolidated sources arrive to peak contribution. The wider Manawatū discharge and sediment load then arrive, delivering increasing levels of mudstone throughout the remainder of the event while mountain range sediment diminishes. Spatial representation of the sediment source contribution was derived from distributing sediment source loads to the spatial extent of the source material according to sub‐catchment sediment loads and was weighted according to slope. This provided an effective means to visualize the origin of the sediment and a better spatial interpretation of sediment fingerprinting results, which is typically limited by poor spatial resolution. [ABSTRACT FROM AUTHOR]

Extreme weather events, such as hurricanes, can cause ecological disturbances that alter energy and nutrients across terrestrial-aquatic boundaries. Yet, relatively few studies have considered the impacts of extreme weather events on biogeochemical dynamics in watersheds at larger spatial scales. Here, we assessed the effects of Hurricanes Harvey and Irma on the export of dissolved organic matter (DOM) and nutrients in ten watersheds from five southeastern states of the United States. We quantified the magnitude of dissolved organic carbon (DOC) and nutrients exported during the storms and assessed the changes in DOM sources and bioreactivity after storms. Our results show that the storm-mobilized DOC and nutrients fluxes were primarily driven by water discharge. The proportions of terrestrial, humic-like DOM compounds increased, and percent autochthonous, protein-like DOM decreased during high flows. Percent bioreactive DOC decreased with increasing discharge. Bioreactivity increased with increasing nitrate concentration, but decreased as percent terrestrial humic-like DOM, aromaticity, and molecular weight increased. These observations suggest that storms may have shifted flow paths to shallower depths that promoted the addition of biorefractory organic matter from topsoils into the water column. Notably, the total flux of bioreactive DOC was at least nearly twice as high at peak discharge, indicating materials transported by large storm flows could strongly enhance microbial activity in streams, although the position of storm-mediated microbial hotspots would depend on the flow rate and other instream parameters. Additionally, compared to forest-dominated watersheds, urban watersheds exported high loads of nutrients and bioreactive DOC, and a wetland-dominated watershed had a prolonged, but relatively subdued export of DOC and nutrients. Together, our findings highlight the ecological significance of extreme weather and climate events in leading to rapid, large-magnitude changes in energy and nutrient availability within drainage networks, and the potential interactions between land use and climate change on watershed biogeochemistry. Unlabelled Image • Hurricane-mediated solute transport was assessed in streams in the Southeast U.S. • Proportion and flux of soil-derived, humic, biorefractory DOM increased. • Percentages of bioreactive DOC decreased but the total flux increased at high flows. • Urban watersheds simultaneously exported bioreactive DOC and inorganic nutrients. • Wetland acted as a buffer for rapid hydrological and chemical disturbances. [ABSTRACT FROM AUTHOR]

This study investigates the capacity of a Spartina alterniflora meadow to attenuate waves during storm events based on field observations in the Chesapeake Bay. These observations reveal that environmental conditions including the ratio between water depth and plant height (hr), the ratio between wave height (HS) and water depth, and current directions impact the wave height decay. Further, we present empirical representations of the bulk drag coefficient (Cd) as a function of the Keulegan‐Carpenter (KC) and Reynolds (Re) numbers, and the hr ratio. When applying the distinction between current directions, this representation exhibits better agreement when using the Re (ρ2 = 54%) and hr (ρ2 = 77%) than with the KC (ρ2 = 39%). Furthermore, we show that the representation of Cd can be improved by using a hr‐based modified Re and KC formulation, yielding correlations of 76% (modified Re) and 78% (modified KC). The proposed expressions are validated during another storm and predicted HS computed within the marsh results in a root‐mean‐square error of 0.014 m, overestimating the largest HS (0.22 m) by 18%. Finally, these expressions are applied to several hypothetical sea conditions. Under similar vegetation characteristics, HS of 1.55 and 0.8 m (close to a 10,000‐ and 100‐year recurrence interval storm) are attenuated by 50% and 70%, respectively, at 250 m from the marsh edge. This study provides evidence that validates the saltmarsh wave attenuation capacity during storms, quantifies this attenuation, and supports the transferability of the existing formulas in the literature across similar coastal marshes. Key Points: Field observations confirm previous wave‐vegetation interaction studies and support the existing theoretical models for wave propagationMendez and Losada's formulation satisfactorily predicts wave attenuation by vegetation under tidal currents up to at least 0.2 m/sNew field‐based formulations demonstrate that 100‐year recurrence interval waves are attenuated by 70% at 250 m from the marsh edge [ABSTRACT FROM AUTHOR]

Coastal zones are permanently under stress by storms, cliff breaks, waves and currents. These events can cause the retreat of the coastline and are currently compensated by beach nourishments. The commonality of these sediment eroding and accumulating processes are turbidity plumes created in coastal waters, increasing the resuspension of particles and possibly nutrient concentrations. To compare sand nourishments and storm events, total suspended solids (TSS) and nutrient measurements were performed during winter season at the German Baltic Sea Coast. A pre-experiment showed that the TSS was homogenous through the water column. There were significant differences between both events, with sand nourishments exceeding the TSS of storms with the factor two. Due to the nourishment mechanism, the relative organic content was lower than during storm events. The nutrient uptake was unsteady. Therefore, sand nourishment can be considered to have more influence on the ecology of sand shores than storm events. • Total suspended solid concentrations are homogenous during sand nourishments. • The turbidity during sand nourishments is almost twice as high as during storms. • Storms cause higher relative content of suspended organic solids than nourishments. • Nutrient influx during nourishments is dependent on the nourishment mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Concentration–discharge (C‐Q) relationships reflect material sources, storage, reaction, proximity, and transport in catchments. Differences in hydrologic pathways and connectivity influence observed C‐Q patterns at the catchment outlet. We examined solute and sediment C‐Q relationships at event and interannual timescales in a small mid‐Atlantic (USA) catchment. We found systematic differences in the C‐Q behaviour of geogenic/exogenous solutes (e.g., calcium and nitrate), biologically associated solutes (e.g., dissolved organic carbon), and particulate materials (e.g., total suspended solids). Negative log(C)–log(Q) regression slopes, indicating dilution, were common for geogenic solutes whereas positive slopes, indicating concentration increase, were common for biologically associated solutes. Biologically associated solutes often exhibited counterclockwise hysteresis during events whereas geogenic solutes exhibited clockwise hysteresis. Across event and interannual timescales, solute C‐Q patterns are linked to the spatial distribution of hydrologic sources and the timing and sequence of hydro‐biogeochemical source contributions to the stream. Groundwater is the primary source of stormflow during the earliest and latest stages of events, whereas precipitation and soil water become increasingly connected to the stream near peakflow. This sequence and timing of flowpath connectivity results in dilution and clockwise hysteresis for geogenic/exogenous solutes and concentration increase and counterclockwise hysteresis for biologically associated solutes. Particulate materials demonstrated positive C‐Q slopes over the long‐term and clockwise hysteresis during individual events. Drivers of particulate and solute C‐Q relationships differ, based on longitudinal and lateral expansion of active channels and changing shear stresses with increasing flows. Although important distinctions exist between the drivers of solute and sediment C‐Q relationships, overall solute and sediment C‐Q patterns at event and interannual timescales reflect consistent catchment hydro‐biogeochemical processes. [ABSTRACT FROM AUTHOR]

The current FORTRAN code of SWAT (SWAT2012) is being rebuilt to ease new model and module development by incorporating object-oriented programming techniques into defining spatial objects and calculating variables. SWAT+, the new SWAT code, is expected to offer flexible watershed representation with linked spatial objects. Ideally, SWAT+ produces outputs that are comparable to SWAT2012, if not identical, when the two versions of SWAT are set with the same input for a watershed. However, the drastic restructuring of the source code may cause unexpected results in the output, especially when compared with the current SWAT2012 model that has a long history of model validation. In this technical note, we compare sub-daily, daily, and monthly hydrographs provided by SWAT2012 and SWAT+ that were prepared for a small urban watershed in Austin, Texas. The model parameters were calibrated to 15 min and daily runoff observed in the watershed. SWAT+ was on par with SWAT2012 in predicting streamflow at daily and monthly scales. However, the HRU-level flow routing scheme newly added to SWAT+ created multiple peaks in the sub-daily hydrographs, suggesting a need to further improve the water transport simulation strategies. This technical note provides ideas of how SWAT+ is organized and if a SWAT modeler can maintain consistency in modeling results when shifting from the original code to the new code. In addition, this technical note discusses the potential for improved SWAT+ modeling. [ABSTRACT FROM AUTHOR]

ABSTRACT Ji, Z.Z.; You, Z.J.; Hou, Z.Q., and Wei, Y., 2018. Development of generalized model for estimation of sediment siltation in coastal waterways of China. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1221–1225. Coconut Creek (Florida), ISSN 0749-0208. Coastal sediment siltation has long been a major problem for design and construction of coastal large-scale ports in the world. Silty sediment siltation often occurs in coastal waterways of China especially during storm events, in which silty sediment is stirred up from the seabed and re-suspended into the water column by storm-induced waves, and transported into the waterways by currents in three forms of suspended load, bedload and sheet-flow load. This study is to derive a generalized model for estimation of sediment siltation rates under both non-storm and storm conditions based on 6-year field data collected in the outer navigation channel of Huanghua Harbor. The sediment siltation data were collected by directly measuring the seabed elevation changes along the port navigation channel from 2002 to 2007. In analyzing the field data collected, a semi-empirical model between effective wind energy and sediment siltation rate is also presented, and found that the newly derived model yields satisfactory agreement with the siltation data collected during the coastal storm events. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) is an important component in the biogeochemistry and ecosystem function of aquatic environments at the highly populated land-ocean interface. The mobilization and transformation of DOM at this critical interface are increasingly affected by a series of notable global changes such as the increasing storm events, intense human activities, and accelerating glacier loss. This review provides an overview of the changes in the quantity and quality of DOM under the influences of multiple global changes. The profound implications of changing DOM for aquatic ecosystem and human society are further discussed, and future research needs are suggested for filling current knowledge gaps. The fluvial export of DOM is strongly intensified during storm events, which is accompanied with notable changes in the chemical composition and reactivity of DOM. Land use not only changes the mobilization of natural DOM source pools within watersheds but also adds DOM of distinct chemical composition and reactivity from anthropogenic sources. Glacier loss brings highly biolabile DOM to downstream water bodies. The changing DOM leads to significant changes in heterotrophic activity, CO2 out gassing, nutrient and pollutant biogeochemistry, and disinfection by-product formation. Further studies on the source, transformations, and downstream effects of storm DOM, temporal variations of DOM and its interactions with other pollutants in human-modified watersheds, photo-degradability of glacier DOM, and potential priming effects, are essential for better understanding the responses and feedbacks of DOM at the land-ocean interface under the impacts of global changes. [ABSTRACT FROM AUTHOR]

Seasonal turbidity patterns and event-level hysteresis analysis of turbidity verses discharge in four 1 km2 headwater catchments in California’s Sierra Nevada indicate localized in-channel sediment sources and seasonal accumulation-depletion patterns of stream sediments. Turbidity signals were analyzed for three years in order to look at the relationships between seasonal turbidity trends, event turbidity patterns, and precipitation type to stream sediment production and transport. Seasonal patterns showed more turbidity events associated with fall and early to mid- winter events than with peak snow-melt. No significant turbidity patterns emerged for periods of snow melt vs. rain. Single event hysteresis loops showed clockwise patterns were dominant suggesting local sediment sources. In successive discharge events, the largest turbidity spike was often associated with the first but not necessarily the largest discharge event-indicating seasonal depletion of local sediment stores. In multi-peaked discharge events, hysteresis loops shifted from clockwise to linear or random patterns suggesting that localized sediment stores are being used up and sufficient flow energy must be reached to start entraining the more consolidated bank/bed sediment or that dominant sediment sources may be shifting to less localized areas such as hill slopes. A conceptual model with phases of accumulation and transport is proposed.

The monitoring, modeling, and prediction of storm events and accompanying heavy rain is crucial for intensively used agricultural landscapes and its settlements and transport infrastructure. In Saxony, Germany, repeated and numerous storm events triggered muddy floods from arable fields in May 2016. They caused severe devastation to settlements and transport infrastructure. This interdisciplinary approach investigates three muddy floods, which developed on silty soils of loess origin tending to soil surface sealing. To achieve this, the study focuses on the test of a historical forecast modeling of three muddy floods in ungauged agricultural landscapes. Therefore, this approach firstly illustrates the reconstruction of the muddy floods, which was performed by high-resolution radar precipitation data, physically-based erosion modeling, and the qualitative validation by unmanned aerial vehicle-based orthophotos. Subsequently, historical radar precipitation forecasts served as input data for the physically-based erosion model to test the forecast modeling retrospectively. The model results indicate a possible warning for two of the three muddy floods. This method of a historical forecast modeling of muddy floods seems particularly promising. Naturally, the data series of three muddy floods should be extended to more reliable data and statistical statements. Finally, this approach assesses the feasibility of a real-time muddy flood early warning system in ungauged agricultural landscapes by high-resolution radar precipitation forecasts and physically-based erosion modeling.

The River Bandon located in County Cork (Ireland) has been time-continuously monitored by turbidity probes, as well as automatic and manual suspended sediment sampling. The current work evaluates three different models used to estimate the fine sediment concentration during storm-based events over a period of one year. The modeled suspended sediment concentration is compared with that measured at an event scale. Uncertainty indices are calculated and compared with those presented in the bibliography. An empirically-based model was used as a reference, as this model has been previously applied to evaluate sediment behavior over the same time period in the River Bandon. Three other models have been applied to the gathered data. First is an empirically-based storm events model, based on an exponential function for calculation of the sediment output from the bed. A statistically-based approach first developed for sewers was also evaluated. The third model evaluated was a shear stress erosion-based model based on one parameter. The importance of considering the fine sediment volume stored in the bed and its consolidation to predict the suspended sediment concentration during storm events is clearly evident. Taking into account dry weather periods and the bed erosion in previous events, knowledge on the eroded volume for each storm event is necessary to adjust the parameters for each model.

Among different Water Sensitive Urban Design options, constructed wetlands (CWs) are used to protect and restore downstream water quality by attenuating nutrients generated by stormwater runoff. This research compared the nutrient attenuation ability during a diverse population of storm events of two CWs: (a) a hybrid CW with multiple alternating surface flow (SF) and laterite-based subsurface flow (SSF) compartments, and (b) a single stage SF CW. Within-storm variability, nutrient concentrations were assessed at 2 to 3-h intervals at both the main inlet and outlet of each CW. Dissolved oxygen concentrations of the surface waters were also monitored at 10-min intervals using high frequency in situ sensors. Nutrient loads into the CWs were observed to be higher when a high rainfall event occurred, particularly after longer antecedent dry conditions. Longer hydraulic retention times promoted higher attenuation at both sites. However, the relative extent of nutrient attenuation differed between the CW types; the mean total nitrogen (TN) attenuation in the hybrid and SF CW was 45 and 48%, respectively. The hybrid CW attenuated 67% total phosphorus (TP) loads on average, while the SF CW acted as a net TP source. Periodic storm events transitioned the lentic CW into a lotic CW and caused riparian zone saturation; it was therefore hypothesized that such saturation of organic matter rich-riparian zones led to release of TP in the system. The hybrid CW attenuated the released TP in the downstream laterite-based SSF compartments. Diel oxygen metabolism calculated before and after the storm events was found to be strongly correlated with water temperature, solar exposure and antecedent dry condition during the pre-storm conditions. Furthermore, the SF CW showed a significant relationship between overall nutrient load attenuation and the change in oxygen metabolism during the storm perturbation, suggesting oxygen variation could be a useful proxy indicator of CW function. [ABSTRACT FROM AUTHOR]

The main objective of this work is to provide researchers with a fast methodology of analysis capable to assess water quality in an urban river catchment during extreme rainfall events without previous elemental quantification. The analytical methodology combines measurement with portable laser-induced breakdown spectroscopy (LIBS) and direct chemometric treatment of the LIBS spectra. With this aim, suspended particular matter (SPM) samples were collected during five storm events, every 2 h with an automatic water sampler in three control points (gauging stations) of an urban river (Deba River, Basque Country, Spain). SPM samples were analyzed in situ by a handheld laser induced breakdown spectrometry (HH-LIBS), and the complete LIBS spectra were statistically analyzed by Principal Component Analysis (PCA) after outlier identification by k-nearest neighbors (kNN). The PCA results showed differentiation between monitored localizations and the period when the storm event occurred. It was also possible to identify important discriminant variables, some of them corresponding to hazardous elements such as Pb, Cr, Ni, and Cu. Basing on the correlation between variables, it was possible to identify their sources (urban/municipal contamination, anthropogenic activities, etc.). Moreover, thanks to this methodology, it was possible to predict the mobilization of hazardous elements at the end of a storm event and determine the environmental risk assessment in an urban river. [ABSTRACT FROM AUTHOR]

Antibiotic resistance presents a critical public health challenge and the transmission of antibiotic resistance via environmental pathways continues to gain attention. Factors driving the spread of antibiotic resistance genes (ARGs) in surface water and sources of ARGs in urban stormwater have not been well-characterized. In this study, five ARGs ( sul 1, sul 2, tet (O), tet (W), and erm (F)) were quantified throughout the duration of three storm runoff events in an urban inland stream. Storm loads of all five ARGs were significantly greater than during equivalent background periods. Neither fecal indicator bacteria measured ( E. coli or enterococci) was significantly correlated with sul 1, sul 2, or erm (F), regardless of whether ARG concentration was absolute or normalized to 16S rRNA levels. Both E. coli and enterococci were correlated with the tetracycline resistance genes, tet (O) and tet (W). Next-generation shotgun metagenomic sequencing was conducted to more thoroughly characterize the resistome (i.e., full complement of ARGs) and profile the occurrence of all ARGs described in current databases in storm runoff in order to inform future watershed monitoring and management. Between 37 and 121 different ARGs were detected in each stream sample, though the ARG profiles differed among storms. This study establishes that storm-driven transport of ARGs comprises a considerable fraction of overall downstream loadings and broadly characterizes the urban stormwater resistome to identify potential marker ARGs indicative of impact. [ABSTRACT FROM AUTHOR]

Organic compounds are removed from the atmosphere and deposited to the Earth's surface via precipitation. In this study, we quantified variations of dissolved organic carbon (DOC) in precipitation during storm events at the Shale Hills Critical Zone Observatory, a forested watershed in central Pennsylvania (USA). Precipitation samples were collected consecutively throughout the storm during 13 events, which spanned a range of seasons and synoptic meteorological conditions, including a hurricane. Further, we explored factors that affect the temporal variability by considering relationships of DOC in precipitation with atmospheric and storm characteristics. Concentrations and chemical composition of DOC changed considerably during storms, with the magnitude of change within individual events being comparable or higher than the range of variation in average event composition among events. Although some previous studies observed that concentrations of other elements in precipitation typically decrease over the course of individual storm events, results of this study show that DOC concentrations in precipitation are highly variable. During most storm events, concentrations decreased over time, possibly as a result of washing out of the below-cloud atmosphere. However, increasing concentrations that were observed in the later stages of some storm events highlight that DOC removal with precipitation is not merely a dilution response. Increases in DOC during events could result from advection of air masses, local emissions during breaks in precipitation, or chemical transformations in the atmosphere that enhance solubility of organic carbon compounds. This work advances understanding of processes occurring during storms that are relevant to studies of atmospheric chemistry, carbon cycling, and ecosystem responses. [ABSTRACT FROM AUTHOR]

Fine particles (1-100 µm), including particulate organic carbon (POC) and fine sediment, influence stream ecological functioning because they may contain or have a high affinity to sorb nitrogen and phosphorus. These particles are immobilized within stream storage areas, especially hyporheic sediments and benthic biofilms. However, fine particles are also known to remobilize under all flow conditions. This combination of downstream transport and transient retention, influenced by stream geomorphology, controls the distribution of residence times over which fine particles influence stream ecosystems. The main objective of this study was to quantify immobilization and remobilization rates of fine particles in a third-order sand-and-gravel bed stream (Difficult Run, Virginia, USA) within different geomorphic units of the stream (i.e., pool, lateral cavity, and thalweg). During our field injection experiment, a thunderstorm-driven spate allowed us to observe fine particle dynamics during both base flow and in response to increased flow. Solute and fine particles were measured within stream surface waters, pore waters, sediment cores, and biofilms on cobbles. Measurements were taken at four different subsurface locations with varying geomorphology and at multiple depths. Approximately 68% of injected fine particles were retained during base flow until the onset of the spate. Retention was evident even after the spate, with 15.4% of the fine particles deposited during base flow still retained within benthic biofilms on cobbles and 14.9% within hyporheic sediment after the spate. Thus, through the combination of short-term remobilization and long-term retention, fine particles can serve as sources of carbon and nutrients to downstream ecosystems over a range of time scales. [ABSTRACT FROM AUTHOR]