Blue-Green Cities and Infrastructure for Urban Flood Risk Management

Dear Colleagues,

Urban flooding is among the most frequent and damaging natural hazards affecting cities worldwide, with significant consequences for infrastructure, economies, and human wellbeing. Historically, urban flood management has relied predominantly on conventional grey infrastructure systems—such as storm sewers, culverts, and channelised waterways—designed under assumptions of stationarity and based on historical rainfall records. While these approaches have been effective under past conditions, they are increasingly inadequate in the face of rapid urbanisation, land-use change, and the growing impacts of climate change.

Over recent decades, the field of hydrology and urban water management has undergone a significant paradigm shift. The limitations of purely engineered solutions have led to the emergence of integrated approaches that combine hydraulic efficiency with environmental sustainability. In this context, Blue–Green Cities and Blue–Green Infrastructure (BGI) have gained prominence as multifunctional systems that mimic natural hydrological processes, improve infiltration and storage, and reduce surface runoff. These systems also provide wider co-benefits, including improved water quality, urban cooling and increased societal resilience.

Concurrently, advances in numerical modelling have played a pivotal role in improving the understanding and management of urban flood processes. Hydrodynamic models—ranging from one-dimensional sewer flow models to fully coupled two-dimensional surface flow simulations—are now widely used to represent complex interactions between rainfall, topography, drainage networks, and urban infrastructure. Recent developments include high-resolution modelling, sub-grid approaches, coupled surface–subsurface simulations, and the integration of data-driven and hybrid modelling techniques.

Despite these advances, several critical challenges remain. Current modelling frameworks often struggle to adequately represent the performance of blue–green systems under extreme events, particularly when considering uncertainty in climate projections and urban development scenarios. Furthermore, there is a need to bridge the gap between modelling, design, and decision-making, ensuring that scientific developments are translated into practical and robust urban flood management strategies.

The aim of this Special Issue is to provide a comprehensive and forward-looking platform for research on the planning, modelling, design, and performance evaluation of Blue–Green Cities and Infrastructure for urban flood risk management. The Special Issue is closely aligned with the journal’s scope in hydrology, particularly in advancing the understanding of urban hydrological processes, flood dynamics, and sustainable water management solutions.

This Special Issue seeks to highlight the role of numerical and hydrodynamic modelling, alongside data-driven and hybrid approaches, in supporting the design and optimisation of blue–green systems. It also aims to address how these approaches can improve resilience under changing climatic and urban conditions.

A key objective is to bring together interdisciplinary contributions that advance both the theoretical and applied aspects of urban flood management, while fostering the integration of hydrological science, engineering practice, and decision-support frameworks.

This Special Issue will particularly emphasise emerging and innovative directions in the field, including:

• Advanced numerical modelling frameworks for simulating urban flood processes and blue–green infrastructure performance;
• Coupled modelling approaches integrating surface flow, drainage systems, and subsurface processes;
• Data-driven and hybrid methods, including machine learning and artificial intelligence, for flood prediction and system optimisation;
• Integration of climate change projections into urban flood modelling and design methodologies;
• Development of digital twins and real-time decision-support tools for resilient urban water systems;
• Uncertainty quantification and risk-based design approaches for blue–green infrastructure;
• Multi-objective optimisation techniques for balancing flood mitigation, cost, and co-benefits;
• Scaling issues and transferability of blue–green solutions across different urban environments.

By addressing these aspects, the Special Issue aims to contribute to the advancement of knowledge in hydrology and urban water management, supporting the transition towards more resilient, adaptive, and sustainable cities.

This Special Issue will welcome original research articles and review papers that address, but are not limited to, the following themes:

• Blue–green infrastructure and nature-based solutions for urban flood mitigation;
• Numerical and hydrodynamic modelling of urban flood processes;
• Coupled and hybrid modelling approaches (physics-based and data-driven);
• Climate change impacts and resilience assessment;
• Decision-support systems and optimisation frameworks for urban flood management;
• Monitoring, data assimilation, and digital twin applications;
• Performance evaluation and uncertainty analysis of blue–green systems.

We look forward to receiving your original research articles and reviews.

Dr. Christos Iliadis
Dr. Vassilis Glenis
Dr. Lampros Vasiliades
Dr. Pierfranco Costabile
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-anonymized peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Hydrology is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• blue–green cities
• blue–green infrastructure
• urban flood risk management
• nature-based solutions
• numerical modelling
• hydrodynamic modelling
• climate resilience
• sustainable urban drainage
• decision-support systems
• urban hydrology