Heavy Rainstorms Research Articles

Increasing areas of aquaculture ponds and reservoirs reshape runoff coefficients: evidence from a subtropical catchment, China.

Detention pond is a key storm water management measure employed both to attenuate surface runoff and to regulate depression storage, yet the effects of aquaculture ponds and reservoirs on runoff coefficient are not well quantified in a subtropical humid monsoon climate zone, China. Here, a set of six subcatchments ranging in size from 0.7 hm2 to 10,000 hm2 were evaluated over the 2011-2015 period. (i) The annual average runoff coefficient differed with different subcatchments due to the spatial heterogeneity of landscape patterns, while the event-based runoff coefficient under the same catchment showed a decreasing trend with increasing rainfall intensity. (ii) The annual average and event-based runoff coefficients initially increased and then decreased with an increase in the area ratio of aquaculture ponds and reservoirs. The critical area ratio of aquaculture ponds and reservoirs for the maximum runoff coefficient in annual, light, and moderate rainfall intensity was about 4%; but this value would be transferred forward to the position of < 4% under the intensity of heavy rain, rainstorms, and heavy rainstorms. (iii) All runoff coefficients decreased with increasing forestland but increased with increasing paddy fields, and the decreasing rate was greater than the increasing rate. The trends of runoff coefficient for the annual and event-based rainfall are opposite between river development coefficient and watershed shape coefficient. The results provide underlying insights for decision-makers in aquaculture land-use planning and the sustainable utilization of water resources in the upstream and downstream systems of a catchment.

Model-Based Mechanism Analysis of “7.20” Flash Flood Disaster in Wangzongdian River Basin

With digital information technology based on limited data, disaster simulation review is an important guideline for analyzing disaster mechanisms, planning post-disaster reconstruction, and improving defense capability. Taking the “7.20” flash flood in the Wangzongdian river basin as a research area, a hydrological-hydrodynamic model was established using limited measured data. The results showed that the extreme rainstorm caused flooding in mountainous areas and the collapse of subgrade water damming, and the high-level flood quickly flowed into Wangzongdian Village in a short distance, which was the main cause of this serious disaster. Considering the collapse due to the congestion of the upstream bridge, the simulated flood flow in Wangzongdian Village reached 782 m3/s, which was basically consistent with the post-disaster survey results, with a relative error of only +8%. The modeling strategy proposed in this paper is applicable in the review of sudden heavy rainstorms and flash floods and can provide technical guidance for future flash flood simulation review analysis in other areas.

Characteristics of Soil Erosion and Nitrogen Loss in Vegetable Field Under Natural Rainfall

The effects of vegetable planting on soil loss and nutrient loss, runoff, soil erosion, and nitrogen (ammonium nitrogen and nitrate nitrogen) losses under individual rainfalls of fruit- and leaf-vegetable fields between April to October in 2021 were observed using in-situ observation testing. The results showed that: ① the runoff, erosion, and nitrogen loss of the fruit-vegetable pattern (eggplant-chili) were 1.27-2.00 times those under the leaf-vegetable pattern (leaf lettuce-sweet potato leaves), especially under the second season vegetable period. Those losses under the second season vegetable accounted for 50.86%-68.83% of the total losses under different vegetable patterns, which were approximately 1.03-2.04 times those under the first season vegetable. The runoff, erosion, and nutrient loss of vegetable fields under different treatments were both concentrated in June and July, and the nitrogen loss was mainly in the form of nitrate nitrogen with surface runoff. ② The runoff, erosion, and nutrient losses under individual rainfalls of vegetable fields under different treatments fluctuated among the vegetable growing season, and the losses were mainly concentrated in several typical rainfall events. On the whole, the loss and concentration of nitrate and ammonium nitrogen in runoff and erosion sediment of vegetables in the first season were lower than those in the second season. The runoff, erosion, and loss of ammonium nitrogen and nitrate nitrogen of fruit-vegetable were higher than those of leaf-vegetable. ③ Both rainfall amount and maximum 30 min rainfall intensity had significantly positive effects on runoff, soil loss, and nitrogen loss. Runoff, erosion, and nutrient losses under different vegetable patterns were mainly generated by moderate rain, heavy rain, and heavy rainstorms, which accounted for 29.58%-46.68%, 24.54%-36.79%, and 24.01%-39.13% of the total losses, respectively. The results also showed that soil erosion and nutrient losses generated by different rainfall grades were obviously different for the fruit- and leaf-vegetable treatments. The results indicated that the vegetable pattern had significant impacts on soil loss and nutrient loss, and the leaf-vegetable pattern could reduce soil erosion and nutrient loss compared with the fruit-vegetable pattern. Furthermore, for different vegetable patterns and vegetable growing seasons, the effects of rainfall on soil loss and nutrient loss were quite different. The results of this study were helpful in clarifying the soil erosion and nutrient loss characteristics of vegetable fields in South China.

Psychological challenges and related factors of ordinary residents after “7.20” heavy rainstorm disaster in Zhengzhou: a cross-sectional survey and study

BackgroundIn 2021, a once-in-a-century heavy rainstorm suddenly attacked Zhengzhou, an important inland city in northern China. However, there have been no studies on the psychological health of disaster-stricken residents. This study is the first to comprehensively report on the mental health status and related factors of local ordinary residents after the heavy rainstorm.ObjectiveThe purpose of this study is to investigate the mental health status and related influencing factors of local ordinary residents after the flood disaster, and to provide reference for government departments to formulate disaster psychological intervention countermeasures based on evidence-driven strategies.MethodsThe snowball sampling technique was used in this study, and measurement tools of Rainstorm Exposure Questionnaire, Subjective Perception of Rainstorm, Post-Traumatic Stress Disorder Checklist-Civilian version (PCL-C), Depression, Anxiety and Stress Scale-21 (DAS-21) and Chinese version of Social Support Rating Scale (SSRS) were used to evaluate the rainstorm exposure, subjective perception of the rainstorm, psychological symptoms and social support of the disaster-stricken residents within a week after the rainstorm. Logistic regression analysis was used to examine the psychological status and related factors of local residents after the rainstorm disaster.ResultsA total of 469 valid samples were obtained in this study. All the subjects were in the disaster area and experienced the rainstorm personally, with normal intelligence. The statistical results showed that 25.37% people had experienced at least three rainstorm-related stresses, nearly 20.26% people had post-traumatic stress disorder (PTSD) symptoms, and 39.3%, 53.92% and 65.83% people had depression, anxiety and stress symptoms, respectively. Multivariable logistic regression analyses indicated that female (all p < 0.05), the divorced, agricultural workers/farmers (all p < 0.05), students (all p < 0.05), people experiencing at least three rainstorm-related stresses (p < 0.05 or p < 0.01), people with lower satisfaction at the social flood fighting measures (p < 0.05 or p < 0.01) and people with low social support (p < 0.05 or p < 0.01) were all independent risk factors for poor psychological health, and college education or above (p < 0.05 or p < 0.01), the lower degree of worrying about themselves (all p < 0.01), family members (all p < 0.01) and family property (all p < 0.01) were all related to higher psychological health among flood survivors after the disaster.ConclusionsRainstorm could cause local residents to have various degrees of psychological symptoms. This study identified factors associated with the psychological health of disaster-stricken residents, which could be used to develop psychological interventions in improving psychological health of local residents.

Riding out the storm: depleted fat stores and elevated hematocrit in a small bodied endotherm exposed to severe weather.

In the mid-continental grasslands of North America, climate change is increasing the intensity and frequency of extreme weather events. Increasingly severe storms and prolonged periods of elevated temperatures can impose challenges that adversely affect an individual's condition and, ultimately, survival. However, despite mounting evidence that extreme weather events, such as heavy rain storms, can impose short-term physiological challenges, we know little regarding the putative costs of such weather events. To determine the consequences of extreme weather for small endotherms, we tested predictions of the relationships between both severe precipitation events and wet bulb temperatures (an index that combines temperature and humidity) prior to capture with body composition and hematocrit of grasshopper sparrows (Ammodramus savannarum) caught during the breeding season at the Konza Prairie Biological Station, Kansas, USA, between 2014 and 2016. We measured each individual's fat mass, lean mass and total body water using quantitative magnetic resonance in addition to their hematocrit. Individuals exposed to storms in the 24hours prior to capture had less fat reserves, more lean mass, more water and higher hematocrit than those exposed to moderate weather conditions. Furthermore, individuals stored more fat if they experienced high wet bulb temperatures in the week prior to capture. Overall, the analysis of these data indicate that extreme weather events take a physiological toll on small endotherms, and individuals may be forced to deplete fat stores and increase erythropoiesis to meet the physiological demands associated with surviving a storm. Elucidating the potential strategies used to cope with severe weather may enable us to understand the energetic consequences of increasingly severe weather in a changing world.

Elevation Angles, Soil Textures, Soil Settlements and WaterHolding Capacity on Landslides: An Experimental Case Study in the Province of Iloilo, Philippines

The soil textures, soil settlements, soil water-holding capacity, and elevation angles are parameters for landslides in the Province of Iloilo. They are usually triggered during heavy rainstorms, causing severe property damage and sometimes causing casualties. This experimental study aims to determine how these parameters are factors for landslides and flood monitoring and uses three methods to provide ease and continuity of measurements. The Fourier transforms infrared (FTIR)spectroscopy analysis for soil textures, the Imhoff cone for the settling and water-holding capacity of the soil, and an improvised apparatus to test how the slopes affect the transportation of soil materials. FTIR Soil analysis reveals that contents of clay and organic matter directly affect soil water-holding capacity due to the larger surface area. The smaller particle sizes, such as clay, have a larger surface area leading to a higher water-holding ability. A landslide-prone zone has a lesser settling time except for the sand that settles fastest due to larger masses. An angle of 20 degrees has more mass movement too much higher slopes like 55 and 85 degrees. The increase in height or angle of the elevation decreases stability, leading to less mass movement. Less mass movement leads to the conclusion that there are rare landslides in the very high slope range due to fewer vibrations or soil movements caused by human activities and being compact or stable. This study is crucial for forecasting and preventing geohydrological processes and developing better landslide warning strategies to mitigate risks and reduce socioeconomic damage.

Deduction of sudden rainstorm scenarios: integrating decision makers' emotions, dynamic Bayesian network and DS evidence theory

Event scenarios serve as the basis for emergency decision making after sudden disasters, and the accuracy of scenario deduction directly determines the effectiveness of emergency management implementation. On July 20, 2021, an exceptionally heavy rainstorm disaster occurred in Zhengzhou, Henan Province, China, causing serious urban waterlogging, river floods, flash floods and landslides and resulting in major casualties and property losses:14.79 million people affected, 398 people killed or missing (380 people in Zhengzhou) and a direct economic loss of 120.06 billion RMB. In order to investigate the complex evolution process of this disaster, a dynamic Bayesian network, evidence theory and emotion update mechanism are integrated to develop an efficient and effective scenario deduction model, with an emphasis on combining subjective and objective factors. In this model, more attention is given to subjective factors such as decision makers' emotions. The elements of scenario deduction are classified into the situation status, meteorological factor, emergency activities, decision makers' emotions and emergency goals, the coupling relationship between the elements are comprehensively analyzed, and the influence of these elements on the evolution mechanism of the rainstorm disaster is investigated, so as to facilitate targeted emergency management measures for the rescue operations. The empirical results show that the proposed dynamic Bayesian network can effectively simulate the dynamic change process of scenario deduction, the improved Dempster–Shafer evidence theory can reduce the subjectivity of the model in dealing with the uncertainty of the evolution process, and the emotion update mechanism can adequately quantify and decrease the influence caused by the emotional changes of decision makers. The model may better replicate actual events, and it may apply to the scenario deduction of other disasters, making an impact on the study of sudden catastrophes.

Analysis on the Role of Party Building Work in Emergency Management

On July 20, 2021, a heavy rainstorm struck Zhengzhou. In the face of this extreme sudden weather, Zhengzhou showed problems such as untimely emergency management and low level of modernization of emergency management, causing 14.786 million people to be affected. 398 people were killed or missing due to the disaster, and the direct economic loss was 120.06 billion yuan. This requires further exertion of the leading role in party building work. This article elaborates on the necessity of party building work, and analyzes the practical path in the process of flood control and disaster relief, and puts forward countermeasures and suggestions to continuously consolidate the safety foundation of social development and reduce emergencies. negative impact.

Comparative Study of Geological Hazard Evaluation Systems Using Grid Units and Slope Units under Different Rainfall Conditions

The selection of evaluation units in geological hazard evaluation systems is crucial for the evaluation results. In an evaluation system, relevant geological evaluation factors are selected and the study area is divided into multiple regular or irregular independent units, such as grids, slopes, and basins. Each evaluation unit, which includes evaluation factor attributes and hazard point distribution data, is placed as an independent individual in a corresponding evaluation model for use in a calculation, and finally a risk index for the entire study area is obtained. In order to compare the influence of the selection of grid units or slope units—two units frequently used in geological hazard evaluation studies—on the accuracy of evaluation results, this paper takes Yuanyang County, Yunnan Province, China, as a case study area. The area was divided into 7851 slope units by the catchment basin method and 12,985,257 grid units by means of an optimal grid unit algorithm. Nine evaluation factors for geological hazards were selected, including elevation, slope, aspect, curvature, land-use type, distance from a fault, distance from a river, engineering geological rock group, and landform type. In order to ensure the objective comparison of evaluation results for geological hazard susceptibility with respect to grid units and slope units, the weighted information model combining the subjective weighting AHP (analytic hierarchy process) and the objective statistical ICM (information content model) were used to evaluate susceptibility with both units. Geological risk evaluation results for collapses and landslides under heavy rain (25–50 mm), rainstorm (50–100 mm), heavy rainstorm (150–250 mm), and extraordinary rainstorm (&gt;250 mm) conditions were obtained. The results showed that the zoning results produced under the slope unit system were better than those produced under the grid unit system in terms of the distribution relationship between hazard points and hazard levels. In addition, ROC (receiver operating characteristic) curves were used to test the results of susceptibility and risk assessments. The AUC (area under the curve) values of the slope unit system were higher than those of the grid unit system. Finally, the evaluation results obtained with slope units were more reasonable and accurate. Compared with the results from an actual geological hazard susceptibility and risk survey, the evaluation results for collapse and landslide geological hazards under the slope unit system were highly consistent with the actual survey results.

Rainstorms drive export of aromatic and concurrent bio-labile organic matter to a large eutrophic lake and its major tributaries

Lakes are hotspots for global carbon cycling, yet few studies have explored how rainstorms alter the flux, composition, and bio-lability of dissolved organic matter (DOM) in inflowing rivers using high-frequency monitoring. We conducted extensive campaigns in the watershed of Lake Taihu and made daily observations for three years in its two largest inflowing tributaries, River Dapu and River Yincun. We found higher DOC, bio-labile DOC (BDOC), and specific UV absorbance (SUVA254) levels in the northwestern inflowing regions compared with the remaining lake regions. DOC and BDOC increased during rainstorms in River Dapu, and DOC declined due to local dilution and BDOC increased during rainstorms in River Yincun. We found that rainstorms resulted in increased DOM absorbance a350, SUVA254, and humification index (HIX) and enhanced percentages of humic-like fluorescent components, %polycyclic condensed aromatic and %polyphenolic compounds as revealed from ultrahigh-resolution mass spectrometry (FT-ICR MS), while spectral slope (S275-295) and the percentages of protein-like C1 and C3 declined during rainstorms compared with other seasons. This can be explained by a combined flushing of catchment soil organic matter and household effluents. The annual inflows of DOC and BDOC to Lake Taihu were 1.15 ± 0.18 × 104 t C yr−1 and 0.23 ± 0.06 × 104 t C yr−1 from River Dapu and 2.92 ± 0.42 × 103 t C yr−1 and 0.53 ± 0.07 × 103 t C yr−1 from River Yincun, respectively, and the fluxes of DOC and BDOC from both rivers increased during rainstorms. We found an elevated frequency of heavy rainfall and rainstorms in the lake watershed during the past six decades. We conclude that an elevated input of terrestrial organic-rich DOM with concurrent high aromaticity and high bio-lability from inflowing rivers is likely to occur in a future wetter climate.

Vegetation regeneration on natural terrain landslides in Hong Kong: Direct seeding of native species as a restoration tool

AbstractLandslides are common in tropical and subtropical regions with hilly terrains and heavy rainstorms, and can cause significant economic, ecological, and social impacts. Natural forest succession is usually slow on landslides due to poor soil structure and lack of woody plant seeds, and often comes with a higher risk of repeated landslides. Active forest restoration has been increasingly suggested as an effective alternative to restore exposed landslide scars. Here, we evaluated the effectiveness of using different seed coatings and surface soil treatments on seed germination and seedling establishment of pioneer and late‐successional tree species on landslide scars in Hong Kong. Our results show that biochar‐dominant seed coating boosted seed germination rate by an additional 9.33% (Standard error = 0.04), while clay‐dominant seed coating did not show significant effects. The effects on seedling survival were not significant in both seed coating and surface soil treatments. Our results also show that large seed and later successional species have significantly higher germination rates than pioneer species and are able to successfully establish on landslide sites. These results suggest that direct seeding using a biochar seed coat with large seeds or late‐successional species is a useful method to enhance tree seed germination—an essential first step to restore the forests after landslide disturbances, with potential to be extended to other humid tropical and subtropical forests.

Effect Analysis of Supporting Structure and Surface Settlement on Deep Foundation Pit by Rainstorm: A Case Study in Zhengzhou

Rainfall usually leads to soil slope sliding and instability, which affects the safety of foundation pit, especially in the case of heavy rainfall. This study took the 7.20 Henan rainstorm as the background, where in the process of construction, after three days of rainstorm of 617.7 mm deep, the horizontal displacement of supporting structures of a foundation pit in Zhengzhou city increased by 6.3 mm. Therefore, it is of great significance to study the mechanism of deformation induced by rainstorm of foundation pits. Five numerical models considering different rainfall factors were developed to simulate the rainstorm process based on the monitoring data. The deformation mechanism and the effect factors of deformation on the foundation pit during rainstorm were analyzed, and some preventive measures were put forward for when the foundation pit engineering faces a heavy rainstorm. Under the action of the rainstorm, the supporting structure and the surface settlement had a signification deformation caused by the heavy rainfall on this typical foundation pit, and the maximum bending moment and maximum displacement of the supporting structure shifted up to different degrees. The main factors affecting the deep foundation pit of the metro by heavy rain are the steel strut falling off and the whole foundation pit filling with water, while the influence caused by the rise in the groundwater level, water standing load, and soil softening is small.

Factors Affecting Behaviors that Precede Evacuation at the Onset of a Heavy Rainstorm in Japan

There exist certain behaviors that people tend to do in disaster situations before evacuation. Such behaviors include warning confirmation behavior (for example, seeking information) and family-oriented behavior (for example, contacting one’s family). Identifying factors that affect these behaviors is of particular importance in building a better understanding of why people often fail to respond quickly to evacuation orders. For this purpose, the present study employed some of the established factors affecting evacuation behavior as predictor variables along with the timing of an evacuation order. A total of 518 participants took part in a 12-item online questionnaire survey that contained a hypothetical disaster scenario. The results of ordinal logistic regression analyses revealed that only risk area residence and disaster preparedness were associated with warning confirmation behavior, while gender, age, disaster preparedness, and risk perception had some associations with family-oriented behavior. Also, the participants were not more likely to engage in these behaviors in the morning and the afternoon than the evening in the hypothetical scenario. These findings imply the possibility that people engage in warning confirmation behavior and family-oriented behavior before evacuation regardless of individual characteristics and the circumstances surrounding them.

Evaluation of the Dynamical–Statistical Downscaling Model for Extended Range Precipitation Forecasts in China

In order to focus on pentad-scale precipitation forecasts, we investigated the coupling relationship between 500 hPa geopotential height (Z500) anomalies and precipitation anomalies using the China Meteorological Administration Global Land Surface ReAnalysis Interim (CRA40/Land) gridded precipitation dataset from 1999 to 2018 and the National Centers for Environmental Prediction 1 reanalysis dataset for Z500. We obtained a dynamical–statistical downscaling model (DSDM) on the pentad scale and used the daily Z500 forecast product for sub-seasonal to seasonal forecasts (15–60 days) of the FGOALS-f2 model as the predictor. Our results showed that pentad-scale prediction of precipitation is the key to bridging the current deficiencies in sub-seasonal forecasts. Compared with the FGOALS-f2 model, the pentad DSDM had a higher skill for prediction of precipitation in China at lead times longer than four pentads throughout the year and of two pentads in the summer months. FGOALS-f2 had excellent precipitation predictability at lead times less than three pentads (15 days), so the proposed pentad DSDM could not perform better than FGOALS-f2 in this period. However, at lead times greater than four pentads, the precipitation prediction scores (such as the anomaly correlation coefficient (ACC), the temporal correlation coefficient (TCC) and the mean square skill score (MSSS)) of the pentad DSDM for the whole of China were higher than those of the FGOALS-f2 model. With the rate of increase ranging from 76% to 520%, the mean ACC scores of pentad DSDM were basically greater than 0.04 after a lead time of five pentads, whereas those of the FGOALS-f2 were less than 0.04. An analysis of the Zhengzhou “720” super heavy rainstorm event showed that the pentad DSDM also had better predictability for the distribution of precipitation at lead times of three pentads than the FGOALS-f2 model for the extreme precipitation event.

A field parcel-oriented approach to evaluate the crop cover-management factor and time-distributed erosion risk in Europe

The crop cover-management (C-) factor in arable landscapes describes the soil erosion susceptibility associated with seasonally cultivated crops. Previous informatic and computational limitations have led many modelling studies to prescribe C-factor values and assume spatial and temporal stationarity. However, the multiple influencing factors ranging from parcel-scale crop cultivation and management to regional-scale rainfall regimes motivates new methods to capture this variation when identifying at-risk areas. Here, we define a multi-component method to derive the C-factor by associating time series of canopy and residue surface cover from Sentinel-2 and climate-specific rainfall erosivity with Integrated Administration and Control System (IACS) field parcel data from European Union member states. A scalable and standardised method is emphasised to increase the future interoperability and inter-comparability of soil erosion modelling studies deploying the C-factor. Additionally, field parcel simulation units with associated crop declarations provide a new reference scale to link predictions of soil erosion risk with specific management decisions and declarations by farmers. After implementing the method on a homogenised subsample of 8600 field parcels covering available IACS regions, several key findings are outlined: 1) time series information provides new opportunities to predict the time-criticality of erosion in specific crop cultivations, 2) the varying (a-)synchronicity between seasonal crop canopy cover and heavy rainstorms means that spatial variability is inherent within the C-factor across Europe, and 3) the addition of agricultural management practices (e.g. tillage practice descriptions) to open-access IACS repositories can facilitate more comprehensive evaluations of the C-factor and soil erosion risk.

Dynamic consensus of large group emergency decision-making under dual-trust relationship-based social network

Trust relationship is an effective basis for reducing the dimensionality of decision makers (DMs) for group decision making (GDM) problems in the context of social networks, and have received extensive attention in the past few years. However, most existing studies describe the trust relationship only from the single perspective of the interpersonal relationships between DMs, which easily leads to inaccurate decision-making results. In this paper, we propose a dynamic consensus method using a dual-trust relationship-based social network (DTRSN) to solve large group emergency decision-making (LGEDM) problems. First, to more accurately reflect the trust relationship among DMs, a DTRSN based on familiarity-based trust and similarity-based trust is developed, which can comprehensively model the interpersonal relationships and opinion similarity between DMs simultaneously. Next, a DTRSN-based clustering method that considers dual-trust relationships is introduced to divide the large-group DMs into several clusters. Subsequently, to improve the efficiency of LGEDM, the exit-delegation mechanism is modified and introduced into our study, which can speed up consensus by excluding some subgroups whose opinions differ greatly from other subgroups and reserve their influence. Subsequently, a dynamic consensus method based on the modified exit-delegation mechanism is proposed to help DMs reach an agreement quickly. Finally, a case study regarding emergency alternative selection to deal with heavy rainstorms in Zhengzhou, China, is conducted to verify the efficiency of our study, and several comparison and simulation analyses are also conducted to demonstrate the feasibility and practicality of the proposed method.

"풍화 산지에서 토사 재해 발생에 영향을 미친 요소들에 대한 연구 - 2020년 충청북도 북부지역을 사례로 -"

Among the reports for damaged area by landslide in Chungju, Jecheon, and Danyang-gun in the northern region of Chungcheongbuk-do, where damage occurred due to heavy rainstorms from July 28 to August 11, 2020, the coordinates of the locations has been confirmed at 438 places. Analyses were conducted for those spots using the landslide information system of the Korea Forest Service, geological information from geobig data, KAKAO map, and satellite images from Google Earth. The most common bedrock in the affected area was granite, followed by gneiss, limestone and other sedimentary rocks, slate and phyllite. As for the slope, sedimentary rocks such as granite and limestone have the steepest slope, and gneiss, granite, slate and phyllite follows it. It seems that the impact by landslide on these types of rocks depended on slope and weathering pattern. The damage type examined in 375 sites out of 438 were due to erosion and sediment runoff from the slope, and debris flow occurred in 63 places. In 31 of them, it was found that the outflow of soil from the slope was connected to the debris flow. As a result of analyzing the rock types, most of the debris flow in the granite area appeared to be ‘runoff-dominant erosion’. It seems that ‘infiltration-triggered soil slip’ was strong in the limestone area. In this study, using Dynamic World, Google’s land cover change tracking service, surface cover changes were tracked between 2018 and 2021-2022 before landslide-related damage occurred, and it was found that small-scale vegetation changes in land use near the study area. It can be seen that changes in Korea’s forestry policy have had a significant impact on this. In particular, significant landslides have occurred after the considerable amount of time followed by anthropogenic change of vegetation and building of forest roads. Therefore, it seems that continuous management is essential to prevent landslide disasters after anthropogenic changes in land cover. In addition, field studies on the condition of soil weathering in mountainous areas and the process of material movement on slopes are essential.

Contrasts in the Evolution and Microphysical Features of Two Convective Systems during a Heavy Rainfall Event along the Coast of South China

On 1 June 2021, a heavy rainstorm hit the coast of South China (148.6 mm in 1 h, 361 mm over 12 h). The storm process was successively affected by two convective systems (CSs). The initial convection of the two CSs occurred at a similar location; however, they subsequently showed different evolution characteristics. Based on multi-source data, including dual-polarimetric radars, wind profiling radars, sounding, and automatic weather stations, we explored the differences in the key characteristics of these two CSs. It was found that the convection was initially triggered at a similar location for both CSs, closely related to the mesoscale boundary and the hilly terrain. After formation, CS1 moved eastward to the regions with lower surface temperature and weaker lower-level convergence but similar humidity, which means the environmental conditions for sustaining the CS became less favorable. As a result, CS1 dissipated rapidly and only lasted for about 90 min, resulting in 5% of the total precipitation of the overall storm. In contrast, during the lifespan of CS2, the southerly wind over the South China Sea became stronger. This caused an intense lower-level convergence zone along the coastal region of Guangdong Province, which provided favorable dynamic conditions for maintaining CS2. Favored by the strong coastal convergence and abundant moisture, new convective cells (CCs) were generated continuously and merged with CS2, acting as another favorable condition for its sustainment. Overall, CS2 lasted for 8 h, and its precipitation accounted for 95% of the total rainfall. In CS1, CCs showed a notable evaporation process below 4 km, manifested by the large raindrops. However, in CS2, the CCs had a higher concentration of small raindrops and higher ice and liquid water content. Since CS2 was close to the coastal region, the warm local environment promoted convection, leading to intense precipitation. In addition, the riming and melting processes were active, leading to a high precipitation efficiency and strong local precipitation during a short period of time.

Impact of spatial discretization resolution on the hydrological performance of layout optimization of LID practices

• Four SWMM models with various spatial discretization resolutions were constructed. • The scale effects on the LID layout optimization are discussed. • Solutions optimized by the finest model performed best under small rainfall events. • Modelling scale had little impact on the layout optimization under a heavy rainstorm. • Layouts optimized by a coarse model overshadowed some types of LID practices. Climate change and increasing urbanization have worsened urban floods and other water problems, and it is generally accepted that the optimization of the spatial layout of low impact development (LID) practices is a promising solution. Existing studies have focused on coupling the hydrological model with optimization methods, but little is known about the effects of the spatial discretization of the model on the optimization results. In this study, the scale effects were examined in a case study in Guangzhou, China. Four models at various spatial discretization levels, namely models R1, R2, R3, and R4, with an average unit size of 0.022*10 4 , 0.405*10 4 , 2.43*10 4 , and 4.865*10 4 m 2 , respectively, were constructed to investigate the performance difference caused by delineation scales. The results show that the highest-resolution model R1 (one unit represented one type of land cover) provides more cost-effective layout schemes, but during a heavy rainstorm, the solution set provided by a coarser model are very similar to that generated by the finest model R1. A coarser model can provide wider solution sets, but most of these schemes overshadow some types of LID practices such rain garden and bio-retention cell, which also have a critical role in urban heat mitigation, air quality improvement, and so on. Due to the cumbersome work of catchment subdividing and time-consuming optimization process, a coarse model would be a good substitute to a large area. These findings provide new insights on how to achieve better performance by subdividing the catchment at a proper scale when optimizing the spatial layout of LID practices.

Evaluating soil water and salt transport in response to varied rainfall events and hydrological years under brackish water irrigation in the North China Plain

• Responses of soil water and salt dynamics to varied rainfall events and hydrological years were evaluated. • Salt leaching and deep drainage occurred mainly due to summer-concentrated rainfall during wet year. • Salt decrease percentage in the CL was greater than that in the GL in all hydrological years. • One brackish water irrigation application is avail salt leaching both in cropland and grassland. Soil salination challenges sustainable agricultural production and management in the lowland area of the North China Plain (NCP). This study investigated the effect of varied rainfall events and hydrological years on deep drainage and salt leaching in Nanpi County in the NCP. Field experiments were conducted to measure soil matric potential (SMP) and soil water electrical conductivity (EC w ) in 300 cm profiles of an irrigated cropland (CL) and unirrigated grassland (GL). The HYDRUS-1D model was calibrated and validated to optimize soil water and salt transport parameters using the SMP and EC w data obtained in 2015 and 2016, respectively. The results showed that the HYDRUS-1D model was reliable to simulate soil water and salt migration in 300 cm profiles at both sites. The salt leaching depths and degrees were positively correlated with precipitation amount. The heavy rain (45 mm) and rainstorm (68 mm) favored salt leaching within 100 cm, and severe and extreme rainstorms resulted in salt leaching within 150–200 cm both in the CL and GL. The SDP in the CL was greater than that in the GL in all hydrological years owing to agricultural cultivation and irrigation. Salt leaching in the 300 cm profiles mainly occurred in the rainy seasons of wet year, with the salt decrease percentage (SDP) being 61% in the CL and 42% in the GL. Salt leaching due to precipitation was sufficient in the irrigated CL in all hydrological years, and precipitation in normal rainfall years could remove 70–80% of soil salts within 50–63 cm soil depth. Grass growth without irrigation led to water deficits and salt accumulation when the annual precipitation amount was less than that in wet years. The results demonstrated that precipitation, combined with irrigation using of brackish and freshwater, could be usefully for soil salt leaching. A recommended irrigation scheme for water saving and salt control in CL and GL is one brackish water irrigation application and three freshwater irrigation applications each year in the NCP.