Basic Study on Flood Management Assessment in Metro Manila, Philippines

Flooding is the most frequent and damaging natural hazard worldwide. The resulting impact of flood disasters on society depends on the economic strength of the affected country prior to the disaster. The larger the disaster and the smaller the economy, the more significant is the impact. This is very clearly seen in developing countries, like the Philippines, where weak economies become much weaker after a devastating flood event. In 2009, tropical storm Ondoy, brought heavy rainfalls that produced destructive floods in the northern islands of the Philippines, leaving inconceivable damages, especially in Metro Manila, which caused the Philippine government to re-evaluate its decades\u27 worth of flood management strategies. Deliberate strategies for flood damage reduction, as well as environmental protection, may aid a country (or a community) to efficiently manage scarce resources for flood mitigation. Nevertheless, many governments lack an adequate institutionalized system for applying cost effective and reliable technologies for disaster prevention, early warnings, and mitigation, mainly due to lack of systematic and reliable flood management assessment strategies. In Metro Manila, important decision elements, such as stakeholders\u27 perception and environmental protection are often overlooked in the development of sustainable flood mitigation plans. Stakeholders can significantly contribute in achieving the desired level of prevention and protection in flood disaster-prone regions. Knowledge of the local conditions and understanding of the public\u27s perception can significantly help address the prioritization issues involved in flood management planning. However, the integration of the stakeholders\u27 perception in the appraisal of flood management systems has not yet been clearly established. In the case of environmental protection, environmental impact assessment (EIA) can provide a certain level of awareness on the benefits of environmentally sound and sustainable urban development. However, the common practice of EIA in the Philippines is generally qualitative and lacks clear methodology in evaluating multi-criteria systems. A study that deals with flood management assessment in Metro Manila is thus necessary to find solutions that may help cope with these inadequacies. This study focuses on the following main objectives: 1) to develop a heuristic analytical strategy that helps identify priority concerns in the flood management systems of Metro Manila using a perception-based appraisal, and 2) to develop a systematic and rational evaluation scheme that would help incorporate environmental assessment in the appraisal of flood mitigation measures. To achieve the first objective, an analytical assessment approach was developed to identify and analyze the flood management gaps using the questionnaire-based stakeholders\u27 perception obtained during the aftermath of the tropical storm Ondoy. For the second objective, a quantitative analytical approach was developed for EIA to further enhance the evaluation process in the planning of flood mitigation projects. This dissertation is composed of six chapters: Chapter 1 is the introduction, which contains the background, motivation, and objectives of this study. A comprehensive review of literature and a description of the scopes and methods were presented in this chapter. Chapter 2 focuses on the performance of the flood management systems in Metro Manila. A brief description of the flood management systems used in Metro Manila, before and during the aftermath of tropical storm Ondoy, was provided. The nature and characteristics of the tropical storm, as well as its effects on the flood management systems, were presented in this chapter. A multi-criteria gap analysis technique was developed to examine the flood disaster risk reduction (FDRR) management systems, which is demonstrated using a questionnaire-based database to obtain an explicit representation of the systems\u27 strengths and weaknesses. In this study, 14 out of 17 municipalities in Metro Manila were investigated. Results revealed that small to medium scale flood management gaps exist within the 14 assessed municipalities. Chapter 3 further explores the potential of a multi-criteria gaps assessment technique in the evaluation of FDRR management systems in Metro Manila. Perception-based assessment is inherently vague and imprecise, which often operates in a fuzzy environment. To cope with this, a fuzzy-based analytical approach was proposed to handle the uncertainties in the evaluation process of flood management gaps. The new approach is demonstrated using the same database in Chapter 2. The results reveal that the municipal-based FDRR management systems in Metro Manila are insufficient in terms of flood disaster prevention, preparedness, response and recovery. Larger gaps were found in the emergency response mechanism of the disaster preparedness management system. Chapter 4 deals with the EIA of nine planned structural flood mitigation measures (SFMMs) in Metro Manila. A modified rapid impact assessment matrix (RIAM) technique was proposed to systematically and quantitatively evaluate the socioeconomic and environmental impacts of the planned SFMMs. The distribution of impacts of each SFMM was estimated for each environmental component of the 4 environmental categories. Based on the results, most of the negative and positive impacts of SFMMs occur during their construction and operation phases, respectively. The modified RIAM approach provided a clear panoramic view of the environmental impacts of each assessed SFMM. Chapter 5 presents a new EIA approach that provides enhancement to the modified RIAM technique in Chapter 4. A utility-based assessment approach using the RIAM technique, coupled with a recursive evidential reasoning approach, was proposed to rationally and systematically evaluate the ecological and socio-economic impacts of 4 planned SFMMs in Metro Manila. This new approach quantitatively characterized the overall impact of each of the planned SFMMs which can provide the means for benefit maximization and optimization. Results show that the overall environmental contributions of each of the planned SFMMs is generally positive, which indicate that the utility of their positive impacts would generally outweigh their negative ones. The results also indicated that the planned river channel improvements have higher environmental benefits than the planned open channels. Chapter 6 presents the overall conclusions and recommendations for the assessment of flood management systems in Metro Manila, including the future research works.首都大学東京, 2014-09-30, 博士(工学), 甲第421号首都大学東