Showing papers by "Slobodan Djordjević published in 2018"

An integrated framework for high-resolution urban flood modelling considering multiple information sources and urban features

Abstract: High accuracy models are required for informed decision making in urban flood management. This paper develops a new holistic framework for using information collected from multiple sources for setting parameters of a 2D flood model. This illustrates the importance of identifying key urban features from the terrain data for capturing high resolution flood processes. A Cellular Automata based model CADDIES was used to simulate surface water flood inundation. Existing reports and flood photos obtained via social media were used to set model parameters and investigate different approaches for representing infiltration and drainage system capacity in urban flood modelling. The results of different approaches to processing terrain datasets indicate that the representation of urban micro-features is critical to the accuracy of modelling results. The constant infiltration approach is better than the rainfall reduction approach in representing soil infiltration and drainage capacity, as it describes the flood recession process better. This study provides an in-depth insight into high resolution flood modelling.

Stability criteria for flooded vehicles: a state‐of‐the‐art review

Abstract: Hazard conditions related to vehicular circulation are important in flood risk management. The knowledge of vehicles stability when those are exposed to flooding is crucial for an informed flood risk management in urban areas. After losing stability, the vehicle becomes buoyant and may be washed away with potential injuries and fatalities. Therefore, the analysis of the stability of vehicles exposed to flooding is important in order to make decisions to reduce the damages and hazards. Herein a comprehensive state-of-the-art on stability of vehicles exposed to flooding is presented. The different studies have been gathered in experimental, theoretical and guidelines proposals and all of them focusing on parked vehicles. There is a clear need to conduct more research in this field by testing a greater variety of models in order to offer a more general methodology to define stability threshold for any vehicle exposed to flooding. Nevertheless, in this work, it has been demonstrate that the most safety stability criterion for vehicles exposed to flooding up to now is the proposed in the Guide AR&R.

Influence of sewer network models on urban flood damage assessment based on coupled 1D/2D models

Abstract: One of the main steps in assessing flood risk in urbanised areas is the quantification of damage costs. Damage is often estimated based on depth-damage curves for which depth maps are obtained (ideally) from coupled flood models. While the comparative analysis of flood damage models has been extensively researched in the literature, the influence of the underlying sewer network model has not been investigated. In this study, a 2D locally inertial equations flood risk analysis model (GWM) is coupled with two stormwater models (SWMM, tested with three different configurations, and SIPSON). The assessment of the network performance is made through the total exchanged volume between the surface and stormwater system, the surcharged conduits and manholes, maximum overland inundation and costs using a stepped version of the multi-coloured manual depth-damage curves for continuous urban fabric. The models behave similarly; however, they do show differences in the head pressures, number of surcharged manholes and maximum depth in some locations. The case study results show that despite the good agreement in damage between the four configurations (≈6% maximum disagreement), some localised high differences in maximum depth observed [0.25 (m)] exist. It was also shown that SWMM needs to be calibrated in order to perform similarly to Preissmann slot models.

On the Characteristics of Velocities Fields in the Vicinity of Manhole Inlet Grates During Flood Events

Abstract: The accurate characterisation of flow from urban surfaces to sewer/stormwater systems is important for urban drainage design and flood modelling/risk identification. However, the geometrical complexity and large variety of drainage structures (linking elements) available makes model calibration and verification difficult. In this study an extensive comparison between experimentally measured and numerically modelled flow characteristics in the vicinity of ten different designs of manhole grate was performed under drainage flow in sub‐critical conditions. Using a 2D surface PIV (sPIV) system the work presents the first detailed characterisation of velocity fields around these linking elements. In addition, it provides the first detailed verification of the ability of a 2D numerical model to describe both velocity fields and drainage flows. The overall comparison shows a close relationship between numerical and the experimental results with some higher inflows in the experimental results as a consequence of a localised transition from weir to orifice condition near the void areas of the grates. It was also noted that velocity differences decreased further from the manhole, due mainly to the more directional flow. Overall the work demonstrates the potential for further use of 2D numerical models to describe flow conditions at linking elements, either directly within modelling simulations or indirectly via the characterisation of energy loss coefficients.

Experimental study on scour at a sharp-nose bridge pier with debris blockage

Abstract: Previous experimental research on the effects of debris on pier scour has focused primarily on circular and rectangular piers with debris present just under flow free surface. Debris-induce...

A new flood risk assessment framework for evaluating the effectiveness of policies to improve urban flood resilience

Abstract: To better understand the impacts of flooding such that authorities can plan for adapting measures to cope with future scenarios, we have developed a modified Drivers-Pressures-State-Impact-Response

Resilience to cope with climate change in urban areas - A multisectorial approach focusing on water - The RESCCUE project

Abstract: The RESCCUE Project is an H2020 research project that aims to help cities around the world to become more resilient to physical, social, and economic challenges, using the water sector as the central point of the approach. RESCCUE will generate models and tools to bring this objective to practice, while delivering a framework enabling city resilience assessment, planning and management. This will be achieved by integrating software tools, methods, and new knowledge related to the detailed urban services performance into novel and promising loosely coupled models (integrated models), multi-risk assessment method, and a comprehensive resilience platform. These tools will allow urban resilience assessment from a multisectorial approach, for current and future climate change scenarios, including multiple hazards and cascading effects. The RESCCUE approach will be implemented in three EU cities (Barcelona, Bristol, and Lisbon) and, with the support of UN-Habitat, disseminate their results among other cities belonging to major international networks. The aim of this paper is to present the main goals of this project, as well as the approach followed and the main expected results after the four years of implementation, so other cities around the world can use the RESCCUE approach to increase their resilience.

Methodological Framework for Analysing Cascading Effects from Flood Events: The Case of Sukhumvit Area, Bangkok, Thailand

Abstract: Impacts from floods in urban areas can be diverse and wide ranging These can include the loss of human life, infrastructure and property damages, as well as other kinds of nuisance and inconvenience to urban life Hence, the ability to identify and quantify wider ranging effects from floods is of the utmost importance to urban flood managers and infrastructure operators The present work provides a contribution in this direction and describes a methodological framework for analysing cascading effects from floods that has been applied for the Sukhumvit area in Bangkok (Thailand) It demonstrates that the effects from floods can be much broader in their reach and magnitude than the sole impacts incurred from direct and immediate losses In Sukhumvit, these include loss of critical services, assets and goods, traffic congestion and delays in transportation, loss of business and income, disturbances and discomfort to the residents, and all these can be traced with the careful analysis of cascading effects The present work explored the use of different visualization options to present the findings These include a casual loop diagram, a HAZUR resilience map, a tree diagram and GIS maps

Back to the future: assessing the damage of 2004 Dhaka flood in the 2050 urban environment

Abstract: Planning to make a city flood resilient needs proper assessment of future conditions. Urban growth models are being used as a planning tool for city development. Within the project Collaborative Research in Flood Resilience in Urban Areas (CORFU), flood management strategies suitable for cities with varied geographic and socio-economic conditions have been developed. In the paper, we adopted urban growth model to project the possible future conditions of Dhaka City, the rapidly developing capital of Bangladesh. Bangladesh lies in the delta of the Himalayan Mountain range and experiences frequent flooding. In 2004 an extreme nationwide flood event occurred, which caused major damage to Dhaka City. If the same event were to occur in 2050, it can be expected that the damage would increase significantly. Through the application of the urban growth, hydraulic and damage assessment models, we were able to determine the damage that can be expected to happen in 2050. The paper also describes the key factors that are important to determine this impact and the associated uncertainties.

A real-time pluvial flood forecasting system for Castries, St. Lucia

Abstract: In the last decade, real-time flood forecasting has become a more feasible approach to reducing the impacts of flooding in urban areas. Two key tools in this context are high resolution hydrodynamic modelling in combination with accurate hydrological forcing. In some cases, when it is not possible to produce such accurate flood forecasts based on high resolution models and data, it may nevertheless be possible to use the resources currently available, accepting that there is a greater degree of uncertainty involved. This paper demonstrates the feasibility of a remotely controlled, real-time, pluvial flood forecasting system for Castries, St. Lucia that utilises the limited data available locally. The results from the study suggest that although Global Forecast System (GFS) rainfall data may be considered coarse for urban applications, there is still a significant amount of skill and usability after it is postprocessed and used in combination with observed rainfall data. Evidence from the study also suggests that the use of images from different sources is invaluable for 2D overland model calibration and validation in urban areas. Conclusions from the study are potentially transferable to other sites in similar data-scare and resource-limited locations.

Wetting and drying numerical treatments for the Roe Riemann scheme

Abstract: Accurate characterization of wetting-drying fronts in free surface flows is challenging because it is difficult and computationally demanding to track the exact position of the interface. This work presents a novel numerical treatment of the wetting-drying fronts applied to an approximate Roe Riemann solver and compares it to four other approaches. The numerical treatments were implemented both for the shallow water equations and for the local inertial equations. The results of this comparison overall showed a good agreement. For the tests conducted it was verified that element removal numerical treatments with global distributing of water can introduce errors and degenerate the solution introducing or displacing water upstream. Local correction and flux restricting numerical treatments show the best results. The negative depth numerical treatments provided similar results to the local correction and flux restricting numerical treatment, although with mass conservation errors.

A Serious Game to Explore Different Flooding Scenarios and their Respective Effects on Infrastructures

Abstract: Using the Unity3d game engine, a Serious Game has been developed to explore different flooding scenarios under climate change in the town of Torbay in Devon, United Kingdom, and discover the resulting consequences on different critical infrastructures, aiming at enhancing their resilience. The system also sports a rather unique 3D navigable information board comprised of a virtual table populated with documents and interactive post-it notes introducing a compelling narrative.

The Nile System Dynamics Model for Water-Food-Energy Nexus Assessment

Abstract: The Nile River is considered one of the most complex rivers in the world because of its transboundary nature and its significance for riparian countries. Currently, the basin experiences challenges stemming from a rapid population increase and the prospect of a significant economic growth, which in turn have sparked development plans aimed at meeting the growing demand for water, energy, and food. A System Dynamics approach provides a unique framework to integrate the physical system and the socio-economic drivers with the ability to capture the interaction and feedback processes between different system components. A water resources model for the entire Nile basin using the System Dynamics approach was developed as a first step. The model results for the flows at gauge locations showed a good agreement with the historical flows measurements, which reflects the SDM ability to capture the dynamic behaviour of the river and reproduce the patterns and trends of the historical flows. A description of the model development process is presented along with simulation results at the key hydrological sites in the basin. The potential to integrate the developed model with food, energy and socio-economic drivers in the basin is provided.

Experimental investigation of scour and pressures on a single span arch bridge under inundation

Abstract: This paper presents two experiments, carried out in a 605mm-wide flume, to investigate scour and hydrodynamic pressure on a scaled model of a single span arch bridge. The geometry of the bridge model is scaled down according to a prototype bridge, with hydraulic conditions of the experiments representing a small river. Measurements showed that verticalcontraction scour by the arch bridge is higher than that of flat-deck bridges. Effect of a single cylindrical debris on scour was also evaluated and found to be negligible at the considered flow depth. Temporal variation of hydrodynamic pressure with scour evolution was also measured. It was found that temporal evolution of scour can reduce hydrodynamic pressure significantly at the initial base of the abutment at downstream face of the bridge, which can erode mortar from the masonry composition of an arch bridge.

Modelling Road Transport Congestion Due to Flooding

Abstract: Transportation is essential for the normal flow of the economy because it is responsible for the movement of people and goods to planned locations. Therefore, traffic disruptions can have detrimental effects on multiple services. Road transportation is vulnerable to many threads, but flooding has the potential to lead to significant road network capacity reductions for a prolonged period of time. To assess the potential impacts of flooding on road transport, a detailed microscopic traffic model (SUMO) is integrated with an InfoWorks 1D–2D flood model. The traffic model simulates individually each vehicle in the network and has an adequate description of congestion, which makes it suitable for representing knock-on effects in transport systems. As both flooding and transport systems exhibit dynamic characteristics in space and time, dynamic model integration is carried out. Depending on the flood characteristics, a flooded road can undergo either a speed limit reduction or a complete closure. Once a road has been closed for traffic, vehicles that originally pass through it are forced to choose alternatives route to reach their unique destinations. That reroute will put an additional strain on a system already suffering reduced network capacity. The most congested roads in the network are identified after a comparison of the traffic conditions under normal conditions and flood conditions. The results suggest that the traffic delays in a dysfunctional network are more significant flood impact than the increased travel distance.

Analysing the Cascading Effects on Critical Infrastructure in Torbay Coastal/Pluvial Flooding with Climate Change

Abstract: Critical Infrastructures (CIs) are commonly designed, built and maintained based on rigorous standards in order to withstand the climate and weather-related pressures. However, shifts in climate characteristics may result in increases of the magnitude and frequency of potential risks, or expose specific CI to new or increased risks not previously considered. As vital components of the normal functioning of modern societies, their resilience encompasses the operational elements, their structural integrity and the capacity to maximize business output under climate stressors. In this work, we propose an integrated and participatory methodological approach to assess the risk and enhance the resilience of interconnected CIs to urban flooding under climate change. The proposed methodology has been applied to the Torbay case study in the EU-CIRCLE project that is also presented in the paper.

Wastewater System Ventilation – A Friend or Adversary?

Abstract: Wastewater systems and their designs have been documented for thousands of years. However, little written evidence exists of the potential unpleasant odours that can be associated with drainage systems until the mid-nineteenth century. This paper presents a holistic overview of historic ventilation systems and wastewater network designs. Modelling the ventilation and potential fugitive emissions from urban drainage systems is a significant challenge. Yet using a revised approach, in association with calibrated and verified case study data, reliable holistic modelling may be achieved. Modern fugitive emissions are discussed and opportunities are further examined with the ventilation and gas in headspace model. This key predictive information may potentially extend asset life and therefore enable cost benefit analysis if the correct corrosion abatements solutions are applied.

Using a Particle Based Simulation to Visualize Sub-Catchments Contribution to Localized Flooding

Abstract: Using the Nvidia off-the-shelf particle based “Flex” simulation engine, we visualize the impact of rainfall over different sub-catchments on flooding in the village of Millbrook in the UK. Stakeholders are able to see what part of the catchment contributes most to which flooded area in the village. Hundreds of thousands of colored particles (balls), whose color is based on the quadrant of the catchment area, are dropped above the terrain and left to roll down while interacting with each other. The approach is similar to the ‘rolling ball’ method, which identifies natural flow pathways by rolling a ball down a digital elevation model, but uses multiple balls instead. Although the visualized results of our approach are of limited hydraulic accuracy, this type of visualization explains causality when analyzing the contribution of different portions of the terrain to the flooding from rainfall. This is possible due to colored deposits resembling well the final flood extent. Consequently, it is a useful technique for implementation in Serious Gaming, with flooding related themes, targeting in improving the understanding of stakeholders/players.