Urban flooding caused by extreme rainfall events is becoming considerably more frequent and more ... more Urban flooding caused by extreme rainfall events is becoming considerably more frequent and more destructive. Thus, enhanced models to predict accurately flood magnitude and location are of paramount importance. These models can then be used for urban planning, flood forecasting, flood management (real-time control, raise of flood alerts (emergency services management, etc.) and, ultimately, to estimate flood damage assessment. This paper demonstrates the capability of the Automatic Overland Flow Delineation (AOFD) methodology developed by the authors for flood damage estimation in urban areas. Properties in risk of flood are identified based on a spatial analysis, using the locations of flood - prone areas (ponds) and the location of buildings. The results obtained in this study open new research directions to estimate flood damage with even more detail, and extend flood damage estimation beyond property level, i.e. considering also traffic disruption, health issues and alike.Plavl...
Sewer asset management gained momentum and importance in recent years due to economic considerati... more Sewer asset management gained momentum and importance in recent years due to economic considerations, since infrastructure maintenance and rehabilitation directly represent major investments. Because physical urban water infrastructure has life expectancies of up to 100 years or more, contemporary urban drainage systems are strongly influenced by historical decisions and implementations. The current decisions taken in sewer asset management will, therefore, have a long-lasting impact on the functionality and quality of future services provided by these networks. These decisions can be supported by different approaches ranging from various inspection techniques, deterioration models to assess the probability of failure or the technical service life, to sophisticated decision support systems crossing boundaries to other urban infrastructure. This paper presents the state of the art in sewer asset management in its manifold facets spanning a wide field of research and highlights existi...
Physically-based overland flow models are computationally demanding, hindering their use for real... more Physically-based overland flow models are computationally demanding, hindering their use for real-time applications. Therefore, the development of fast (and reasonably accurate) overland flow models is needed if they are to be used to support flood mitigation decision making. In this study, we investigate the potential of Self-Organizing Maps to rapidly generate water depth and flood extent results. To conduct the study, we developed a flood-simulation specific SOM, using cellular automata flood model results and a synthetic DEM and inflow hydrograph. The preliminary results showed that water depth and flood extent results produced by the SOM are reasonably accurate and obtained in a very short period of time. Based on this, it seems that SOMs have the potential to provide critical flood information to support real-time flood mitigation decisions. The findings presented would however require further investigations to obtain general conclusions; these further investigations may inclu...
Lead time between rainfall prediction results and flood prediction results obtained by hydraulic ... more Lead time between rainfall prediction results and flood prediction results obtained by hydraulic simulations is one of the crucial factors in the implementation of real-time flood forecasting systems. Therefore, hydraulic simulation times must be as short as possible, with sufficient spatial and temporal flood distribution modelling accuracy. One of the ways to reduce the time required to run hydraulic model simulations is increasing computational speed by simplifying the model networks. This simplification can be conducted by removing and changing some secondary elements using network simplification techniques. The emphasis of this paper is to assess how the level of urban drainage network simplification influences the computational time and overall simulation results' accuracy. The models used in this paper comprise a sewer network and an overland flow drainage system in both 1D/1D and 1D/2D approaches. The 1D/1D model is used as the reference model to generate several models ...
In order to simulate surface runoff and flooding, one-dimensional (1D) overland flow networks can... more In order to simulate surface runoff and flooding, one-dimensional (1D) overland flow networks can be automatically delineated using digital elevation models (DEM). The resulting network comprises flow paths and terrain depressions/ponds and is essential to reliably model pluvial (surface) flooding events in urban areas by so-called 1D/1D models. Conventional automatic DEM-based flow path delineation methods have problems in producing realistic overland flow paths when detailed high-resolution DEMs of urban areas are used. The aim of this paper is to present the results of research and development of three enhanced DEM-based overland flow path delineation methods; these methods are triggered when the conventional flow path delineation process stops due to a flow obstacle. Two of the methods, the ‘bouncing ball and buildings’ and ‘bouncing ball and A*’ methods, are based on the conventional ‘bouncing ball’ concept; the third proposed method, the ‘sliding ball’ method, is based on the ...
Flash flooding is characterised by a rapid flooding phenomenon caused by intense rainfall. Despit... more Flash flooding is characterised by a rapid flooding phenomenon caused by intense rainfall. Despite being an extreme event with high uncertainty, the rainfall-runoff process is often regarded as deterministic (rather than stochastic). In this paper, the Soil Conservation Service (SCS) flood hydrograph uncertainty is quantified based on the Total Error Framework (TEF), and introduced into the model by applying perturbation in the input data and model parameters. The random perturbation component is stochastically modelled. A sensitivity analysis was carried out on the stochastic model parameters, using a real case study in the Azores (Portugal). The results showed that the flood hydrograph uncertainty varies over time, with its largest deviations occurring at the beginning of the flooding due to the uncertainty associated with the SCS method curve number parameter (correlation coefficient R2 of 0.86). Rainfall uncertainty was responsible for the uncertainty in the hydrograph peaks’ magnitude (R2=0.93) while uncertainty in the propagation velocity was responsible for the uncertainty in the peaks’ time (R2=0.97).
iGPI, the National Initiative for Infrastructure Asset Management (April 2012 - October 2013), is... more iGPI, the National Initiative for Infrastructure Asset Management (April 2012 - October 2013), is a Portuguese collaborative project led by LNEC (National Civil Engineering Laboratory, Portugal) through which 19 water utilities develop their own IAM systems and plans through a joint training and capacitation programme. Technical assistance to the participating utilities is ensured by LNEC, by a team from IST (Technical University of Lisbon) and by Addition, a software development company. The water utilities get collective as well as one-on-one support, specific training, and benefit from networking with the other utilities in a common and simultaneous process, with similar difficulties and challenges, leading to an effective sharing of solutions. The developed products, including training materials, templates and guidelines for developing strategic and tactical IAM plans, are available to the general public. This project has greatly contributed to the establishment of reference met...
Page 1. REHABILITATION INTERVENTIONS IN URBAN WATER SUPPLY ASSETS USING THE MULTICRITERIA DECISIO... more Page 1. REHABILITATION INTERVENTIONS IN URBAN WATER SUPPLY ASSETS USING THE MULTICRITERIA DECISION TOOL ELECTRE III Nelson Carriço 1 , Dídia IC Covas 1 , Maria do Céu Almeida 2 , João P. Leitão ...
A more reliable flood forecasting could benefit from higher-resolution rainfall forecasts as inpu... more A more reliable flood forecasting could benefit from higher-resolution rainfall forecasts as inputs. However, the prediction lead time of the operational rainfall forecasting models will substantially diminish while sub-hourly (e.g., 5-min) rainfall forecasting is required. A method that integrates the SVM (Support Vector Machine) and Cascade-based downscaling techniques is therefore developed in this work to carry out high-resolution (5-min) precipitation forecasting with longer lead time (45-60 minutes). The 5-min raingauge observations from Coimbra (Portugal) are employed to assess the proposed methodology. A comparison with the conventional SVM is also conducted to study the possible benefit of using the proposed methodology to carry out short-term rainfall forecasting.
ABSTRACT iGPI, the National Initiative for Infrastructure Asset Management is a Portuguese collab... more ABSTRACT iGPI, the National Initiative for Infrastructure Asset Management is a Portuguese collaborative project led by LNEC (National Civil Engineering Laboratory, Portugal) through which 19 water utilities develop their own infrastructure asset management (IAM) systems and plans in a joint training and capacitation programme. Technical assistance to the participating utilities is ensured by LNEC, IST (Technical University of Lisbon) and Addition, a software development company. The water utilities get collective as well as one-on-one support and specific training. They benefit from networking with the other utilities in a common and simultaneous process, with similar difficulties and challenges, leading to an effective sharing of solutions. The developed products, including training materials, templates and guidelines for developing strategic and tactical IAM plans, are available to the general public. This project has greatly contributed to the establishment of reference methodologies and standards for IAM planning, in a range of utilities of widely diverse size and context, effectively defining an accepted best practice. This paper discusses the project's format and its advantages, and goes on to describe the main outcomes, including selected cases and final products. http://www.tandfonline.com/eprint/TUcpPQeZpNAsbIjCMSYp/full
This paper presents the contributions of Geographic Information Systems (GIS) and location models... more This paper presents the contributions of Geographic Information Systems (GIS) and location models towards planning regional wastewater systems (sewers and wastewater treatment plants) serving small agglomerations, i.e. agglomerations with less than 2,000 inhabitants. The main goal was to develop a decision support tool for tracing and locating regional wastewater systems. The main results of the model are expressed in terms of number, capacity and location of Wastewater Treatment Plants (WWTP) and the length of main sewers. The decision process concerning the location and capacity of wastewater systems has a number of parameters that can be optimized. These parameters include the total sewer length and number, capacity and location of WWTP. The optimization of parameters should lead to the minimization of construction and operation costs of the integrated system. Location models have been considered as tools for decision support, mainly when a geo-referenced database can be used. In these cases, the GIS may represent an important role for the analysis of data and results especially in the preliminary stage of planning and design. After selecting the spatial location model and the heuristics, two greedy algorithms were implemented in Visual Basic for Applications on the ArcGIS software environment. To illustrate the application of these algorithms a case study was developed, in a rural area located in the central part of Portugal.
Urban flooding caused by extreme rainfall events is becoming considerably more frequent and more ... more Urban flooding caused by extreme rainfall events is becoming considerably more frequent and more destructive. Thus, enhanced models to predict accurately flood magnitude and location are of paramount importance. These models can then be used for urban planning, flood forecasting, flood management (real-time control, raise of flood alerts (emergency services management, etc.) and, ultimately, to estimate flood damage assessment. This paper demonstrates the capability of the Automatic Overland Flow Delineation (AOFD) methodology developed by the authors for flood damage estimation in urban areas. Properties in risk of flood are identified based on a spatial analysis, using the locations of flood - prone areas (ponds) and the location of buildings. The results obtained in this study open new research directions to estimate flood damage with even more detail, and extend flood damage estimation beyond property level, i.e. considering also traffic disruption, health issues and alike.Plavl...
Sewer asset management gained momentum and importance in recent years due to economic considerati... more Sewer asset management gained momentum and importance in recent years due to economic considerations, since infrastructure maintenance and rehabilitation directly represent major investments. Because physical urban water infrastructure has life expectancies of up to 100 years or more, contemporary urban drainage systems are strongly influenced by historical decisions and implementations. The current decisions taken in sewer asset management will, therefore, have a long-lasting impact on the functionality and quality of future services provided by these networks. These decisions can be supported by different approaches ranging from various inspection techniques, deterioration models to assess the probability of failure or the technical service life, to sophisticated decision support systems crossing boundaries to other urban infrastructure. This paper presents the state of the art in sewer asset management in its manifold facets spanning a wide field of research and highlights existi...
Physically-based overland flow models are computationally demanding, hindering their use for real... more Physically-based overland flow models are computationally demanding, hindering their use for real-time applications. Therefore, the development of fast (and reasonably accurate) overland flow models is needed if they are to be used to support flood mitigation decision making. In this study, we investigate the potential of Self-Organizing Maps to rapidly generate water depth and flood extent results. To conduct the study, we developed a flood-simulation specific SOM, using cellular automata flood model results and a synthetic DEM and inflow hydrograph. The preliminary results showed that water depth and flood extent results produced by the SOM are reasonably accurate and obtained in a very short period of time. Based on this, it seems that SOMs have the potential to provide critical flood information to support real-time flood mitigation decisions. The findings presented would however require further investigations to obtain general conclusions; these further investigations may inclu...
Lead time between rainfall prediction results and flood prediction results obtained by hydraulic ... more Lead time between rainfall prediction results and flood prediction results obtained by hydraulic simulations is one of the crucial factors in the implementation of real-time flood forecasting systems. Therefore, hydraulic simulation times must be as short as possible, with sufficient spatial and temporal flood distribution modelling accuracy. One of the ways to reduce the time required to run hydraulic model simulations is increasing computational speed by simplifying the model networks. This simplification can be conducted by removing and changing some secondary elements using network simplification techniques. The emphasis of this paper is to assess how the level of urban drainage network simplification influences the computational time and overall simulation results' accuracy. The models used in this paper comprise a sewer network and an overland flow drainage system in both 1D/1D and 1D/2D approaches. The 1D/1D model is used as the reference model to generate several models ...
In order to simulate surface runoff and flooding, one-dimensional (1D) overland flow networks can... more In order to simulate surface runoff and flooding, one-dimensional (1D) overland flow networks can be automatically delineated using digital elevation models (DEM). The resulting network comprises flow paths and terrain depressions/ponds and is essential to reliably model pluvial (surface) flooding events in urban areas by so-called 1D/1D models. Conventional automatic DEM-based flow path delineation methods have problems in producing realistic overland flow paths when detailed high-resolution DEMs of urban areas are used. The aim of this paper is to present the results of research and development of three enhanced DEM-based overland flow path delineation methods; these methods are triggered when the conventional flow path delineation process stops due to a flow obstacle. Two of the methods, the ‘bouncing ball and buildings’ and ‘bouncing ball and A*’ methods, are based on the conventional ‘bouncing ball’ concept; the third proposed method, the ‘sliding ball’ method, is based on the ...
Flash flooding is characterised by a rapid flooding phenomenon caused by intense rainfall. Despit... more Flash flooding is characterised by a rapid flooding phenomenon caused by intense rainfall. Despite being an extreme event with high uncertainty, the rainfall-runoff process is often regarded as deterministic (rather than stochastic). In this paper, the Soil Conservation Service (SCS) flood hydrograph uncertainty is quantified based on the Total Error Framework (TEF), and introduced into the model by applying perturbation in the input data and model parameters. The random perturbation component is stochastically modelled. A sensitivity analysis was carried out on the stochastic model parameters, using a real case study in the Azores (Portugal). The results showed that the flood hydrograph uncertainty varies over time, with its largest deviations occurring at the beginning of the flooding due to the uncertainty associated with the SCS method curve number parameter (correlation coefficient R2 of 0.86). Rainfall uncertainty was responsible for the uncertainty in the hydrograph peaks’ magnitude (R2=0.93) while uncertainty in the propagation velocity was responsible for the uncertainty in the peaks’ time (R2=0.97).
iGPI, the National Initiative for Infrastructure Asset Management (April 2012 - October 2013), is... more iGPI, the National Initiative for Infrastructure Asset Management (April 2012 - October 2013), is a Portuguese collaborative project led by LNEC (National Civil Engineering Laboratory, Portugal) through which 19 water utilities develop their own IAM systems and plans through a joint training and capacitation programme. Technical assistance to the participating utilities is ensured by LNEC, by a team from IST (Technical University of Lisbon) and by Addition, a software development company. The water utilities get collective as well as one-on-one support, specific training, and benefit from networking with the other utilities in a common and simultaneous process, with similar difficulties and challenges, leading to an effective sharing of solutions. The developed products, including training materials, templates and guidelines for developing strategic and tactical IAM plans, are available to the general public. This project has greatly contributed to the establishment of reference met...
Page 1. REHABILITATION INTERVENTIONS IN URBAN WATER SUPPLY ASSETS USING THE MULTICRITERIA DECISIO... more Page 1. REHABILITATION INTERVENTIONS IN URBAN WATER SUPPLY ASSETS USING THE MULTICRITERIA DECISION TOOL ELECTRE III Nelson Carriço 1 , Dídia IC Covas 1 , Maria do Céu Almeida 2 , João P. Leitão ...
A more reliable flood forecasting could benefit from higher-resolution rainfall forecasts as inpu... more A more reliable flood forecasting could benefit from higher-resolution rainfall forecasts as inputs. However, the prediction lead time of the operational rainfall forecasting models will substantially diminish while sub-hourly (e.g., 5-min) rainfall forecasting is required. A method that integrates the SVM (Support Vector Machine) and Cascade-based downscaling techniques is therefore developed in this work to carry out high-resolution (5-min) precipitation forecasting with longer lead time (45-60 minutes). The 5-min raingauge observations from Coimbra (Portugal) are employed to assess the proposed methodology. A comparison with the conventional SVM is also conducted to study the possible benefit of using the proposed methodology to carry out short-term rainfall forecasting.
ABSTRACT iGPI, the National Initiative for Infrastructure Asset Management is a Portuguese collab... more ABSTRACT iGPI, the National Initiative for Infrastructure Asset Management is a Portuguese collaborative project led by LNEC (National Civil Engineering Laboratory, Portugal) through which 19 water utilities develop their own infrastructure asset management (IAM) systems and plans in a joint training and capacitation programme. Technical assistance to the participating utilities is ensured by LNEC, IST (Technical University of Lisbon) and Addition, a software development company. The water utilities get collective as well as one-on-one support and specific training. They benefit from networking with the other utilities in a common and simultaneous process, with similar difficulties and challenges, leading to an effective sharing of solutions. The developed products, including training materials, templates and guidelines for developing strategic and tactical IAM plans, are available to the general public. This project has greatly contributed to the establishment of reference methodologies and standards for IAM planning, in a range of utilities of widely diverse size and context, effectively defining an accepted best practice. This paper discusses the project's format and its advantages, and goes on to describe the main outcomes, including selected cases and final products. http://www.tandfonline.com/eprint/TUcpPQeZpNAsbIjCMSYp/full
This paper presents the contributions of Geographic Information Systems (GIS) and location models... more This paper presents the contributions of Geographic Information Systems (GIS) and location models towards planning regional wastewater systems (sewers and wastewater treatment plants) serving small agglomerations, i.e. agglomerations with less than 2,000 inhabitants. The main goal was to develop a decision support tool for tracing and locating regional wastewater systems. The main results of the model are expressed in terms of number, capacity and location of Wastewater Treatment Plants (WWTP) and the length of main sewers. The decision process concerning the location and capacity of wastewater systems has a number of parameters that can be optimized. These parameters include the total sewer length and number, capacity and location of WWTP. The optimization of parameters should lead to the minimization of construction and operation costs of the integrated system. Location models have been considered as tools for decision support, mainly when a geo-referenced database can be used. In these cases, the GIS may represent an important role for the analysis of data and results especially in the preliminary stage of planning and design. After selecting the spatial location model and the heuristics, two greedy algorithms were implemented in Visual Basic for Applications on the ArcGIS software environment. To illustrate the application of these algorithms a case study was developed, in a rural area located in the central part of Portugal.
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Papers by Joao P. Leitao