Single Storm Research Articles

Using the check dam deposit for an individual event to document the sources and erosional loss of sediment-associated organic carbon from a small catchment on the Chinese Loess Plateau

Information on the sources and fate of organic carbon mobilized by soil erosion is crucial for understanding the impact of erosion on carbon (C) cycling. However, few studies have evaluated this in low-order stream systems. In this study, we adopted a novel approach, that used the sediment deposited behind a check dam constructed at the outlet of the Fengzigou catchment (0.91 km2) on the Chinese Loess Plateau by a single high magnitude storm event, to simplify the field sampling requirements. The total sediment-associated organic carbon (TOC) was fractionated into particulate organic carbon (POC) and mineral associated organic carbon (MOC). These results were combined with those from a sediment source tracing exercise. This made it possible to explore further the source and loss of the sediment-associated organic carbon. The results showed that the inter-gully areas contributed the most eroded TOC (52.3 ± 7.6 %) and, together with the gully walls, represented the main TOC source. The primary contributor of the POC fraction in the deposited sediment was the inter-gully areas (80.5 ± 12.6 %), whereas the gully walls were the main contributor of the MOC fraction (54.9 ± 10.2 %). The total output of sediment produced by the event was 1304 ± 48 t and the equivalent value for sediment-associated TOC was 2.94 ± 0.26 t, of which the POC fraction accounted for 27.6 ± 3.6 % and the MOC fraction 72.4 ± 9.8 %. The TOC lost (0.3 ± 0.02 t) through the mobilization and delivery processes was 10.2 ± 1.2 % of the TOC mobilized by erosion, and the lost carbon was dominated by the POC fraction (86.7 ± 8.8 %). The specific TOC output from the catchment associated with the event documented was 0.3 t km−2. This work demonstrates the potential for erosion-induced carbon redistribution to provide a source for atmospheric CO2 in the study area.

Combined effects of layered heterogeneity and cutoff wall on groundwater salinization caused by storm surge inundation: Numerical simulations

Layered heterogeneity and cutoff wall may exacerbate storm surge-induced salinization of coastal groundwater. Earlier studies focused on the separate effects of layered heterogeneity or cutoff wall on aquifer recovery after storm surge events. However, their combined effect on aquifer recovery after a single storm surge event remains unclear. This problem was addressed numerically based on a coastal aquifer with typical stratified heterogeneity (i.e., the presence of a low-permeability layer (LPL) between two high-permeability layers). The results show that the total amount of saltwater intrusion is significantly reduced by the combined effect of LPL and cutoff wall; however, the natural recovery capacity of the aquifer will be weakened. As the depth of cutoff wall increases, the total amount of saltwater intruding into aquifer and the recovery time of aquifer (Tre) decreases stepwise, while the maximum salinized extent shows a nonmonotonic upward trend. If the base of cutoff wall locates within LPL, the salinization of aquifer changed non-monotonically as the distance between cutoff wall and ocean increases, but Tre shows an overall decreasing trend. Maximum salinized extent and saltwater intrusion mass decrease monotonically with increasing LPL thickness, but there is a non-monotonic relationship between Tre and LPL thickness. The maximum salinized extent and saltwater intrusion mass changed non-monotonically with LPL elevation, and Tre shows a non-monotonic upward trend. The study also found that a decrease in the hydraulic conductivity of LPL does not necessarily lead to an increase in Tre. This study has important implications for freshwater management and cutoff wall construction in coastal aquifers facing the risk of ocean-surge inundation.

Standardization of Dual-Doppler Radar–Derived Wind Fields during a Hurricane Landfall

Abstract A new methodology for standardizing radar-derived elevated dual-Doppler (DD)-synthesized wind maps to the near surface is presented, leveraging the spatial variability found within the horizontal wind speed fields. The methodology is applied to a dataset collected by Texas Tech University (TTU) using two TTUKa-band mobile radar systems during the landfall of Hurricane Delta (2020) in coastal Louisiana. Relevant portions of the DD wind fields are extracted from multiple heights between 100 and 400 m above ground level, combined into 10-min segments and standardized to a reference height of 10 m and an open exposure roughness length of 0.03 m. Extractions from these standardized wind fields are compared and validated against the standardized wind measurements from a micronet of seven TTU StickNet platforms providing “ground truth” within the DD analysis domain. The validation efforts confirm the developed DD wind field standardization methodology yields robust results with correlation coefficients greater than 0.88 and mean biases less than 1%. The results of this study provide a new means for incorporating elevated DD radar data into new and existing surface wind field analysis systems geared toward generating a wind field of record during a hurricane landfall. Significance Statement This work presents a new methodology for using radar-generated wind fields during a hurricane landfall to support the construction of a surface wind field analysis. Because radar-based wind measurements are inherently elevated above the surface and because the wind conditions well above the ground do not directly translate to the wind conditions experienced at the ground, a method for standardizing the elevated radar wind fields to the surface provides tremendous value to generating a spatially continuous wind field of record during a hurricane landfall event to better inform event response and recovery efforts. In addition, the need for detailed wind fields of record from landfalling hurricanes that approach structural design limits is critical as a single design-level storm can alter building code return period analysis. Detailed wind fields for these high-impact events can directly inform associated updates in building codes ultimately contributing to a more resilient built environment.

The role of hyetograph shape and designer subjectivity in the design of an urban drainage system.

Even though it has been established that a hyetograph's shape affects the results of hydrological simulations, common engineering practice does not always account for this fact. Instead, a single design storm is often considered sufficient for designing a urban drainage system. This study examines the impact that this design paradigm, combined with the uncertainty introduced by subjective choices made during the design process, has on the robustness of a designed system. To do so, we evaluated a set of individual designs created by engineering students using the same Chicago hyetograph as a design storm. We then created ensembles of hyetographs with the same precipitation volume and duration as the Chicago hyetograph and evaluated the designs' hydrological responses. The results showed that designs, which performed equally well for the initial design storm, triggered varying responses for the storms in the ensembles and, consequently, showed different levels of robustness, hinting at a need to adapt the current design approach.

ULF Wave Transport of Relativistic Electrons in the Van Allen Belts: Criteria for Transition to Radial Diffusion

AbstractRelativistic electrons in the radiation belts can be transported as a result of wave‐particle interactions (WPI) with ultra‐low frequency (ULF) waves. Such WPI are often assumed to be diffusive, parametric models for the radial diffusion coefficient often being used to assess the rates of radial transport. However, these WPI transition from initially coherent interactions to the diffusive regime over a finite time, this time depending on the ULF wave power spectral density, and local resonance conditions. Further, in the real system on the timescales of a single storm, interactions with finite discrete modes may be more realistic. Here, we use a particle‐tracing model to simulate the dynamics of outer radiation belt electrons in the presence of a finite number of discrete frequency modes. We characterize the point of the onset of diffusion as a transition from separate discrete interactions in terms of wave parameters by using the “two‐thirds” overlap criterion (Lichtenberg & Lieberman, 1992, https://doi.org/10.1007/978‐1‐4757‐2184‐3), a comparison between the distance between, and the widths of, the electron's primary resonant islands in phase space. Further, we find the particle decorrelation time in our model system with typical parameters to be on the timescale of hours, which only afterward can the system be modeled by one‐dimensional radial diffusion. Direct comparison of particle transport rates in our model with previous analytic diffusion coefficient formulations show good agreement at times beyond the decorrelation time. These results are critical for determining the time periods and conditions under which ULF wave radial diffusion theory can be applied.

Comparison of two hydrodynamic models for their rain-on-grid technique to simulate flash floods in steep catchment

In this study, two hydrodynamic models, TELEMAC-2D and HEC-RAS 2D, were compared for their Rain-on-Grid (RoG) technique with a particular focus on runoff generation processes in a small and steep catchment. Curve number (CN) method was applied in both the models to simulate two single storm events up to 20 h of duration, whereas the Green-Ampt Redistribution (GAR) method was additionally applied in HEC-RAS 2D for a multi-peak flood event with sustained flow between the peaks. CN and GAR methods were compared for this flood event, and a sensitivity analysis of the GAR parameters was also done. Moreover, the two models were compared for their calibration process, computational time, mesh size and shape, and model availability, in general, as well as the results including inundated areas, water depth, and velocity. The results indicate that both the models are capable of reproducing short duration single storm floods. NSE and R2 for both models ranged from 0.70 to 0.90 and from 0.93 to 0.95. However, the models struggled to reproduce the long- duration multi-peak flood event. The sensitivity analysis showed that the results are not very sensitive to the two GAR parameters which are responsible to influence the flow of the second peak in the flood event. Neither the CN nor the GAR infiltration method successfully replicated such events because the hydraulic models permanently lose infiltrated water from the domain. The returned sub-surface flow significantly contributes to river flow during these flood events; however, none of the model incorporates a return flow algorithm.

Distribution and recovery phase of geomagnetic storms during solar cycles 23 and 24

Abstract Coronal mass ejections (CMEs) and Stream Interaction Regions (SIRs) are the main drivers of intense geomagnetic storms. We study the distribution of geomagnetic storms associated with different drivers during solar cycles 23 and 24 (1996-2019). Although the annual occurrence rate of geomagnetic storms in both cycles tracks the sunspot cycle, the second peak in storm activity lags the second sunspot peak. SIRs contribute significantly to the second peak in storm numbers in both cycles, particularly for moderate to stronger-than-moderate storms. We note semiannual peaks in storm numbers much closer to equinoxes for moderate storms, and slightly shifted from equinoxes for intense and stronger-than-intense storms. We note a significant fraction of multiple-peak storms in both cycles due to isolated ICMEs/SIRs, while single-peak storms from multiple interacting drivers, suggesting a complex relationship between storm steps and their drivers. Our study focuses on investigating the recovery phases of geomagnetic storms and examining their dependencies on various storm parameters. Multiple-peak storms in both cycles have recovery phase duration strongly influenced by slow and fast decay phases with no correlation with the main phase buildup rate and Dst peak. However, the recovery phase in single-peak storms for both cycles depends to some extent on the main phase buildup rate and Dst peak, in addition to slow and fast decay phases. Future research should explore recovery phases of single and multiple-peak storms incorporating in-situ solar wind observations for a deeper understanding of storm evolution and decay processes.

Measuring and modeling soil moisture and runoff at solar farms using a disconnected impervious surface approach

AbstractGround‐mounted photovoltaic sites are often treated as impervious surfaces in stormwater permits. This ignores the pervious soils beneath and between solar arrays and leads to an overestimation of runoff. Our objective was to improve solar farm stormwater hydrology models by explicitly considering the disconnected impervious nature of solar design and site characteristics. Experimental sites established on utility scale solar farms in Colorado, Georgia, Minnesota, New York, and Oregon had perennial vegetative plantings with mean precipitation ranging from 40.6 to 124.5 cm, and soil texture ranging from loamy sand to clay. Soil moisture measurements were collected beneath arrays, under drip edges, and in the vegetated area between arrays at each site. Hydrus‐3D models for soil moisture and stormwater hydrology were developed that accounted for precipitation falling on solar panels, drip edge redistribution of rainfall, infiltration, and runoff in the pervious areas between solar arrays and beneath panels. Drip edge runoff averaged 3‐ to 10‐times incident precipitation at the New York and Minnesota sites, respectively. Root mean square error values between measured sub‐hourly soil moisture and predicted moisture for large measured single storm events averaged 0.029 across all five sites. Predicted runoff depths were strongly affected by precipitation depth, soil texture, soil profile depth, and soil bulk density. Runoff depths across the five experimental sites averaged 13%, 25%, and 45% of the 2‐, 10‐, and 100‐year design storm depths, clearly showing that these solar farms do not behave like impervious surfaces, but rather as disconnected impervious surfaces with substantial infiltration of runoff in the vegetated areas between and beneath solar arrays.

Biological Characterisation of Hailstones from Two Storms in South Brazil

Although studies focusing on the physicochemical properties of aerosols/clouds have not been performed extensively, even less attention has been given to hailstones and their biological composition. Here, we present the results of the physical and microbiological characterisation of 20 hailstones collected in Southern Brazil originating from two storms. Nearly half of the hailstones (9 out of 20, or 45%) did not contain any cultivable bacteria or fungi. A total of 18 bacterial species were found in hailstones from both storms, and the genus Bacillus was found in 5 out of the 11 hailstones, with Bacillus cereus being the most frequent bacterial species. Fungi, on the other hand, were only present in four hailstones derived from a single storm, with three fungal species identified and Epicoccum nigrum being the most frequent fungal species. HYSPLIT modelling indicated the different flow of air masses from the Amazon and Pacific Ocean that contributed to the loading of microorganisms found in the clouds at the time of the two storms. Our findings suggest that ca. 50% of hailstones have cultivable bacterial or fungal species, which came mainly from the local landscape with intrusions of air masses derived from the Amazon and the Pacific Ocean.

A ten-year statistical radar analysis of an operational hail suppression program in Alberta

Hailstorms represent a significant natural hazard worldwide and can result in severe socioeconomic impacts. In Canada, the province of Alberta experiences the highest rate of hail occurrences causing tremendous damage to cities, properties, vehicles and crops. Cloud seeding is often adopted to reduce the hailstorm impacts; however, the efficacy of this mitigation measure is still unclear. In this study, a ten-year set of hailstorm events (2011−2020) in Alberta was analyzed using radar-based records to evaluate the potential effects of seeding. The radar completed a full volume-scan every four minutes, and a three-dimensional radar reflectivity threshold-based method was utilized to identify hailstorms. A single 3D storm is tracked over time and the ensemble is called a “storm track” in this contribution. 176 storm tracks persisting for more than one hour were considered for further analysis. We used two radar-derived metrics as proxies for hail damage potential, namely, VILmax (Vertically Integrated Liquid calculated from the maximum reflectivity profile in the storm) and hail mean coverage area (defined as the mean area with reflectivity greater than 60 dBZ). Seeding was performed by releasing silver iodide aerosols from aircraft, and seeded scans of the storm were identified based on the location and seeding time. The efficacy of seeding was evaluated by comparing the characteristics of the storms before, during and after seeding. Results show that for nearly 60% of cases, the median values of the largest (quantile 99) VILmax and mean area corresponding to the seeded scans are lower than those of the unseeded portions. For around 8% and 20% of cases, there is no change, while for approximately 17% to 30% of cases, the values are higher. The effects of seeding are more pronounced after 30 min than at the initiation of seeding. Furthermore, statistical analyses using Mann-Whitney and Wilcoxon's tests reveal that differences in VILmax and mean area between the seeded and unseeded scan groups are statistically significant. These findings suggest that cloud seeding could potentially influence the hail damage potential of storms, particularly those with high VILmax values.

INFLUENCE ON EVENT-SPECIFIC CALIBRATION DATA IN MODELLING SUBAERIAL STORM EROSION UNDER COMPLEX BATHYMETRY

Key parameters in the process-based model for morphological changes during storm events (i.e., XBeachX, Roelvink et al., 2018) should be adjusted to simulate morpho-hydrodynamics to a specific area of interest, leading to site-, profile-, and event-specific calibration. Although 2-dimensional simulations (area model) eliminate variability in calibrated parameters along with each profile in complex bathymetry, the degree to which datasets having different wave conditions influence model performance is still unclear in the area model at a given parameter space. The main objective of this study is to examine the influence of event-specific calibration data (single storm event and storm clusters) in modelling subaerial storm erosion under complex bathymetry. Using bathymetric field data over four different storm conditions, this study presented guidance for the selection of event-specific data in modeling calibration.

MODELLED AND OBSERVED IMPACT OF THE APRIL 2021 SOUTHERN OCEAN STORM

Wind-wave extreme events are a major driver of coastal erosion (Lowe et al., 2010). As such, accurate estimates of metocean extremes are crucial to implement efficient and resilient coastal defense strategies. Global wave reanalysis datasets are commonly used to estimate wind and wave statistical properties for coastal engineering purposes. However, despite the impressive accuracy of such datasets in representing average significant wave height conditions (global biases against observations of less than 5 cm), models usually underestimate metocean extremes (Cavaleri et al. 2009; Cavaleri et al., 2020). To obtain an understanding of model performance under extreme conditions, we focus on a single storm event generated in the Southern Ocean on April 7th, 2021.

Mapping Surface Water Presence and Hyporheic Flow Properties of Headwater Stream Networks With Multispectral Satellite Imagery

AbstractGrowth and contraction of headwater stream networks determine habitat extent, and open a window to the hyporheic zone. A fundamental challenge is observation of this process: wetted channel extent is dynamic in space and time, with wetted channel length varying by orders of magnitude over the course of a single storm event in headwater catchments. To date, observational data sets are produced from boots‐on‐the‐ground campaigns, drone imaging, or flow presence sensors, which are often laborious and limited in their spatial and temporal extents. Here, we evaluate satellite imagery as a means to detect wetted channel extent via machine learning methods trained on local surveys of wetted channel extent. Even where channel features are smaller than the imagery's spatial resolution, the presence of surface water may be imprinted upon the spectral signature of an individual pixel. For two catchments in northern California with minimal riparian canopy cover and highly dynamic wetted channel extent, we train a random forest model on RapidEye imagery captured contemporaneously with the existing surveys to predict wetted channel extent (accuracy >91%). The model is used to produce length‐discharge (L‐Q) relations and to calculate spatially distributed estimates of channel hyporheic flow capacity and exchange. A sharp break in hyporheic flow capacity occurs from main stem channels to lower order tributaries, resulting in a stepped L‐Q relationship that cannot be captured by traditionally used power law models. Remotely sensed imagery is a powerful tool for mapping wetted channels at high spatial resolution.

Assessing flash flood inundation from an extreme rainfall event: case study: Wadi Al Jizzi Oman

Abstract Flash floods present a significant risk to urbanized arid regions, and assessing their inundation patterns is crucial for effective disaster management. Extreme hydrologic events due to aridity and climate change are shaping human lives and major activities in numerous countries at an unprecedented pace. This study aims to assess flash floods from extreme storm events in an arid catchment using high-resolution data. The study applied two models on the event of a single storm, namely the IHACRES and AHP models. The observed flow was used for models' validation. The average flow output determined with the IHACRES model was approximately 0.47 m3/s while the flow output resulting from the AHP model was 0.45 m3/s. The efficiency showed that the IHACRES performed better in evaluating extreme events with an average of 0.88 while the AHP model showed an efficiency of 0.68. The quantitative simulation of both models is likely to have good applicability for simulating single storm events in arid catchments. The validated IHACRES and AHP models offer valuable tools for simulating flash flood. The study's outcomes have implications for flood management policy and infrastructure planning, ensuring a more resilient response to extreme flood events in arid regions globally.

Delayed response of low latitudes TEC during thirty-six geomagnetic storms from 2014 to 2017

Ionospheric response to the onset of geomagnetic storms is an important aspect for developing models towards better understanding and prediction of ionospheric parameters, particularly over the equatorial and low latitude sectors that are associated with several complexities. Our paper discusses the time response of the ionosphere (Δtiono), where Δtiono is the time elapsed from the onset of sudden storm commencement (SSC) of a magnetic storm to the absolute maximum value of DVTEC (TEC: total electron content). Over the period 2014 to 2017, thirty-six storms are reviewed, and their Δtiono are analyzed along with the magnetic and solar parameters. We defined a threshold value of TEC to be 8 TECU. Three storms are studied in detail as a reference for the entire range of storms (March 2015, June 2015, and September 2015). The stations used are Kourou (KOUR; 5.25°N/52.80°W) in the American longitude sector, Addis Ababa (AAE; 9.03N°/38.76°E) in the African longitude, Port Blair (PBRI; 11.63°N/92.71°E) and Patumwan (CUSV; 13.73°N/100.53°E) in the Asian longitude sector. In the Asian and American sectors, for all storms combined, there is no significant correlation (0.44 for the Asian sector and 0.22 for the American sector) between the delay (SSC time/time of maximum DVTEC) and the minimum of the Dst as found by previous studies. Instead, we considered geomagnetic storms satisfying the criteria: a) SSC occurs on the day side, and b) the origin of the magnetic storm on the solar disk must be far from the limb or does not belong to the far side, to obtain a much better correlation. The highest correlation value is observed at Thailand (0.84), followed by India (0.79) and South America (0.759), and the minimum value at Africa (0.641). The average response time in our study was found to be about 27.2 h. We observed positive and negative ionospheric storms, five negative storms in South America followed by two in Asia and a single negative storm in Africa from which it is realized that the most negative storms are in the time range of 9–15 LT. Nevertheless, there is hardly any relationship between the strength of DVTEC amplitude and the intensity of magnetic storms irrespective of longitude sectors.

A multi-year analysis of factors affecting ecosystem metabolism in forested and meadow reaches of a Piedmont stream

Studies of stream ecosystem metabolism over decades are rare and focused on responses to a single factor, e.g., nutrient reduction or storms. Numerous studies document that light, temperature, allochthonous inputs, nutrients, and flow affect metabolism. We use measurements spanning ~ 40 years to examine the interplay of all these influences on metabolism in forested and meadow reaches of a rural stream in southeastern Pennsylvania, USA. Measurements made in 1971–1975 used benthic substrata transferred to chambers (Period 1, P1), and ones in 1997–2010 used open system methodology (P2). Metabolism was greater in the Meadow reach both periods. Gross primary productivity (GPP) was driven primarily by light and chlorophyll, and respiration (R) by temperature and inclusion of hyporheic metabolism. Annually, processes were nearly balanced (Forested reach) or dominated by autotrophy (Meadow reach) in P1. Heterotrophy predominated in both reaches in P2, fueled by litter inputs (Forested reach) and fine particulate organic matter from the agricultural watershed (Meadow reach). Storms reduced GPP, R, and chlorophyll in proportion to storm size, but had less influence than other environmental factors. Riparian-zone reforestation of the P1 Meadow reach resulted in incident light and GPP similar to that in the permanent Forested reach within ~ 20 years.

Exploring near-optimal locations for bioretention systems in catchment scale using many-objective evolutionary optimization

ABSTRACT Low impact developments (LIDs) are control measures to restore the hydrologic regime and enhance stormwater quality. Due to LID’s expensive capital and maintenance cost, the placement of LID controls in a watershed is an important planning task and still an open question in the specialized literature. This study proposes a simulation-optimization approach to place bioretention systems within a watershed to optimize their effectiveness. The Stormwater Management Model (SWMM) and the Non-dominated Sorting Genetic Algorithm III (NSGAIII) were coupled to identify the near-optimal locations of bioretentions for near-optimal quality and quantity controls, considering runoff volume, peak flow, total suspended solids, total nitrogen, and cost. Trade-offs were identified between cost versus other objective functions. The results suggest no specific spatial preference in placement of bioretentions under different rainfall regimes in watershed scale. However, in subcatchment scale, the near-optimal placement under single storm events is either maximum or none, while distributed under continuous simulation.

Long‐term drivers of shoreline change over two centuries on a headland‐embayment beach

AbstractShoreline evolution over the last two centuries was analysed for Dundrum Bay, Co. Down, Northern Ireland, using historical and recent shoreline datasets from 1833 to 2020. The area of interest comprises two sandy beaches and vegetated coastal dune fields, Newcastle–Murlough and Ballykinler, separated by an inlet channel which connects the inner with the outer bay. Twenty‐four temporal shorelines were extracted, and a quantitative assessment of their positional uncertainty was performed. This was combined with analysis of foredune volume variations by applying the Structure‐from‐Motion‐Multi‐View‐Stereo technique to 1963 aerial photography and comparing it with a 2014 Light Detection And Ranging (LiDAR) dataset to better inform on links between the sediment dynamics and the observed shoreline changes. Storm events were identified using recorded extreme water levels (EWLs) (1901–2020) and hindcasted wave data (1948–2020). In the first 87 years, the shoreline was largely stable, and change was focused at the inlet area. In the 20th century, localised retreat characterised the western (Newcastle–Murlough) sector, whereas the eastern sector (Ballykinler) experienced general shoreline advance. The rate and extent of shoreline retreat in the western sector increased post‐1997 in concert with accelerated accretion at Ballykinler. The strongest erosional episodes were recorded in 1920–1951, 1997–2005, and 2012–2014. Although no direct link was established between single storms and shoreline retreat rates, the three major retreat periods coincided with several consecutive EWLs or EWLs with a return period greater than 100 years. These were generated by storm directions ranging from south to southwest. The long‐term pattern of shoreline change points to a complex coastal system that is still evolving.

Mechanical fatigue in trees mitigated by annual growth: A theoretical model

Mechanical forces applied over a period of time tend to cause fatigue failure in natural organisms and in engineering structures. Here, the theoretical approach known as Continuum Damage Mechanics is applied to study fatigue damage development in trees. It is found that growth in the form of an annual ring of new material is a very effective strategy to limit fatigue damage, due to the fact that, over time, each ring moves inside the trunk, reducing stress. If (as is generally assumed) the tree grows so as to keep the bending stress on its trunk constant, then fatigue failure will be effectively impossible until the tree is very old. One interpretation of this finding is that high cycle fatigue simply never occurs in trees: they don’t accumulate fatigue damage but rather fail by instantaneous overload or low cycle fatigue during a single storm. Another interpretation is that the bending stress is maybe not kept constant but changes as the tree grows, which would be a more efficient strategy making the best use of material. These findings are considered using data from the literature and their implications for the creation of biomimetic products are discussed. Possible experiments to test these theoretical predictions are suggested.

Importance of catchment hydrological processes and calibration of hydrological‐hydrodynamic rainfall‐runoff models in small rural catchments

AbstractIn recent years, many two‐dimensional (2D) hydrodynamic models have been extended to include the direct rainfall method (DRM). This allows their application as a hydrological‐hydrodynamic model for the determination of floodplains in one model system. In previous studies on DRM, the role of catchment hydrological processes (CaHyPro) and its interaction with the calibration process was not investigated in detail. In the present, case‐oriented study, the influence of the spatiotemporal distribution of the processes precipitation and runoff formation in combination with the 2D model HEC‐RAS is investigated. In a further step, a conceptual approach for event‐based interflow is integrated. The study is performed on the basis of a single storm event in a small rural catchment (low mountain range, 38 km2) in Hesse (Germany). The model results are evaluated against six quality criteria and compared to a simplified baseline model. Finally, the calibrated improved model is contrasted with a calibrated baseline model. The results show the enhancement of the model results due to the integration of the CaHyPro and highlight its interplay with the calibrated model parameters.