Maximum Flow Depth Research Articles

Non-contact discharge estimation at a river site by using only the maximum surface flow velocity

The study proposes a novel method of computing river discharge based on the maximum surface velocity recorded using a non-contact-based measurement at a singular water surface point. This location, generally, coincides with the maximum flow depth of the cross-section and accounts for the dip phenomena, where the maximum instream velocity occurs below the water surface. The method is based on information entropy theory developed by Shannon (1948) and applied to river hydraulics. In this study an alternate form of entropy is used to compute discharge as a function of the cross-sectional mean velocity, maximum velocity and shear velocity (Keulegan,1938) by minimizing the error of the state equilibrium constant, ΦM, which is the ratio between the mean and maximum flow velocity, and that estimated using the Keulegan-based relationship. To test the accuracy of the proposed method, the maximum surface flow velocities measured at two gauging stations, each located on two different Italian rivers were studied. The estimated discharges by the proposed method were found to be comparable with the existing non-contact discharge method advocated by Moramarco et al. (2017) and, the traditional velocity-area method, using, e.g., the mean-section approach, based on the following metrics: the Nash-sutcliffe Efficiency (NSE), the coefficient of correlation and the percent bias (PBIAS). The mean velocity error emulates a Gaussian distribution for both the gauging stations and was within 95% and 5% confidance levels. Further, the entropy-based velocity profiles generated by the proposed method at the y-axis are consistent with those of the depth-based velocity profiles observed by the mechanical-current meter, thus, proving the appropriateness of the proposed discharge estimation method.

Effects of bed pumice content on lahar erosion: An example from Changbaishan volcano, China

Understanding the erosion of sediments by lahars contributes to future modeling and hazard assessment. However, studying the erosion mechanism of lahars in the field is challenging due to their suddenness and danger. We conducted a series of experiments to investigate the erosion associated with five different bed sediments (with a volume percentage of pumice ranging from 3%–32%), four channel slopes and released flows with four different discharges. The experiments showed that a pumice content of 32% in the erodible bed induces significant changes in the flow dynamics, erosion patterns, and erosion intensity of lahars. The maximum flow depth and mean velocity of lahars are positively related to the channel slope and discharge and inversely related to the pumice content. The initial peak erosion depth appears at the front of the erodible bed or slightly downstream, with additional erosion peaks occurring in the middle and lower reaches of the bed. The maximum erosion depth shifts from downstream to upstream as the pumice content increases. The erosion intensity of lahars exhibits a positive correlation with the bed pumice content, channel slope, discharge, and shear stress. Increasing the pumice content reduces the bed resistance and enhances the collisional stress and erosion wave effect of lahars, thus intensifying erosion. The pumice upwelling and erosion wave effect result in an irregular profile in the erodible bed. A new entrainment formula for erodible bed containing pumice was developed based on flume tests and theoretical analysis. This study helps to understand the effects of bed composition on lahar erosion and provides new insights into lahar erosion mechanism.

Small-Scale Experimental Evidence On The Use Of Date Palm Forest To Mitigate Tsunami In The Arabian Sea

Because of the multi-scale benefits, ecosystem-based disaster risk reduction (Eco-DRR) has received much attention in coastal disaster mitigation. Coastal forests are considered a sustainable and economical solution to mitigate inundations from tsunamis. Owing to the rare occurrence of tsunamis and reported local tsunami heights being small, the coastal forests are a potential solution to protect from tsunamis in the Arabian Sea. The potential of date palm trees to mitigate tsunami inundations was investigated in an experimental study. The experiments were conducted at a geometric scale of 1:100 with the Froude-Cauchy similitudes. It found that the canopy of the tree played a key role in flow energy reduction. If the tsunami height was higher than the canopy height a significant tsunami depth was reduced behind the forest compared to the case that the tsunami height was lower than the canopy height. The highest percentage reduction in the maximum flow depth behind the forest was 37% for the forest length of 180 m and tsunami height of 7 m.

Challenges in block-and-ash flow hazard assessment: The July 10–11, 2015 eruption of Volcán de Colima, Mexico

On July 10 and 11, 2015, Volcán de Colima, one of the most active Mexican volcanoes, underwent its largest eruption since the 1913 Plinian event. Highly mobile block-and-ash flows (BAF) originated from the dome collapse and subsequent extrusion of bubble gas-rich magma from the conduit. The volume and runout of flows were at least one order of magnitude higher (106 m3) than the events observed previously in the 2004–2005 eruptive episode (105 m3) and only comparable with the pyroclastic density currents emplaced during the Vulcanian eruptive phase that preceded the 1913 Plinian eruption. The TITAN2D code is here used to understand the factors controlling the mobility of the dense BAF undercurrents emplaced during the 2015 eruption. The selection of different input parameters was based on field data, on the seismic signal of the BAFs recorded by a broadband station located a few meters away from the channel, and by considering the different eruptive mechanisms of the July 10 eruptive phase (collapsing dome) with respect to the July 11 event (rapid extrusion of degassed magma directly from the conduit). A collapsing pile best fits the July 10 BAF, with an initial spread on the proximal reach and subsequent emplacement along the Montegrande ravine. Instead, for the July 11 BAF, an influx source best replicates the observed distribution, including the overspilling down the San Antonio ravine at the middle reach and the aggradation at the final depositional fan. Both events were better reproduced with the Voellmy-Salm rheology with respect to the Mohr-Coulomb model. Still, the mobility of the July 11 BAF was controlled mainly by the channel reduced capacity due to the 10 July BAF infilling. This was assessed by modeling the 11 July BAF on the real terrain and on a DEM whose altitude was modified based on the maximum flow depth obtained from the simulation of the former flow. Deep knowledge of the eruptive mechanism and flow behavior during the 2015 eruption allowed us to understand the main factors controlling concentrated pyroclastic density current mobility during sustained, multi-phase eruptions, especially for valley-confined BAF. The results presented here set the basis to improve the hazard zonation for pyroclastic density currents at Volcán de Colima, which should be based on a multifactor, probabilistic analysis.

Analysis of Uncertainty and Sensitivity in Tailings Dam Breach-Runout Numerical Modelling

AbstractTailings dam breaches (TDBs) and subsequent flows can pose significant risk to public safety, the environment, and the economy. Numerical runout models are used to simulate potential tailings flows and understand their downstream impacts. Due to the complex nature of the breach-runout processes, the mobility and downstream impacts of these types of failures are highly uncertain. We applied the first-order second-moment (FOSM) methodology to a database of 11 back-analyzed historical tailings flows to evaluate uncertainties in TDB runout modelling and conducted a sensitivity analysis to identify key factors contributing to the variability of the HEC-RAS model output, including at different locations along the runout path. The results indicate that prioritizing resources toward advancements in estimating the values of primary contributors to the sensitivity of the selected model outputs is necessary for more reliable model results. We found that the total released volume is among the top contributors to the sensitivity of modelled inundation area and maximum flow depth, while surface roughness is among the top contributors to the sensitivity of modelled maximum flow velocity and flow front arrival time. However, the primary contributors to the sensitivity of the model outputs varied depending on the case study; therefore, the selection of appropriate rheological models and consideration of site-specific conditions are crucial for accurate predictions. The study proposes and demonstrates the FOSM methodology as an approximate probabilistic approach to model-based tailings flow runout prediction, which can help improve the accuracy of risk assessments and emergency response plans.

Understanding flow characteristics from tsunami deposits at Odaka, Joban Coast, using a deep neural network (DNN) inverse model

Abstract. The 2011 Tohoku-oki tsunami inundated the Joban coastal area in the Odaka region of the city of Minamisoma, up to 2818 m from the shoreline. In this study, the flow characteristics of the tsunami were reconstructed from deposits using the DNN (deep neural network) inverse model, suggesting that the tsunami inundation occurred in the Froude supercritical condition. The DNN inverse model effectively estimated the tsunami flow parameters in the Odaka region, including the maximum inundation distance, flow velocity, maximum flow depth, and sediment concentration. Despite having a few topographical anthropogenic undulations that caused the inundation height to fluctuate greatly, the reconstructed maximum flow depth and flow velocity were reasonable and close to the values reported in the field observations. The reconstructed data around the Odaka region were characterized by an extremely high velocity (12.1 m s−1). This study suggests that the large fluctuation in flow depths on the Joban Coast compared with the stable flow depths in the Sendai Plain can be explained by the inundation in the supercritical flow condition.

Supercritical fluvial styles and the shifting aridity in the Early Triassic: the example of the Sanga do Cabral Formation, Paraná Basin, Brazil

Abstract Froude-supercritical bedforms and associated sedimentary structures are formed in turbulent flows when the value of the Froude number is Fr > 1. They have been increasingly studied in recent years, and while they were previously considered to be of rare preservation, they have been increasingly identified in modern settings and the rock record. In alluvial systems, these structures are being recognized as characteristic of rivers with high variability of discharge, especially in arid, semiarid, and subhumid tropical and subtropical climates. However, the development of facies models for such rivers remains tentative, particularly for the rock record, and with the exception of Australia, examples in Gondwana are scarce. The Early Triassic Sanga do Cabral Formation represents an arid to semiarid ephemeral fluvial system cropping out in southern Brazil, southwestern Gondwana. This study reinterprets the sedimentary structures in this formation as Froude-supercritical structures and identifies three fluvial styles (FS). FS1 predominantly consists of fine-grained massive sandstone with interruptions of intraclastic conglomerates, and occasionally visible faint lamination and mud-intraclast levels. It is interpreted as deposited by unconfined flows in the distal part of a fluvial system, generating hyperconcentrated flows which resulted in thin beds of fine-grained sandstone with massive structure or planar lamination and incipient antidunes. FS2 was deposited by flash floods occurring repeatedly within a short period during a wet season. This resulted in a fining-upwards succession of intraclastic conglomerates with supercritical-flow structures, through sandstones with supercritical-flow structures, to sigmoidal cross-stratification and ripple marks with diffuse lamination. FS3 was deposited by catastrophic flash floods characterized by high discharge and flow velocity, possibly generated by erratic storms, which poured in single events. These catastrophic flows generated large-scale sandy antidunes and other Froude-supercritical bedforms with mud intraclasts, which deposited sandstone in undulatory laminae, and other supercritical-flow structures. These floods waned extremely rapidly, bypassing the stability field of lower-flow-regime bedforms. Measurements taken from undulatory stratification, interpreted as antidune deposits, allowed the estimation of paleoflow velocity and depth. The largest antidunes had a maximum estimated wavelength of 28.92 m (with a mean of 15.4 m) and maximum estimated height of 1.42 m (with a mean of 0.85 m), resulting in an estimated paleoflow velocity of up to 6.72 ms−1 (with a mean of 4.9 ms−1) and a maximum flow depth of 1.59 m (with a mean of 0.9 m). These parameters are comparable to those observed in modern fluvial floods. This study reinforces the significance of Froude-supercritical structures in enhancing our understanding of fluvial systems characterized by high variability in discharge, allowing a finer interpretation of their discharge patterns. This approach can be applied to better understand the many arid, semiarid, or strongly seasonal environments of the Early Triassic period in Gondwana, and potentially other regions and geological times.

Detailed investigation and analysis of the dynamic evolutionary process of rainstorm debris flows in mountain settlements: a case study of Xiangbizui Gully

Short-term heavy rainfall often causes large-scale rainstorm debris flows in mountainous areas of Southwest China. Aiming to investigate the accumulation and movement of potential source material for the formation of debris flow hazards under extreme short-term heavy rainfall, this paper takes the Xiangbizui debris flow gully, Southwest China, as a case study. A detailed field engineering and geological investigation was carried out on the valley characteristics, formation conditions, provenance types, distribution range, loose solid material reserves that can be transformed into debris flows, and characteristics showing the variation in the grain size of the accumulated solids along the gully to further explore the characteristics of rainstorm-induced debris flow movement. The dynamic processes of debris flow movement and accumulation are numerically simulated to analyze the maximum velocity, accumulation height, range of influence, and evolutionary process based on the theory of continuous media of the approximate Voellmy solution and a high-precision three-dimensional model. The results indicated that rainstorms and steep terrain are the main factors stimulating debris flows. The amount of loose solid material in the channel is approximately 1550.61 × 104 m3, and the dynamic material reserves are approximately 396.41 × 104 m3. The maximum flow depth and velocity are approximately 3.5 m/s and 13 m/s, respectively, which mainly occur in the upper and middle reaches of the channel and in the accumulation fan at the outlet of the channel. The evolutionary process of the debris flow includes four stages: a 0–1,500 m initial acceleration stage, a 1,500–2,200 m fast forward movement stage, a 2,200–3,400 m acceleration stage in the middle and lower reaches, and a 3,400–4,300 m deceleration and end of accumulation stage. The research findings can provide a scientific basis and strong support for risk assessment and avoidance, as well as prevention and control of debris flows in mountainous areas with severe climate change.

A joint investigation of Saturn’s deep zonal flow via its gravitational field and Ohmic dissipation

ABSTRACT The Cassini Grand Finale provided a unique opportunity to study Saturn’s deep zonal flow. In this paper, we present a comprehensive deep zonal flow model for Saturn using a joint inversion of observed gravity and zonal flow-induced Ohmic dissipation in the semi-conducting region, under the assumption that the planet’s cloud-level wind is limited to a shallow weather layer. Our model unveils a strong equatorially symmetric zonal flow (O(100) m s−1) and a weaker antisymmetric zonal flow (O(1) m s−1) beneath the cloud-level winds. Furthermore, we show that the maximum depth of the deep zonal flow is around 7800 km, surpassing previous results derived from gravity alone and with the assumption that the rapid cloud-level winds extend deep into the planet’s interior. The meridional profile of the deep zonal flow differs significantly from the cloud-level zonal winds and predicts a strong westward zonal flow in the region with latitude around ±23°, where the observed cloud-top winds remain eastward. We also demonstrate that the zonal flow inside and outside the tangent cylinder exhibits significant differences in speed and scale. Moreover, our findings suggest that the coupling between the deep zonal flow and cloud-level winds varies across latitudes, with the shallow-wind model applicable to polar regions within the tangent cylinder and the deep-wind model more relevant to equatorial regions outside the tangent cylinder. Our findings highlight the importance of accounting for the planet’s deep zonal flow in future studies of Saturn’s atmospheric dynamics.

Comparison of two 2-D numerical models for snow avalanche simulation

Snow avalanches are gravitational processes characterised by the rapid movement of a snow mass, threatening inhabitants and damaging infrastructure in mountain areas. Such phenomena are complex events, and for this reason, different numerical models have been developed to reproduce their dynamics over a given topography. In this study, we focus on the two-dimensional numerical simulation tools RAMMS::AVALANCHE and FLO-2D, aiming to compare their performance in predicting the deposition area of snow avalanches. We also aim to assess the employment of the FLO-2D simulation model, normally used in water flood or mud/debris flow simulations, in predicting the motion of snow avalanches. For this purpose, two well-documented avalanche events that occurred in the Province of Bolzano (IT) were analyzed (Knollgraben, Pichler Erschbaum avalanches). The deposition area of each case study was simulated with both models through back-analysis processes. The simulation results were evaluated primarily by comparing the simulated deposition area with the observed one through statistical indices. Subsequently, the maximum flow depth, velocity and deposition depth were also compared between the simulation results. The results showed that RAMMS::AVALANCHE generally reproduced the observed deposits better compared to FLO-2D simulation. FLO-2D provided suitable results for wet and dry snow avalanches after a meticulous calibration of the rheological parameters, since they are not those typically considered in avalanche rheology studies. The results showed that FLO-2D can be used to study the propagation of snow avalanches and could also be adopted by practitioners to define hazard areas, expanding its field of application.

The role and safety of UVA and UVB in UV-induced skin erythema.

Different wavelengths of ultraviolet (UV) light cause skin damage through different mechanisms. Minimal erythema dose (MED) is usually used to clinically evaluate skin sensitivity to ultraviolet radiation by inducing skin erythema using ultraviolet B (UVB) or ultraviolet A (UVA) + UVB. In this study, we detected changes in the blood flow at the MED erythema caused by UVB and UVA + UVB radiation through optical coherence tomography (OCT) to explain the role of different bands of ultraviolet rays in erythema induction. Two MED irradiation areas on the subjects' back were irradiated with UVB alone or UVA + UVB (UVA: UVB = 8:1). The absolute energy of UVB remained the same in UVB and UVA+UVB. At 24 h after the irradiation, the changes in the blood flow in the MED area were detected using OCT. Compared with the blank control, the maximum blood flow depth, blood flow peak, and total blood flow of UVB-MED and UVA+UVB-MED were significantly increased. Notably, the maximum blood flow depth and blood flow peak of UVB-MED were higher than UVA+UVB-MED. There was no significant difference in total blood perfusion between UVA+UVB-MED and UVB-MED. Under the same UVB energy, the skin erythema caused by UVA + UVB was weaker than UVB alone. The analysis of local blood flow by OCT showed that the peak and maximum depth of local blood flow caused by UVB alone were significantly higher than UVA + UVB.

Sea-Level Rise Effects on Changing Hazard Exposure to Far-Field Tsunamis in a Volcanic Pacific Island

Coastal flooding exacerbated by climate change is recognised as a major global threat which is expected to impact more than a quarter of all people currently residing in Pacific Island countries. While most research in the last decade has focused on understanding the dynamics and impacts of future coastal flooding from extreme sea levels, the effects of relative sea level rise (RSLR) on exacerbating tsunami hazards are not well understood. Far-field or distant sourced tsunamis tend to have relatively lower impacts in Pacific Island states compared with locally sourced events, but there is limited understanding of how the impact of far-field tsunamis changes over time due to RSLR. Using the hydrodynamics software BG-Flood, we modelled the Tōhoku-oki tsunami from propagation to inundation in Samoa under incremental SLR to examine the effects that RSLR has on changing the exposure of the built environment (e.g., buildings) to a far-field tsunami. Outputs of maximum tsunami inundation and flow depth intensities which incorporate incremental SLR were then combined with digital representations of buildings and depth-damage functions in the RiskScape multi-hazard risk modelling software to assess the changes in building exposure over time. Results suggest that the impacts of Tōhoku-oki-type far-field tsunamis become significant once RSLR reaches 1 m above present levels. Present-day building exposure will increase by approx. 500% with 1 m RSLR by 2080–2130, and approx. 2350% with 2 m RSLR by as early as 2130–2140. These findings provide useful insights for application to tsunami hazard risk assessments under changing sea level conditions in analogous island environments.

Hurricane-induced lahars at Volcán de Colima (México): seismic characterization and numerical modeling

The Volcán de Colima, one of the most active volcanoes in Mexico, has experienced several volcanic crises over the last century with the emplacement of voluminous block-and-ash flow deposits providing large volumes of loose material along the main ravines. During the rainy season, this material is easily eroded forming lahars. Over 40 events with variable magnitude (105-106 m3) have been detected each year. The largest events that cause damages to infrastructure are usually triggered during the hurricane season (from mid-August to October) when more than 250 mm of rain usually are accumulated over a few days. On 23 October 2015, Hurricane Patricia hit the Volcán de Colima. The hurricane was announced as having reached category 5 thereby representing the largest ever recorded hurricane event in Mexico. It rapidly weakened after landfall but followed a straight trajectory toward the volcano. Up to 400 mm of rain were recorded over 30 hours. The event was recorded at a monitoring station located in the middle reaches of the La Lumbre ravine on the SW flank of the volcano, which was equipped with a rain gauge, a geophone (10 Hz), and a video camera. A multi-pulse lahar started around 8 pm (GMT) and lasted for more than five hours. The seismic signal and the video images were analyzed to identify the timing of the main pulses, the sediment concentrations, and maximum flow peak discharge. Data show that the lahar was characterized by three main pulses, in the range of debris flows with maximum flow-depth of 8 m, interspersed by more dilute tails as hyperconcentrated flow, as also observed from the frequency contents of the seismic signal. A total volume of 2.5 × 106 m3 was estimated based on the strong correlation between the seismic amplitude and the flow discharge. The lahar destroyed one bridge and ~500 m of the interstate road leaving several villages cut off for a few days. Based on the flow magnitude, duration, and the associated damage, this event probably represents the largest one recorded over the last 20 years. The FLO-2D model was used to replicate the observed event to estimate the maximum inundation limits of lahars along the five principal ravines of the volcano, in an attempt to design a hazard map for catastrophic hurricane-induced events.

Numerical Simulation on the Fluid Flow, Air Entrainment, Heat Transfer, and Solidification during Top Pouring and Cooling of a 303 Ton Heavy Ingot

Herein, a mathematical model combined with the k–ε turbulence model, volume of fluid multiphase model, and heat transfer and solidification model is established to investigate the steel–air two‐phase flow and solidification during the filling process of a 303 ton heavy steel ingot. The measured temperatures at different times are employed to validate the current mathematical model. The results show that the predicted results are in good agreement with the measured results. At the initial stage of the filling process, a double‐roll flow pattern is formed near the junction between the liquid surfaces due to the high speed of the jet flow. The maximum impinging depth of the jet flow is 1.8 m and the maximum splash height of the molten steel is 0.3 m. An empirical formula for the variation of the entrained air volume with time is proposed. The maximum growth rate in the horizontal direction is 0.08 mm s−1. In the vertical direction, the maximum growth rate of the solidified shell on the central axis is 0.12 mm s−1. The distribution of primary dendrite arm spacing and secondary dendrite arm spacing is obtained by combining the predicted cooling rate.

Impact of cross‐sectional orientation in one‐dimensional hydrodynamic modeling on flood inundation mapping

AbstractFlood management activities require development of flood maps that depict the spatial and temporal extent of floods with the help of hydrodynamic models. Two‐dimensional (2‐D) hydrodynamic models are frequently employed for flood inundation modeling and mapping with the help of high‐end computational resources and high‐resolution terrain information such as LiDAR (light detection and ranging) data. However, LiDAR data are either unavailable or not freely accessible in many parts of the world, especially in nations belonging to Global South. Hence, one‐dimensional (1‐D) models are still in practice owing to their lesser computational cost and data requirement. Nonetheless, the successful application of a 1‐D model depends mainly on the representation of the natural river and floodplain geometry, which is the primary input in the form of discrete cross‐sections. The assumed flow directions on floodplains while orienting the cross‐sections in 1‐D models induce some uncertainty in the model simulations. This study aims to evaluate the variability in the model simulations caused by the cross‐sectional orientations. Flood simulations were performed using a 1‐D hydrodynamic model for six different cross‐sectional realizations for three river reaches, having distinct morphological and topographical characteristics, and were compared with the simulations of a 2‐D hydrodynamic model and available reference inundation maps. The study suggests that the simulations of flood inundation extent and maximum flow depth variation are influenced by the cross‐sectional orientation on flood plains in river reaches characterized by broad flood plains with complex local topographical variations. In contrast, for reaches with relatively less wide and complex terrains, 1‐D models can generate robust simulations of flood inundation extent and spatial variation in maximum flood depth (R2 and NSE greater than 0.89) for high flood events.

Assessing tsunami vertical evacuation processes based on probabilistic tsunami hazard assessment for west coast of Aceh Besar, Indonesia

BackgroundTsunamis are rare events compared to other disasters but have devastating consequences. In the last 100 years, more than 24 tsunamis and more than 235,000 fatalities have occurred globally. Indonesia has a high risk of a tsunami disaster. Since the devastating 2004 tsunami in the Indian Ocean, much research and preparatory work have been done to reduce the impact of future tsunamis in Indonesia, including in the province of Aceh, especially along the western coast where West Aceh is located. This coastal area was destroyed by a tsunami as high as 15–30 m, resulting in the loss of life, housing, tourist areas, industrial areas, and other public facilities. Given that tsunami disasters are rare and sometimes occur long in advance, human memory and awareness are reduced, making research on the level of tsunami awareness of disasters a challenging task.MethodProbabilistic Tsunami Hazard Assessment (PTHA) is a method that has been developed to predict tsunami hazards with a return period of hundreds to thousands of years, beyond the limited availability of historical data. The PTHA method can provide important information that supports tsunami risk management measures. This study aims to estimate recurrence period-based tsunami risk on the west coast of the district of Aceh Besar using the PTHA method. In this study, the source of the tsunami is caused by fault activity at sea. Seven tsunami scenarios based on fault parameters (earthquakes of magnitudes Mw 8.0 to 9.2 with interval 0,2) with the fault location focusing on the Aceh-Andaman Mega Thrust Segment, as applied in this study. This segment was a similar source to the 2004 Indian Ocean tsunami that created a rupture area along a distance of 1155 km, with six parts of the fault.ResultThe maximum inundation distance reached 6 km for the flat area, with a flow depth of 13 m. The site has a cliff that is close to the shoreline, with an inundation distance shorter than the distance across the flat area. With an arrival time of less than 25 min, it is recommended to have an evacuation building and evacuation road in a wide inundated area, and an arrangement of hills close to the beach as an evacuation area, in order to reduce the number of casualties. For 100 years return period or exceedance probability rate 0.01, the average flow depth on the coast may exceed 5 m, and the maximum flow depth for a 1000-year return period or annual probability of 0.001 is 12 m. With the potential tsunami in the future, continuous tsunami drills and tsunami education are needed so that people can maintain an awareness of the threat posed by tsunamis.

Hazard assessment of potential debris flow: A case study of Shaling Gully, Lingshou County, Hebei Province, China

The debris flows in the Taihang Mountain region in North China are basically triggered by rainstorms. Firstly, the debris flow susceptibility of the Shaling Gully, Lingshou County, Hebei Province, China was analyzed in this paper to evaluate its hazard and effect on the downstream proposed structures. Secondly, the maximum flow depth and velocity of the potential debris flow in Shaling Gully were numerically simulated based on the FLO-2D model, and the simulation results indicate that the flow depths under the 50-year and 100-year rainstorms will have some effect on the downstream proposed structures. With debris flow intensity classification, the hazard of potential debris flow in Shaling Gully was classified. According to the flow depths and velocities simulated by FLO-2D model, the ARCGIS10.8 software was adopted to optimize the hazard zones, and therefore the hazard zonation map was established. With consideration of simulation results under natural conditions and other factors such as gully feature, a 4 m high and 40 m wide retaining dam was designed. The numerical simulation results show that the retaining dam may decrease the debris flow hazard to a negligible level, which offers some beneficial reference to the subsequent engineering design for Shaling Gully.

Expansion of pipeless drainage functions for draining poorly permeable soils

Due to climate change, in the next 30-50 years, an increase in precipitation during the growing season is predicted in the Non-Chernozem zone of Russia. However, even now, traditional methods of draining poorly permeable soils in a number of cases have proved to be ineffective due to the insufficiency of operational and capital measures to accelerate the removal of surface water and the weak hydraulic connection between the arable layer and drains. The experience of operation of drainage systems in the Nonchernozem zone of Russia has shown that at large distances between channels, the removal of surface runoff is difficult. A rational solution is to reduce the distances between the conductive channels. In this case, instead of open collectors, we propose to use cavityless collectors for drainage, which do not interfere with the movement of heavy agricultural machinery. A complete analysis of the functioning of cavityless collectors has been carried out. In the part of hydrology, accounting for the increase in precipitation is discussed and a method is given for calculating the maximum average daily module of drainage flow for the early spring and summer-autumn periods. A geotechnical calculation of the settlement during the passage of a heavy general-purpose tractor of the 5th traction class K-744R1 (Kirovets) was performed. It is shown that under the design conditions, the settlements will be about 1 cm. An example of a hydraulic calculation of the reservoir with the calculation of the initial and maximum depth of the filtration flow in it is given. Hydraulic calculation is carried out according to a proven method, the theoretical foundations of which were developed by the authors in previously published articles. An important feature is that all possible filtration modes are taken into account in the hydraulic calculation: laminar, transitional and turbulent.

Accelerating Tsunami Modeling for Evacuation Studies through Modification of the Manning Roughness Values

The role of the Manning roughness coefficient in modifying a tsunami time series of flow depth inundation was studied in Iquique, Chile, using a single synthetic earthquake scenario. A high-resolution digital surface model was used as a reference configuration, and several bare land models using constant roughness were tested with different grid resolutions. As previously reported, increasing the Manning n value beyond the standard values is essential to reproduce mean statistics such as the inundated area extent and maximum flow depth. The arrival time showed to be less sensitive to changes in the Manning n value, at least in terms of the magnitude of the error. However, increasing the Manning n value too much leads to a critical change in the characteristics of the flow, which departs from its bore-like structure to a more gradual and persistent inundation. It was found that it is possible to find a Manning n value that resembles most features of the reference flow using less resolution in the numerical grids. This allows us to speed up inundation tsunami modeling, which could be useful when multiple inundation simulations are required.

Hazard Zonation and Risk Assessment of a Debris Flow under Different Rainfall Condition in Wudu District, Gansu Province, Northwest China

Debris flows induced by heavy rainfall are a major threat in Northwest and Southwest China, due to its abrupt occurrence and long runout. In light of this, this work presents the runout simulation and risk assessment of the Boshuigou debris flow under different rainfall conditions in Wudu district, Gansu Province, Northwest China. Based on field reconnaissance, the geomorphological feature and main source of the Boshuigou debris flow were described. With the application of the FLO-2D simulation, the potential flow depth and flow extent of the Boshuigou debris flow under 100-year return-period rainfall and 50-year return-period rainfall were calculated. The maximum flow velocities of the Boshuigou debris flow under the 100-year return-period rainfall and 50-year return-period rainfall were 5.46 and 5.18 m/s, respectively. Accordingly, the maximum flow depths were 5.85 and 5.57 m. Then, the hazard zonation was conducted in combination of the construction and other properties within the potential impact zone, and the risk assessment of the Boshuigou debris flow under the 100-year return-period rainfall and 50-year return-period rainfall was finally completed. This work presents a method for debris flow risk assessment considering the solid source and water flow, which can provide a basic reference for mitigation and reduction of geohazards induced by torrential rainfall.