Recent Rainfall Events Research Articles

A Weighted Overlay Analysis for Assessing Urban Flood Risks in Arid Lands: A Case Study of Riyadh, Saudi Arabia

Urban flooding poses a significant problem in arid regions, where unusual rainfall events can lead to disastrous consequences. This study used geographic information systems (GIS) to identify and predict potential flood risk zones in Riyadh City, Saudi Arabia. A comprehensive flood risk map was created by integrating various datasets, including digital elevation models (DEM), lithology, precipitation patterns, slope, and drainage density. Through a weighted overlay analysis, Riyadh was segmented into zones with different levels of flood susceptibility, ranging from low to very high risk. The study area spans 905 km2. Of this total area, 32% is at a low risk of flooding, while 31%, 24%, and 12% of the area are at a moderate, high, and very high risk of flooding, respectively. The findings of the study were validated through field surveys conducted before and after recent rainfall events. These validation efforts corroborated the high-risk areas predicted by the model, thereby ensuring the reliability of the map for future urban planning and risk mitigation strategies.

A multi-modal machine learning approach to detect extreme rainfall events in Sicily

In 2021 almost 300 mm of rain, nearly half of the average annual rainfall, fell near Catania (Sicily Island, Italy). Such events took place in just a few hours, with dramatic consequences on the environmental, social, economic, and health systems of the region. These phenomena are now very common in various countries all around the world: this is the reason why, detecting local extreme rainfall events is a crucial prerequisite for planning actions, able to reverse possibly intensified dramatic future scenarios. In this paper, the Affinity Propagation algorithm, a clustering algorithm grounded on machine learning, was applied, to the best of our knowledge, for the first time, to detect extreme rainfall areas in Sicily. This was possible by using a high-frequency, large dataset we collected, ranging from 2009 to 2021 which we named RSE (the Rainfall Sicily Extreme dataset). Weather indicators were then been employed to validate the results, thus confirming the presence of recent anomalous rainfall events in eastern Sicily. We believe that easy-to-use and multi-modal data science techniques, such as the one proposed in this study, could give rise to significant improvements in policy-making for successfully contrasting climate change.

The impact of flooding on food security across Africa

Recent record rainfall and flood events have prompted increased attention to flood impacts on human systems. Information regarding flood effects on food security is of particular importance for humanitarian organizations and is especially valuable across Africa's rural areas that contribute to regional food supplies. We quantitatively evaluate where and to what extent flooding impacts food security across Africa, using a Granger causality analysis and panel modeling approaches. Within our modeled areas, we find that ∼12% of the people that experienced food insecurity from 2009 to 2020 had their food security status affected by flooding. Furthermore, flooding and its associated meteorological conditions can simultaneously degrade food security locally while enhancing it at regional spatial scales, leading to large variations in overall food security outcomes. Dedicated data collection at the intersection of flood events and associated food security measures across different spatial and temporal scales are required to better characterize the extent of flood impact and inform preparedness, response, and recovery needs.

Preliminary analysis of some characteristics of coseismic landslides induced by the Hokkaido Iburi-Tobu earthquake (September 5, 2018), Japan

At 18:07 on September 5, 2018 (UTC), a Mw 6.6 earthquake struck the Iburi-Tobu area of Hokkaido, Japan. The Hokkaido Iburi-Tobu (HIT) earthquake is a reverse-slip earthquake with a focal depth of 33.4 km at 42.69°N and 142.07°E. According to the detailed landslide interpretations, there were approximately 7059 landslides induced by this earthquake concentrated in an area of 466 km2. The landslides induced by the HIT earthquake are mostly shallow landslides whose sources are mainly an air-fall pumice layer from the Tarumai volcano, and these landslides exhibit an obvious characteristic of a “low affected area, large landslide area”. The landslide area follows an exponential distribution, and many landslides are composed of multiple subsource areas. There are at least 8778 source areas in the whole landslide area. The landslides present high mobility, and the landslide deposits not only accumulate on the foot but also “flow” down along the gullies, similar to debris flows, despite the gullies being gentle (<6%), which may be related to recent heavy rainfall events. Most landslides occur on gentle hills with an elevation range of 100–250 m, and the landslide height is mainly concentrated between 15 m and 45 m. Major slide directions follow a nearly SSE-NNW direction, and all the landslides occur with PGA (peak ground acceleration) ≥0.5 g.

Estimation of suspended sediment concentration in an intermittent river using multi-temporal high-resolution satellite imagery

There is a shortage of sediment-routing monitoring worldwide, despite its relevance to environmental processes. In drylands, where water resources are more vulnerable to the sediment dynamics, this flaw is even more harmful. In the semi-arid Caatinga biome in the North-east of Brazil, rivers are almost all intermittent and hydro-sedimentological monitoring is scarce. In the biome, water supply derives from thousands of surface reservoirs, whose water availability is liable to be reduced by siltation and sediment-related pollution. The goal of this research was to evaluate the potential of multi-temporal high-resolution satellite imagery (RapidEye) to assess the suspended sediment concentration (SSC) in the medium-sized intermittent Jaguaribe River, Brazil, during a 5-year period. We validated 15 one-, two- and three-band indices for SSC estimation based on RapidEye spectral bands deduced in the context of the present investigation and nine indices proposed in the literature for other optical sensors, by comparing them with in-situ concentration data. The in-situ SSC data ranged from 67 mg.L−1 to 230 mg.L−1. We concluded that RapidEye images can assess moderate SSC of intermittent rivers, even when their discharge is low. The RapidEye indices performed better than those from literature. The spectral band that best represented SSC was the near infrared, whose performance improved when associated with the green band. This conclusion agrees with literature findings for diverse sedimentological contexts. The three-band spectral indices performed worse than those with only one or two spectral bands, showing that the use of a third band did not enhance the model ability. Besides, we show that the hydrological characteristics of semi-arid intermittent rivers generate difficulties to monitor SSC using optical satellite remote sensing, such as time-concentrated sediment yield; and its association with recent rainfall events and, therefore, with cloudy sky.

Stationary and Non-Stationary Frameworks for Extreme Rainfall Time Series in Southern Italy

This study tests stationary and non-stationary approaches for modelling data series of hydro-meteorological variables. Specifically, the authors considered annual maximum rainfall accumulations observed in the Calabria region (southern Italy), and attention was focused on time series characterized by heavy rainfall events which occurred from 1 January 2000 in the study area. This choice is justified by the need to check if the recent rainfall events in the new century can be considered as very different or not from the events occurred in the past. In detail, the whole data set of each considered time series (characterized by a sample size N &gt; 40 data) was analyzed, in order to compare recent and past rainfall accumulations, which occurred in a specific site. All the proposed models were based on the Two-Component Extreme Value (TCEV) probability distribution, which is frequently applied for annual maximum time series in Calabria. The authors discussed the possible sources of uncertainty related to each framework and remarked on the crucial role played by ergodicity. In fact, if the process is assumed to be non-stationary, then ergodicity cannot hold, and thus possible trends should be derived from external sources, different from the time series of interest: in this work, Regional Climate Models’ (RCMs) outputs were considered in order to assess possible trends of TCEV parameters. From the obtained results, it does not seem essential to adopt non-stationary models, as significant trends do not appear from the observed data, due to a relevant number of heavy events which also occurred in the central part of the last century.

Human Bacteroides and total coliforms as indicators of recent combined sewer overflows and rain events in urban creeks

Combined sewer overflows (CSOs) are a known source of human fecal pollution and human pathogens in urban water bodies, which may present a significant public health threat. To monitor human fecal contamination in water, bacterial fecal indicator organisms (FIOs) are traditionally used. However, because FIOs are not specific to human sources and do not correlate with human pathogens, alternative fecal indicators detected using qPCR are becoming of interest to policymakers. For this reason, this study measured correlations between the number and duration of CSOs and mm of rainfall, concentrations of traditional FIOs and alternative indicators, and the presence of human pathogens in two urban creeks. Samples were collected May–July 2016 and analyzed for concentrations of FIOs (total coliforms and E. coli) using membrane filtration as well as for three alternative fecal indicators (human Bacteroides HF183 marker, human polyomavirus (HPoV), pepper mild mottle virus (PMMoV)) and nine human pathogens using qPCR. Four of the nine pathogens analyzed were detected at these sites including adenovirus, Enterohemorrhagic E. coli, norovirus, and Salmonella. Among all indicators studied, human Bacteroides and total coliforms were significantly correlated with recent CSO and rainfall events, while E. coli, PMMoV, and HPoV did not show consistent significant correlations. Further, human Bacteroides were a more specific indicator, while total coliforms were a more sensitive indicator of CSO and rainfall events. Results may have implications for the use and interpretation of these indicators in future policy or monitoring programs.

Ground-Level Rainfall Variation in Jefferson County, Kentucky

AbstractIn urban hydrology, accurate temporal and spatial rainfall observations are a key factor for managing urban hydrologic systems and stormwater runoff, particularly in the current era of higher variability in recent rainfall events. To study this issue, rain gauge data from a ground-based rainfall measurement network operated by the local stormwater management agency, Metropolitan Sewer District (MSD), in Jefferson County, Kentucky is evaluated. Rainfall spatial characteristics are evaluated through correlation spectrum by distance indicating a spatial rainfall variation concave relationship. The correlations at a 5-km distance are [0.63, 0.74, 0.80, and 0.86] for temporal resolutions of (15 min, 30 min, 1 h, and 3 h), respectively. A decreasing correlation with increased rainfall intensity is observed at temporal resolutions less than 1 h, and correlation increases at higher rainfall intensities and temporal resolution coarser than 1 h. This case study provides a context for the use of recent histo...

Coliform risk assessment through use of the clam Anomalocardia brasiliana as animal sentinel for shellfish harvesting areas in Brazil's northeast.

Outbreaks of food-borne diseases related to consumption of contaminated shellfish have been reported in many countries, but not in Brazil, possibly due to deficient reporting. Here we investigated the suitability of the clam Anomalocardia brasiliana as an animal sentinel for coliform monitoring in shellfish harvesting areas of Brazil's northeast. Samples of shellfish meats (40 clams per sample; n = 8 per collection) were collected at random from April 2009 through March 2010 in the bay area of Mangue Seco (state of Pernambuco). The numbers of thermotolerant coliforms were analyzed through the most probable number technique, and these contamination levels were tentatively correlated with the precipitation recorded on the day of sampling or 24 to 48h beforehand. A. brasiliana shellfish meats from local retail shops (250g per sample/ n = 3 per market) sold frozen were also investigated from August 2010 through June 2011. We found that the highest coliform contamination levels were correlated with recent rainfall events, limited to 24h before sampling. However, irrespective of the rainfall level, the mean contamination above the Brazilian legal threshold of < 3 × 10(2) MPN/ 100g for shellfish harvesting areas ranged from 18.7 to 93.7% of samples analyzed monthly. Additionally, a large number of samples obtained from retail shops were also highly contaminated by coliforms during rainy periods, and therefore were not proper for human consumption. We conclude that A. brasiliana can be successfully used to monitor the contamination levels of coliforms in shellfish harvesting areas in Brazil's northeast coast.

Recent rainfall events and geotechnical thinking

Recent rainfall events and geotechnical thinking

Analysis of flash flood scenarios in an urbanized catchment using a two-dimensional hydraulic model

Abstract. In Italy, growing urbanization is leading to a higher risk of flooding of small water courses, especially in steep catchments of limited area, where severe flash flood events can occur. The assessment of flash flood hazard requires new modelling tools that can reproduce both the rainfall–runoff processes in the catchment, and the flow processes in the drainage network. In this paper we propose the use of a simple two-dimensional hydraulic model for analysing a flood scenario in a small valley within the urban area of the city of Bologna, Italy. Historically this area has been prone to severe flood events, the most recent of which occurred in 1955 and 1932. Since then there has been a significant increase in urbanization of the lower portion of the catchment, while the natural stream bed has been partially replaced by a culvert. The two-dimensional hydraulic model was therefore applied at catchment scale, in order to simulate the possible effects of historical scenarios in the present catchment configuration. Rainfall and runoff data measured during recent rainfall events were used to calibrate model parameters. Model results show that the current culvert section would be insufficient to drain the runoff produced by intense rainfall events, with potential inundation of surrounding urban areas.

Climate changes, floods, and health consequences

In the European Region, floods are the most common natural disaster, causing extensive damage and disruption. In Italy, it has been estimated that over 68% of municipalities are at high hydrogeological risk and with the recent intense rainfall events local populations have been facing severe disruptions. The health consequences of floods are wide ranging and are dependent upon the vulnerability of the environment and the local population. Health effects can be a direct or indirect consequence of flooding. The immediate health impacts of floods include drowning, heart attacks, injuries and hypothermia. The indirect effects include, injuries and infections, water-borne infectious disease, mental health problems, respiratory disease and allergies in both the medium and long term after a flood. Future efforts should be addressed to integrate health preparedness and prevention measures into emergency flood plans and hydrological warning systems.

An operational flood warning system for poorly gauged basins: demonstration in the Guadalhorce basin (Spain)

This paper deals with the presentation of a flood warning system (GFWS) developed for the specific characteristics of the Guadalhorce basin (3,200 km2, SE of Spain), which is poorly gauged and often affected by flash and plain floods. Its complementarity with the European flood alert system (EFAS) has also been studied. At a lower resolution, EFAS is able to provide a flood forecast several days in advance. The GFWS is adapted to the use of distributed rainfall maps (such as radar rainfall estimates), and discharge forecasts are computed using a distributed rainfall–runoff model. Due to the lack of flow measurements, the model parameters calibrated on a small watershed have been transferred in most of the basin area. The system is oriented to provide distributed warnings and fulfills the requirements of ungauged basins. This work reports on the performance of the system on two recent rainfall events that caused several inundations. These results show how the GFWS performed well and was able to forecast the location and timing of flooding. It demonstrates that despite its limitations, a simple rainfall–runoff model and a relatively simple calibration could be useful for event risk management. Moreover, with low resolution and long anticipation, EFAS appears as a good complement tool to improve flood forecasting and compensate for the short lead times of the GFWS.

Modeling Hydrologic Benefits of Low Impact Development: A Distributed Hydrologic Model of The Woodlands, Texas

AbstractLow Impact Development (LID) is alternative design approach to land development that conserves and utilizes natural resources to minimize the potential negative environmental impacts of development, such as flooding. The Woodlands near Houston, Texas is one of the premier master‐planned communities in the United States. Unlike in a typical urban development where riparian corridors are often replaced with concrete channels, pervious surfaces, vegetation, and natural drainage pathways were preserved as much as possible during development. In addition, a number of detention ponds were strategically located to manage runoff on site. This article uses a unique distributed hydrologic model, Vflo™, combined with historical (1974) and recent (2008 and 2009) rainfall events to evaluate the long‐term effectiveness of The Woodlands natural drainage design as a stormwater management technique. This study analyzed the influence of LID in The Woodlands by comparing the hydrologic response of the watershed under undeveloped, developed, and highly urbanized conditions. The results show that The Woodlands drainage design successfully reflects predeveloped hydrologic conditions and produces peak flows two to three times lower than highly urbanized development. Furthermore, results indicate that the LID practices employed in The Woodlands successfully attenuate the peak flow from a 100‐year design event, resulting in flows comparable to undeveloped hydrologic conditions.

Karst flash-flood forecasting in the city of Nîmes (southern France)

In southern France, karst flash-floods may be the result of two, potentially cumulative, phenomena:−Floods from highly localized events that mostly occur during autumn and are locally known as Cevenol rain events;−Floods exacerbated by recent rainfall events that contributed to saturation of the aquifer before the storm event, thereby increasing runoff.In any case, flash floods occurring in a karst landscape are directly linked to the structure and hydraulic properties of the karst aquifer.A methodology was developed for the city of Nîmes for forecasting these dangerous events, based on the study and modelling of karst-aquifer response to rain events. This work was composed of: (i) Definition of how the Nîmes system functions, leading to a conceptual model; (ii) Modelling of this conceptual model; (iii) Definition of a tool for hazard management, presented as an abacus and tested on particular strong rainfall event.

Longitudinal Poisson Regression To Evaluate the Epidemiology of Cryptosporidium, Giardia, and Fecal Indicator Bacteria in Coastal California Wetlands

Fecal pathogen contamination of watersheds worldwide is increasingly recognized, and natural wetlands may have an important role in mitigating fecal pathogen pollution flowing downstream. Given that waterborne protozoa, such as Cryptosporidium and Giardia, are transported within surface waters, this study evaluated associations between fecal protozoa and various wetland-specific and environmental risk factors. This study focused on three distinct coastal California wetlands: (i) a tidally influenced slough bordered by urban and agricultural areas, (ii) a seasonal wetland adjacent to a dairy, and (iii) a constructed wetland that receives agricultural runoff. Wetland type, seasonality, rainfall, and various water quality parameters were evaluated using longitudinal Poisson regression to model effects on concentrations of protozoa and indicator bacteria (Escherichia coli and total coliform). Among wetland types, the dairy wetland exhibited the highest protozoal and bacterial concentrations, and despite significant reductions in microbe concentrations, the wetland could still be seen to influence water quality in the downstream tidal wetland. Additionally, recent rainfall events were associated with higher protozoal and bacterial counts in wetland water samples across all wetland types. Notably, detection of E. coli concentrations greater than a 400 most probable number (MPN) per 100 ml was associated with higher Cryptosporidium oocyst and Giardia cyst concentrations. These findings show that natural wetlands draining agricultural and livestock operation runoff into human-utilized waterways should be considered potential sources of pathogens and that wetlands can be instrumental in reducing pathogen loads to downstream waters.

Use of a soil moisture network for drought monitoring in the Czech Republic

Since 2000, the network of stations that make up the Czech Hydrometeorological Institute (CHMI) has measured the soil moisture content at the 0- to 0.9-m layer using sensors placed within the natural soil profile under closely cropped grass cover. Using information from 8 years of continuous observation at seven stations throughout the Czech Republic, we verified the usefulness of the Soil Moisture Index (SMI). The SMI is a potentially useful index for calculating the water deficit in the Czech Republic and Central Europe. During this period, a statistically significant decrease in moisture content was detected, and negative SMI values predominated. There were frequent occurrences of flash drought, defined as a very rapid decline in soil moisture during a 3-week period. The CHMI can use SMI values below −3 in the Integrated Warning Service System. The routine calculation of SMI values can alert agricultural producers to the development of flash drought conditions and provide them with information regarding the effectiveness of recent rainfall events. An increase in soil moisture, in contrast, could serve as a warning sign for hydrology because it creates the preconditions for flooding. The complex study of soil humidity regimes is becoming more significant in connection with current global climatic change warnings in hydrological cycles.

Energy balance and water use in a subtropical karst woodland on the Edwards Plateau, Texas

summary Woody encroachment into karst grasslands and savannas is presumed to reduce water availability and aquifer recharge, in part, because deep roots extract large quantities of water from perennial sources within the fractured bedrock underlying shallow soils. If true, energy balance partitioning and transpiration in woody ecosystems should be decoupled to an extent from rainfall, and sensitivity of the energy balance and evapotranspiration (ET) to rainfall and water deficits should be dampened. We evaluated responses of energy and water vapor fluxes to rainfall and water deficits in a live oak (Quercus virginiana)-Ashe juniper (Juniperus ashei) woodland on the karst Edwards Plateau, TX, USA, over a 2-year period using eddy covariance measurements of the turbulent fluxes. Total ET during the two years was 1416 mm, 92% of total rainfall. We observed large and rapid reductions in kE and increases in H during drying cycles, and high correlation between ET and soil water content in the upper 20 cm of the root zone. In most cases, ET declined at the same time as soil water content, indicating that the woodland relied heavily on water from recent rainfall events, rather than antecedent water. We found no evidence that deep roots were extracting significant amounts of water from a perennially stable supply of water. Excavations at the woodland site revealed a rock layer at 20 cm below the soil surface, with a dense root mat above the rock and penetration of relatively few roots into the rock through cracks and fissures. Thus, the most likely sources of water for trees were soil water and a limited supply of water stored in near-surface fractured rock layers.

Hydrogeochemical investigations of recharge and subsequent salinization processes at Al-Raudhatain depression in Kuwait / Analyses hydrogéochimiques de la recharge et des processus associés de salinisation dans la dépression de Al-Raudhatain au Koweit

Fresh groundwater is uniquely present in the northern parts of Kuwait at Al-Raudhatain and Umm Al-Aish depressions, where it occurs in the form of lenses floating on top of Kuwait Group's brackish water. Earlier studies have provided a wealth of data on these depressions. Nonetheless, information on the recharge process is both scarce and scattered among different studies. Based on existing information, chemical and isotopic investigations, and geochemical modelling, a coherent description of the recharge and salinity evolution processes at Al-Raudhatain freshwater lenses is presented. Radioactive isotope (14C, 13C and 3H) results indicate that the groundwater sampled at the depression and its vicinity contain significant portions of recharge from recent (less than 500 years) rainfall events. Furthermore, the results of stable isotopes (18O and 2H) specify that recharging rainfall events took place during the last three to four decades. Examining the relationship of 18O/2H along with the Emirates meteoric water line (i.e. the nearest available meteoric water line) reveals that samples are showing sings of insignificant evaporation, which indicates rapid infiltration. Given the established low infiltration rates at the depression and the lack of surface runoff at the wadis, it was concluded that most of the recharge comes from infiltration outside the depression, followed by subsurface runoff to the depression where recharge takes place. Reverse geochemical modelling showed that the main processes controlling the geochemistry of the water in the depression are halite, albite, illite dissolution, as well as K-feldspar weathering and calcite precipitation. These processes take place during infiltration, subsurface runoff and percolation to the groundwater. The contribution of the recharge water in the makeup of the body of the lens versus the regional brackish groundwater was estimated according to their contribution in total dissolved solids concentrations using the salinity stratification and the results of 18O.

An Experiment Using the High Resolution Eta and WRF Models to Forecast Heavy Precipitation over India

In the present study using the Weather Research and Forecasting (WRF) and Eta models, recent heavy rainfall events that occurred (i) over parts of Maharastra during 26 to 27 July, 2005, (ii) over coastal Tamilnadu and south coastal Andhra Pradesh during 24 to 28 October, 2005, and (iii) the tropical cyclone of 30 September to 3 October, 2004/Monsoon Depression of 2 to 5 October 2004, that developed during the withdrawal phase of the southwest monsoon season of 2004 have been investigated. Also sensitivity experiments have been conducted with the WRF model to test the impact of microphysical and cumulus parameterization schemes in capturing the extreme weather events. The results show that the WRF model with the microphysical process and cumulus parameterization schemes of Ferrier et al. and Betts-Miller-Janjic was able to capture the heavy rainfall events better than the other schemes. It is also observed that the WRF model was able to predict mesoscale rainfall more realistically in comparison to the Eta model of the same resolution.