Arlex Sanchez

Holistic approach to flood risk assessment in areas with cultural heritage: a practical application in Ayutthaya, Thailand

This research proposes a holistic approach to flood risk assessment that combines quantitative and qualitative aspects. This approach was developed and applied in the Ayutthaya region in Thailand, which is a UNESCO World Heritage Site. First, flood risk was assessed traditionally as a product of hazard and vulnerability. Both qualitative and quantitative data were gathered from publicly available sources and through interviews, questionnaires, and focus group discussions to assess the vulnerability, using various weights for the different vulnerability dimensions. The hazard was assessed using a coupled 1D-2D flood model, and the resulting vulnerability and risk were mapped. Second, an alternative flood risk map was produced based on group mapping exercises with local residents, which captures the level of perceived risk. The traditional flood risk map was adjusted by varying the vulnerability weights to better match the perceived risk map. The analysis of these two maps revealed that two approaches to flood risk assessment can be used effectively in gaining different insights of the phenomena, and as such, they both should be used in flood risk management planning.

Capturing the multifaceted phenomena of socioeconomic vulnerability

Vulnerability and disaster risk assessment has been evaluated from different perspectives with focus on global or national scale. There is a lack of methodologies on city scale, which are able to capture inner-city disparities with regard to socioeconomic aspects. Therefore, the main objective was to develop a transparent and comprehensive indicator-based approach which is flexible in terms of data availability and is not tied to a specific case study side. This research proposes two flexible methodological approaches on how to perform socioeconomic vulnerability assessment. Susceptibility, Coping and Adaptation are the main elements of a modular hierarchical structure to capture the societal sphere of vulnerability. The first method is completely based on official census data at block scale. The second method is an expansion and includes data derived from a field survey to add components of risk perception. The proposed methodologies were developed and applied in the city of Genoa (Italy). The results are displayed spatially explicit on maps. Furthermore statistical analysis, to reveal the driving forces which influence vulnerability, was performed. The census-based approach revealed that vulnerability is forced along the river by the inherent susceptibility, as well as the lack of adaptation. The two approaches can be used effectively in gaining different insights. The flexibility of the framework proved to be suitable to the objective of the research. However, the values computed in this research do not claim completeness, and the aim was to provide useful information for stakeholders in decision making process to reduce vulnerability and risk.

Multi-objective Evaluation of Urban Drainage Networks Using a 1D/2D Flood Inundation Model

The present paper describes a framework for the evaluation of a drainage system’s capacity in order to get a better understanding of the interactions between three rehabilitation measures: the Upgrading of Pipes (UP), Distributed Storage (DS) and the combination of both (UP+DS). It is posed as a multi-objective optimisation problem with the aim of minimising rehabilitation costs and flood damage. The approach of Expected Annual Damage Cost (EADC) was also introduced as the probabilistic cost caused by floods for a number of probable flood events (i.e. the accumulation of damage during a timeframe). The study combines computational tools such as a 1D/2D flood inundation model and an optimisation engine in the loop to compute potential damages for different rainfall events and to optimise combinations of rehabilitation measures. The advantages of this approach are demonstrated on a real-life case study in Dhaka City, Bangladesh. The optimal solutions confirm the usefulness and effectiveness of the proposed approach where both rehabilitation and damage costs are reduced by the optimal implementation of the UP and DS measures. In addition, the results of the proposed EADC approach indicate a damage cost reduction of at least 56% by implementing UP and of 27% by implementing DS, and both measures have lower rehabilitation costs. The proposed approach can be found appealing to water/wastewater utilities who are often challenged to achieve optimal design and rehabilitation of urban drainage systems.

Multi-criteria Approach for Selection of Green and Grey Infrastructure to Reduce Flood Risk and Increase CO-benefits

Continuous changes in climate conditions combined with urban population growth pose cities as one of the most vulnerable areas to increasing flood risk. In such an atmosphere of growing uncertainty, a more effective flood risk management is becoming crucial. Nevertheless, decision-making and selection of adequate systems is a difficult task due to complex interactions between natural, social and built environments. The combination of green (or sustainable) and grey (or traditional) options has been proposed as a way forward to ensure resilience in advance of extreme events, and at the same time to obtain co-benefits for society and the environment. The present paper describes a novel method for selection of urban flood measures, based on a multi-criteria analysis that includes flood risk reduction, cost minimization and enhancement of co-benefits. The aim of this method is to assist decision makers in selecting and planning measures, which afterwards can be part of either high level scoping analysis or more complex studies, such as model based assessment. The proposed method is implemented within a tool which operates as a standalone application. Through this tool, the method has been applied in three study cases. The findings obtained indicate promising potential of the method here introduced.