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Urban floods are becoming a great concern of growing cities. Urban growth pressed by poverty and social drivers, together with possible climate change, may pose difficult challenges and increasing risk to safety and urban livability. In the face of this growing risk, urban drainage management is being pressed to move towards a flood risk management approach and that builds city resilience, or the capacity to continue functioning even in future hazardous conditions. In this context, this study proposes the development of an integrated Flood Resilience Index, departing from mathematical modelling tools and flood risk concepts. The Flood Resilience Index was built to support decision-making process in choosing design alternatives that improve flood control responses in future scenarios that surpass design standards. This way, flood control design decisions would be made under a quantitative assessment of the performance of a design alternative on potential flooding events in the long term. Flood Resilience Index was successfully tested in a watershed in the metropolitan region of Rio de Janeiro/Brazil where there is uncontrolled urban growth. It identified the best alternative to be a combined approach including sustainable urban drainage measures with river restoration techniques. When looking to the city centre area, this alternative scored a Flood Resilience Index of 47 over 100 against a conservative alternative of a dam, which only scored 20.

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Abstract:The development of cities has always had a very close relation with water. However, cities directly impact land use patterns and greatly change natural landscapes, aggravating floods. Considering this situation, this paper intends to discuss lowland occupation and city sustainability in what regards urban stormwater management, fluvial space, and river restoration, aiming at minimizing flood risks and improving natural and built environment conditions. River plains tend to be attractive places for a city to grow. From ancient times, levees have been used to protect lowland areas along major watercourses to allow their occupation. However, urban rivers demand space for temporary flood storage. From a systemic point of view, levees along extensive river reaches act as canalization works, limiting river connectivity with flood plains, rising water levels, increasing overtopping risks and transferring floods downstream. Departing from this discussion, four case studies in the Iguaçu-Sarapuí River Basin, a lowland area of Rio de Janeiro State, Brazil, are used to compose a perspective in which the central point refers to the need of respecting watershed limits and giving space to rivers. Different aspects of low-lying city planning are discussed and analyzed concerning the integration of the built and natural environments. OPEN ACCESSSustainability 2015, 7 11069

Urban flood modelling has been evolving in recent years, due to computational facilities as well as to the possibility of obtaining detailed terrain data. Flood control techniques have also been evolving to integrate both urban flood and urban planning issues. Land use control and flow generation concerns, as well as a set of possible distributed measures favouring storage and infiltration over the watershed, also gained importance in flood control projects, reinforcing the need to model the entire basin space. However, the use of 2D equations with highly detailed digital elevation models do not guarantee good results by their own. Urban geometry, including buildings shapes, walls, earth fills, and other structures may cause significant interference on flood paths. In this context, this paper presents an alternative urban flood model, focusing on the system behaviour and its conceptual interpretation. Urban Flood Cell Model-MODCEL is a hydrological-hydrodynamic model proposed to represent a complex flow network, with a set of relatively simple information, using average values to represent urban landscape through the flow-cell concept. In this work, to illustrate model capabilities, MODCEL is benchmarked in a test proposed by the British Environmental Agency. Then, its capability to represent storm drains is verified using measured data and a comparison with Storm Water Management Model (SWMM). Finally, it is applied in a lowland area of the Venetian continental plains, representing floods in a complex setup at the city of Noale and in its surroundings.

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Urbanisation greatly changes the natural environment-city growth may cause urban sprawl, increasing land consumption and infrastructure demands, with consequent built and natural environments degradation. To face this challenge, the supporting capacity of the natural environment needs to be addressed in the urban planning process. This chapter will particularly discuss urban drainage role in the planning context, integrating engineering, urbanism and landscaping in order to set the basic conditions towards a sustainable city development. Urban drainage systems (and the related urban rivers) play a crucial role in city planning, once it intermediates the needs of the built environment, providing safe areas free from flooding, and the demands of the natural environment, giving space and passage to floods. This particular feature gives to the drainage system a spatial structuring characteristic and it provides opportunities to revitalise city areas, improving biodiversity and recovering environmental values. On the other side, a city open spaces system is the main reserve of urban areas for sustainable urban drainage interventions. The adequate land use planning and consequent management of these open spaces shall be in the core discussion to produce integrated and functional solutions for built and natural environments.