Individual Storms Research Articles

Validating city-scale surface water flood modelling using crowd-sourced data

Surface water and surface water related flood modelling at the city-scale is challenging due to a range of factors including the availability of subsurface data and difficulty in deriving runoff inputs and surcharge for individual storm sewer inlets. Most of the research undertaken so far has been focusing on local-scale predictions of sewer surcharge induced surface flooding, using a 1D/1D or 1D/2D coupled storm sewer and surface flow model. In this study, we describe the application of an urban hydro-inundation model (FloodMap-HydroInundation2D) to simulate surface water related flooding arising from extreme precipitation at the city-scale. This approach was applied to model an extreme storm event that occurred on 12 August 2011 in the city of Shanghai, China, and the model predictions were compared with a ‘crowd-sourced’ dataset of flood incidents. The results suggest that the model is able to capture the broad patterns of inundated areas at the city-scale. Temporal evaluation also demonstrates a good level of agreement between the reported and predicted flood timing. Due to the mild terrain of the city, the worst-hit areas are predicted to be topographic lows. The spatio-temporal accuracy of the precipitation and micro-topography are the two critical factors that affect the prediction accuracies. Future studies could be directed towards making more accurate and robust predictions of water depth and velocity using higher quality topographic, precipitation and drainage capacity information.

Pebble and cobble transport on a steep, mega-tidal, mixed sand and gravel beach

Natural tracer pebbles and cobbles were deployed on a steep (slope: 0.1) mixed sand and gravel mega-tidal beach located at the head of the Bay of Fundy. Two experiments were carried out to investigate the response of natural pebble- and cobble-sized material, both to energetic wave conditions during individual storm events, and to tidal-only forcing conditions between storms. Net displacement of different tracer sizes was the focus of the first experiment, while the effect of different shapes was tested in the second. The pebbles and cobbles were painted in fluorescent colors, labeled, and their positions measured at low tide over periods of 10–12days. The tracers were emplaced at mid-tide level on the beach face at low water, and later recovered and re-deployed on successive low tides. Net travel distance and direction were measured upon recovery. Hydrodynamic forcing conditions and local morphology at mid-tide level on the beach face were monitored continuously during the experiments. In the first experiment, recovery rates were 100% during calm and moderate wave conditions (Hs≤ 0.5m), but decreased significantly in more energetic wave forcing (Hs up to 1m). Recovery rates were lower for smaller tracers. During a three day wind-wave event, net displacements of up to 48m were measured. Comparable net displacements were observed for all tracers. Maximum displacements were 39m onshore, 42m offshore, and 46m alongshore. In calm conditions, maximum displacements were less than 1m, indicating that the bottom stresses due to tidal currents alone are too low to cause significant tracer displacement on time scales of weeks, despite the high tidal range. In the second experiment, recovery rates were lower, due to more energetic wave forcing: significant wave heights reached Hs >0.5m on 80% of the particle tracking days and Hs >1m on 30% of the days. Flat pebbles and cobbles reached the longest transport distances, with a maximum net displacement of 98m. The flat tracers were observed to be flipped by the shore break and to “ride” the swash bore, and were in this manner transported long distances, shoreward up to 66m. In both experiments, the directions of alongshore displacements were consistent with deviations of the angle of wave incidence from the shorenormal. Tracer burial and re-exposure was observed – via rotary imaging sonar – with the evolution and migration of m-wavelength ripples. The study allowed a direct correlation of pebble and cobble tracer displacements to hydrodynamic forcing during individual storm events, with consideration of tracer particle size, and shape.

Temporal and Spatial Dynamics of Estuarine Shoreline Change in the Albemarle-Pamlico Estuarine System, North Carolina, USA

Many shoreline studies rely on historical change rates determined from aerial imagery decades to over 50 years apart to predict shoreline position and determine setback distances for coastal structures. These studies may not illustrate the coastal impacts of short-duration but potentially high-impact storm events. In this study, shoreline change rates (SCRs) are quantified at five different sites ranging from marsh to sediment bank shorelines around the Albemarle-Pamlico estuarine system (APES) for a series of historical (decadal to 50-year) and short-term (bimonthly) time periods as well as for individual storm events. Long-term (historical) SCRs of approximately −0.5 ± 0.07 m year−1 are observed, consistent with previous work along estuarine shorelines in North Carolina. Short-term SCRs are highly variable, both spatially and temporally, and ranged from 15.8 ± 7.5 to −19.3 ± 11.5 m year−1 at one of the study sites. The influence of wave climate on the spatial and temporal variability of short-term erosion rates is investigated using meteorological observations and coupled hydrodynamic (Delft3D) and wave (SWAN) models. The models are applied to simulate hourly variability in the surface waves and water levels. The results indicate that in the fetch-limited APES, wind direction strongly influences the wave climate at the study sites. The wave height also has an influence on short-term SCRs as determined from the wave simulations for individual meteorological events, but no statistical correlation is found for wave height and SCRs over the long term. Despite the significantly higher rates of shoreline erosion over short time periods and from individual events like hurricanes, the cumulative impact over long time periods is low. Therefore, while the short-term response of these shorelines to episodic forcing should be taken into account in management plans, the long-term trends commonly used in ocean shoreline management can also be used to determine erosion setbacks on estuarine shorelines.

Modeling soil loss at plot scale with EUROSEM and RUSLE2 at stony soils of Khamesan watershed, Iran

The present study was carried out to evaluate the EUROSEM and RUSLE2 models for predicting soil loss on stony steep lands in Khamesan watershed using single event data obtained from natural rainfall. For this purpose, eighteen plots of 24m long by 1.8m wide were used to measure runoff and soil loss on six rangeland hillslopes (3 replicates) over three years. Twenty-four rainfall events occurred during the study period. The input data were continuously monitored for both models including rainfall, surface runoff, soil loss and soil properties. Sensitivity analysis and calibration results showed that saturated hydraulic conductivity had a large effect on EUROSEM simulation results, especially on runoff estimation. Validation of EUROSEM model showed that this model is applicable for predicting both runoff and soil loss for studied hillslopes (R2=0.7, R2=0.85, respectively). Efficiency tests indicated that the EUROSEM model outputs were affected by rock fragment cover in the study area. RUSLE2 model was able to predict soil loss in individual storms somewhat well (R2=0.53), but under the higher EI30 index, the over or under-prediction was higher. Including direct consideration of runoff in the event rainfall–runoff factor (average annual KUM associated with the QREI30 index) increased RUSLE2 efficiency in estimating event soil loss (R2=0.69). Calibration of the K-factor in RUSLE2 led to considerable improvement of model efficiency (R2=0.82). Comparison of the two models showed that EUROSEM revealed better model efficiency in estimation of event soil loss than calibrated RUSLE2, although in some hillslopes, performance of calibrated RUSLE2 model was more than EUROSEM model. With respect to spatially non-uniform canopy cover and ground cover as well as the stoniness of soils and direct and indirect impacts of surface and subsurface rock fragments on runoff and sediment yield, also existence of lime at low to high levels in the study area, more research is needed to examine the effect of these parameters on input and output of the models, especially for the RUSLE2. In addition to characteristics of studied hillslopes, it seems that storm pattern had a significant effect on estimations of two models. The results showed that effects of intra-storm variations in rainfall intensity on runoff and soil loss production have not been sufficiently considered in equations of two models, especially RUSLE2 model.

Comparing hurricane and extratropical storm surge for the Mid-Atlantic and Northeast Coast of the United States for 1979–2013

This letter examines the magnitude, spatial footprint, and paths of hurricanes and extratropical cyclones (ETCs) that caused strong surge along the east coast of the US between 1979 and 2013. Lagrangian cyclone track information, for hurricanes and ETCs, is used to associate surge events with individual storms. First, hurricane influence is examined using ranked surged events per site. The fraction of hurricanes among storms associated with surge decreases from 20%–60% for the top 10 events to 10%–30% for the top 50 events, and a clear latitudinal gradient of hurricane influence emerges for larger sets of events. Secondly, surges on larger spatial domains are examined by focusing on storms that cause exceedance of the probabilistic 1-year surge return level at multiple stations. Results show that if the strongest events in terms of surge amplitude and spatial extent are considered, then hurricanes are most likely to create the hazards. However, when slightly less strong events that still impact multiple areas during the storm life cycle are considered, the relative importance of hurricanes shrinks as that of ETCs grows. Furthermore we find distinct paths for ETCs causing multi-site surge at individual segments of the US east coast.

The Influence of the Annual Number of Storms on the Derivation of the Flood Frequency Curve through Event-Based Simulation

This study addresses the question of how to select the minimum set of storms that should be simulated each year in order to estimate an accurate flood frequency curve for return periods ranging between 1 and 1000 years. The Manzanares basin (Spain) was used as a study case. A continuous 100,000-year hourly rainfall series was generated using the stochastic spatial–temporal model RanSimV3. Individual storms were extracted from the series by applying the exponential method. For each year, the extracted storms were transformed into hydrographs by applying an hourly time-step semi-distributed event-based rainfall–runoff model, and the maximum peak flow per year was determined to generate the reference flood frequency curve. Then, different flood frequency curves were obtained considering the N storms with maximum rainfall depth per year, with 1 ≤ N ≤ total number of storms. Main results show that: (a) the degree of alignment between the calculated flood frequency curves and the reference flood frequency curve depends on the return period considered, increasing the accuracy for higher return periods; (b) for the analyzed case studies, the flood frequency curve for medium and high return period (50 ≤ return period ≤ 1000 years) can be estimated with a difference lower than 3% (compared to the reference flood frequency curve) by considering the three storms with the maximum total rainfall depth each year; (c) when considering only the greatest storm of the year, for return periods higher than 10 years, the difference for the estimation of the flood frequency curve is lower than 10%; and (d) when considering the three greatest storms each year, for return periods higher than 100 years, the probability of achieving simultaneously a hydrograph with the annual maximum peak flow and the maximum volume is 94%.

Stream turbidity responses to storm events in a pristine rainforest watershed on the Coral Coast of southern Fiji

On the Coral Coast of Viti Levu Island in Fiji, inadequate knowledge of suspended sediment delivery patterns in small pristine coastal watersheds hinders any future assessment of accelerated erosion in disturbed areas nearby. This study adopts a rainfall–stream turbidity monitoring approach in the Votua Creek, which drains a small, steep but minimally-disturbed coastal rainforest catchment. Storm rainfall characteristics, stream depth and water turbidity were continuously monitored over one complete Fiji wet season from October 2009 to April 2010. The aim was to evaluate whether these parameters provide sufficient information to illustrate basic features of storm–sediment transport responses, in the case of limited stream gauging and very simple sediment rating curves. This is important because Pacific Island nations like Fiji do not have the resources to initiate long-term gauging and sediment sampling programmes across numerous small catchments.A significant power function demonstrates that turbidity (T) is a suitable proxy for total suspended solids (TSS) for turbidity measurements above 5 NTU, with TSS=0.930T1.111 (r=0.98, P<0.001). Over the study period, 10 individual storms 11.2–120.1mm in size produced a ‘significant turbidity response’ (STR) in the Votua Creek. Rainfall parameters (totals and intensities) showed positive linear relationships (r=0.72–0.94) with stream turbidity parameters (mean, maximum, duration), whilst relationships of similar strength (r=0.76–0.98) were also derived between stream flow depth and turbidity. This implies that for small rainforest watersheds in Fiji, rainfall parameters offer no substantial disadvantage over flow as predictors of stream sediment responses to major storms. Event-based analysis revealed that negative (anticlockwise) hysteresis is a typical flow–turbidity pattern for STR events. Negative hysteresis is produced when secondary episodes of renewed (heavy) rainfall occur after maximum intensity, in the later phase of storm events. Tropical Cyclone Mick in December 2009 generated the largest flood and the greatest turbidity response (Tmax=1021 NTU, Tmean=207 NTU). This concurs with earlier work confirming that tropical cyclones are the most important events for sediment transport in Fiji stream networks.

Smarter Stormwater Systems.

Existing stormwater systems require significant investments to meet challenges imposed by climate change, rapid urbanization, and evolving regulations. There is an unprecedented opportunity to improve urban water quality by equipping stormwater systems with low-cost sensors and controllers. This will transform their operation from static to adaptive, permitting them to be instantly "redesigned" to respond to individual storms and evolving land uses.

Examining runoff generation processes in the Selke catchment in central Germany: Insights from data and semi-distributed numerical model

Abstract Study region Our study is focussed on a mesoscale catchment, Selke, in central Germany having an area of 463 km 2 with spatially diverse land-use from upland to the low-lying areas in the vicinity of the catchment outlet. Study focus This study used rainfall-runoff data available on daily time step to examine the spatio-temporal variation of runoff coefficients. We then applied a validated semi-distributed hydrological model, HYPE, for examining the spatio-temporal variation of runoff generating mechanisms. HYPE model was modified in a minor fashion and simulations were conducted again to find out the portion of discharge originating from different runoff generation mechanisms. New hydrological insights for the region We examined the spatio-temporal variation of runoff generating mechanisms on the sub-basin level on seasonal basis. Our analysis reveals that the runoff generation in the Selke catchment is primarily dominated by shallow sub-surface flow and very rarely the contribution from Dunne overland flow exceeds sub-surface flow. Runoff generated by Hortonian mechanism is very infrequent and almost negligible. We also examined the spatio-temporal variation of runoff coefficients on seasonal basis as well as for individual storms. Due to higher precipitation and topographic relief in the upland catchment of Silberhutte, the runoff coefficients were consistently higher and its peak was found in winter months due to lower evapotranspiration.

Late Pleistocene-Holocene alluvial stratigraphy of southern Baja California, Mexico

Abstract A late Pleistocene to Holocene alluvial stratigraphy has been established for the basins of La Paz and San Jose del Cabo, in the southern tip of the Baja California peninsula, Mexico. Six discrete alluvial units (Qt1 through Qt6) were differentiated across the region using a combination of geomorphologic mapping, sedimentological analysis, and soil development. These criteria were supported using radiocarbon, optically stimulated luminescence and cosmogenic depth-profile geochronology. Major aggradation started shortly after ∼70 ka (Qt2), and buildup of the main depositional units ended at ∼10 ka (Qt4). After deposition of Qt4, increasing regional incision of older units and the progressive development of a channelized alluvial landscape coincide with deposition of Qt5 and Qt6 units in a second, incisional phase. All units consist of multiple 1–3 m thick alluvial packages deposited as upper-flow stage beds that represent individual storms. Main aggradational units (Qt2-Qt4) occurred across broad (>2 km) channels in the form of sheetflood deposition while incisional stage deposits are confined to channels of ∼0.5–2 km width. Continuous deposition inside the thicker (>10 m) pre-Qt5 units is demonstrated by closely spaced dates in vertical profiles. In a few places, disconformities between these major units are nevertheless evident and indicated by partly eroded buried soils. The described units feature sedimentological traits similar to historical deposits formed by large tropical cyclone events, but also include characteristics of upper-regime flow sedimentation not shown by historical sediments, like long (>10 m) wavelength antidunes and transverse ribs. We interpret the whole sequence as indicating discrete periods during the late Pleistocene and Holocene when climatic conditions allowed larger and more frequent tropical cyclone events than those observed historically. These discrete periods are associated with times when insolation at the tropics was higher than the present-day conditions, determined by precessional cycles, and modulated by the presence of El Nino-like conditions along the tropical and northeastern Pacific. The southern Baja California alluvial record is the first to document a precession-driven alluvial chronology for the region, and it constitutes a strong benchmark for discrimination of direct tropical influence on any other alluvial record in southwestern North America.

Source, variability, and transformation of nitrate in a regional karst aquifer: Edwards aquifer, central Texas

Many karst regions are undergoing rapid population growth and expansion of urban land accompanied by increases in wastewater generation and changing patterns of nitrate (NO3−) loading to surface and groundwater. We investigate variability and sources of NO3− in a regional karst aquifer system, the Edwards aquifer of central Texas. Samples from streams recharging the aquifer, groundwater wells, and springs were collected during 2008–12 from the Barton Springs and San Antonio segments of the Edwards aquifer and analyzed for nitrogen (N) species concentrations and NO3− stable isotopes (δ15N and δ18O). These data were augmented by historical data collected from 1937 to 2007. NO3− concentrations and discharge data indicate that short-term variability (days to months) in groundwater NO3− concentrations in the Barton Springs segment is controlled by occurrence of individual storms and multi-annual wet-dry cycles, whereas the lack of short-term variability in groundwater in the San Antonio segment indicates the dominance of transport along regional flow paths. In both segments, longer-term increases (years to decades) in NO3− concentrations cannot be attributed to hydrologic conditions; rather, isotopic ratios and land-use change indicate that septic systems and land application of treated wastewater might be the source of increased loading of NO3−. These results highlight the vulnerability of karst aquifers to NO3− contamination from urban wastewater. An analysis of N-species loading in recharge and discharge for the Barton Springs segment during 2008–10 indicates an overall mass balance in total N, but recharge contains higher concentrations of organic N and lower concentrations of NO3− than does discharge, consistent with nitrification of organic N within the aquifer and consumption of dissolved oxygen. This study demonstrates that subaqueous nitrification of organic N in the aquifer, as opposed to in soils, might be a previously unrecognized source of NO3− to karst groundwater or other oxic groundwater systems.

Limited-area atmospheric energetics: illustration on a simulation of the CRCM5 over eastern North America for December 2004

The seminal work of Lorenz on global atmospheric energetics has allowed understanding much on the physical processes responsible for the general circulation, its maintenance and the development of synoptic-scale weather systems. In mid-latitudes, potential energy generated by the differential heating of the planet by the Sun is converted into kinetic energy by the weather systems and eventually dissipated by friction. While a corresponding study of atmospheric energetics over a limited region would have the advantage of focusing on the details of individual storms and the processes taking place over a domain of interest, such study has encountered several pitfalls and has been challenging. Here we build upon our earlier work on the energy cycle of inter-member variability in ensembles of limited-area model simulations to develop a regional-scale atmospheric energy cycle formulated in terms of available enthalpy and kinetic energy. The approach is then applied to study the energetics of a short simulation made with the fifth-generation of the Canadian Regional Climate Model (CRCM5) over an eastern North American domain for December 2004. The results obtained for a specific storm and monthly mean climatology confirm the current understanding that available enthalpy of the atmospheric time-mean state is mainly generated by the covariance of diabatic heating and temperature, and that the most important conversions of energy are found to correspond to baroclinic processes that take place along the storm track, where perturbations of temperature and wind are important. Finally, transient-eddy kinetic energy is mainly dissipated by friction in the boundary layer.

Assessment of beach and dune erosion and accretion using LiDAR: Impact of the stormy 2013–14 winter and longer term trends on the Sefton Coast, UK

An important question for coastal management concerns the importance of individual storms and clusters of storms on longer term beach sediment budgets, beach and dune erosion, and coastal flood risk. Between October 2013 and March 2014 a series of deep Atlantic low pressure systems crossed the Northeast Atlantic, and strong winds, high waves and high water levels affected many coastal areas in the UK and other parts of western Europe. Net dune recession of up to 12.1m occurred around Formby Point. On 5 December 2013 the highest water level ever recorded at Liverpool (6.22m ODN) coincided with waves of Hs of 4.55m and Tp of 9.3s in Liverpool Bay. Wave trimming of the dune toe occurred along the entire length of the Sefton coast, but significant dune erosion occurred only where the upper beach (between the mean high water spring tide level and the dune toe) was <25m wide. Sediment budget calculations based on LiDAR surveys in October 2013 and May 2014 indicated a net loss of 127×103m3 of sediment from the beach (above 0m ODN) and a loss of 268×103m3 from the frontal dune system, mostly at Formby Point. However, some parts of the beach to the south of Formby Point gained sediment, indicating net north to south transport over the winter. When considered in a longer term context, the 2013–14 winter represents only a small perturbation on the longer-term coast trend of erosion at Formby Point and progradation to the north and south. Analysis of LiDAR data over a longer time period 1999–2014 indicated upper beach and dune sediment loss of 780×103m3 from the north-central part of Formby Point, with net gains of 806×103m3 and 2116×103m3 in areas to the north and south, respectively. This indicates a net onshore transport of 2142×103m3 from Liverpool Bay towards the coast between Birkdale and Altcar, with a further net total of 210×103m3 transported towards the shore between Altcar and Crosby. In view of the demonstrated value of airborne LiDAR surveys for the quantification of storm impacts and longer term coastal changes, it is recommended that such surveys should be undertaken before and after each winter storm period, covering the area between mean low water spring tide level and a line 200m landward of the dune toe, of as a part of the regional coastal monitoring programme.

Inconsistency in rainfall characteristics estimated from records of different rain gauges

The goal of this work is to assess the effect of utilizing different types of tipping bucket rain gauges in investigating rainfall characteristics. A dual tipping bucket (TB) rain gauge station is installed in the upper catchment of Numan basin in Saudi Arabia. The main difference between the two gauges is that the Hydrological Services (HS) gauge is equipped with a siphon tube which reduces undercatchment particularly during heavy rainfall. Records of both gauges for the period 2006 to 2013 are collected, analyzed, and compared, focusing on the characteristics of rainfall events as well as rainfall temporal variability. The HS gauge recorded higher values of total rainfall depth compared to the Texas Electronics (TEMM) gauge. For the individual storms as well as the 5-min rainfall, HS gauge also reported higher mean rainfall depths. Regarding temporal characteristics of reported rainfall, no significant variations are observed between the values of storm duration of the two gauges. The TEMM gauge has the advantage of recoding more storms with depth less than 1 mm. The current study suggests the use of a corrective factor for rainfall record of the TEMM gauge.

Paired stable isotopologues in precipitation and vapor: A case study of the amount effect within western tropical Pacific storms

AbstractUnderstanding controls on the stable isotopic composition of precipitation and vapor in the West Pacific Warm Pool is vital for accurate representation of convective processes in models and correct interpretation of isotope‐based paleoclimate proxies, yet a lack of direct observational evidence precludes the utility of these isotopic tracers. Results from a measurement campaign at Manus Island, Papua New Guinea from 28 April to 8 May 2013 demonstrate variability in the stable isotopic composition (δD and δ18O) of precipitation and vapor in individual precipitation events and over a 10 day period. Isotope ratios in water vapor and precipitation progressively increased throughout the period of measurement, coincident with a transition from high to low regional convective activity. Vapor isotope ratios approached equilibrium with seawater during the quiescent period and likely reflected downwind advection of distilled vapor and re‐evaporation of rainfall during the period of regional convection. On a 5 min timescale across individual storms, isotope ratios in precipitation were strongly correlated with isotope ratios in surface vapor. However, individual precipitation isotope ratios were not strongly correlated with surface meteorological data, including precipitation rate, in all storms. Yet across all events, precipitation deuterium excess was negatively correlated with surface temperature, sea level pressure, and cloud base height and positively correlated with precipitation rate and relative humidity. Paired surface precipitation and vapor isotope ratios indicate condensation at boundary layer temperatures. The ratio of these paired values decreased with increasing precipitation rate during some precipitation events, suggesting rain re‐evaporation and precipitation in equilibrium with an isotopically distinct upper level moisture source. Results from the short campaign support the interpretation that isotope ratios in precipitation and vapor in the western tropical Pacific are indicators of regional convective intensity at the timescale of days to weeks. However, a nonstationary relationship between rain rate and stable isotope ratios in precipitation during individual convective events suggests that condensation, rain evaporation, moisture recycling, and regional moisture convergence do not always yield an amount effect relationship on intraevent timescales.

Aeolian dust deposition in the southern Aral Sea region (Uzbekistan): Ground-based monitoring results from the LUCA project

Abstract As larger parts of the former Aral Sea have been desiccated, more (and harmful) dust storms (DS) and dust deposition (DD) occur more frequently in the surrounding area. Due to the prevalent wind directions, the southern Aral Sea region is affected stronger by these DS and DD as other areas around the former Aral Sea. The densely populated study area belongs to the autonomous republic of Karakalpakstan and the autonomous oblast (district) Khorezm within the Republic of Uzbekistan. For improving the knowledge about the spatial and temporal distribution of DD in the study region, seven sampling stations of the Uzbek meteorological survey have been equipped with passive deposition samplers between 2003 and 2012. The monthly amount of dust, the grain sizes, the mineralogical and chemical composition were determined and in several cases individual dust storm events were analyzed as well. Although the monthly average dust deposition was relatively low (598.4 kg/ha), the peak deposition during dust storms was up to 160 times higher than this average. While the seasonal DD rate was increasing from spring to fall, the health related threshold excess showed the highest intensity during spring and summer. At most stations the grain size composition of the dust samples (85–90% are silt and clay dominated) was very similar to the composition of the near surface soils. The stations Muynak and Jaslyk, representing dust originating from the Aral Kum, are characterized by dust rich in HCO3, SO4 and Ca. Among the trace elements, heavy metals were analyzed because of their health-affecting potential. The total heavy metal concentrations in the southern Aral Sea region are relatively low compared to the results from other parts of Uzbekistan. Zinc showed the greatest dominance close to the Aral Kum, while chromium on the other hand increased its percentage with a growing distance to the former Aral Sea. The spatial and temporal dynamics of the dust deposition as well as the distribution of heavy metals indicate a further need for ground based research for the improvement of the database and a better understanding of the dust mobilization, transport and deposition mechanisms in the Aral Kum and the southern Aral Sea region.

The influence of storm characteristics on hydrological connectivity in intermittent channel networks: implications for nitrogen transport and denitrification

Summary Intermittent channel networks pose particular challenges for monitoring the extent of material transport and retention in arid river basins as a result of pulsed and highly variable rainfall‐runoff dynamics. Here, we examine how rainfall characteristics influence hydrological connectivity along a terrestrial–aquatic flowpath from upland hillslopes to low order intermittent channel networks. In addition, we explore the implications for nitrogen loss via denitrification as a function of variable flowpath length and soil water conditions associated with intermittent flow. The size, timing and intensity of storms influenced the extent of hydrological connectivity and highest order channel flow. During summer monsoons, highest order channel flow increased most strongly with storm size, while in winter, the combination of days since last storm and storm intensity provided the best model; however, models containing storm size were also highly ranked. Riparian terrace and vegetated hillslope soils had the highest denitrification potential; however, rates in channel sediments also were appreciable. Deep channel sediments dried slowly and may therefore remain biologically active for longer periods, increasing the potential for N losses via denitrification. The extent of N transport, storage and denitrification is in large part driven by the frequency, intensity and duration of individual rainfall events. Individual storm characteristics influence the magnitude of vertical and horizontal hydrological connectivity in the catchment, and therefore, the magnitude of transport, solute storage and biogeochemical processing in intermittent channel basins.

An efficient artificial intelligence model for prediction of tropical storm surge

Process-based models have been widely used for storm surge predictions, but their high computational demand is a major drawback in some applications such as rapid forecasting. Few efforts have been made to employ previous databases of synthetic/real storms and provide more efficient surge predictions (e.g. using storm similarity of an individual storm to those in the database). Here, we develop an alternative efficient and robust artificial intelligent model, which predicts the peak storm surge using the tropical storm parameters: central pressure, radius to maximum winds, forward velocity, and storm track. The US Army Corp of Engineers, North Atlantic Comprehensive Coastal Study, has recently performed numerical simulations of 1050 synthetic tropical storms, which statistically represent tropical storms, using a coupled high resolution wave–surge modeling system for the east coast of the US, from Cape Hatteras to the Canadian border. This study has provided an unprecedented dataset which can be used to train artificial intelligence models for surge prediction in those areas. While numerical simulation of a storm surge at this scale and resolution (over 6 million elements scaling from 20 m to more than 100 km) is extremely expensive, the artificial intelligence takes the advantage of the previous simulations, and effectively learns the relationship between storm parameters representing storm forcing and surge. The artificial neural network method which was used for this study, was shown to outperform support vector machine for extreme storms. ANN model, which is based on a neurobiological analogy, can be conveniently developed, retrained by new data, and is nonparametric. The AI model, which was developed for Rhode Island, was validated using a set of randomly selected synthetic storms as well as real tropical storms in this region. The model performance was found satisfactory with root-mean-square error of <35 cm for observed and synthetic storms. It was also shown that it is not possible to develop a reliable artificial intelligence model for this region using a limited number of data (e.g. 200 storms), which is usually available in historical records.

A Runoff and Sediment Routing Model for Open Lot Beef Feeding Facilities

Abstract. Feedlot runoff is a potential environmental contaminant and requires proper management to minimize impact on water quality. In designing runoff management systems, accurately assessing the amount of runoff that will be generated is of foremost importance. Along with overall quantity of runoff, the temporal pattern, both throughout the year and within an individual storm event, can have important implications for sizing control system components, in determining the performance the control system achieves, and in the overall pollution potential of the feedlot. This review summarizes the hydraulic properties of the feedlot surface, specifically focusing on variables that impact the total volume of effluent generated and the resulting amount of sediment transported. The work cumulates in development of a feedlot runoff routing model, presented as a series of equations that are implemented within the updated Iowa State University-Vegetative Treatment Area model, with a sediment transport/erosion component. Overall, the results indicated that a curve number of 91 was best for estimating runoff volumes, but substantial variation about this value could occur. The calibrated model was able to accurately estimate average total solids concentrations of lots of different size, shape, and surface condition under different hydraulic situations (R 2 = 0.92 for calibration and the slope of the measured vs. modeled data was not different than one during model validation). Most calibration and validation feedlots were earthen, had the majority of runoff from rainfall events, had mounds within the pen, and were scraped only once or twice per production cycle; thus model performance may be limited for other situations. The feedlot runoff and sediment routing components were used to assess the impact of various feedlot design characteristics, including feedlot area, aspect ratio, and slope, on solids transport from the feedlot surface. This model can be used to evaluate the risk that feedlot runoff poses to water quality for prioritizing feedlots that are in need of enhanced runoff control systems, and to evaluate the hydraulic and sediment loadings that a runoff control system is required to handle.

Quantitative Framework for Preferential Flow Initiation and Partitioning

Core Ideas Preferential flow can be predicted from the distribution of mesoscale matrix infiltrability. Soil matrix material, rather than the characteristics of macropores, largely controls preferential flow. Two different scales of representative areas are needed to predict matrix–macropore partitioning. A model for preferential flow in macropores is based on the short‐range spatial distribution of soil matrix infiltrability. It uses elementary areas at two different scales. One is the traditional representative elementary area (REA), which includes a sufficient heterogeneity to typify larger areas, as for measuring field‐scale infiltrability. The other, called an elementary matrix area (EMA), is smaller, but large enough to represent the local infiltrability of soil matrix material, between macropores. When water is applied to the land surface, each EMA absorbs water up to the rate of its matrix infiltrability. Excess water flows into a macropore, becoming preferential flow. The land surface then can be represented by a mesoscale (EMA‐scale) distribution of matrix infiltrabilities. Total preferential flow at a given depth is the sum of contributions from all EMAs. Applying the model, one case study with multi‐year field measurements of both preferential and diffuse fluxes at a specific depth was used to obtain parameter values by inverse calculation. The results quantify the preferential–diffuse partition of flow from individual storms that differed in rainfall amount, intensity, antecedent soil water, and other factors. Another case study provided measured values of matrix infiltrability to estimate parameter values for comparison and illustrative predictions. These examples give a self‐consistent picture from the combination of parameter values, directions of sensitivities, and magnitudes of differences caused by different variables. One major practical use of this model is to calculate the dependence of preferential flow on climate‐related factors, such as varying soil wetness and rainfall intensity.