The urban drainage system plays an important role in the urban infrastructure resilience discussion. Its functional failures can trigger cascading effects on other urban systems and critical infrastructures. The main aim of this work is to investigate and quantify urban flood resilience, offering an integrated methodological approach. In this process, the flooding consequences were quantified by hydrodynamic simulations, using a case study in an exploratory research method. A set of indicators was proposed to map the cascading effects generated by floods and the consequent quantification of urban flooding resilience. Two simulation scenarios were proposed to validate the methodological assessment framework proposed in this work. The first scenario represented the current flooding situation and showed the negative effects on the city systems resulting from disordered urban growth. The second scenario considered the improvement of the drainage behavior, considering a sustainable urban drainage approach supported by the concept of blue-green infrastructure integrated with the urban open spaces system. A comprehensive flood resilience assessment over time was conducted by analyzing the evolution of the System Integrity Index on both scenarios. The results showed that water dynamics play an important role in ordering land use and that preserving water spaces can efficiently respond to urban developing threats, dealing with floods in an earlier development moment, proving the importance of the drainage system as a preliminary structuring driver for supporting a sustainable urban planning, ordered according to environmental constraints defined by water dynamics.

This article investigates how to make the implementation of blue-green infrastructure (BGI) more attractive to solve urban problems in densely occupied watersheds that lack flood control and environmental quality protection infrastructure. Considering the obstacles related to implementing multifunctional solutions in developing countries, measuring its co-benefits (in addition to flood control) may influence greater public and political acceptance. Thus, the paper uses a multifunctional design approach using the urban open space system and combining the blue-green and gray infrastructure. A hydrodynamic model was used to support flood mapping. This approach also increases the land value and the environmental quality of the urban spaces. Two quantitative aspects support this evaluation. The first one represents the land value increase as a positive effect, while the second one assesses the environmental quality of the urban space using the Environmental Quality Assessment Index (EQAI). The results obtained from the urban and environmental evaluation proved that blue and green corridors could promote multiple co-benefits for consolidated urban areas. The increased environmental quality and land value were only possible due to the combined use of BGI and gray infrastructure since BGI can add benefits that the gray infrastructure is not capable of providing.

The city of Riohacha (Colombia) has a complex urban setting that, under the pressure of recurring intense rains, experiences increasing flood damage. With the aim of identifying a systemic solution to flood problems, a hydrodynamic mathematical modelling exercise was conducted. Within the modelling process, calibration and validation are two fundamental actions that must precede the use of the model. However, most of the river basins around the world lack hydrometeorological information, which is indispensable for the calibration process. This paper presents an original approach to collecting such information for the calibration process, based on interviewing inhabitants. The results of this effort were surprisingly good, when considering the kind of approximations involved in using people's answers as hard data. This encouraged us to promote it as a working solution for many other similar cases, which all suffer from lack of suitable data.

Technological evolution survey allowed the broad use of 2D mathematical models for flood simulation. However, it is possible that the answer required for a given problem does not need a 2D approximation or even does not configure a 2D surface solution. Urban flood simulations may fall in this second case, since urban structures may interact with flood flows and introduce discontinuities in the surface solution. This study aims to highlight the discussion about the physical interpretation and the modeller role as key elements in the interpretation and representation of physical systems. To support this proposal, the MODCEL, a Quasi-2D flow-cell model, was used in two different ways: in a detailed raster approach, similarly to usual 2D model uses; and in an alternative conceptual and interpretive way, using larger cells representing homogeneous portions of the territory. The modelling results showed that equivalent responses can be obtained. Although other models can be used and could offer different absolute results, the relative analysis offered sufficient support to the research hypothesis that a physical-based process conducted by a conscient modeller is crucial for model reliability and optimization.

Numerous countries and regions have embraced implementing a separate sewer system, segregating sanitary and storm sewers into distinct systems. However, the functionality of these systems often needs to improve due to irregular interconnections, resulting in a mixed and malfunctioning system. Sewage collection is crucial for residential sanitation, but untreated collection significantly contributes to environmental degradation. Analyzing the simultaneous operation of both systems becomes vital for effective management. Using mathematical tools for precise and unified diagnosis and prognosis becomes imperative. However, municipal professionals and companies need more tools specifically designed to evaluate these systems in a unified way, mapping all the hydraulic connections observed in practice. This study proposes a unified simulation method for stormwater and sanitary sewer urban systems, addressing real-world scenarios and potential interferences. The primary goal is to develop a simulation method for both systems, considering system interconnections and urban layouts, involving hydrodynamic and water quality simulations. The practical application of this method, the Multilayer Hydrodynamic Simulation Method (MODCEL-MHUS), successfully identifies issues in urban water networks and suggests solutions, making it a valuable tool for urban water management and environmental engineering professionals.