Urbanization increases imperviousness and reduces infiltration, retention, and evapotranspiration, frequently aggravating urban flooding due to greater runoff and higher and faster discharge peaks. Effective strategies to mitigate flood risks require a better understanding of the watershed dynamics and space to reverse the negative impacts. However, often cities do not have proper data sets to feed mathematical models that would be helpful in mapping water dynamics. Attempts to reduce flood risks have been made for decades by means of structural interventions but were frequently designed within the logic of a local scale, using limited available spaces and often merely shifting flooding downstream. Therefore, assessing urban floods requires a modeling approach capable of reflecting the watershed scale, considering interactions between hydraulic structures and urban landscape, where best practices and non-structural measures aim to improve community flood resilience through the reduction of social and financial costs in the long run. This paper proposes an integrated approach to analyze low impact development (LID) practices complemented by non-structural measures in a case study in southern Italy, supported by mathematical modeling in a strategy to overcome a context of almost no available data and limited urban open spaces.

Risk can be defined as the relationship between the likelihood of a hazard causing a potential disaster and its consequences. This study aims to assess the likelihood that a new industrial region, located in the state of São Paulo (Brazil), will be flooded, causing the disruption of the mobility system and local economic activities. To fulfill this aim, a new approach is proposed by combining the vector information of the highway network that serves the region with the result of a quasi 2-D raster flood model, generating a set of interpreting rules for classifying the safety of routes. The model called MODCEL is a quasi-2D hydrodynamic model that represents the watershed using compartments called cells, and it was adapted to work using a raster file format in which each pixel is represented as a flow cell connected to its surroundings by the Saint-Venant equations without the inertia terms. Therefore, this study proposes an assessment framework that can be replicated for similar problems of flood risks to mobility. The possible effects of flood events on the accessibility to areas of interest are determined, indicating a possible disruption to economic activities and transportation and allowing for planning alternatives in advance.

Technological evolution survey allowed the broad use of 2D mathematical models for flood simulation. However, it is possible to happen 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.

A identificação de áreas com predisposição à ocorrência de desastres naturais surge como informação importante, principalmente no contexto urbano. Sendo assim, o objetivo desse estudo é propor uma metodologia para o mapeamento de áreas de risco de fluxo de detritos, considerado como um dos acidentes naturais que mais provocam mortes e perdas materiais. Para tanto, esse estudo fez a modelagem de estabilidade das encostas diretamente num software GIS, em que foram utilizados o Modelo do Talude Infinito, para o cálculo da estabilidade, e do Método CN do SCS, como modelo de infiltração. Na análise de risco, considerou-se que Risco é definido pelo produto da probabilidade de ocorrência de um fluxo de detritos (Perigo), onde é avaliada a influência das características do meio físico e do seu processo deflagrador; com a severidade das suas consequências, medidas em termos de população afetada (Exposição) e suas fragilidades (Vulnerabilidade).

Morais Canedo de Magalhães, Paula; Sayão, Alberto de Sampaio Ferraz Jardim (advisor). Mapping of debris flow risk areas based on a GIS model. Rio de Janeiro, 2021. 138 p.