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0 pages, 4714 KB

Open AccessArticle

Impacts of the Degree of Heterogeneity on Design Flood Estimates: Region of Influence vs. Fixed Region Approaches

by Ali Ahmed, Mohammad A. Morshed, Sadia T. Mim, Ridwan S. M. H. Rafi, Zaved Khan, Rajib Maity and Ataur Rahman

Water 2025, 17(18), 2765; https://doi.org/10.3390/w17182765 - 18 Sep 2025

Viewed by 463

Abstract

In regional flood frequency analysis (RFFA), the formation of homogeneous regions is commonly regarded as a necessary condition for reliable regional flood estimation. However, achieving true homogeneity is often challenging in practice. This study investigates the formation of homogeneous regions by applying two [...] Read more.

In regional flood frequency analysis (RFFA), the formation of homogeneous regions is commonly regarded as a necessary condition for reliable regional flood estimation. However, achieving true homogeneity is often challenging in practice. This study investigates the formation of homogeneous regions by applying two region delineation approaches—fixed regions and the region-of-influence (ROI) method—accompanied by the widely used heterogeneity measure (H₁) proposed by Hosking and Wallis. The analysis utilizes data from 201 stream gauging stations across southeast Australia, evaluating a total of 1211 candidate regions. The computed H₁-statistics range from 13 to 30 for fixed regions and from 6 to 30 for ROI-based regions, indicating a consistently high level of heterogeneity across the study area. This suggests that the assumption of homogeneity may not be realistic for many parts of southeast Australia. Moreover, regression equations developed for regional flood estimation yield absolute median relative errors between 29% and 56%, with a median of 39% across return periods from 2 to 100 years. These findings underscore the limitations of relying solely on homogeneity in regional flood modelling and highlight the need for more flexible and robust approaches in RFFA. The outcomes of this research have significant implications for improving flood estimation practices and are expected to contribute to future enhancements of the Australian Rainfall and Runoff (ARR) national guidelines. Full article

(This article belongs to the Special Issue Urban Flood Mitigation and Sustainable Stormwater Management—2nd Edition)

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20 pages, 8465 KB

Open AccessArticle

Research on Urban Flood Risk Assessment Based on Improved Structural Equation Modeling (ISEM) and the Extensible Matter-Element Analysis Method (EMAM)

by Lin Yan, Lihong Zhang, Weichao Yang, Caixia Chen, Jianxin Lin, Zhenxian Chen, Xuefeng Jiang, Haoyang Liang, Peijiang Cong, Jinhua Gao and Tuo Xue

Water 2025, 17(13), 2025; https://doi.org/10.3390/w17132025 - 5 Jul 2025

Viewed by 664

Abstract

With the rapid development of the global economy, urban flood events are occurring more frequently. Scientific risk assessment methods are of great significance in reducing the loss of life and property. This study is devoted to developing an integrated urban flood risk assessment [...] Read more.

With the rapid development of the global economy, urban flood events are occurring more frequently. Scientific risk assessment methods are of great significance in reducing the loss of life and property. This study is devoted to developing an integrated urban flood risk assessment approach based on improved structural equation modeling and the extensible matter-element analysis method. Firstly, a flood risk assessment index system containing four dimensions (hazard, exposure, vulnerability, and regional shelter capability) is established according to a hydrological–hydrodynamic model and a literature survey. Subsequently, improved structural equation modeling (ISEM) coupled with Pearson’s correlation coefficient is introduced to determine indicator weights while eliminating correlations among indicator variables, thereby enhancing the accuracy of the weight calculation. Finally, the extensible matter-element evaluation analysis method (EMAM) is employed to conduct the urban flood risk assessment, providing a more scientific evaluation of urban flood risks through the calculation results of the correlation degree between index factors and risk levels. The integrated flood risk assessment approach was applied in the Liwan District in Guangzhou City, China, and the results demonstrated that the novel approach effectively enhances the accuracy of urban flood risk assessment by 23.69%. In conclusion, this research offers a novel and high-precision methodology for risk assessment, contributing to decision-making in disaster prevention and control. Full article

(This article belongs to the Special Issue Urban Flood Mitigation and Sustainable Stormwater Management—2nd Edition)

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21 pages, 3168 KB

Open AccessArticle

Detection and Driving Factor Analysis of Hypoxia in River Estuarine Zones by Entropy Methods

by Tianrui Pang, Xiaoyu Zhang, Ye Xiong, Hongjie Wang, Sheng Chang, Tong Zheng and Jiping Jiang

Water 2025, 17(13), 1862; https://doi.org/10.3390/w17131862 - 23 Jun 2025

Viewed by 423

Abstract

Hypoxia in river estuaries poses significant ecological and water safety risks, yet long-term high-frequency monitoring data for comprehensive analysis remain scarce. This study investigates hypoxia dynamics in the Shenzhen River Estuary (southern China) using two-year high-frequency monitoring data. A hybrid anomaly detection method [...] Read more.

Hypoxia in river estuaries poses significant ecological and water safety risks, yet long-term high-frequency monitoring data for comprehensive analysis remain scarce. This study investigates hypoxia dynamics in the Shenzhen River Estuary (southern China) using two-year high-frequency monitoring data. A hybrid anomaly detection method integrating wavelet analysis and temporal information entropy was developed to identify hypoxia events. The drivers of hypoxia were also identified with correlation coefficients and transfer entropy (TE). The results reveal frequent spring–summer hypoxia. Turbidity and total nitrogen (TN) exhibited significant negative correlations and time-lagged effects on dissolved oxygen (DO), where TE reaches a peak of 0.05 with lags of 36 and 72 h, respectively. Wastewater treatment plant (WWTP) loads, particularly suspended solids (SSs), showed a linear negative correlation with estuarine DO. Notably, the 2022 data showed minimal correlations (except SSs) due to high baseline pollution, whereas the post-remediation 2023 data revealed stronger linear linkages (especially r = −0.81 for SSs). The proposed “high-frequency localization–low-frequency assessment” detection method demonstrated robust accuracy in identifying hypoxia events, and mechanistic analysis corroborated the time-lagged pollutant impacts. These findings advance hypoxia identification frameworks and highlight the critical role of Turbidity and SSs in driving estuarine oxygen depletion, offering actionable insights for adaptive water quality management. Full article

(This article belongs to the Special Issue Urban Flood Mitigation and Sustainable Stormwater Management—2nd Edition)

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18 pages, 240 KB

Open AccessArticle

Municipality–Property Owner Collaboration for Climate-Robust Stormwater Management: Experiences and Perspectives from Swedish Actors

by Erik Glaas, Sofie Storbjörk and Mattias Hjerpe

Water 2025, 17(7), 925; https://doi.org/10.3390/w17070925 - 22 Mar 2025

Cited by 1 | Viewed by 949

Abstract

Climate change and urban development patterns amplify the risks of flooding and water pollution. While climate-robust stormwater management has the potential to reduce these risks, its implementation remains slow. Enhanced and new forms of collaboration between municipalities and property owners are proposed as [...] Read more.

Climate change and urban development patterns amplify the risks of flooding and water pollution. While climate-robust stormwater management has the potential to reduce these risks, its implementation remains slow. Enhanced and new forms of collaboration between municipalities and property owners are proposed as the keys to advancing the volume and effectiveness of such measures. However, the practical outline of new collaborative practices between these actor categories within existing built urban environments is still in its early stages. This study uses the experiences and visions of respondents from eleven municipalities and six property companies in Sweden to start examining the challenges, needs, and requirements for such forms of collaboration. The study identifies current challenges, including ambiguous legislation, organizational differences, unclear roles and responsibilities, and weak economic incentives. Requirements for improved collaboration opportunities include overcoming perceived legal obstacles, assigning collaboration coordinators, establishing long-term collaborative forums, and clarifying financial principles and cost-sharing arrangements. Creating the conditions for collaboration thus requires changes in formal national frameworks, as well as changes in local organizational structures, norms, and traditions. Full article

(This article belongs to the Special Issue Urban Flood Mitigation and Sustainable Stormwater Management—2nd Edition)

15 pages, 12466 KB

Open AccessArticle

Development of a Block-Scale Spatial Flood Vulnerability Index—Case Study: Morelia, Mexico

by Claudia Ximena Roblero-Escobar, Jaime Madrigal, Sonia Tatiana Sánchez-Quispe, Julio César Orantes-Avalos and Liliana García-Romero

Water 2025, 17(3), 422; https://doi.org/10.3390/w17030422 - 3 Feb 2025

Cited by 1 | Viewed by 1294

Abstract

The study of urban floods is increasingly crucial due to their growing frequency and impact on densely populated areas, often characterized by inadequate drainage and located in flood-prone zones. The consequences extend beyond physical damage, significantly affecting economies and livelihoods, necessitating substantial economic [...] Read more.

The study of urban floods is increasingly crucial due to their growing frequency and impact on densely populated areas, often characterized by inadequate drainage and located in flood-prone zones. The consequences extend beyond physical damage, significantly affecting economies and livelihoods, necessitating substantial economic resources for recovery and infrastructure rebuilding. Urban planning now must integrate flood risk management, emphasizing not only infrastructural resilience but also comprehensive policies that address environmental and social vulnerabilities to better prepare and protect urban environments against future flood risks. This study addresses the critical issue of urban flood vulnerability through a focused analysis of Morelia, a city known for its susceptibility to flooding due to its geographical and hydrological characteristics and accelerated urban growth. Employing a multifaceted approach that integrates hydrological, socio-economic, and land use data within a Geographic Information Systems (GIS) framework, the research develops a Spatial Flood Vulnerability Index (SFVI). This index is meticulously applied at the urban block level, offering a precise mapping of flood risks across the city. By correlating the SFVI results with historical flood data, the study identifies the most vulnerable areas in Morelia, which are primarily impacted due to their proximity to water bodies, economic density, and infrastructural settings. The methodology not only highlights immediate flood risks but also aids in strategic urban planning to enhance resilience against future flooding events. This paper contributes a novel approach to flood risk assessment, providing a replicable model for similarly affected cities worldwide, aiming to balance structural measures with strategic planning tailored to local needs. Full article

(This article belongs to the Special Issue Urban Flood Mitigation and Sustainable Stormwater Management—2nd Edition)

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16 pages, 6033 KB

Open AccessArticle

Urban Waterlogging Simulation and Disaster Risk Analysis Using InfoWorks Integrated Catchment Management: A Case Study from the Yushan Lake Area of Ma’anshan City in China

by Kun Wang, Jian Chen, Hao Hu, Yuchao Tang, Jian Huang, Youbing Wu, Jingyu Lu and Jinjun Zhou

Water 2024, 16(23), 3383; https://doi.org/10.3390/w16233383 - 25 Nov 2024

Cited by 5 | Viewed by 1495

Abstract

Under the dual pressures of climate change and urbanization, cities in China are experiencing increasingly severe flooding. Using the Yushan Lake area in Ma’anshan City, Anhui Province, as a case study, we employed the InfoWorks Integrated Catchment Management (ICM) hydraulic model to analyze [...] Read more.

Under the dual pressures of climate change and urbanization, cities in China are experiencing increasingly severe flooding. Using the Yushan Lake area in Ma’anshan City, Anhui Province, as a case study, we employed the InfoWorks Integrated Catchment Management (ICM) hydraulic model to analyze the drainage and flood prevention system of the region and assess the current infrastructure for drainage and flood control. There are 117 pipelines with a return period lower than one year for stormwater and combined sewer systems, accounting for 12.3% of the total number of pipelines. The number of pipelines meeting the one-year but not the three-year return period standard is 700, representing 70.2%. Only 17.5% of the pipelines are capable of handling events exceeding the one-year standard. In simulating a 24 h, 30-year return period rainfall event, the results indicate that floodwater accumulation in the study area is predominantly between 0.15 m and 0.3 m. Most risk areas are classified as low risk, covering an area of 36.398 hectares, followed by medium and high-risk areas, which cover 8.226 hectares and 3.087 hectares, respectively. The Ma’anshan Yushan Lake area has, overall, certain flood control capabilities but faces flood risks during storms with return periods exceeding three years. This research offers valuable insights for improving urban flood management in Ma’anshan City through the development of a stormwater management model for the Yushan Lake area. Full article

(This article belongs to the Special Issue Urban Flood Mitigation and Sustainable Stormwater Management—2nd Edition)

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Review

Jump to: Research, Other

20 pages, 5116 KB

Open AccessReview

Assessment of the Hydrological Performance of Grass Swales for Urban Stormwater Management: A Bibliometric Review from 2000 to 2023

by Xuefei Wang, Run Zhang, Qi Hu, Chuanhao Sun, Rana Muhammad Adnan Ikram, Mo Wang and Guo Cheng

Water 2025, 17(10), 1425; https://doi.org/10.3390/w17101425 - 9 May 2025

Cited by 1 | Viewed by 1050

Abstract

Grass swales have emerged as a cost-effective and sustainable stormwater management solution, addressing the increasing challenges of urbanization, flooding, and water pollution. This study conducted a bibliometric analysis of 224 publications to assess research trends, key contributors, and knowledge gaps in grass swale [...] Read more.

Grass swales have emerged as a cost-effective and sustainable stormwater management solution, addressing the increasing challenges of urbanization, flooding, and water pollution. This study conducted a bibliometric analysis of 224 publications to assess research trends, key contributors, and knowledge gaps in grass swale applications. Findings highlighted the growing emphasis on optimizing hydrological performance, particularly in response to intensifying climate change and urban flood risks. Experimental and simulation-based studies have demonstrated that grass swale efficiency is influenced by multiple design factors, including vegetation type, substrate composition, hydraulic retention time, and slope gradient. Notably, pollutant removal efficiency varies significantly, with total suspended solids (TSS) reduced by 34.09–89.90%, chemical oxygen demand (COD) by 7.75–56.71%, and total nitrogen (TN) by 32.37–56.71%. Additionally, studies utilizing the Storm Water Management Model (SWMM) and TRAVA models have demonstrated that integrating grass swales into urban drainage systems can result in a 17% reduction in total runoff volume and peak flow attenuation. Despite these advancements, key research gaps remain, including cost-effective design strategies, long-term maintenance protocols, and integration with other green infrastructure systems. Future research should focus on developing innovative, low-cost swale designs, refining optimal vegetation selection, and assessing seasonal variations in performance. Addressing these challenges will enhance the scientific foundation for grass swale implementation, ensuring their sustainable integration into climate-resilient urban planning. Full article

(This article belongs to the Special Issue Urban Flood Mitigation and Sustainable Stormwater Management—2nd Edition)

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Other

Jump to: Research, Review

12 pages, 737 KB

Open AccessTechnical Note

Limited Time Resolution of Event Data Loggers Can Bias Intensity Measurements from Tipping-Bucket Rain Gauges

by David Dunkerley

Water 2025, 17(9), 1391; https://doi.org/10.3390/w17091391 - 6 May 2025

Viewed by 583

Abstract

Event data loggers are frequently used to record the date and time of tip events in tipping-bucket rain gauges. The HOBO^® pendant event data logger is one such commercially available device commonly used for this purpose. It can record the contact closure [...] Read more.

Event data loggers are frequently used to record the date and time of tip events in tipping-bucket rain gauges. The HOBO^® pendant event data logger is one such commercially available device commonly used for this purpose. It can record the contact closure of a TBGR reed switch at a maximum timing resolution of 1 s, tied to the timing of the logger clock, which is set each time the logger is launched. These event loggers are ideal for the routine recording of rainfall. This paper addresses the issue of whether they can also be relied upon when estimating short-term intensities, for which they were not designed. New experiments show that for a series of switch closures at fixed intervals other than exact multiples of 1 s, the HOBO^® logger fails to record evenly spaced tip events. Thus, for example, with pulses at fixed 2.75 s intervals, the logger records some events as occurring at 2 s intervals and others at 3 s intervals. This quantization error means that there can be large errors in the logged time between bucket tip events. In natural rainfall, tip events can occur at any time, and inter-tip times, from which intensity can be estimated, will generally not be an integral number of seconds. Consequently, particularly in intense rain, the logger behaviour just described can lead to erroneous estimates of the rainfall rate estimated from the duration of individual inter-tip times. Possible solutions are discussed. Full article

(This article belongs to the Special Issue Urban Flood Mitigation and Sustainable Stormwater Management—2nd Edition)

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