Marcelo Gomes Miguez

Urban Flood Control through a Mathematical Cell Model

Abstract This study models urban flood behavior by the flow cell scheme. The flow cell concept has origins in the Mekong River Delta Model (Zanobetti et al., 1970) and is historically used to simulate large rural floodplains. The flow cell concept was used to model the Pantanal Matogrossense, a large Brazilian marsh watershed of ecological importance (Mascarenhas and Miguez, 1993). That work is here adapted to model the diversity of drainage in the city of Joinville, Santa Catarina in southern Brazil.

Planning and Design of Urban Flood Control Measures: Assessing Effects Combination

Different approaches related with urban flood problems treatment are evolving and there is a large set of possible engineering measures that can be applied. Lately, the traditional approach, focusing on improving channel conveyance, is being complemented by distributed structural measures and nonstructural measures, considering the basin under a systemic point of view and aiming to recover natural flow patterns prior to urbanization. In this context, it becomes necessary to evaluate the potential use of different combinations of the possible interventions, in such a way that the efficacy of these sets in terms of flood mitigation can be optimized. This kind of analysis is of crucial importance and involves technical and economic aspects. Combined effects of the chosen measures may produce a result that is not equivalent to what would be expected from the summation of its individual effects. The systemic behavior of an urban watershed, especially when the drainage system works jointly with flooded urban la...

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.

Enhancing ecosystem services for flood mitigation: a conservation strategy for peri-urban landscapes?

A key reason why some ecosystem services are undervalued is because they are not easily perceived both by beneficiaries and potential providers. Hydrological modeling allows us to assess, quantify, and visualize the causal link between a particular human intervention and the positive or negative impacts this has on flooding. This study uses such a model to test hypothetical changes in land use in the Brazilian coastal city of Paraty. We discuss how the adoption of higher density patterns of urban development can respond to the needs of a growing population, while safeguarding cultural landscapes of high environmental value against unsustainable urban sprawl and encroachment. Results of the modeling exercise show how water-flow regulation services can be improved, and to what extent restoring natural functions and properties of peri-urban floodplains may reduce urban flooding.

Urban Flood Control, Simulation and Management - an Integrated Approach

History shows that places near rivers were attractive as sites for ancient civilisation development. Mesopotamia, China, Egypt and Rome are some examples. Fertile lands, transportation and water supply were main factors. During the industrial revolution, however, stormwater started to be considered as a great matter for urban life. Urban floods started to increase in magnitude and frequency. Street gutters were used to convey stormwater and wastewater as well. Diseases spread around the industrial city and waters had to be discharged as faster as possible. As a consequence, urban drainage started to play an important role in cities life. It is possible to say that urbanisation is an inexorable trend. The urban population has been increasing significantly in the last two centuries, since industrial revolution took place. The consequences of this process incurs in great changes of the natural environment. Urbanisation process tends to substitute natural vegetation for impervious surfaces, thus reducing infiltration. It also tends to eliminate natural detention ponds, to rectify river courses, among other actions, that greatly interfere with superficial flows. In general, floods in urban areas present greater runoff volumes and flow velocities, resulting in higher flow peaks and water stages. This way, urbanisation aggravates floods and, as it could be seen in cities development, it was not always possible to accomplish urban growing with the adequate infrastructure, especially in developing and poor countries. Even in wealthy countries, urban growth stresses the existing infrastructure. Urban floods disrupts social systems and cause significant economic losses. Among the impacts produced, there are health hazards and losses of human lives, flooding of housing, commercial and industrial properties, flooding of streets and intersections, causing traffic delays, disruption of services such as water supply, power supply and sewerage. Flood control is, thus, one of the major issues with which urban planners must deal nowadays, once floods play a dramatic role in the cities. Additionally, the lack of planning frequently worsens this situation. Many times, the absence of systemic design tools capable to represent the problem in an integrated approach leads to a decision process in which local solutions may be inadequate for the whole system needs. An important tool to be considered refers to the mathematical modelling of hydrologic and hydraulic processes. 10

Policy dimensions of land-use change in peri-urban floodplains: the case of Paraty

Peri-urban floodplains located in upstream reaches of urban areas play a key role in the resilience of social-ecological systems. The need to adapt to increasing flood risks by protecting these natural assets represents a huge challenge for many cities facing rapid expansion and limited financial resources for the mitigation of environmental impacts. To understand how better governance and management can be put in place, there is a need to map the key players shaping and/or being impacted by land-use change processes and assess the barriers keeping them from playing a more constructive role in the collaborative governance of cities, the natural resources which sustain them, and the environmental risks that pose a threat. A conceptualization of power regarding natural resource governance is presented and its implications for the relationships between actors and the many scales of decision making is discussed. Drawing on existing literature, we develop a heuristic framework for analyzing policy dimensions of land-use change processes, and reflect on the possible ways for key stakeholders to become over time more committed to and involved in a collaborative approach to the development of land use policies for urban flood prevention. We apply this framework to the Brazilian city of Paraty, a case study through which the recurring problem of flooding exposes the deepening tensions between conservation and development. Empirical results demonstrate the need to acknowledge the politicization of floodplain change and the importance of trying to bridge the gap between sectors and actors with conflicting interest in urban environmental management.

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.

Stepping towards sustainable urban drainage practices at Acari River Basin in Rio de Janeiro.

Acari River basin, located at the north zone of Rio de Janeiro city, is one of the most populated regions of this city (with 20% of its total population) and encompasses an area of 107 km. This watershed is characterized by medium and low-income occupations and suffers from various different problems due to its non-planned urbanisation. Flooding is one of the most critical and complex issues in this region of the city. This problem is worsened by factors such as intense urbanisation, high imperviousness rates, riverbanks and floodplain occupation, existence of hydraulic singularities, tidal influence, among others. In order to manage this situation, the Municipality proposed a canalisation project based on the enlargement of Acari River. This measure alone was not able to solve the problem as it could transfer the flood downstream to highly occupied low-lying areas. In order to adjust design concepts, Federal University of Rio de Janeiro conducted a research searching for a more sustainable flood control measures set. The study was carried out with the support of a hydrodynamic cell model. The model was calibrated based on an intense real flood event and applied to the simulation of scenarios representing present situation and combinations of several structural measures (including the canalisation project). The results have shown that a sustainable solution can be achieved through the combination of the proposed channel design project with other measures such as storage structures, multifunctional landscapes and communities relocation.

Multifunctional Landscapes For Urban FloodControl: The Case Of Rio De Janeiro

The urbanisation process changes the natural landscape, generally aggravating fl ood problems. In developing countries, urbanisation is not always accomplished by the implementation of the adequate infrastructure required. Lack of planning frequently worsens this situation. Focus on urban fl ood problems has been changing in the past few decades. The traditional approach that basically focused on improving conveyance, by canalising and rectifying watercourses, is being complemented or substituted by different conceptions. This new approach tries to equate an integrated solution for the basin, with distributed interventions aiming to recover pre-urbanisation fl ow patterns and combining water quality and quantity control aspects. These newer concepts deal with storage and infi ltration techniques. In densely urbanised environments, however, it is not always easy to fi nd suitable areas available for construction of detention/retention reservoirs or extensive infi ltration measures. In such situation, an interesting option may be the use of multifunctional landscapes, in which urban solutions gain additional hydraulic functions, gathering urban planning and hydraulic engineering aspects in order to revitalise urban environment and control fl oods in a sustainable approach. The use of existing parks and squares, remodelled to aggregate permanent or temporary ponds, can be an interesting option. In most developing countries, as in the example of Rio de Janeiro City, Brazil, water quality problems due to untreated sewer disposal are generally more crucial than those associated with watershed wash-off. Worse than this is the fact that water quantity problems are still so severe that quality control is a secondary concern. In this context, this chapter presents and discusses a revision on urban fl ood problems and two case studies, where multifunctional landscapes are proposed. The fi rst one is related to www.witpress.com, ISSN 1755-8336 (on-line) WIT Transactions on State of the Art in Science and Engineering, Vol 50,