Maximum Rainfall Intensity Research Articles

Rainfall pattern over the North-West Himalayan region: historical time period vs. future warming scenarios

Events like melting glaciers, rising sea level, and changing weather patterns are being observed across the globe due to widely reported global warming. The monsoon season rainfall in the North-Western Himalayan region (NWH) becomes more uncertain as there is considerable variation between the duration of the monsoon season and the amount of rainfall during the season. The NWH region receives substantial amount of rainfall and witness various disasters during the monsoon season. In this context, the present study deals with the analysis of the rainfall patterns under various future warming scenarios (2076–2100), namely representative concentration pathway scenario 4.5 (RCP 4.5) and RCP 8.5 (RCP 8.5) with respect to the reference historical time period (1976–2000) during the principal monsoon season (i.e. 1st June to 30th September) of two Indian states (Uttarakhand and Himachal Pradesh) of the NWH region. To serve this purpose, six attributes are defined as follows; start date of the rainy season (SRS), date of the 50% of the seasonal total rainfall (HRS), end date of the rainy season (ERS), length of the rainy season (LRS), 1 day maximum intensity (MRS) and the day corresponding to the maximum rainfall intensity (MDRS). These attributes are estimated for both historical time period and various future warming scenarios based on the archives of five coupled climate models which participated in the Climate Model Inter-comparison Project Phase 5 (CMIP5). Considering huge inter-model variations amongst the CMIP5 models, results are presented here based on the multi-model mean (MME). Characteristics of various attributes of rainfall during the historical time period are compared with that of the two future warming scenarios viz.; RCP 4.5 and RCP 8.5 by means of statistical techniques. There is a possibility of early SRS, delayed ERS and extended LRS along with intense MRS under different future warming scenarios over Himachal Pradesh (HP) as compared with the historical time period; however, results are significant only for 1 day maximum rainfall under RCP 8.5. Similarly, over the Uttarakhand (UK) region, changes in the rainfall pattern are noted under two future warming scenarios viz.; RCP 4.5 and RCP 8.5 as compared with the historical time period; nonetheless, significant changes are noted in MRS and MDRS only under RCP 8.5. It is anticipated that both of the NWH states of HP and UK would experience enhanced MRS under the warmest future warming scenario (i.e. RCP 8.5). Based on the present analysis, intense rainfall events are expected which could act as an initiator for various meteorological hazards over the NWH region in future.

Analysis of Urban Whale Drainage Capability Pekanbaru to the Maximum Intensity of Rainfall

Drainage becomes an essential tool in an urban area. A city can be said neat and orderly if its drainage facility can accommodate any existing water discharge, either from rain or the flow of household disposal. Jalan Pope Pekanbaru is the connecting road between Tuanku Tambusai road and Arifin Achmad street. Pope road condition is very strategic then Pope street becomes one of business area in Pekanbaru. ). This study aims to determine the capacity of the drainage channel of the city of Pekanbaru whales against the intensity of rainfall in the city of Pekanbaru. The method used is direct survey sampling to the field then analysing precipitation, frequency and probability of rain by using four types of distribution used in the field of hydrology that is Normal Distribution, Normal Log Distribution, Log Person Distribution III and Gumbel Distribution type 1, rain intensity with mononobe method. Because short-term data is not available, Calculates the discharge plan and the drainage channel. Based on the results of the 5-year Planet Bit Flow analysis using the Gumbel type 1 method of 247.53 m / s, the flow of existing drainage (Q) is 0.6245 m / sec, while the peak flood flow (Qp) is m / seconds

Impacts of Anthropogenic Heat Flux and Urban Land-Use Change on Frontal Rainfall near Coastal Regions: A Case Study of a Rainstorm over the Pearl River Delta, South China

AbstractThis study investigated heavy frontal rainfall that occurred on 13–14 October 2011 over the Pearl River Delta (PRD) in China. The frontal rainstorm was simulated using the WRF-ARW Model (version 3.3), which included its urban canopy model. Although the model-simulated convection occurred 2 h early and the second precipitation peak was underestimated, the model represented the formation, development, and extinction of the frontal rainfall and captured the distribution of the peak value. In addition, the averaged value of 49.7 W m−2was taken as the anthropogenic heat flux (AHF) of the PRD, and two land-use datasets were adopted: one for 1992 and the other for 2011. The simulation revealed that AHF and urban land-use change (ULUC) increased the total rainfall over the PRD by 6.3% and 7.4% and increased the maximum hourly rainfall intensity by 24.6% and 21.2%, respectively. Furthermore, to elucidate the mechanism of AHF and ULUC influence, the rainstorm structure, low-level jet (LLJ), and CAPE of the rainfall event were analyzed. It was found that AHF and ULUC enhanced two strong southward LLJs located over the urban areas, which carried abundant water vapor to the PRD and generated additional upper-level CAPE. This not only sustained steady ascent of the air, but it also created conditions favorable for downward motion, resulting in large persistent convective clouds and heavy frontal rainfall.

Intensity-duration-frequency of maximum rainfall in Mato Grosso State

Intensive rainfall is an important meteorological variable that is of technical interest in hydraulic projects. This study therefore generated Intensity-Duration-Frequency equations (IDF) for 14 weather stations in Mato Grosso State, based on pluviograph analysis. Annual maximum rainfall data regarding 10-to-1440-minute long rainfall events were collected from digitized daily pluviographs. Data adherence to the generalized extreme value distribution (GEV) was checked through the Kolmogorov-Smirnov test at a 20% significance level. Next, the maximum probable rainfall for return periods such as 2, 5, 10, 20, 30, 50 and 100 years was calculated and the IDF equations were adjusted. The performance of the IDF equations was evaluated based on mean absolute error (MAE), root mean square error (RMSE), bias, Willmott's concordance index and Nash-Sutcliffe efficiency index (ENS). Adjusting the IDF equations was only possible for rainfall durations ranging from 10 to 360 min at each station due to the low frequency of longer rainfalls. High variation was present in parameters of the IDF equation and in maximum rainfall intensity between stations. The satisfactory performance of the models, as attested to by statistical indices, allows using IDF equations adjusted for rainfall durations from 10 to 360 min, and return periods from 2 to 100 years, in the regions of the Mato Grosso weather stations.

Thresholds for post‐wildfire debris flows: Insights from the Pinal Fire, Arizona, USA

AbstractWildfire significantly alters the hydrologic properties of a burned area, leading to increases in overland flow, erosion, and the potential for runoff‐generated debris flows. The initiation of debris flows in recently burned areas is well characterized by rainfall intensity‐duration (ID) thresholds. However, there is currently a paucity of data quantifying the rainfall intensities required to trigger post‐wildfire debris flows, which limits our understanding of how and why rainfall ID thresholds vary in different climatic and geologic settings. In this study, we monitored debris‐flow activity following the Pinal Fire in central Arizona, which differs from both a climatic and hydrogeomorphic perspective from other regions in the western United States where ID thresholds for post‐wildfire debris flows are well established, namely the Transverse Ranges of southern California. Since the peak rainfall intensity within a rainstorm may exceed the rainfall intensity required to trigger a debris flow, the development of robust rainfall ID thresholds requires knowledge of the timing of debris flows within rainstorms. Existing post‐wildfire debris‐flow studies in Arizona only constrain the peak rainfall intensity within debris‐flow‐producing storms, which may far exceed the intensity that actually triggered the observed debris flow. In this study, we used pressure transducers within five burned drainage basins to constrain the timing of debris flows within rainstorms. Rainfall ID thresholds derived here from triggering rainfall intensities are, on average, 22 mm h−1 lower than ID thresholds derived under the assumption that the triggering intensity is equal to the maximum rainfall intensity recorded during a rainstorm. We then use a hydrologic model to demonstrate that the magnitude of the 15‐min rainfall ID threshold at the Pinal Fire site is associated with the rainfall intensity required to exceed a recently proposed dimensionless discharge threshold for debris‐flow initiation. Model results further suggest that previously observed differences in regional ID thresholds between Arizona and the San Gabriel Mountains of southern California may be attributed, in large part, to differences in the hydraulic properties of burned soils. © 2019 John Wiley & Sons, Ltd.

Determinação de curva IDF para o município de Governador Newton Bello no estado do Maranhão

A necessidade de informações sobre as precipitações de determinadas durações e frequências é muito grande em projetos hidráulicos diversos. Assim, o objetivo do trabalho é ajustar a função cumulativa de probabilidades de Gumbel para se obter as intensidades máximas de precipitações esperadas para diferentes períodos de retorno, obtendo-se a equação de intensidade-duração-frequência, por meio do método das isozonas, para dados de precipitação máxima diária anual. Nesse caso, foram adotados os dados pluviométricos da estação pluviométrica Newton Belo no período entre 1985 e 2013. Uma série de máxima intensidade pluviométrica para um dia de precipitação foi elaborada, utilizando-se a metodologia de Gumbel. Os valores extremos para os períodos de retorno de 5, 10, 20, 30, 50 e 100 anos foram estimados, pelo método das isozonas, ajustando-se a curva IDF, que foi comparada a curvas IDF da região nordeste e sudeste, demonstrando boa estimativa para as intensidades de chuvas. Essa comparação sugere que a equação gerada pode ser utilizada para o cálculo da intensidade máxima de chuvas com diferentes durações e períodos de retorno para estudos de engenharia hidráulica e de recursos hídricos na região de Governador Newton Bello.

Hydraulic Properties in Different Soil Architectures of a Small Agricultural Watershed: Implications for Runoff Generation

Soil architecture exerts an important control on soil hydraulic properties and hydrological responses. However, the knowledge of hydraulic properties related to soil architecture is limited. The objective of this study was to investigate the influences of soil architecture on soil physical and hydraulic properties and explore their implications for runoff generation in a small agricultural watershed in the Three Gorges Reservoir Area (TGRA) of southern China. Six types of soil architecture were selected, including shallow loam sandy soil in grassland (SLSG) and shallow loam sandy soil in cropland (SLSC) on the shoulder; shallow sandy loam in grassland (SSLG) and shallow sandy loam in cropland (SSLC) on the backslope; and deep sandy loam in grassland (DSLG) and deep sandy loam in cropland (DSLC) on the footslope. The results showed that saturated hydraulic conductivity (Ksat) was significantly higher in shallow loamy sand soil under grasslands (8.57 cm h−1) than under croplands (7.39 cm h−1) at the topsoil layer. Total porosity was highest for DSLC and lowest for SSLG, averaged across all depths. The proportion of macropores under SLSG was increased by 60% compared with under DSLC, which potentially enhanced water infiltration and decreased surface runoff. The landscape location effect showed that at the shoulder, Ksat values were 20% and 47% higher than values at the backslope and footslope, respectively. It was inferred by comparing Ksat values with 30 min maximum rainfall intensity at the watershed, that surface runoff would be generated in SSLC, DSLG, and DSLC sites by storms, but that no overland flow is generated in both sites at the shoulder and SSLG. The significantly higher Ksat under grasslands in comparison to croplands at the backslope indicated that planting grasses would increase infiltration capacity and mitigate runoff generation during storm events. The findings demonstrated that croplands in footslope positions might be hydrologically sensitive areas in this small agricultural watershed.

Modelling of Intensity-Duration Frequency curves for Upper Cauvery Karnataka through Normal Distribution

The IDF Curves accessible are for the most part done by fitting arrangement of yearly greatest precipitation force to parametric dispersions. Intensity-duration-frequency (IDF) curves represent the relationship between storm intensity, storm duration and return period. Environmental change is relied upon to intensify the boundaries in the atmosphere factors. Being prone to harsh climate impacts, it is very crucial to study extreme rainfall-induced flooding for short durations over regions that are rapidly growing. One way to approach the extremes is by the application of the Intensity-Duration-Frequency (IDF) curves. The annual maximum rainfall intensity (AMRI) characteristics are often used to construct these IDF curves that are being used in several infrastructure designs for urban areas. Thus, there is a necessity to obtain high temporal and spatial resolution rainfall information. Many urban areas of developing countries lack long records of short-duration rainfall. The shortest duration obtained is normally at a daily scale/24 h. Thus, it is very crucial to find a methodology to construct IDF curves for short-duration rainfall (sub-daily) for these urban areas. The fast extension of urban area that does not have adequate preparedness to cope with climate change is certainly a big risk to life and economy. The study region lies in Karnataka India. The sub-daily IDF curves for current and future climate for the region were constructed from 1 to 24 h based on the Normal Distribution approach. Rainfall data of 23 (Twenty three) hydrological years of all stations were used. Maximum rainfall frequency analysis was made by Normal Distribution method. Finally Equations were developed for different return periods.

Application of the Modified Rational Formula to Time-Distributed Rainfall Events and Comparison with the Rational Formula Application

This study compares two approaches (the average rainfall intensity method and the modified rational formula) for use with the rational formula with time-distributed rainfall events. Here, the average rainfall intensity method is used to consider the maximum mean rainfall intensity during the time of concentration for a basin around the peak rainfall such that the rational formula can be applied. This study considers artificial basins with times of concentration from 1 to 24 hours and a symmetric rainfall event time-distributed by the Yen & Chow model. The rainfall duration is assumed to be 12 hours to consider all the possible combinations of rainfall duration and time of concentration. The results can be summarized as follows. First, this study proposes a new method of applying a modified rational formula that considers the horizontally divided components of a rainfall event. This proposed method is effective in estimating peak flow and peak time. Second, the biggest difference between the applications of the average rainfall intensity method and the modified rational formula is evident when the rainfall duration is longer than the time of concentration. The applications of the average rainfall intensity method run the risk of underestimating the peak flow. However, this problem can be alleviated when the time of concentration becomes longer than the rainfall duration. Under the assumption of a basin with a rectangular shape, this difference nearly disappears. These findings are also confirmed in the other applications with different rainfall durations. Keywords: Rational Formula, Modified Rational Formula, Rainfall Temporal Distribution, Peak Flow

Role of groundcover management in controlling soil erosion under extreme rainfall in citrus orchards of southern China

Extreme rainfall is becoming more frequent and intense due to climate change and increasing human activity. Changes in rainfall will increase the risks and uncertainty of water erosion from orchards. Groundcover management is an important factor affecting hydrological and erosive processes of orchards. However, the roles of different groundcover managements for controlling soil water erosion caused by extreme rainfall are not fully understood. In this study, four groundcover managements (i.e., control bare land, orchard with no cover, orchard with grass cover and orchard with cover crops) were used to analyze runoff and erosion characteristics related to extreme and ordinary rainfalls in the red soil region of China. Based on the rainfall-runoff data measured on runoff plots, 356 natural rainfall events from 2001 to 2012 were analyzed, and rainfall depths and maximum 30-min rainfall intensities were used to select extreme rainfall events, according to the criteria of the World Meteorological Organization for extreme rainfall. There were 25 extreme rainfall events with a probability of 7.0% during the study period. Extreme rainfall events played the destructive role in inducing soil loss. The average extreme runoff coefficient and soil loss amount were 2.8 and 11.1 times higher than the values from ordinary rainfall, respectively. The contribution of extreme rainfall to sediment yield was 44.2%, which far higher than those to runoff generation (15.8%). Moreover, the runoff coefficients and erosion amounts varied greatly among the different groundcover managements under extreme rainfall, and were ranked in the following order: control bare land > orchard with no cover > orchard with cover crops > orchard with grass cover. However, the highest percentage of soil loss amount caused by extreme rainfalls were 59.0% in orchard with cover crops, and the lowest in orchard with grass cover (26.0%). Therefore, extreme rainfall should cause more attention in improving the groundcover management strategy for orchard soil erosion control, and groundcover like grass cover was extremely needed even after interplanting crops for the serious soil loss.

Effects of biocrusts and rainfall characteristics on runoff generation in the Mu Us Desert, northwest China

AbstractHow the presence of biocrusts regulates runoff generation in the Mu Us Desert is not well known. Runoff experiments under natural and artificial rainfalls and numerical simulations were conducted in semiarid environments to evaluate the effects of biocrust type and rainfall characteristics on runoff. The experimental results showed that the water drop penetration time (WDPT) of the moss-dominated biocrusts was 68.7% higher than that of lichen-dominated biocrusts. Nevertheless, the saturated hydraulic conductivity (Ks) for moss-dominated biocrusts was 72.7% lower than that for the lichen-dominated biocrusts. Runoff yield for moss-dominated biocrusts was significantly higher than that for lichen-dominated biocrusts. Runoff yield was mainly explained by rainfall amount (or maximum 5-min rainfall intensity, I5max) (P < 0.001) and WDPT (P = 0.001). The influences of biocrust type, rainfall intensity, and their interaction on runoff coefficient were significant at the probability level of 0.01. The results of numerical simulations concluded that surface runoff was generated for lichen- and moss-dominated biocrusts when rainfall intensity reached 73.5 and 49 mm h–1, respectively. Runoff coefficient in the moss-covered soil increased obviously when rainfall intensity changed from 49 to 73.5 mm h–1. The results suggest that runoff could be changed substantially under increasing trends in rainfall intensity in the Mu Us Desert.

Análise de chuvas intensas visando ao dimensionamento de estruturas de conservação do solo para a região de Chapecó, Santa Catarina

As práticas mecânicas ou obras hidráulicas fazem parte dos princípios do manejo conservacionista do solo e são dimensionadas em função de alguns fatores, entre eles, as características da chuva local. Nesse sentido, este trabalho buscou analisar os dados de chuva intensa visando subsidiar o dimensionamento de projetos de conservação do solo na região de Chapecó, SC. Utilizou-se como base a série histórica de precipitação diária obtida na estação pluviométrica de Chapecó. Foram ajustados os parâmetros da distribuição de Gumbel-Chow com base na série histórica de chuvas máximas anuais para o período de 1973 a 2016. A partir da desagregação das chuvas máximas diárias, procedeu-se o ajuste da equação de chuvas intensas. Observou-se que há maior frequência de eventos extremos de chuva no outono, e menor no verão. A chuva máxima diária, com período de retorno de 10 anos adotada como critério para o dimensionamento de terraços em nível foi 146,9mm; já para terraços de drenagem, adotou-se a intensidade da chuva máxima de 141,9mm h-1, com duração de 15 minutos e período de retorno de 10 anos. Termos para indexação: terraços; drenagem agrícola; erosão; hidrologia.

Influence of soil moisture content and soil and water conservation measures on time to runoff initiation under different rainfall intensities

Time to runoff initiation (TRI) is an important factor related to water infiltration, runoff generation, and hillslope erosion. This study assesses TRI values for six different plots and investigates the effects of rainfall intensity, surface soil moisture content at depths of 0–5 cm, soil and water conservation measures (longitudinal ridges, cross ridges, grass, forest, and flat field under fruit trees), and vegetation on TRI for bare soil, longitudinal ridges under maize, cross ridges under peanut crops, grass, forest, and flat field under fruit trees. Results showed that bare soil exhibited the shortest TRI, followed by the longitudinal ridges under maize and cross ridges under peanut crops. The remaining three plots did not generate runoff. The first principal component affecting TRI was soil moisture content, which contributed 69.87%, 64.88%, and 85.73% to the TRI of bare soil, longitudinal ridges under maize, and cross ridges under peanut crops, respectively. The second major component of these three plots were combined rainfall intensity, comprehensive rainfall and vegetation factors, and vegetation factors, which contributed 27.98%, 33.73%, and 14.27%, respectively. Maximum load factor was generated during runoff with maximum rainfall intensity (0.969), stalk diameter (0.985), and maize height (0.864). In conclusion, soil moisture content are the main factors influencing TRI, and soil and water conservation measures provided key benefits for improving the time to runoff initiation and reduction of runoff erosion in the farmlands.

Bioretention performance under different rainfall regimes in subtropical conditions: A case study in São Carlos, Brazil

Low Impact Development practices have emerged as alternative solutions for traditional urban drainage by restoring the pre-development hydrologic regime. In subtropical climate areas, the performance of these systems is still poorly understood. This study aims to assess the performance of a bioretention basin in a subtropical climate area during an entire hydrological year in order to analyze the differences between dry and rainy seasons. The main climatic factors and conditions influencing the runoff retention efficiency and peak attenuation were also analyzed in order to support bioretention design for flood control purposes. Data of 29 precipitation events were collected over three years (2016–2018). The results show that the bioretention system retained between 9% and 100% of the runoff volume with an average efficiency of 65% during a whole hydrological year. The average runoff retention efficiency was of 73% and 61% for dry and rainy seasons, respectively. This difference is explained by the climatic factors which affected the bioretention performance. During dry periods, the antecedent soil moisture condition and runoff generation rate were found to be more important than the total precipitation depth, while the runoff retention efficiency was primarily influenced by the total rainfall depth and the maximum rainfall intensity during the wet period. Future research should focus on each of these periods in more detail, including water quality aspects.

Modeling of probability in obtaining intensity-duration-frequency relationships of rainfall occurrence for Pelotas, RS, Brazil

ABSTRACT Based on historical series, for each locality, equations can characterize the relationship between intensity, duration and frequency of rainfall occurrence. The objective of this study was to present two equations that can describe the occurrence of intense rainfall in Pelotas, RS state, over the period 1982-2015. The two equations were denominated conventional and hybrid, depending on the probabilistic model used. Following the conventional methodology, the parameters of Normal, Log-Normal, Gumbel and Gamma probability distributions were adjusted by the maximum likelihood method for return periods of 2, 5, 10, 20, 25, 50 and 100 years. The maximum intensity values for the hybrid equation were obtained using the empirical model of Weibull, considering return periods of 2, 5, 10, 20 and 25 years. On the other hand, the same theoretical distributions used in the conventional equation were applied to return periods of 50 and 100 years. The Kolmogorov-Smirnov test was used to select the best fitting distribution for the data. In order to verify the information acquired through the Weibull empirical model in comparison to the theoretical distributions, the t-test was applied to the angular coefficients. Significant differences were not verified between the values of maximum rainfall intensities obtained using the two methodologies, for the pre-established durations and return periods. Thus, considering the maximum rainfall intensities values (durations of 5-1440 min) and return periods of 2-100 years in the municipality of Pelotas, RS, Brazil, both the hybrid and the conventional intense rainfall equations can be used.

Study on Hydrological Characteristics of Large Permeable Parking lot in Sponge City

Pervious pavement of large parking lot in sponge city is a new structural form, which is conducive to solving the problem of deterioration of urban ecological environment. The hydrological characteristics of large permeable parking lot are studied. The results show that the effect of large permeable parking lot on flow delay is obvious. No runoff occurs in the structure of large permeable parking lot when the maximum rainfall intensity reaches 0.968 mm/min. When the recurrence period increases from one year to 100 years, the percentage of total runoff reduction are 100%, 66%, 56%, 48%, 44%, and the peak flow reduction rate are 100%, 58%, 50%, 46%, 41%, respectively. With the extension of rainfall recurrence period, the total amount of runoff reduction in large permeable parking lots increased, and the reduction rate showed a downward trend. The research results can provide reference for the construction of large permeable parking lot in sponge city.

Intensity-duration-frequency relationships of rainfall through the technique of disaggregation of daily rainfall

ABSTRACT Rainfall intensity-duration-frequency (IDF) relationships are a tool that can be used in modeling the transformation of rainfall to runoff, required for the design of hydraulic works. The objective of this study was to verify if there is a significant difference between the intensity-duration-frequency relationships generated using pluviographic records and those determined from pluviometric data. Maximum annual rainfall intensity values were obtained from the disaggregation of maximum daily rainfall and rainfall records in the durations of 5, 10, 15, 20, 30, 60, 120, 360, 720 and 1440 min and for the return periods of 2, 5, 10, 20, 25, 50 and 100 years, in the locality of Pelotas, Rio Grande do Sul state, Brazil (31° 46’ 34’’ S; 52° 21’ 34’’ W, altitude of 13.2 m). By Student’s t-test, it was verified that there is no significant difference between the values of maximum rainfall intensity obtained from pluviographic records and those determined from pluviometric data.

Rainfall Intensity-Duration-Frequency Relationships for Risk Analysis in the Region of Matopiba, Brazil

Abstract The region of study was MATOPIBA, located in the north of Brazilian Savanna biome (Cerrado), encompassing part of north/northeast of Brazil. The region has been gaining prominence in the last years due to the expansion of agricultural over this area. The aims of this study were: to adjust parameters for rainfall intensity-duration-frequency; and to identify the most vulnerable agricultural areas to erosion based on erosivity and erodibility. The rainfall intensity-duration-frequency function were adjusted using series of maximum annual rainfall event from 105 rainfall gauges. Gumbel model was the most efficient to simulate the maximum rainfall intensity, where these data were used to adjusted the rainfall intensity-duration-frequency model based on K, a, b and c parameters. The most rainfall gauges showed intensity between 51 and 80 mm h-1 and 81 and 120 mm h-1, respectively, for return period of 2 and 100 years with rainfall duration of 30 minutes. The higher rainfall intensity was observed mainly in the central-north of the region associated with rainfall systems. The rainfall intensity showed a huge capacity to cause soil erosion based on the erosivity energy, while the moderate erodibility was observed for areas with Ferralsols and Leptosols and low erodibility for areas with Arenosols.

Initiation and runout characteristics of debris flow surges in Ohya landslide scar, Japan

The characteristics of debris flows (e.g., velocity, discharge, kinematic energy) are highly dependent on surges incurring abrupt changes to flow height, velocity, and boulder concentration. Therefore, understanding the initiation and runout characteristics of surges is essential when planning debris flow mitigation. Monitoring performed using 10 time-lapse cameras (TLCs) in Ohya landslide, central Japan, where debris flows occur frequently due to mobilization of storage (i.e., talus cone and channel deposits), allowed us to obtain data on a series of surge processes, from initiation to termination, which occurred during each debris flow event. We also analyzed temporal changes in the spatial distribution of storage in the debris flow initiation zone, associated with sediment supply from hillslopes and evacuation of sediment by the occurrence of debris flows, through periodic measurements of topography using unmanned aerial vehicles (UAVs). Debris flow surges were mainly induced by repetitive mass movement of storage through the erosion of channel deposits by overland flow, sliding of channel deposits, and sediment and water supply from channel banks and tributaries. Development of a spontaneous wave on the flow surface was not an important formation process of surges in the Ohya landslide. Many debris flow surges initiated at channel sections with deep storage (>2 m in depth), located <30 m below a junction with a tributary, when the maximum 10-min rainfall intensity exceeded 5 mm. Partly saturated flow, which has an unsaturated layer in its upper part, was the predominant flow type in the steep initiation zone, while fully saturated flow was predominant in the gentle transportation and deposition zones. Flow type often changed as the surges descended. Partly saturated flow was predominant when the volume of storage in the initiation zone was large, whereas fully saturated flow was predominant when the volume of storage was small. When we compared debris flows with similar total sediment volume, travel distance was long when fully saturated flow with high flow mobility was predominant because of the small volume of storage in the initiation zone. The volume of storage also affected flow path avulsion on the debris flow fan by controlling the flow mobility of surges. Consequently, the spatial distribution and total volume of storage are important factors controlling the initiation location, predominant flow type, and termination location of surges.

A Study of Change in Rainfall Pattern in Anand (middle Gujarat) in the last 60 years (1958-2017)

The analysis of rainfall records for long period provides information about rainfall pattern and variability. The long term monthly rainfall data for the period 1958-2017 (60 years) was studied. And also rainfall studies are the utmost utility for understanding the nature and behaviour of climate change. In this study, trends in rainfall, maximum rainfall intensity and rainy day for 1958-2017 were examined. Long term data analysed for 60 years (1958-2017) annual data suggest that there is a significant change in rainfall over the last decade. It observed that total mean rainfall June to October but in by 50.04mm last 60 years and annual rainy days decreased by 0.017 mm per year. From the average monthly rainfall analysis, it is observed that rainfall variation for first 20 years (1958-1978) and second 20 years (1979-1999) are similar rainfall pattern whereas it differs for last decade (2000-2017) because of the change in magnitude however the overall trend is similar. Average monthly rainfall analysis indicates there is maximum rainfall in the month of June and minimum rainfall in the month of October.