Flood Events Research Articles

Impact of extreme rainfall and flood events on harmful cyanobacterial communities and ecological safety in the Baiyangdian Lake Basin, China

Globally, climate change has intensified extreme rainfall events, leading to substantial hydrological changes in aquatic ecosystems. These changes, in turn, have increased the frequency of harmful algal blooms, particularly those of cyanobacteria. This study examines cyanobacterial community dynamics in the Baiyangdian Lake Basin, China, after heavy rainfall and flooding events. The aim was to clarify how such extreme hydrological events affect cyanobacterial populations in floodplain ecosystems and assess related ecological risks. The results demonstrated a significant increase in cyanobacterial diversity, exemplified by an increase of the Shannon diversity index from an average of 1.7 to 2.1 (p < 0.05). Following heavy rainfall and subsequent flooding, the average relative abundance of cyanobacteria in the microbial community increased from 7.59 % to 9.62 %, along a notable rise in the abundance of harmful cyanobacteria. The community structure exhibited notable differences after flooding, showing an increase in species richness, but a decrease in community tightness and clustering, as well as a reduction in niche overlap among harmful cyanobacteria. Environmental factors such as dissolved oxygen, water temperature, and pH were identified as crucial predictors of harmful cyanobacterial community differences and abundance variations resulting from flooding. These findings provide a critical framework for predicting ecological risks associated with the expansion of bloom-forming cyanobacteria in large shallow lake basins, particularly under intensified rainfall and flooding events. This insight is essential to anticipate potential ecological disruptions in sensitive aquatic ecosystems.

China is suffering from fewer but more severe Drought to flood abrupt alternation events

Drought to flood abrupt alternation (DFAA) events, as a special category of compound extreme events that suddenly shift from drought to flood conditions, have significantly greater impacts than individual drought or flood events. In this paper, we have utilized a multifactorial drought index and flood index to identify daily DFAA events occurring in mainland China and in major impact areas during the period 1961-2022. Based on drought and flood index, we have used entropy weighting method to measure the intensity of DFAA events. Our findings indicate that China's DFAA events primarily occur in the hotspots of Huang-Huai-Hai River Basin, the middle and lower Yangtze River Basin, the southeastern coastal area, and the southwestern part of the country. The most frequent and intense DFAA events occur from June to September, with varying subseasonal patterns in the frequency and intensity of events in each hotspot. The frequency of DFAA events in mainland China shows a significant decreasing trend declining at a rate of 0.25 pre year in year-round. While DFAA events occurring in the warm season tend to decrease more significantly compared to the year-round at a rate of 0.26 per year. However, the intensity of DFAA events is increasing with a rate of 0.1 per decade in both the year-round and warm season. The evolution of DFAA events and their direct causes vary non-uniformly across regions and months. Subseasonally, frequency and intensity trends diverged monthly across regions, notably with the Huang-Huai-Hai Basin and southeast coast experiencing a July decline in frequency but a surge in intensity. Our research deepens the understanding of changes in DFAA events and provides practical reference for preventing and mitigating drought-to-flood disasters in mainland China.

A review of paleofloods in the middle-lower reaches of the Yangtze River during the Holocene: Processes, causes and effects

The understanding of the flooding processes in the entire basin of the middle-lower reaches of the Yangtze River (MLRYR) during the Holocene remains elusive. This is primarily attributed to the constraints posed by site-scale data characterized by limited spatiotemporal resolutions, compounded by conflicting results of the reconstructed Holocene paleoflood records in some of the previous studies. In this study, by synthesizing 114 paleoflood data with robust evidence of flood occurrence (including timing and location of flood occurrence), we comprehensively reconstructed the first continuous Holocene paleoflood record that cover the entire basin of the MLRYR. The results show that at the onset of the Holocene, flood frequency peaked notably in the middle reaches of the Yangtze River (MRYR), with no corresponding peak observed in the lower reaches of the Yangtze River (LRYR). However, in both the MRYR and LRYR, a significant flood frequency peak emerged around 8.0 ± 0.5 ka BP, and scarce flood occurrences appeared approximately 7.5–5.0 ka BP. This scarcity shifted abruptly to a surge in flood frequency from 5.0–4.0 ka BP. Following this, the MRYR witnessed three successive peaks in flood frequency, occurring at approximately 3.0 ka BP, 1.8 ka BP, and 1.0 ka BP, respectively. In contrast, flood events in the LRYR were infrequent during the 3.0–2.0 ka BP period, followed by a surge in frequency from 2.0 ka BP onwards. We further explored the driving mechanisms of paleofloods in the MLRYR and found that floods were more likely to occur during periods of weakened EASM, characterized by wet and unstable climate conditions in the MLRYR. Marine erosion may be also a key factor in the lack of geological evidence for palaeofloods during the early Holocene. Additionally, variations in the ISM and human activities during the late Holocene have significantly influenced the occurrence of floods in the MLRYR. By comparing the paleoflood frequency with the spatial distribution and number of archaeological sites in the MLRYR, respectively, we propose that the period of flood scarcity during the middle Holocene may have facilitated the development of rice agriculture and the prosperity of ancient settlements. In contrast, during flood-prone period, ancient societies adapted and coped with floods by migrating to higher terrain during the early Holocene and implementing simple hydraulic engineering techniques during the late Holocene.

Validating ex210Pb sediment dating methods applied to a large anthropogenically-impacted river basin

Sediment dynamics in five sites within the Mobile River Basin, Alabama, impacted by (i) dam-and-lock use, (ii) urbanization, (iii) industrial/mining practices, (iv) flooding, and (v) storm surge events were evaluated to understand better anthropogenic impacts on regional sediment budgets. Three widely used sediment dating models based on excess 210Pb (ex210Pb) (i.e., Constant Rate of Supply, CRS, Constant Initial Concentration, CIC, and Advective Dispersion Equation, ADE) and two recently developed ones (i.e., Porosity Variation, PV and Porosity Variation Without Diffusion, PVWD) were tested to determine their applicability to these anthropogenically altered lacustrine and coastal areas. To verify results from ex210Pb models, we used conventional time markers, including regional hydrograph records and historical aerial images. We found that the traditional time-marker 137Cs is no longer helpful due to its current low inventories in the sediments. Drainage-to-lake area ratios were used to determine relative runoff and atmospheric radionuclide contributions. Statistical analysis of physical properties such as porosity, bulk and dry density, water content, and sediment geochemical compositions were utilized to support sediment transport and site development hypotheses. When constructing the sediment history at each site using these proxies, we found that the conventional CIC and ADE models produced unreliable ages because of violation of requirements for exponentially decreasing porosity and ex210Pb activity with depth. We found that two new models, PV and PVWD, that account for heterogeneous porosity, produced more reliable sediment ages. These two models produced ages with lower uncertainties than the CRS model, outperforming the other conventional models tested. We conclude that the PV and PVWD models are more appropriate for environments experiencing erosional and abrupt depositional events, which in our study resulted from dam construction and storm-surge events. Model sensitivity analysis showed that decreasing average particle density produces younger sediment ages by the PV and PVWD models. Higher ex210Pb activity analytical uncertainty resulted in lower sedimentation rates and higher estimated ages by all five models.

Drastic change in estuarine ostracod assemblages after the 2020 Kyushu floods, Japan: a fundamental approach with application to past flood events

Drastic change in estuarine ostracod assemblages after the 2020 Kyushu floods, Japan: a fundamental approach with application to past flood events

Enhancing flood forecasting accuracy in Data-Scarce regions through advanced modeling approaches

Flood forecasting in data-scarce regions poses significant challenges due to irregular rainfall patterns and limited hydrological monitoring networks, particularly in semi-arid regions in Africa, South America, and Asia. However, despite significant efforts and advancements, there remains a substantial gap in the accurate prediction of flood events necessary for effective risk management and mitigation, evidenced by the recurrence of devastating floods in middle to low-income countries in recent years. Here, we address this problem by testing advanced modeling techniques in a local African case, using a combination of statistical methods for extreme event prediction, hydrodynamic modeling, and remote sensing data, to recommend the most adapted and accurate approach under a variety of settings. Our case study is an emerging urban area in Northern Morocco, situated in a triangular plain interposed between adverse geomorphological and precipitation settings, and unregulated expansion flow, creating an exceptionally overwhelming context for disastrous floods. In the absence of previous studies, we integrate frequency distribution analysis to predict extreme rainfall events and flood flow modeling to simulate floodplain inundation. Data sources included high-resolution remote sensing, local hydrological measurements, fine topographical data, and interviews with stakeholders. We found the Pearson Type 3 distribution to be the most suitable for modeling extreme precipitation in coastal areas, whereas the Generalized Extreme Value (GEV) distribution better fits inland areas. For flood flow assessment, the Gradex method proved to be the most accurate, while other empirical methods outlined critical limitations. Findings reveal that advanced hydrodynamic models significantly enhance flood hazard assessments, even in regions with limited data, showing outstanding correlations with previous flood records and stakeholder feedback. The outcomes carry critical implications for highlighting the importance of selecting appropriate models based on geographical and climatic conditions to inform more resilient urban planning and disaster management practices. We anticipate that these insights will support local decision-makers and urban planners in developing strategies that enhance community resilience and reduce the adverse impacts of flooding. Our work contributes to the broader field of flood risk management, providing a foundation for future developments and practical applications in similar regions worldwide.

Small Farmers’ Agricultural Practices and Adaptation Strategies to Perceived Soil Changes in the Lagoon of Venice, Italy

Farmers have a pivotal responsibility in soil conservation: they can either preserve or deplete it through their choices. The responsibility of agriculture increases when practised in delicate ecosystems, such as lagoonal ones. The Venetian Lagoon islands, which are increasingly subjected to natural and anthropic subsidence, occasional flooding events (acqua alta), and eustatic sea level rise, are constantly exposed to erosive processes that challenge farmers to play with their adaptive capability. This research was carried out on the islands of Sant’Erasmo and Vignole, the most representative of island agriculture in the Venetian Lagoon: they almost exclusively rely on agriculture, which is non-existent in the other islands. This empirical research aimed to explore farmers’ agricultural practices, perceptions of soil changes, and how they adapt to them. It was fundamental for this study that the field research involved direct human contact with farmers (through semi-structured interviews) for data collection and using qualitative methods for data analysis, integrating scientific and non-scientific forms of knowledge and actors. The final purpose was to demonstrate the sustainability (valued on the potential depletion or regeneration capability) of agricultural practices and adaptation strategies on a theoretical basis. Despite their polycultural landscape (maintained by low-input farming systems), escaped from the predominant landscape oversimplification, Sant’Erasmo and Vignole are also subjected to unsustainable agricultural practices, including heavy mechanisation and synthetic inputs. Coupled with natural soil salinity that is exacerbated by increasing drought periods, these practices can contribute to soil degradation and increased salinity. The reported adaptation strategies, such as zeroed, reduced, or more conscious use of machines, were guided by the need to reduce the negative impact of soil changes on productivity. Our research revealed some of them as sustainable and others as unsustainable (such as increasing irrigation to contrast soil salinity). Participatory action research is needed to support farmers in designing effective sustainable agricultural practices and adaptation strategies.

Impacts of Climate Change: Examining Precipitation, Temperature Anomalies, and Effects on Water Resources in Turkey

Climate change is a significant global issue that affects our everyday lives and water resources. One of the most critical impacts of climate change is on our water resources, which are vital for sustaining life and supporting various ecosystems. Understanding the complex relationship between climate change and water resources is crucial for developing effective mitigation and adaptation strategies. This study aims to investigate the impact of climate change on water resources and to shed light on the importance of addressing this issue. Water is a limited resource, and its availability and quality directly affect human well-being, agriculture, energy production, and ecosystem health. However, climate change alters the patterns and dynamics of precipitation, temperature, and evaporation, leading to significant changes in water availability and distribution. Increasing global temperatures cause glaciers and ice caps to melt, progressively depleting freshwater resources. Moreover, changing precipitation patterns are leading to more frequent and severe droughts in some regions, while others experience increased rainfall and flooding events. The effects of these changes are profound. As water scarcity becomes more widespread, competition for limited resources intensifies, potentially leading to conflicts and social unrest. Given the importance of water resources and the undeniable impact of climate change on their availability and quality, it is imperative that we deepen our understanding of this complex relationship. This study aims to assess the socio-economic and environmental impacts of climate change on water resources. By doing so, it seeks to provide policymakers, scientists, and communities with information that will guide decision-making processes and direct effective climate change adaptation and mitigation strategies. In conclusion, the impact of climate change on water resources cannot be overstated. This study aims to contribute to our understanding of this critical issue by highlighting the urgency of addressing climate change and its consequences on water resources and sustainability. This study examines the effects of changing precipitation patterns and increasing temperatures due to climate change on underground and surface water resources in Turkey. By conducting this research, we hope to pave the way for informed decision-making and encourage collective responsibility to protect our water resources for future generations.

Urban drainage efficiency evaluation and flood simulation using integrated SWMM and terrain structural analysis.

A method for evaluating urban drainage system efficiency and simulating pluvial flooding is presented, incorporating rainwater inlet limitations through an integrated SWMM and terrain structural analysis (the corrected model). The corrected model is calibrated using data from two flood events and compared to an overflow model (non-corrected, without considering inlet restrictions) under the same conditions to assess its performance. The results show that the relative error of the flood peak in simulations ranges from 0.27 % to 2.80 %, while the Nash efficiency coefficient ranges from 0.3184 to 0.9504, indicating reasonable accuracy and significant comparability to the overflow model. Drainage efficiency evaluation reveals significant variation among drainage units, decreasing with increasing rainfall until surface depressions fill, after which surface drainage improves notably. This highlights the critical role of surface drainage in overall system efficiency and flood dynamics. Furthermore, two types of urban storm-induced floods are identified: infiltration excess and saturation excess floods. Modeling all floods as saturation excess may lead to substantial misestimations, stressing the need for accurate modeling that accounts for drainage unit characteristics. Understanding urban flood mechanisms is essential for improving modeling accuracy and optimizing drainage system design and flood management strategies.

Advancing Water Security and Agricultural Productivity: A Case Study of Transboundary Cooperation Opportunities in the Kabul River Basin

The Kabul River Basin (KRB) is witnessing frequent flood and drought events that influence food production and distribution. The KRB is one of the world’s poorest regions regarding food security. Food security issues in the KRB include shifts in short-term climate cycles with significant river flow variations that result in inadequate water distribution. Due to the lack of hydro-infrastructure, low irrigation efficiency, and continuing wars, the Afghanistan portion of the KRB has experienced low agricultural land expansion opportunities for food production. This research assesses the relationship between flood mitigation, flow balances, and food production and, cumulatively, assesses the social and economic well-being of the population of the KRB. SWAT modeling and climate change (CCSM4) implications are utilized to assess how these relationships impact the social and economic well-being of the population in the KRB. The intricacies of transboundary exchange and cooperation indicate that the conservation of ~38% of the water volume would nearly double the low flows in the dry season and result in the retention of ~2B m3/y of water for agricultural developmental use. Results show that the peak flood flow routing in reservoirs on the Afghanistan side of the KRB would have a substantial positive impact on agricultural products and, therefore, food security. Water volume conservation has the potential to provide ~44% more arable land with water, allowing a ~51% increase in crop yield, provided that improved irrigation efficiency techniques are utilized.

Heavy metal bioaccumulation based on seasonal monsoon impact in benthic macroinvertebrates of Korean streams.

This study investigates the influence of seasonal monsoon flooding on heavy metal contamination and bioaccumulation in benthic macroinvertebrate communities within a stream ecosystem. We analyzed sediment and benthic macroinvertebrate samples for eight heavy metals [zinc (Zn), chromium (Cr), nickel (Ni), lead (Pb), copper (Cu), arsenic (As), cadmium (Cd), and mercury (Hg)] ) before (BF) and after (AF) a major flooding event. Significant spatial and temporal variations in heavy metal concentrations were observed, with generally higher levels detected after the flood. Chironomidae consistently exhibited high bioaccumulation factors (BAFs) for several metals, highlighting their role as bioindicators. Notably, elevated Cu accumulation was observed in multiple species, including Radix auricularia (R. auricularia), Cipangopaludina chinensis malleata (C. c. malleata), and Palaemon spp. Non-metric multidimensional scaling (NMDS) analysis revealed shifting correlations between environmental variables and bioaccumulation patterns before and after flooding. Pre-flood, total nitrogen (TN) showed a strong positive correlation with Hg bioaccumulation, while post-flood, large sand content emerged as a more influential factor for Zn, Cr, Ni, and Pb bioaccumulation. Our findings emphasize the complex interplay between seasonal flooding, environmental factors, and heavy metal dynamics, with potential implications for ecological risk assessment and water quality management.

Midge Paleo-Communities (Diptera Chironomidae) as Indicators of Flood Regime Variations in a High-Mountain Lake (Italian Western Alps): Implications for Global Change

Sediments of alpine lakes serve as crucial records that reveal the history of lacustrine basins, offering valuable insights into the effects of global changes. One significant effect is the variation in rainfall regimes, which can substantially influence nutrient loads and sedimentation rates in lacustrine ecosystems, thereby playing a pivotal role in shaping biotic communities. In this study, we analyze subfossil chironomid assemblages within a sediment core from an alpine lake (western Italian Alps) to investigate the effects of rainfall and flood regime variations over the past 1200 years. Sediment characterization results highlight changes in sediment textures and C/N ratio values, indicating phases of major material influx from the surrounding landscape into the lake basin. These influxes are likely associated with intense flooding events linked to heavy rainfall periods over time. Flooding events are reflected in changes in chironomid assemblages, which in our samples are primarily related to variations in sediment texture and nutrient loads from the surrounding landscape. Increased abundances of certain taxa (i.e., Brillia, Chaetocladius, Cricotopus, Psectrocladius, Cricotopus/Orthocladius Parorthocladius) may be linked to higher organic matter and vegetation inputs from the surrounding landscape. Biodiversity decreased during certain periods along the core profile due to intense flood regimes and extreme events. These results contribute to our understanding of alpine lake system dynamics, particularly those associated with intense flooding events, which are still understudied.

Flood fragility and vulnerability functions for residential buildings in the Province of Leyte, Philippines

AbstractThe Philippines experiences frequent flooding, but, despite expansive tools for risk reduction, there remain gaps in understanding generalised relationships between flood events and damage to residential structures for regions outside the nation's capital. This gap has limited the ability to model flood risk and damage without robust functions to link hazards and housing vulnerability. This research draws on 394 household surveys to empirically derive a suite of flood fragility and vulnerability functions for residential structures in the Province of Leyte for light material, elevated light material and masonry structures. The results showed that masonry construction was more resilient to floods compared to light material counterparts. Elevated light material structures also exhibited lower damages at low inundations but tend to fail abruptly at flood depths greater than 3 m. By empirically deriving flood damage functions, the findings contribute to a more localised approach to quantifying housing vulnerability and risk that can be used for catastrophe and risk modelling, with applications for government agencies, the insurance industry and disaster risk researchers. This research lays the foundation for future flood risk mapping with growing significance under climate change.

Rainfall Variability, Flood Hazards and Adaptation Strategies in Douala IV and V Municipalities, Littoral Region of Cameroon

Excessive rainfall resulting to floods remain a thorny problem in developing countries including Cameroon. This follows the negative impacts of floods on the population, infrastructure and public services. This study examines rainfall variability, population vulnerability to floods and measures put in place by the population and other stakeholders to adapt to the situation in the Douala IV and V municipalities in Littoral Cameroon. The study exploits both primary and secondary sources data for its realization. Heads of households, quarter’s heads, municipal authorities and its personnel, and public administrative officials were contacted for data collection. The data focused on floods manifestation, their effects on the city, and adaptation strategies put in place to mitigate the negative outcomes. Data from semi structured interview conducted were analyzed using content analysis methods. Sociological and spatial data also collected were analyzed using remotely sensed techniques and statistical tools such as SPSS and Microsoft excel. Climatic data were collected from the urban council, the meteorological units in the town and the National Observatory on Climate Change of Cameroon. Sequential analyses (linear trend curves, standard deviations, and cumulative balances) were used to evaluate the evolution of rainfall and correlation to floods events. The result revealed that floods in Douala IV and V result from rainfall variability, characterized by deficit and excessive rains in the months of June, July, August and September. These heavy rains accompanied by human induced factors such as uncontrolled urbanization, anarchy in construction and occupation of wetlands, poor waste management, pollution of water ways and lack of drains for stagnant water evacuation leads to floods. Also, natural drivers such as the low relief of the area, a dense hydrographic network and contact with the Atlantic Ocean via the Wouri estuary result to floods. These floods are a problem to the health of the population, public services and infrastructure and sustainability of the city. Faced with the numerous damages caused by floods, remediation strategies such as: the construction of traditional dikes, solid house foundations, water embankments, and periodic weather forecasting by the National Observatory on Climate Change of Cameroon to reduce the negative outcomes of flooding has been ineffective in reduction of floods outcomes. Consequently, floods still remains a concern in Douala town. Good environmental practices such as civil education on hygiene and sanitation, periodic cleaning of drains, combats on deforestation of mangroves and afforestation campaigns, government investment on decentralization of waste collection and management will be productive in reducing the effects of floods in Douala. The implementation of all these remedial measures will not only ensure the safety of vulnerable civilian populations but the protection of their activities.

Geospatial Capacity Building for Flood Resilience in the Sahel: the SLAPIS project case study

Abstract. This study focuses on the development of a people-centred early warning system (EWS) against floods in the Sirba River basin between Niger and Burkina Faso. This densely populated area has witnessed an increase in extreme flooding events in recent years. Several flood forecasting systems in the Sahel exist, although there is no EWS that integrates the four components of people-centred EWSs, namely risk knowledge, monitoring and warning service, dissemination and communication, and response capacity. The proposed EWS, named SLAPIS, includes a risk knowledge component that involves defining four levels of vigilance. Its monitoring and alert component involves a user-friendly web application containing real-time data collected through automatic stations. The EWS communicate seamlessly with the national alert system. The response capacity is strengthened through the creation of a flood zone atlas. In this framework, the EWS integrates significant geoinformatics in preparation of local risk reduction plans and the awareness of local communities. In the SLAPIS case study, multi-temporal classifications were conducted using Sentinel-2 data and high-resolution images (approximately 10 cm) generated through Structure from Motion (SfM) techniques. Digital Terrain Model (DTM) creation for hydraulic model calibration employed a multiscale approach, incorporating GNSS survey data processed via Precise Point Positioning (PPP), HydroSHEDS (approximately 100m resolution), and commercial 10m resolution data. All information was calibrated, harmonised, and integrated into the EWS model, which is accessible via a web platform. Capacity building encompassed direct training and field implementation to streamline the primary EWS generation steps.

Development and Application of Reservoir Operation Method Based on Pre-Release Index for Control of Exceedance Floods

The pre-release operation has the potential to enhance the ability of a reservoir to manage exceedance floods. However, the mechanisms for the initiation and termination of such operations are unclear, and a clear method for calculating the pre-release water amount at each time step of the scheduling phase is lacking. To address this, the framework and mathematical expression for a pre-release index are proposed herein, and a refined pre-release scheduling model is developed based on the pre-release indices and their thresholds. Then, the proposed pre-release operation model is applied to the Shuifumiao Reservoir in the Lianshui River Basin in Hunan Province, China. The simulation results demonstrate that the refined pre-release scheduling model can effectively prevent exceedance floods, ensuring the safety of flood control without compromising the effectiveness of water supply safety. The proposed model provides a valuable framework and tool for enhancing the ability of reservoir operators to manage flood events and improve overall flood control safety.

Framing of Flood News in The Borneo Post, a Regional Malaysian Newspaper

In recent years, climate change and unpredictable weather are causing more frequent severe floods in various areas, but little is understood about how regional newspapers shape public reactions to and preparations for natural disasters. This study investigated the framing of flood news by The Borneo Post, an English-language newspaper circulated in Sarawak, Malaysia. The specific aspects examined were: (a) frequency of thematic and episodic framing of flood events and (b) frame dimensions used in articles. Altogether 76 articles (25,676 words) on floods published by The Borneo Post from 1 January to 31 December 2023 were analysed. All articles were in the episodic frame. The main frame dimension was attribution of responsibility (79%), where authorities act as disseminators and narrators of disaster facts. However, the absence of thematic framing of floods lowers attribution of responsibility to authorities to plan long-term solutions to flooding. The economic consequences frame ranked second (14.5%), emphasising losses suffered. Little attention was given to human interest (3.9%) or conflict (1.3%). There was no morality frame, and 1.3% of articles were fact-filled and did not have an obvious frame dimension. The findings suggest that fact-focused flood reporting lacking the humanity element may not move readers to action.

Intraurban spatial configuration, hydrologic similarity areas and their roles in urban drainage dynamics

ABSTRACT Hydrologic Similarity Areas (HSA) were delimited in the Belém catchment, and their responses on the water balance were evaluated. A cluster analysis of intraurban spatial configuration was conducted to delimit six HSA. The urban water balance was performed in the Aquacycle model, whose calibration resulted in satisfactory adherence to the measured streamflow. Indeed, the modeling results show that the intraurban spatial heterogeneity is reflected in the annual and daily water balance. The evapotranspiration rates can represent 25% to 50% precipitation in the different HSA. Moreover, infiltration and runoff can range five times among the HSA. In analyzing the daily events, we identified the areas that most contributed to runoff and those with higher infiltration capacity during flood events. Such results may support future studies on understanding flood dynamics and guide the implementation of sustainable urban drainage solutions that aim to reduce runoff and control flood risk.

Experimental evaluation of water surface profiles upstream and downstream of a culvert with and without an apron

Culverts are structures designed to facilitate the transfer of water beneath roadways, effectively connecting two areas within a catchment. Several critical parameters influence the design of a culvert and its surrounding environment. Among these, the flow conditions and the management of water levels at both the inlet and outlet are essential for the culvert's operation, particularly regarding its performance during flood events. This article examines the impact of variations in the longitudinal slope of the culvert and the elevation of the downstream bed—both with and without an apron—on the flow profile entering and exiting the culvert. To investigate this, a series of 80 experiments were conducted in a straight laboratory channel under steady flow conditions. The objective of these tests is to analyze the water level profiles both upstream and downstream of the culvert under various scenarios. The results indicated that increasing the culvert slope led to a rise in water level on the upstream side of the culvert. Specifically, the maximum water level upstream increased by 14 %, 56 %, and 65.1 % when the culvert slope was raised from zero to 2.5 %, 4 %, and 5.5 %, respectively. Additionally, the minimum water level upstream also increased by 19.1 %, 70.6 %, and 83.1 % under the same slope changes. The average maximum and minimum water levels for all scenarios were calculated and compared. The findings of this research will be valuable for analyzing water transfer both upstream and downstream of the culvert structure, as well as for enhancing hydraulic c alculations related to its performance.

Impact of Flooding on Lands with Emerging Contaminants on the Quality of Receiving Water Bodies

Among crucial factors that control flooding events are extreme climate, urban growth, and mismanagement. Islands in the Nile River have experienced successive cycles of flooding and drying due to recent rainy years in the Nile Basin countries. This paper focuses on the impact of floods on the amounts of ammonium-N released, total concentrations of heavy metals, enzyme activities, and microbial biomass (C and N) in flood soils of 11 Nile River islands. Field moist soils and their airdried counterparts were collected from the outskirts of the island and incubated for 15 days at 30 °C to be analyzed. Results reflected that the amounts of released NH4-N were higher in airdried than in wet soils. The average hydrolysis rates of the studied six enzyme substrates were correlated significantly with organic C, organic N, microbial bio-mass C and N in the field moist soils. The highest correlation coefficients (r) were with rates of hydrolysis of substrates of asparaginase, amidase, and β-glycosaminidase. A significant intercorrelation between rates of hydrolysis of the six studied enzyme substrates and r values which range from 0.81 to 0.98. At 10 mmol kg−1 soil, Co+2, Cd+2, Pb+2, Cu+2, Cr+3, and Ni+2 inhibited the release of NH4-N. Arginine hydrolysis was inhibited by the six heavy metals at 5 mmol kg−1 soil; the most effective inhibitors were Pb+2, Ni+2, and Cr+3. Due to the complex soil enzymatic and organic nitrogen hydrolase activities that occur during floods, fertile fields on the Nile River islands should not be fertilized before the summer flood seasons, which will prevent contamination of the Nile River water and loss of its island soil fertility.