Aline Pires Veról

City Growth and Urban Drainage Alternatives: Sustainability Challenge

Since the 1970s, growing concerns about urban development’s effects on the natural environment have been prompting efforts to find more sustainable solutions for the problems arising from the built environment. In this context, this work discusses the need to integrate innovative stormwater drainage practices with the urban planning process, especially regarding the limitation associated with the increase of impervious surfaces, while trying to handle the runoff generated by the urban sprawl. The interaction between urban growth and stormwater management is investigated, using a case study in the metropolitan region of Rio de Janeiro to illustrate the main findings. To fulfill this objective, the present flooding scenario for this area is modified under two premises: considering a traditional drainage system approach, focusing on channelization measures, and a distributed stormwater management approach, based on the sustainable urban drainage system (SUDS) concepts. Then, these two solutions are tested for their effectiveness under three different scenarios of future urban growth and land-use changes, ranging from uncontrolled urbanization to planned urban growth with land-use control. The capacity of these two approaches to maintain their design functions is verified for the proposed future urban patterns. The quantitative evaluation of urban flooding prospective scenarios is supported by mathematical modeling. From the results of the conducted simulations, one can confirm the crucial importance of land-use planning in the urban flood control process. Decentralized stormwater controls, although more resilient than traditional channelization measures, tend to fail in the long term if land-use planning is not properly addressed. A key element for flood control is the integration of drainage solutions with urban development, in a systemic way and considering the basin scale as the planning and design reference.

Sustainable Drainage Systems: An Integrated Approach, Combining Hydraulic Engineering Design, Urban Land Control and River Revitalisation Aspects

Floods are natural and seasonal phenomena, which play an important environmental role, but when they take place at the built environments, many losses of different kinds occur. By its side, urban growth is one of the main causes of urban floods aggravation. Changes in land use occupation, with vegetation removal and increasing of impervious rates lead to greater run-off volumes flowing faster. Intense urbanisation is a relatively recent process; however, floods and drainage concerns are related to city development since ancient times. Drainage systems are part of a city infrastructure and they are an important key in urban life. If the drainage system fails, cities become subjected to floods, to possible environmental degradation, to sanitation and health problems and to city services disruption. On the other hand, urban rivers, in different moments of cities development history, have been considered as important sources of water supply, as possible defences for urban areas, as a way of transporting goods, and as a means of waste conveying.

A catchment scale Integrated Flood Resilience Index to support decision making in urban flood control design

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.

Multilayer Modelling as a Supporting Tool for Flood Diagnosis and Drainage System Design

The use of dual drainage models have increased significantly in the past decades, mostly because of advances in mathematical and GIS tools methods. This type of modelling provides precise diagnosis and can be applied to evaluate storm water infrastructure and diverse drainage alternatives. This study aimed to analyse minor and major drainage relations in Dona Eugenia River Basin, located in the metropolitan area of Rio de Janeiro, Brazil. Two alternatives were simulated using MODCEL. The first one considered only the terrain surface layer, while in the second the layer containing a designed storm sewer was introduced. The results provided information on where minor drainage gaps were located and on the effects of the storm sewer network discharges in the major drainage system.

Alternative Solutions for Sustainable Urban Drainage Systems Integrating Areas of Irregular Urban Growth with the Formal City

The main objective of this paper is to propose an alternative for the stormwater management in low-income communities, settled in urban vertical slums, located in areas with insufficient infrastructure and degraded environment. A case study located in Rio de Janeiro City, Brazil, is presented. The high slopes of the studied area are used to favor the superficial flows, generating alternatives for the traditional stormdrains used to collect the runoff of the upstream reaches. A small reservoir is proposed for each house, reducing flood volumes by allowing rainwater harvesting, and a greater retention reservoir is introduced as a storage measure for connecting the microdrainage coming from the informal city to the formal city. The different scenarios were simulated with the aid of a mathematical model called MODCEL and the results showed that it is possible to apply an effective drainage system solution in informal areas, without affecting the already implemented downstream formal drainage network. The retention reservoir proposed also introduces the possibility to act in improving the water quality to downstream areas, although this complementary aspect is not developed in this study.