Assessing Rehabilitation Strategies Of Urban Drainage Systems Based On Future Scenarios Of Urbanization

Population growth and urbanisation are creating a big need to improve the planning processes and management of urban infrastructures. Urban drainage networks are one of the vital services needed for any urban area, modelling its growth and expansion is a challenge because of the dynamics of the system. This work describes the integration of a cellular automata model, to simulate urban land use changes, with algorithms to deduct the future layout of the drainage network and with SWMM 5.0 as the hydraulic engine to assess the performance of the drainage systems in the current condition and in the future. The model was built using Dinamica EGO to simulate the land use changes in the future. The model was setup using a set of two land use maps for the municipality of Birmingham in the UK, for the year 2000 and 2006. The model was connected with the NSGAII algorithm to handle the calibration process. Once the model is calibrated three scenarios of future population growth and urbanization are run for the year 2040. The future generated map is then used to classified and cluster the areas of new developments that are suitable to expand the drainage network. Two algorithms are used to predict the future layout of the network. Once the new layout of the network is defined, the system can be connected to the existing urban drainage network and the performance of the expanded network can be assessed. To upgrade the system several rehabilitation strategies are tested to improve the capacity of the system. The integration of these models allows the exploration of several planning scenarios, in this way is possible to help the decision makers with tools and methods to anticipate bottlenecks and solutions in the urban drainage system

Merging Quantitative And Qualitative Analyses For Flood Risk Assessment At Heritage Sites, The Case Of Ayutthaya, Thailand

The present paper presents a flood risk assessment approach for urban areas with mixed land-use including cultural sites. Destruction of heritage properties through disasters creates a serious loss for the national and local communities, not only because of the cultural importance of heritage assets but also for their socio-economic value. At the same time, studies have shown that protecting heritage promotes resilience since heritage contributes to social cohesion, sustainable development and psychological well-being (Jigyasu et. al [3]). Although disaster risk management activities have been developed intensively, a very few methodologies are developed specifically for preservation of heritage sites. Economic as well as intrinsic values embodied within cultural assets require combination of both quantitative and qualitative analyses (i.e., holistic analysis) for flood risk assessment. Moreover, it has been acknowledged that community-based and active stakeholder participation approaches are needed to facilitate comprehensive flood risk assessment. The work presented in this paper aims to develop a framework for active stakeholder participation which combines qualitative and quantitative methods for flood risk assessment at heritage sites. It also seeks to provide a base overview of potential benefits from participatory planning process for both stakeholders and flood risk experts

Flood Resilience Assessment In Urban Drainage Systems Through Multi-Objective Optimisation

In future years, economic development, urbanisation and heavy rainfall events are expected to increase in urban areas, in particular in developing countries. It is well known that urban development has a strong impact on the water cycle such as increase of flood peaks and volume, decrease of base flow, hydraulic stress and water pollution. Resilience measures are still needed to improve urban flood risk, the possibilities to provide indicators that could be used to characterize urban resilience related to flooding is outmost importance. The work described here presents an optimisation framework for urban drainage rehabilitation that incorporates in the decision space the concept of resilience in order to find an optimal rehabilitation strategy. The approach has been tested in the City of Dhaka, Bangladesh by coupling 1D/2D model of the drainage system and linked within the optimisation algorithm. The preliminary results obtained suggest that the proposed approach could be effective in order to reach acceptable level of flood resilience of urban drainage systems, balancing investment and risk within the systems. Further work is recommended to expand and generalize the methodology

Multi-Objective-Rehabilitation Of Urban Drainage Systems Within The Flood Risk Framework

Urban drainage systems are one of the most valuable public utilities in any community, which protects public health and the environment, nevertheless is one of the most overlooked infrastructures until considerable failures occurred. If there are not recurrent rehabilitation programs in place this vital infrastructure will decrease the level of service. This work presents an approach to find optimal rehabilitation measures based on the hydraulic performance of the system. To assess the performance of the urban drainage system a coupled 1D-2D model was developed. The model uses SWMM 5.0 for the 1D transport; to simulate the overland flow from the manholes when the capacity of the sewer pipes is exceeded a coupled 1D-2D non inertia model was used. The results are matrices composed of flood water depths and velocities values per each scenario of the flood event. These outputs are the main parameters to assess flood hazard. Furthermore, the vulnerability was assessed based on the socio-economic condition of the residents in the study area, located in a catchment area in Quito, Ecuador. The assessment of hazard and vulnerability were combined to estimate the flood risk damage. Several simulations were made for different flood events (10, 20, 50 and 100 year return period), obtaining Pareto sets per each event. However in order to have more realistic solutions the approach of expected annual flood risk cost were implemented to obtain integrated solutions for a number of flood events. Besides of these new solutions generated, the concept of cost-benefit analysis was applied to help in the identification of the most cost-effective solution. Keywords: Urban drainage systems, flood hazard, vulnerability, flood risk assessment, SWMM5, NSGAII, multi-objective-rehabilitation, genetic algorithms

Holistic Flood Risk Assessment In Coastal Areas - The PEARL Approach

Coastal floods are one of the most dangerous and harmful natural hazards affecting urban areas adjacent to shorelines. The present paper discusses the FP7-ENV-2013 EU funded PEARL (Preparing for Extreme And Rare events in coastaL regions) project which brings together world leading expertise in both the domain of hydro-engineering and risk reduction and management services to pool knowledge and practical experience in order to develop more sustainable risk management solutions for coastal communities focusing on present and projected extreme hydro-meteorological events. The PEARL approach draws upon the complexity theory and the use of complex adaptive system (CAS) models as tools to identify root causes of vulnerabilities and their multi-stressors and to analyze risk and the behavior of key actors

Evaluation of Pollutant Removal Efficiency by Small-Scale Nature-Based Solutions Focusing on Bio-Retention Cells, Vegetative Swale and Porous Pavement

Rapid urbanization, aging infrastructure, and changes in rainfall patterns linked to climate change have brought considerable challenges to water managers around the world. Impacts from such drivers are likely to increase even further unless the appropriate actions are put in place. Floods, landslides, droughts and water pollution are just a few examples of such impacts and their corresponding consequences are in many cases devastating. At the same time, it has become a well-accepted fact that traditional (i.e., grey infrastructure) measures are no longer effective in responding to such challenges. Nature-based solutions (NBS) have emerged as a new response towards hydro-meteorological risk reduction and the results obtained to date are encouraging. However, their application has been mainly in the area of water quantity management with few studies that report on their efficiency to deal with water quality aspects. These solutions are based on replicating natural phenomena and processes to solve such problems. The present paper addresses the question of three NBS systems, namely, bio-retention cells, vegetative swales and porous pavements, for the removal of total suspended solids (TSS), total nitrogen (TN) and total phosphorus (TP) when applied in different configurations (single or networked). The results presented in this paper aim to advance the understanding of their performances during varying rainfall patterns and configurations and their potential application conditions

Multi-objective Optimisation Framework for Assessment of Trade-Offs between Benefits and Co-benefits of Nature-based Solutions

Urbanization and climate change are producing an escalation in the prevalence of urban problems, particularly those connected to flooding, prompting authorities and stakeholders to recognize the need for sustainable solutions. Nature-Based Solutions are progressively replacing traditional engineering solutions as an alternative since they are more eco-friendly. By re-activating the urban hydrological cycle processes, NBS intends to increase the natural water storage capacity to help decrease urban flooding. The work described here outlines a framework for optimising the efficacy of NBS for flood risk reduction and its co-benefits, as well as defining the trade-offs among these co-benefits. The framework integrates 1D hydrodynamic models with multi-objective optimisation techniques. To demonstrate the applicability of the framework and its methods it has been used in Sint Maarten, which is an island located in the Caribbean Sea. Four NBS measure were identified as having good potential to be applied in the case study, namely: green roof, permeable pavement, bio-retention pond, and open detention basin. The results showed that the developed framework has the ability to represent the link between benefits and costs when evaluating various NBS, hence aiding the decision-making process to select and implement NBS.</p

Planning and Suitability Assessment of Large-scale Nature-based Solutions for Flood-risk Reduction

Adverse effects of climate change are increasing around the world and the floods are posing significant challenges for water managers. With climate projections showing increased risks of storms and extreme precipitation, the use of traditional measures alone is no longer an option. Nature-Based Solutions (NBS) offer a suitable alternative to reduce the risk of flooding and provide multiple benefits. However, planning such interventions requires careful consideration of various factors and local contexts. The present paper provides contribution in this direction and it proposes a methodology for allocation of large-scale NBS using suitability mapping. The methodology was implemented within the toolboxes of ESRI ArcMap software in order to map suitability for four types of NBS interventions: floodplain restoration, detention basins, retention ponds, and river widening. The toolboxes developed were applied to the case study area in Serbia, i.e., the Tamnava River basin. Flood maps were used to determine the volume of floodwater that needs to be stored for reducing flood risk in the basin and subsequent downstream areas. The suitability maps produced indicate the potential of the new methodology and its application as a decision-support tool for selection and allocation of large-scale NBS

A Framework for Assessing Benefits of Implemented Nature-Based Solutions

Nature-based solutions (NBS) are solutions that can protect, sustainably manage, and restore natural or modified ecosystems in urban and rural areas, while providing many benefits and co-benefits including stormwater mitigation, biodiversity enhancement, and human well-being. As such, NBS have the potential to alleviate many of the environmental, social, and economic issues that we face today. Grey infrastructure, such as lined trenches and catch basins, pipes, and concrete dikes are frequently used for stormwater management and flood protection, but they do not provide many of the co-benefits that are common with NBS. Grey infrastructure is designed to quickly collect and remove rainwater, whereas NBS keep rainwater where it falls, and where it can be used by the environment. Many stakeholders lack knowledge of the capabilities and benefits of NBS, and as a result, they continue to rely on grey infrastructure in their projects. When information is made available on the benefits and how they can be quantitatively measured, it is hoped that NBS will be promoted to a mainstream infrastructure choice. A valuable way to quantify and highlight the benefits of NBS is by using an evaluation framework. There are several evaluation frameworks that qualitatively assess the potential benefits of possible NBS, however there is a need for quantitative frameworks that can assess the actual benefits (or performance) of implemented (or existing) NBS. This article presents an evaluation framework that aims to quantify the benefits and co-benefits of implemented NBS. The framework involves five main steps: (1) selection of NBS benefit categories, (2) selection of NBS indicators, (3) calculation of indicator values, (4) calculation of NBS grade, and (5) recommendations. The outcome of the framework is a single numerical grade that reflects the benefit functioning for an NBS site and values for each performance indicator. This information may be used by decision makers to determine their budget allocations to expand or construct a new NBS site, to update maintenance plans that will improve the benefits of that site, to set up programs to monitor the NBS benefits and co-benefits over time, and to schedule labour and resources for other NBS projects. The framework was tested and validated on a case study of NBS in Thailand. Through conversations with stakeholders and knowledge of the case study area, relevant categories and indicators were chosen. Using data and information obtained through various means, values for each indicator and the overall NBS grade were calculated. The values revealed which benefits were pronounced, those that were weak, and where improvements were required

Review of environmental benefits and development of methodology for EUNIS habitat changes from nature-based solutions: Application to Denmark and the Netherlands

Nature-Based solutions (NBS) are the measures supported by natural processes that can adapt to changing climates and generate diverse social, economic, and environmental benefits. Recognising the potential for additional NBS benefits, and quantifying these benefits is essential as it encourages decision-makers to implement and scale-up NBS initiatives. This paper presents findings from a systematic literature review. The review focused on tools and methodologies used for assessing the environmental benefits of implementing NBS. This review provides a detailed compilation of environmental indicators supported by assessment tools. It also includes a catalogue of tools for evaluating environmental benefits, thereby identifying research gaps. Moreover, this research proposes a methodology that uses an ArcGIS (Architecture of Geographic Information Systems) toolbox to identify habitat changes resulting from the implementation of NBS. The methodology translates CORINE (Coordination of Information on the Environment) land cover classes to EUNIS (European Nature Information System) habitat classes. The developed toolbox was applied to two case studies: Denmark (12 NBS) and the Netherlands (3 NBS). The assessment aimed to compare the habitat changes between 2000 and 2018 as two extreme time points for NBS implementation for both case studies. Results indicate that NBS implementation can change habitats leading to an increase in the Red-necked Grebe population in Denmark and a decline in the Black-tailed Godwit population in the Netherlands (two threatened species). The population change highlights the potential positive and potential negative impacts of NBS in their respective cases. These findings suggest Denmark could benefit from lake construction and restoration projects. At the same time, the Netherlands could invest in wetlands and meadows construction and restoration projects to protect the respective species. They could establish designated breeding zones to ensure their population does not decline rapidly.BT/Environmental BiotechnologyHydraulic Structures and Flood Ris