Time Distribution Of Rainfall Research Articles

Equações universais para as distribuições de chuva dos métodos SCS e Huff

ABSTRACT The temporal distribution of design rainfall hyetographs can be obtained through various procedures. One such method involves using temporal distribution curves to disaggregate a rainfall value of longer duration into chronological values within shorter time intervals. This is demonstrated by SCS distribution curves for durations of 6 and 24 hours and the well-known Huff curves. Another approach involves deriving temporal distribution using design hyetograph calculation methods, such as the Chicago and alternating block methods, based on Intensity-Duration-Frequency (IDF) equations. This paper aims to combine these approaches and develop universal equations capable of accurately fitting smooth rainfall time distribution curves. The advantage is the replacement of tables, like SCS and Huff, with analytical equations, enhancing usability in spreadsheets. Furthermore, these universal equations can determine the temporal rainfall distribution using an IDF equation or fitting a specified design hyetograph like Euler type II. Four numerical examples are provided.

Water environment characteristics and control countermeasures of typical hilly cities in Southeast China

Abstract Due to population growth and economic development, problems such as uneven distribution of freshwater resources and degradation of water quality are becoming increasingly prominent. Many measures have been adopted to address water resources issues; however, few studies have focused on specific changes in water quality after policy implementation. In this study, Yiwu City, Zhejiang Province, a typical hilly city with a well-developed water system, was selected to analyze the changes in water quality. By analyzing the rainfall series and hydrology characteristics, and water quality characteristics, this paper revealed the water environment characteristics and put forward some suggestions for water management in hilly cities. Results showed that the historical rainfall time distribution is uneven, and the water environment capacity of urban inland rivers exhibits strong variability in Yiwu City. The contents of ammonia nitrogen (NH3-N) and total phosphorus (TP) decreased significantly since the policy implementation of ‘Five water cohabitation’. Urban rivers presented regional pollution and surface source pollution characteristics, and the water quality fluctuated significantly with the increase in rainfall. At the same time, the study confirmed that scientific water replenishment measures can effectively improve water quality, providing reference ideas for the protection and management of China's urban water environment.

Flooding time nomograph for urban river flood prediction: Case study of Dorim stream basin, Seoul

AbstractGlobal climate change is intensifying flood damage in urban rivers. Notably, most small and medium‐sized urban rivers have a brief concentration period and are highly vulnerable to sudden heavy rains that lead to a rapid increase in water levels. Therefore, rapid flood forecasting must be performed through accurate flood occurrence and timing prediction. In this study, a flooding time nomograph (FTN) was proposed to predict the flood occurrence time according to rainfall conditions, such as intensity, time distribution, and duration. In addition, rainfall–runoff simulations were performed by establishing different virtual rainfall scenarios using Huff's quartile rainfall time distribution. The simulation results were used to formulate the relationship between the rainfall intensity and flood occurrence time to generate the FTN. The applicability of this tool was verified through a comparison with the observed flood occurrence time for an actual rainfall event, which was highly accurate in the target watershed, with a correlation coefficient >0.8 and Nash–Sutcliffe efficiency >0.6. Therefore, the proposed FTN can be used to reasonably predict the occurrence of floods and the time of flood occurrence using only predicted rainfall information.

Development and Application of Urban Flood Prediction System for Smart Cities

To preemptively respond to urban flood disasters, a flood prediction system that provides a connection service with a smart city data hub was developed. The systems developed in this study provide real-time and predicted rainfall data, 1D and 2D flood prediction data, manhole-based flood prediction and warning information, and flood vulnerability index by administrative district. A one-dimensional analysis for the water depth and overflow amount of each manhole was calculated using the Storm Water Management Model (SWMM). A two-dimensional inundation analysis, the Two-Dimensional Inundation System (2DIS), which is capable of two-dimensional surface inundation analysis, was applied. The model can simulate surface flooding using the manhole overflow rate of the SWMM model. In the system, the flood prediction information was made based on the rainfall scenario, and the applied rainfall is 30-90 mm per hour, while the rainfall time distribution is Huff 3rd quartile. The propagation of flood conditions in the system can provide a five-stage (Safety, Attention, Caution, Alert, and Serious) scale depending on the water depth and surcharge conditions of the pipeline. The flood prediction model developed in this study was compared and verified with the existing flood survey data in the Dalseo Drainage Basin in 2002, and the model verification showed that the probability of flood detection (POD) was more than 80%.

The effects of lithological formations of the monotonous landscape in the Niger delta region

The Niger Delta is an area criss-crossed by network of Rivers and streams, its distributaries flood, erode transport and shape their channels, thereby determining the surrounding land-use and soil characteristics, as well as the lithological formations. The physical characteristics of the region is classified into five ecological zones of mangrove forest and coastal vegetation, freshwater swamp forest zone, lowland rainforest, derived savannah zone. Its geomorphologic factors are composed of sediment deposits washed from the inland and the flood plain of the region has river channels such as Orashi river, whereby the stream energy directed from side to side of the river channel, results in the widening of the valleys. Also the meteorological factors as a result of rainfall excesses are determined primarily by the amount, duration, intensity and time distribution of rainfall. In the Niger Delta the mean annual rainfall ranges between 3000mm to 4000mm that results into the wide distribution of swamps within the area, while the soil factor is being influenced by the climate, vegetation, lithology (rock type) and topography, thus the lithological formations along Orashi river are essentially alluvial and friable, do not resist any erosional tendencies, but rather tend to succumb and aggravate the situation.

A CASE STUDY TO INCREASE THE BENEFITS ON INTERLINKING OF PAR-TAPI-NARMADA LINK PROJECT

The complexity of uneven distribution of rainfall in time and space necessitates need for storages and transfer of water from water surplus region to water deficit regions. The ILRP advocates diversion of water outside command area of catchment up to storage site to fill up gap between availability and requirements of water. The research is aimed to conduct critical analysis of project benefits, Irrigated area, quantum of water to be transferred and enhancement of benefits of one of interlinking project viz Par-Tapi-Narmada link basic genesis of feasibility level proposal of Par-Tapi-Narmada link. An attempt has been made to review the proposal at Feasibility Stage and suggest measures for improvement. The Par-Tapi-Narmada Link ILR proposal at Feasibility Stage (2005) was finalized with diversion of 1350 MCM of water out of which a major portion was used for supplementing Narmada Command and later use of saved water by substitution in Narmada Command of Saurashtra and Kutch. The cost of Rs. 60,164 Million was mainly for 7 Dams and 400 km long canal only. Thus, there was a need to optimize benefits by using better irrigation techniques. At that time perhaps there was less or no practice of micro irrigation in Project Command which could have served 169 thousand hectares in less or no water thus making more water available for target command in Saurashtra and Kutch region. There is possibility of optimizing water utilization by reducing irrigation intensity in enroute command. Reduction of water can be done by deleting dams and B-C ratio can be increased from 1.08 to 1.29 as observed in various combinations. Therefore, there is need for re considering 7 dams in position and adopting 5 to 6 dams. An introduction of micro irrigation in the command area by switching over from gravity flow irrigation increases the Benefit Cost ratio of the project considerably. The B C ratio goes on increasing with the increase in percentage of micro irrigation. While working out the same, the yield/benefits of the crops have been kept as per FR. In addition to above, possibility of mitigation of climate change and generating solar power at top canal has been explored.

Study on the Classification of Urban Waterlogging Rainstorms and Rainfall Thresholds in Cities Lacking Actual Data

Extreme rainfall is the main influencing factor of urban waterlogging. Different types of rainfall often have different characteristics of waterlogging. In order to establish a more accurate urban flood control system, it is necessary to classify waterlogging rainstorms and divide their thresholds. This study proposes a method for applying web crawlers to identify waterlogging rainfall in cities lacking waterlogging observation data and classifying them using the rainfall intensity–duration curves. By selecting appropriate duration thresholds and return period, waterlogging rainstorms are divided into rainfall intensity waterlogging (IW), rainfall amount of waterlogging (AW), combined waterlogging (CW) and no waterlogging (NW). In the application of Zhengzhou City, China, the urban flood control standard and the rainfall time distribution characteristics are used as the basis for the selection of the return period and duration thresholds, and the storm water management model (SWMM) is constructed to simulate the 4 kinds of rainfall characteristics of waterlogging, which is similar to actual situations. It proves that the method is suitable for the classification and thresholds division of different waterlogging rainfall in cities. The results show that the best duration thresholds in Zhengzhou are 20 min (M20) and 60 min (M60), and the best return period standard is 2 a. The thresholds for the 4 types of waterlogging rainstorm are: M20 ≥ 26.47 mm, M60 ≥ 43.80 mm, CW; M20 ≥ 26.47 mm, M60 < 43.80 mm, IW; M20 < 26.47 mm, M60 ≥ 43.80 mm, AW; M20 < 26.47 mm and M60 < 43.80 mm, No waterlogging.

Effect of Slope on Infiltration Capacity and Erosion of Mount Merapi Slope Materials

Infiltration which occurs on slope has a specific behavior that can be parameterized. One of the reasons is because the slope generates less ponding on the sloping soil surface. This condition affects infiltration rate and surface runoff proportion of water from any kind of rainfall distribution in time. Since surface runoff tends to be higher, erosion rate is also to be higher on slope. The slope steepness is the most important parameter of a slope. In this study, the effect of slope steepness on infiltration capacity and erosion rate of Mount Merapi bare slope material were tested in a laboratory using rainfall simulator. Three values of slope steepness of 36%, 47%, and 58% were used. The rainfall intensity was set constant and was found has rate of 116,312 mm/hour. The infiltration rate was measured by volumetric balance principle and the erosion rates were measured by collecting the eroded grains at the downstream end tank. Infiltration rate was evaluated by using Horton method and the average erosion were analyzed from the eroded grain data for each test. After fitting the recorded infiltration rate data to the Horton equation, the infiltration capacity was obtained. The results were the relationship between slope steepness and the affected the infiltration capacity and erosion for each test. Infiltration capacity is found to increase and the decrease with the increase of slope steepness while erosion rate is found to increase on the steeper slope. The increase of erosion range is between 15% to 33% for each 1o increase of slope steepness. In addition, polynomial and exponential equations were developed to express the relationship between slope steepness and infiltration capacity and also the erosion rate.

Climate-Related Trends of Within-Storm Intensities Using Dimensionless Temporal-Storm Distributions

AbstractHuff curves are probabilistic time distributions of rainfall expressed as dimensionless cumulative percentages of storm depth and duration. Previous studies have documented development fact...

Analysis of the Temporal Distribution of Rainfall Using the Heavy Storm Distribution Method Reflecting Concentrated Duration Characteristics in Busan

In this study, we proposed and analyzed a rainfall temporal distribution model for determining the flood discharge of a hydraulic structure. The heavy storm distribution (HSD) method proposed in this study can generate the temporal distribution of rainfall more suitably than existing techniques by reflecting the concentrated duration characteristics of extreme rainfall events. Here, the concentration duration means a time period in which rainfall comprises 70% to 80% of the total duration of an extreme rainfall event, and the concentrated duration of 24 h heavy rainfall is about 3 h. For the application of the HSD method, extreme rainfall events were selected using actual rainfall data from Busan, and the characteristics of the concentrated duration were analyzed. Through this, the type of HSD in Busan was determined and the temporal distribution of rainfall was produced. In addition, we compared this method with the Huff method, Yen and Chow method, Mononobe method, and SCS method. As a result, the HSD method proposed in this study better reflected the intensive duration characteristics of extreme rainfall events compared to existing methods. Keywords: Rainfall Time Distribution, HSD, Huff, Concentrated Duration

Soil water content variability drives productivity responses of a model grassland system to extreme rainfall events under elevated CO2

Climate change is significantly altering rainfall patterns globally and will likely cause increases in extreme rainfall events. Grassland systems are particularly vulnerable to these changes as their productivity is strongly mediated by soil water content (SWC). SWC mean and variability are driven by the amount of rainfall received as well as the distribution through time of that rainfall. In this study, we used a model grassland system in a controlled glasshouse experiment to identify whether SWC mean or variability is a stronger driver of productivity. We then examined how extreme rainfall events alter this driver and the resulting effect this has on productivity and biomass allocation under ambient and elevated carbon dioxide (CO2). Rainfall amount was held constant, but distribution through time varied (control, one in 20 years event, one in 100 years event). SWC variability was a stronger driver of productivity (mesocosm biomass) than SWC mean, with increasing extreme rainfall event magnitude resulting in greater SWC variability. Surprisingly, elevated CO2 only had a small effect on these productivity and biomass allocation responses which may be due to the relatively small CO2 difference tested. Our results suggest that distribution of rainfall in time is an important driver of grassland productivity and that increases in extreme rainfall events, for a given total rainfall, will result in reduced grassland productivity.

Impact of rainfall on Aedes aegypti populations

Aedes aegypti is the main vector of multiple diseases, such as dengue, Zika, and chikungunya. Due to modifications in weather patterns, its geographical range is continuously evolving. Temperature is a key factor for its expansion into regions with cool winters, but rainfall can also have a strong impact on the colonization of these regions, since larvae emerging after a rainfall are likely to die at temperatures below 10 °C. As climate change is expected to affect rainfall regimes, with a higher frequency of heavy storms and an increase in drought-affected areas, it is important to understand how different rainfall scenarios may shape Ae. aegypti's range. We develop a model for the population dynamics of Ae. aegypti, coupled with a rainfall model to study the effect of the temporal distribution of rainfall on mosquito abundance. Using a fracturing process, we then investigate the effect of a higher variability in the daily rainfall. As an example, we show that rainfall distribution is necessary to explain the geographic range of Ae. aegypti in Taiwan, an island characterized by rainy winters in the north and dry winters in the south. We also predict that a higher variability in the rainfall time distribution will decrease the maximum abundance of Ae. aegypti during the summer. An increase in daily rainfall variability will likewise enhance its extinction probability. Finally, we obtain a nonlinear relationship between dry season duration and extinction probability. These findings can have a significant impact on our ability to predict disease outbreaks.

Review on Application of Rainfall Time Distribution using Observed Rainfall

Review on Application of Rainfall Time Distribution using Observed Rainfall

Rainfall variability and meteorological drought in the Horn of Africa

Basic rainfall characteristics and drought over the Horn of Africa (HoA) is investigated, from 1901 to 2010. Standard Precipitation Index (SPI) is used to study drought variability, mainly focusing on 3-month SPI. The dominant mode of variability of seasonal rainfall was analyzed by performing Empirical orthogonal functions (EOF) analysis. Gridded data is sourced from Climate Research Unit (CRU), spanning from 1901 to 2010. The HoA experiences predominantly bimodal rainfall distribution in time; March to May (MAM) and October to December (OND). The spatial component of the first eigenvector (EOF1) shows that the MAM and OND seasonal rainfalls are dominated by negative and positive loadings, respectively. The EOF1 explain 34.5% and 58.9% variance of MAM and OND seasonal rainfall, respectively. The EOF2, 3 and 4 are predominantly positive, explaining less than 25% in total of the seasonal rainfall variance in the two seasons. The last two decades experienced the highest negative anomaly, with OND seasonal rainfall showing higher anomalies as compared to MAM season. The OND season recorded 9% more drought events as compared to MAM season. The frequency of occurrence of moderate, severe and extreme dryness was almost the same in the two seasons. These results give a good basis for regional model validation, as well as mapping out drought hotspots and projections studies in the HoA.

Urban Area Response to Flash Flood–Triggering Rainfall, Featuring Human Behavioral Factors: The Case of 22 October 2015 in Attica, Greece

Abstract Over the past several decades, flash floods that occurred in Attica, Greece, caused serious property and infrastructure damages, disruptions in economic and social activities, and human fatalities. This paper investigated the link between rainfall and flash flood impact during the catastrophic event that affected Attica on 22 October 2015, while also addressing human risk perception and behavior as a response to flash floods. The methodology included the analysis of the space–time correlation of rainfall with the citizens’ calls to the emergency fire services for help, and the statistical analysis of people’s responses to an online behavioral survey. The results designated critical rainfall thresholds associated with flash flood impact in the four most affected subareas of the Attica region. The impact magnitude was found to be associated with the localized accumulated rainfall. Vulnerability factors, namely, population density, geographical, and environmental features, may have contributed to the differences in the impact magnitudes between the examined subareas. The analysis of the survey’s behavioral responses provided insights into peoples’ risk perception and coping responses relative to the space–time distribution of rainfall. The findings of this study were in agreement with the hypothesis that the more severe the rainfall, the higher peoples’ severity assessment and the intensity of emotional response. Deeper feelings of fear and worry were found to be related to more adjustments to the scheduled activities and travels. Additionally, being alert to the upcoming rainfall risk was found to be related to decreased worry and fear and to fewer changes in scheduled activities.

The temporal variability of a rainfall synthetic hyetograph for the dimensioning of stormwater retention tanks in small urban catchments

The paper presents issues relating to the influence of time distribution of rainfall on the required storage capacity of stormwater reservoirs. The research was based on data derived from simulations of existing drainage systems. The necessary models of catchments and the drainage system were prepared using the hydrodynamic modelling software SWMM 5.0 (Storm Water Management Model). The research results obtained were used to determine the critical rainfall distribution in time which required reserving the highest capacity of stormwater reservoir. In addition, it can be confirmed based on the research that dimensioning of enclosed structures should rely on using the critical precipitation generated as the characteristics of a synthetically developed rainfall vary dynamically in time. In the final part of the paper, the results of the analyses are compared and followed with the ensuing conclusions. The results of the research will have impact on the development of methodologies for dimensioning retention facilities in drainage systems.

Development of synthetic rainfall distribution curves for Sinai area

Abstract Rainfall time distribution hyetograph of the design storm is highly needed to run hydrological models. This paper derives a dimensionless rainfall time distribution from observed storms based on the SCS TP149 procedure of re-arranging the storm pattern so that the greatest depth values occurs at the middle of the total duration. One hundred twenty-seven rainfall storms for Sinai area were categorized into four groups according to the total duration. Finally, the cumulative design distribution curves are calculated and renamed WRRI distribution. The developed synthetic rainfall distribution curves were compared to the most common distributions such as the standard 4 Soil Conservation Service (SCS) profiles. The performance of the developed rainfall pattern is evaluated using real cases. There was a significant difference in computing runoff between the proposed WRRI and SCS distributions. The research recommends using the developed curves to create storm hyetograph of any design storm for Sinai.

Potential of Rainwater Harvesting and Greywater Reuse for Water Consumption Reduction and Wastewater Minimization

Northeastern Mexico is a semiarid region with water scarcity and a strong pressure on water sources caused by the rapid increase of population and industrialization. In this region, rainwater harvesting alone is not enough to meet water supply demands due to the irregular distribution of rainfall in time and space. Thus, in this study the reliability of integrating rainwater harvesting with greywater reuse to reduce water consumption and minimize wastewater generation in the Tecnológico de Monterrey, Monterrey Campus, was assessed. Potable water consumption and greywater generation in main facilities of the campus were determined. Rainwater that can be potentially harvested in roofs and parking areas of the campus was estimated based on a statistical analysis of the rainfall. Based on these data, potential water savings and wastewater minimization were determined. Characterization of rainwater and greywater was carried out to determine the treatment necessities for each water source. Additionally, the capacity of water storage tanks was estimated. For the selected treatment systems, an economic assessment was conducted to determine the viability of the alternatives proposed. Results showed that water consumption can be reduced by 48% and wastewater generation can be minimized by 59%. Implementation of rainwater harvesting and greywater reuse systems in the Monterrey Campus will generate important economic benefits to the institution. Amortization of the investments will be achieved in only six years, where the net present value (NPV) will be on the order of US $50,483.2, the internal rate of return (IRR) of 4.6% and the benefits–investment ratio (B/I) of 1.7. From the seventh year, the project will present an IRR greater than the minimum acceptable rate of return (MARR). In a decade, the IRR will be 14.4%, more than twice the MARR, the NPV of US $290,412.1 and the B/I of 3.1, denoting economic feasibility. Based on these results, it is clear that integrating rainwater harvesting with greywater reuse resulted in a more feasible and reliable strategy than those strategies based only on rainwater harvesting. Furthermore, the investments can be amortized in a shorter period of time.

Time distribution of heavy rainfall events in south west of Iran

Accurate knowledge of rainfall time distribution is a fundamental issue in many Meteorological-Hydrological studies such as using the information of the surface runoff in the design of the hydraulic structures, flood control and risk management, and river engineering studies. Since the main largest dams of Iran are in the south-west of the country (i.e. South Zagros), this research investigates the temporal rainfall distribution based on an analytical numerical method to increase the accuracy of hydrological studies in Iran. The United States Soil Conservation Service (SCS) estimated the temporal rainfall distribution in various forms. Hydrology studies usually utilize the same distribution functions in other areas of the world including Iran due to the lack of sufficient observation data. However, we first used Weather Research Forecasting (WRF) model to achieve the simulated rainfall results of the selected storms on south west of Iran in this research. Then, a three-parametric Logistic function was fitted to the rainfall data in order to compute the temporal rainfall distribution. The domain of the WRF model is 30.5N–34N and 47.5E–52.5E with a resolution of 0.08 degree in latitude and longitude. We selected 35 heavy storms based on the observed rainfall data set to simulate with the WRF Model. Storm events were scrutinized independently from each other and the best analytical three-parametric logistic function was fitted for each grid point. The results show that the value of the coefficient a of the logistic function, which indicates rainfall intensity, varies from the minimum of 0.14 to the maximum of 0.7. Furthermore, the values of the coefficient Bof the logistic function, which indicates rain delay of grid points from start time of rainfall, vary from 1.6 in south-west and east to more than 8 in north and central parts of the studied area. In addition, values of rainfall intensities are lower in south west of IRAN than those of observed or proposed by the SCS values in the US.

불포화 토사사면 해석에 대한 강우사상과 분포의 영향

The time distribution of rainfall is one of the most important considerations for evaluating soil slope stability. In order to study the rainfall-induced slope failure, the rainfall pattern has generally been assumed as uniform rainfall intensity for rainfall duration. However, it should be noted that the time distribution of the design rainfall method has a significant effect on the soil slope instability. The study implemented Mononobe, Huff, and uniform method as three types of time distribution method of the design rainfall to estimate the factor of safety of soil slopes by rainfall duration. As a result, the difference of soil suction and unsaturated hydraulic properties in a soil by rainfall pattern was found through the application of an appropriate time distribution method to numerical simulation for rainfall-induced slope stability.