Channel Location Research Articles

The Effects of the Number and Position of Comfort Channels in Cylinders on Comfort and Road Handling Performance in Twin-Tube Telescopic Dampers

The damper is a component found between the chassis and the wheels of vehicles that absorbs impacts and vibrations from the road surface. Its primary function is to improve the comfort of the vehicle during driving and to ensure the stability of the vehicle by minimizing any shocks and vibrations that may occur, responding to road conditions. In conventional dampers, there are many parameters that affect damper performance. Key parameters can be listed as damper valve type, subcomponents used in the valves, the type and amount of oil, and whether the product is gas-filled or not. In valve groups, there are an infinite number of combinations that can be considered. By changing the sequence and parameters of the shims and discs, an infinite number of combinations and damping forces can be achieved. In twin-tube rear dampers, which consist of a body tube and cylinder components, there is generally no comfort channel in the cylinder parts. Comfort channels are special channels or passageways located around the piston of the damper. These channels allow the fluid inside the damper to flow in a way that creates resistance against the piston movement. Comfort channels are an important design feature that improves passenger comfort and vehicle stability by more effectively absorbing the vibrations and shocks during driving in commercial vehicles and twin-tube passive dampers. In this study, the effects of different quantities, sizes, and locations of comfort channels on damping force and road handling performance were examined on the same damper. As a result of the study, increasing the quantity and depth of the comfort channels was shown to reduce road vibrations more effectively and improve driving comfort. However, since a high depth of the channels and a large number of comfort channels increase the variation in the transition zone, they cannot reduce the shock effect at high speeds. From a performance perspective, maintaining a smaller difference in the transition zones helps to improve road handling by ensuring vehicle stability. This improvement arises from the dampers’ ability to absorb high-speed shocks more effectively. Similarly, the length of the comfort channel should be determined according to the design position of the vehicle and the total stroke values. Otherwise, although the comfort channel length contributes significantly to damping vibrations, it could have a negative impact on safety.

Numerical study on lightning strike protection method for composite rotor blade based on air breakdown and insulating adhesive layer

The protection effectiveness of traditional Lightning Strike Protection (LSP) for composite rotor blade of helicopter can be diminished due to the explosion risk in overlapping attachment under lightning strike, so a new protection method based on Air Breakdown and insulating adhesive layer (AB-LSP method) was designed to avoid it. In this study, a numerical method was developed to simulate the electrical breakdown, and verified by experiment results. Based on this method, a Finite Element Model (FEM) was established to investigate the effect of two factors (breakdown strength and initial ablation temperature of adhesive layer) on the LSP effectiveness. The results show that the breakdown strength impacts more to the ablation damage in composite than that of high-temperature resistance. Then, another FEM was established to predict the ablation damage by lightning strike in the AB-LSP method protected composite rotor blade. The mechanisms and potential key parameters (magnitude of lightning current, discharge channel location, adhesive layer thickness, and air gap width) that could affect the protection effectiveness were analyzed. The introduction of air breakdown changes the current conduction path and reduces explosion risk. After rational design, this method can offer effective lightning protection for composite helicopter rotor blade and other composite structures.

Geomorphology and Sedimentology of a Rapidly Retreating Alpine Glacier: Insights From the Taschachferner, Tirol, Austria

The rapid retreat and fragmentation of Alpine glaciers is widely reported as humanity faces dramatic climate change in mountainous regions. This rapid change leads to changes in sedimentary processes, which are exposed in recently deglaciated regions. These Alpine glacier forefields offer a wide spectrum of settings through which the ancient sedimentary record can be interpreted. Glacial valley orientation, slope inclination and lithology, and plumbing of subglacial and englacial meltwater drainage all influence the immediate preservation potential of glacial sediments upon deposition. In this contribution, we explore the geomorphology and sedimentology of the Taschachferner (a valley glacier), presenting a new geological-geomorphological map. This small glacier drains an icefield in the Ötztal Alps, and its current ice margin lies at approximately 2550 m a.s.l. Thus far, the glacial sedimentology and its bedrock geology have not been subject to investigation. The bedrock geology is dominated by E-W striking units of paragneiss and amphibolite, and the latter exhibit a series of well-preserved striations together with meltwater-sculpted bedforms (p-forms). The lower region of the glacier can be divided into two parts: (i) a clean-ice part, on the northern valley side with a low, subdued profile and (ii) a debris-covered part at the southern valley side, covered with supraglacial debris. The valley margins are dominated by several generations of lateral moraines, the most prominent of which corresponds to the 1852 Little Ice Age Maximum. A well-developed “hanging sandur” is observed immediately in front of the ice margin. This consists of a series of sand and gravel bars cradled in the lee of an interpreted regional fault cross-cutting the bedrock. Sandur deposition is currently influenced and overprinted by dead ice, influencing the trajectory and location of river channels and gravel bars. This paper provides clear lessons regarding the distribution of ice-margin facies associations, which must be incorporated into models of glacier decay in the context of a rapidly warming climate.

Assessing the Effectiveness of Audio-Visual vs. Visual Neurofeedback for Attention Enhancement: A Pilot Study with Neurological, Behavioural, and Neuropsychological Measures.

Electroencephalogram (EEG) based Neurofeedback training has gained traction as a practical method for enhancing executive functions, particularly attention, among healthy individuals. The neurofeedback protocols based on EEG channel locations, frequency bands, or EEG features has been tested. However, the improvement in attention was not measured by comparing different feedback stimulus types. We believe that multisensory nature feedback even with few training sessions may induce strong effect. Therefore, this study compares the effect of audio-visual and visual feedback stimuli for attention enhancement utilizing neurophysiological, behavioural and neuropsychological measures. Total 21 subjects were recruited, undergoing six alternate days of neurofeedback training sessions to upregulate EEG beta power of frontocentral (FC5). Dwell time, fractional occupancy and transition probability were also estimated from the EEG beta power. Audiovisual group (G1) as compared to visual group (G2) demonstrate a significant increase of global EEG beta activity alongside improved dwell time (t = 2.76, p = 0.003), fractional occupancy (t = 1.73, p = 0.042) and transition probability (t = 2.46, p = 0.008) over the course of six neurofeedback training sessions. Similarly, the group (G1) shows higher scores (t = 2.13, p = 0.032) and faster reaction times (t = 2.22, p = 0.028) in Stroop task, along with increased score in Mindfulness Attention Awareness Scale (MAAS-15) questionnaire (t = 2.306, p = 0.012). Audiovisual neurofeedback may enhance training effectiveness, potentially achieving the same outcomes in fewer sessions compared to visual-only feedback. However, sufficient training days are essential for effect consolidation. This highlights the feasibility of completing neurofeedback training, a significant challenge in practice.

EEG Channel Estimation using CNN-Based Depression Classifier

Depression is a mental disorder that results to deteriorating effects in the lives of many people around the world. Traditional methods of diagnosing depression are based on interviews and questionaries. However, there were studies that have shown the possibilities of detecting depression biomarkers and perform classification. Electroencephalogram (EEG) analysis is one way of doing this. A series of signal processing techniques were used to streamline EEG data into a form which are recognizable by a machine learning algorithm. In this study, a convolutional neural network (CNN) – based depression classifier was used to classify depression using three EEG systems with 5, 16, and 128 channel locations. The aim is to estimate if there are differences in terms of classification performance. Results show that a system with locations for 5 and 16 EEG channels can achieve 98% accuracy like a 128-channel system. Hence, EEG systems with fewer number of electrodes can be utilized for depression classification applications.

Adjoint‐based observation impact on meteorological forecast errors in the Arctic

AbstractAccurate weather forecasting using numerical weather prediction in the Arctic remains a challenge owing to the complex atmospheric dynamics and relatively sparse observations of the region. Nevertheless, the impact of observations used for data assimilation (DA) on forecast errors (observation impacts, OIs) in the Arctic has not been fully explored. This study evaluated the OIs on 24 hr forecast errors in the Arctic by the adjoint‐based forecast sensitivity OI (FSOI) method using the Polar Weather Research and Forecasting (WRF) model, three‐dimensional variational DA, and adjoint model of WRFPLUS. The time‐averaged FSOI during August 2018 was analyzed in terms of the type, variable, satellite channel, altitude, and horizontal location of the observations. The results showed that the total FSOI was greatest for aircraft observations (AIRCRAFT), followed by sonde observations, scatterometer sea‐surface winds, advanced microwave sounding unit‐A radiance data from each satellite, and surface synoptic observations. The impact of AIRCRAFT in reducing forecast errors was greater in the Arctic than in other regions of the globe. The total FSOI of the advanced microwave sounding unit‐A radiance data from all four satellites was the greatest among the total FSOI of the individual observation types. For both AIRCRAFT and sonde observations, the FSOI per observation increased at higher latitudes, indicating that forecast errors in the Arctic could be reduced when upper atmospheric in‐situ observations at higher latitudes are used for DA. The beneficial ratio of the Global Positioning System precipitable water in the Arctic was greater than that in the midlatitudes with relatively moist atmospheres that cause greater uncertainties in converting zenith wet delay. The results of this study can contribute to configuring an optimal observing system in the Arctic by presenting the relative importance of observations for reducing forecast errors.

Transforming of scalp EEGs with different channel locations by REST for comparative study

ObjectiveThe diversity of electrode placement systems brought the problem of channel location harmonization in large-scale electroencephalography (EEG) applications to the forefront. Therefore, our goal was to resolve this problem by introducing and assessing the reference electrode standardization technique (REST) to transform EEGs into a common electrode distribution with computational zero reference at infinity offline. MethodsSimulation and eye-closed resting-state EEG datasets were used to investigate the performance of REST for EEG signals and power configurations. ResultsREST produced small errors (the root mean square error (RMSE): 0.2936–0.4583; absolute errors: 0.2343–0.3657) and high correlations (>0.9) between the estimated signals and true ones. The comparison of configuration similarities in power among various electrode distributions revealed that REST induced infinity reference could maintain a perfect performance similar (>0.9) to that of true one. ConclusionThese results demonstrated that REST transformation could be adopted to resolve the channel location harmonization problem in large-scale EEG applications.

Integrating Habitat Suitability and Larval Drift Modeling for Spawning‐To‐Nursery Functional Habitat Connectivity Analysis in Rivers

AbstractHabitat suitability modeling is a commonly used methodology to plan and assess in‐stream habitat enhancement in rivers, such as for the key fish life stages spawning and juvenile development. However, their use only allows modeling the spatial distribution of habitats, but not their connectivity. By integrating micro‐scale habitat modeling and a larval drift model, we assess the functional connectivity between spawning and larval nursery habitats for four rheophilic and litophilic fish species in a channelized and hydropower impacted reach of the lower Inn River (Bavaria, Germany), in which two restoration measures, a bypass channel and an island side‐channel system, have been constructed to improve longitudinal connectivity and habitat conditions. The study aims to (a) map spawning and larval nursery habitats, (b) quantify their connectivity, and (c) optimize functional habitat connectivity through an alternative bypass channel location. Results show that the channel's morphological complexity influences quantity and quality of available spawning and nursery habitats and their connectivity. Despite the presence of nursery habitats across the analyzed channel, the slow lateral larval dispersion during drift limits their accessibility to only the left river bank, making only 33% of available habitats useable. The degree of functional connectivity and hence the percentage of useable habitats can however be increased up to 95.3 % when considering different spatial configurations of habitats, which were explored in two alternative restoration scenarios. The results demonstrate the importance of considering functional habitat connectivity in habitat assessments and restoration planning.

Late Cenozoic mass transport deposits in the offshore Tanzania continental margin

Sediment mass movements and their associated Mass Transport Deposits (MTDs) have been widely studied due to their economic and geohazard potentials. This study combines 2D and 3D seismic reflection data with a seismic facies approach and attribute analysis to reveal the presence and distribution of different MTDs in the southernmost region offshore Tanzania. Results of seismic facies analysis show that the study area contains different Late Cenozoic MTDs. The MTDs have limited petroleum reservoir potential and include slides, slumps, debris flow deposits and occasional turbidites. The formation of these MTDs was caused by tectonic events associated with the development of the East African Rift System. Seismic attribute maps have shown the locations of channels, remnant blocks, headwall scars, and grooves confirming downslope sediment mass mobilization. The seabed attribute maps have shown areas where recent mass mobilizations were initiated. Some of these areas coincide with faults which have dissected the seabed, forming potential future gravity failure sites. Other future gravity failure sites include channel banks and slope edges, which may be present over the whole Tanzania continental margin. Sediment mass movements may be catastrophic, and therefore future infrastructure installations in the area must involve detailed mapping of the seabed to assess geohazard risks and act accordingly.

Historic channel dynamics of a highly developed dryland river

AbstractUnderstanding how river systems adjust to hydrologic alterations is critical to sustainable river management. Remote sensing and geographic information systems (GIS) provide a reliable and cost‐effective approach to studying river adjustment, including the possible attainment of dynamic equilibrium. We used this approach to study the highly managed lower South Platte River in northeastern Colorado, USA. We assessed the active channel (inclusive of open water, sand bars and adjacent sparsely vegetated areas) in three 30 km study sections, using General Land Office (GLO) maps circa 1870, and a time series of eight sets of aerial photographs from 1941 to 2015. In the GLO surveys, the active channel was 72–80% larger and 65–85% wider than in the later aerial photographs. Mean daily discharge in the prior photo interval was the strongest hydrologic predictor of channel area, while mean June daily discharge was the strongest predictor of channel width. Maximum daily discharge was the only significant predictor of lateral movement of the main channel. The highest rates of channel movement occurred when the primary channel switched locations to occupy a pre‐existing secondary channel. An average of 17% of the total active channel area was persistent, defined as consisting of channels at ≥7 of the eight photo years, and there was a narrow, persistent active channel throughout 68–72% of the length of each section. Thus, the location of the river has been stable since 1941, though flanking the channel location were areas of the active channel that were more temporally dynamic. After 1956, the post‐development lower South Platte River channel planform achieved a state of dynamic equilibrium, fluctuating thereafter within a relatively narrow range of values. As conditions in the basin change in the future due to increased municipal and industrial water demand and climate change, we can expect the river to also change.

Three-dimensional CFD analysis of PHWR exposed core under postulated severe accident condition

A three-dimensional steady-state thermal–hydraulic analyses of a large sized Pressurized Heavy Water Reactors (PHWRs) with varying levels of exposure is carried out for degraded core heat transfer assessment and presented in this paper. Low-frequency postulated severe accident without mitigating actions leads to exposure of fuel channels in PHWRs. Such exposure of fuel channels leads to their heat-up, governed by interdependent heat transfer mechanisms such as radiation, convection and conduction heat transfer and thermo-chemical interactions among the core constituents. In order to understand such complex behavior and plan the severe accident management guidelines, numerical analyses of the exposed core are of necessary. This paper illustrates the influence of the temperature and velocity profiles vis-à-vis different regions of the exposed core on the fuel channel heat-up. The interesting interdependency of convection and radiation heat transfer on fuel channel heat-up is reported. The dominance of convection heat transfer is observed for initial exposures of the fuel channels. However, the advanced stages of fuel channel exposures are observed to be dominated by radiation heat transfer. Intriguingly, it is observed that the convective cooling of exposed fuel channels by steam flow is counter-acted by exothermic heat generation from Zircaloy-made calandria tube surface and steam interaction. This leads to supplemental power addition for fuel channel heat-up. Moreover, it is interesting to note that the heat-up of fuel channels is restricted to central regions of the exposed core due to degraded steam cooling and higher-powered fuel channels. It is worth noting that fuel channel disassembly is observed in the advanced levels of fuel channel exposures. Moreover, fuel channel length equivalent to nearly 7–8 fuel bundle lengths undergo disassembly depending upon the fuel channel elevation and location in the core. The calandria vault water is observed to undergo film boiling at the onset of fuel channel disassembly.

EVALUATION OF SURFACE DETERIORATION RESULTING FROM THERMAL FATIGUE IN THE OPERATIONAL STATE OF AN H13 PRESSURE DIE CASTING DIE

The failure rate of pressure die casting dies is increasing due to cracks on the die surfaces, leading to thermal fatigue and fracture. This paper aims to investigate the thermal fatigue failure of H13 die-casting die in running conditions by measuring the surface crack dimensions at core and cavity zones of the die during regular intervals of the die-casting process. The effect of length and width of the cracks on the die surface concerning coolant channel positions was analyzed. Transient thermal analysis was performed to investigate the temperature distribution, principal stress and total deformation of the die concerning to the coolant channel position using ANSYS. The maximum deformation of core insert was 0.0094 mm. Zone C of the core insert, which was 223.52 mm from the coolant channel location and corresponding to 139,237 cycles, had the longest crack, measuring 18.98 mm. Owing to greater temperature gradients, Zone Z of the cavity insert, which is situated 76.25 mm from the coolant channel, had the largest crack width, measuring 0.29 mm. The durability of the die casting die obtained from the numerical model (2.8×105 cycles) was in agreement with experimental studies (2.89×105 cycles).

Frequency-Selective, Multi-Channel, Self-Powered Artificial Basilar Membrane Sensor with a Spiral Shape and 24 Critical Bands Inspired by the Human Cochlea.

A spiral-artificial basilar membrane (S-ABM) sensor is reported that mimics the basilar membrane (BM) of the human cochlea and can detect sound by separating it into 24 sensing channels based on the frequency band. For this, an analytical function is proposed to design the width of the BM so that the frequency bands are linearly located along the length of the BM. To fabricate the S-ABM sensor, a spiral-shaped polyimide film is used as a vibrating membrane, with maximum displacement at locations corresponding to specific frequency bands of sound, and attach piezoelectric sensor modules made of poly(vinylidene fluoride-trifluoroethylene) film on top of the polyimide film to measure the vibration amplitude at each channel location. As the result, the S-ABM sensor implements a characteristic frequency band of 96-12,821Hz and 24-independent critical bands. Using real-time signals from discriminate channels, it is demonstrated that the sensor can rapidly identify the operational noises from equipment processes as well as vehicle sounds from environmental noises on the road. The sensor can be used in a variety of applications, including speech recognition, dangerous situation recognition, hearing aids, and cochlear implants, and more.

Metallurgical insight of premature failure of a Blast Furnace copper stave

Present study investigates the premature failure (leakage) of copper (Cu) cooling staves placed at the lower stack region of a Blast Furnace (BF). This failure resulted in an increased frequency of make-up/ reserve water compensation every 10 h instead of average 24hrs. Detailed macro and microstructural analysis were carried out to understand the mechanism of failure in the Cu stave using phenomena observations, dial gauge measurements, metallographic investigation, and chemical analysis. Directional accretion of burden fines and puncture (leakage) profile were observed macroscopically. Puncture occurred from outer surface to inner surface of the channels of the stave. Micrographs of puncture location revealed non-uniform microstructure and grain deformation. Analysis suggested surface wear of the Cu stave due to a combined effect of continuous accretion of burden along with hot gas flow. Wear led to reduction in thickness and subsequent puncture/ leakage took place at the channel locations having a minimum cross-sectional thickness. With the help of this study, a failure mechanism of BF Cu Stave, a process critical component, has been explored. Recommendations such as insert modification, using more wear-resistant material or protective layer and conducting intermittent ultrasonic thickness measurements have been proposed to get an early warning of any untoward damages and process delays.

Study on MHD hybrid nanofluid flow with heat transfer in a stretchable converging/diverging channels embedded in a porous medium with uncertain volume fraction

This study considers a hybrid nanofluid flow in a non-parallel plate embedded in permeable stretchable convergent and divergent channels. It investigates the impact of the magnetic field and heat transmission on the velocity and temperature profiles of the hybrid nanofluid flow. Here, the walls of the stationary channels are considered to be allowed to stretch or shrink, and the hybrid nanofluids are Cu-Ag, with water as the base fluid. The nanoparticle volume fraction of hybrid nanofluid is considered an uncertain parameter, represented with a triangular fuzzy number ranging from 0.0 − 0.04 . A novel double parametric homotopy approach is used to study the impacts of the relevant parameters on the velocity and temperature profiles and validate the obtained result by comparing it with previously published literature in the crisp case without the porous medium. Finally, the fuzzy velocity and temperature profiles at distinct channel locations are graphically illustrated, accompanied by numerical representations of velocity and temperature bounds at various positions along the stretchable convergent/divergent channels.

Upgraded Low-Frequency 3D Lightning Mapping System in North China and Observations on Lightning Initiation Processes

The three-dimensional (3D) low-frequency lightning mapping system (LF-LMS) in north China has been updated. The lightning electric field derivative (dE/dt) sensor and continuous acquisition mode has been newly designed to ensure a capability of entire lightning processes detection, especially weak discharges during lightning the initiation process. The twice cross-correlation delay estimation and the grid iteration nested optimization location algorithm are used to realize the 3D location of the discharge channel, and the location resolution and calculation speed are balanced consequently. The location results of the rocket-triggered lightning demonstrated that the system achieved a high-resolution mapping of lightning discharge channels, which coincided well with the optical images. The horizontal and vertical location error for rocket triggered lightning was less than 40 m in both horizontal and vertical. Intracloud (IC) lightning flashes were observed to be initiated by three different discharge processes, initial breakdown pulse (IBP), narrow bipolar event (NBE), and initial E-change (IEC). The corresponding initial height was 10.5 km, 6.9 km, and 9.2 km, respectively. The upward negative leader was initially located, followed by scatter radiation sources and negative recoil leaders in the lower negative charge region for all cases. The electric field characteristics of the IEC and subsequent IBPs indicated that they are different discharge processes with the same current direction. The IEC process might correspond to the discharge process with continuous current and less noticeable current changes.

Riverine aquatic plants trap propagules and fine sediment: Implications for ecosystem engineering and management under contrasting land uses

AbstractPlants in streams act as physical ecosystem engineers, both influencing and responding to hydrogeomorphic processes such as fine sediment retention. Instream vegetation may also influence propagule dispersal and retention, shaping plant community dynamics. These plant‐sediment interactions may result in synergistic feedback promoting hydrogeomorphic complexity and biogeomorphic succession. However, the role of aquatic plants (submerged or mostly submerged) in trapping propagules, fine sediment and organic matter in degraded lowland streams is uncertain. In this study, we sampled sediment (≤5 cm depth) from eight streams ranging in land use from rural to urban, including within patches of aquatic vegetation and unvegetated locations. We conducted a propagule bank trial to identify the abundance and diversity of propagules and analysed the particle size and organic matter composition of the samples. A total of 8,365 seedlings from 113 plant species were recorded with a range of hydrological tolerances. Aquatic plants retained 56% more propagules and 32% more species, and marginal vegetation retained 250% more propagules and 48% more species, than open channel locations (the least retentive location). Similar patterns were found for fine sediment and organic matter retention. Propagule bank communities were different across land‐use types but not sampling locations. The trapping effect of aquatic vegetation diminished as catchments became more urbanised. This study provides evidence that aquatic plants retain more propagules and species, and fine sediment and organic matter than vegetation‐free channel locations. Improving aquatic vegetation in streams may be an important early step in restoring hydrogeomorphic complexity and propagule retention, and the facilitation of biogeomorphic succession in degraded streams. Unfortunately, heavily urbanised streams with flashy flow regimes are unlikely to benefit from this function unless catchment‐scale hydrology is addressed.

Analysis of the solid breakdown characteristics under high voltage pulse

As an efficient breakage technology, high voltage pulse breakage technology (HVP) has been an attractive topic due to its selective advantages. Typically, HVP is conducted in water and it is believed that the breakdown strength of water is higher than that of solids, and the discharge channel will be formed in solids under short voltage front rise time. The location of the discharge channel is important for understanding and optimizing of HVP. The study focuses on solid breakdown and the location of the discharge channel. The breakdown type during the HVP process is analyzed, the breakage characteristics of solid particles are investigated, the breakdown parameters are compared between water and solid, and the influence of solid composition on breakdown type is revealed. Under the settled conditions of this study, the results showed that: the discharge channel is easier to be formed inside the solid particle with the particle in contact with the electrode. And the discharge channel is formed in water with water gap between the solid and the electrode. The location of the discharge channel is affected by solid composition and the electrical breakdown probability can be improved with other compositions embedded in solid particles.

The grain size of sediments delivered to steep debris‐flow prone channels prior to and following wildfire

AbstractDebris flows are powered by sediment supplied from steep hillslopes where soils are often patchy and interrupted by bare‐bedrock cliffs. The role of patchy soils and cliffs in supplying sediment to channels remains unclear, particularly surrounding wildfire disturbances that heighten debris‐flow hazards by increasing sediment supply to channels. Here, we examine how variation in soil cover on hillslopes affects sediment sizes in channels surrounding the 2020 El Dorado wildfire, which burned debris‐flow prone slopes in the San Bernardino Mountains, California. We focus on six headwater catchments (<0.1 km2) where hillslope sources ranged from a continuous soil mantle to 95% bare‐bedrock cliffs. At each site, we measured sediment grain size distributions at the same channel locations before and immediately following the wildfire. We compared results to a mixing model that accounts for three distinct hillslope sediment sources distinguished by local slope thresholds. We find that channel sediment in fully soil‐mantled catchments reflects hillslope soils (D50 = 0.1–0.2 cm) both before and after the wildfire. In steeper catchments with cliffs, channel sediment is consistently coarse prior to fire (D50 = 6–32 cm) and reflects bedrock fracture spacing, despite cliffs representing anywhere from 5% to 95% of the sediment source area. Following the fire, channel sediment size reduces most (5‐ to 20‐fold) in catchments where hillslope sources are predominantly soil covered but with patches of cliffs. The abrupt fining of channel sediment is thought to facilitate postfire debris‐flow initiation, and our results imply that this effect is greatest where bare‐bedrock cliffs are present but not dominant. A patchwork of bare‐bedrock cliffs is common in steeplands where hillslopes respond to channel incision by landsliding. We show how local slope thresholds applied to such terrain aid in estimating sediment supply conditions before two destructive debris flows that eventually nucleated in these study catchments in 2022.

Bank erosion and erosion processes from dendrogeomorphology in southern U.S. prairie streams

AbstractStreambank erosion processes influence the amount of soil material contributed to rivers and sedimentation rates in receiving reservoirs. However, the amount of data on bank erosion rates is limited both in range and extent affecting planning for mitigation and watershed management. Dendrogeomorphology is used to determine the date of wood anatomy changes in annual growth increments of roots exposed by erosion of stream banks that when coupled with measurement of the distance of roots to the channel side can be used to calculate the bank retreat rate. Erosion rates derived from dendrogeomorphology are important because these provide erosion data over longer time scales (decades). Here, we use this method to quantify erosion for three different sized watersheds (4 to 3781 km2) located in the water‐scarce southern U.S. prairies that are heavily reliant on surface water and reservoir storage. From 49 roots from the two smaller drainages, erosion ranged from 1.5 to 25.4. For 19 roots collected from the larger subbasin erosion rates were larger ranging from 7.4 to 325.0 cm/years with the larger values and variance associated with two high‐flow events that occurred a year before sampling. We also found differences in straight and meandering portions of the streams where the distance to bank was strongly and positively correlated with the years since root exposure in straight sections. In contrast, meandering bends also showed a positive but low correlation for root exposure date and distance collected. We attribute this difference to erosional processes (i.e., scour and mass wasting) occurring at these channel locations. When compared with other erosion studies across the southern U.S. prairie, our values were similar in magnitude but with low correlation to drainage area indicating site specificity of erosion mechanisms, and watershed landcover influence for different drainages, despite being in the same ecological region.