Urban Flood Simulation and Integrated Flood Risk Management
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Urban Flood Simulation and Integrated Flood Risk Management – Case Study in Changsha Central City, China Dissertation submitted in partial fulfillment of the requirements of the degree “Doctor of Engineering (Dr.-Ing.)” of the Faculty of Spatial Planning at the Technical University of Dortmund, Germany By: Mu Yang Doctoral Committee: Supervisor: Prof. Dr. rer. nat. habil. Nguyen Xuan Thinh Supervisor: Prof. Dr. rer. nat. Jochen Schanze Chairman of Committee: Prof. Dr.-Ing. Stefan Greiving Date of Disputation: July 27, 2017 I ACKNOWLEDGMENT I would like to express my special appreciation and thanks to my supervisor Professor Dr. Nguyen Xuan Thinh, you have been a tremendous mentor to me. I would like to thank you for encouraging my research and for allowing me to grow as a research scientist. Your advice on both research as well as on my career have been priceless. I would also like to appreciate my second supervisor Professor Dr. Jochen Schanze, your guidance and advice on my work benefit me a lot. I still remember the day when we discussed my dissertation in Berlin. I would also like to thank my colleagues, Cheng Li, Yan Chen, Yong Xu, Jie Zhao, Kiet, Tran, Jacob Kopec and Florian Spieß, for serving even in hardship. All of you have been there to support me when I recruited patients and collected data for my Ph.D. thesis. I also want to thank you for letting my defense be an enjoyable moment, and for your brilliant comments and suggestions, thanks to you. I would especially like to thank Mustafa, Haniyeh and Dr. Yantao Xi. Your comfort and encouragement helped me go through a tough time. A special thanks to my family. Words cannot express how grateful I am to my mother, and father and my sisters for all the sacrifices that you have made on my behalf. Your encouragement to me was what sustained me thus far. I would also like to thank all my friends who supported me in writing and incented me to strive towards my goal. At the end, I would like express appreciation to my beloved wife Qianwen Wang who spent sleepless nights with and was always my support in the moments when there was no one to answer my queries. Finally, I appreciate the financial support from the China Scholarship Council (Grant No.: 20120642007) that funded the research. III ABSTRACT Climate change induces the probability of occurring natural disasters; e.g. floods, Sea Level Rise, Green House Gases. Flood is considered one of the most dangerous phenomena that tremendously and dramatically threatening the human being and environment worldwide. Rapid urban growth, demographic explosion, and unplanned land uses have exacerbated the problem of urban flooding, particularly in the cities of China. In addition to that, the concept of flood risk management and adaptation measures and strategies are still missed in the cities’ development future plans. The main objective of this Ph.D. dissertation is to investigate the flood risk analysis and assessment based on flood simulation and adaptive strategies for flood event through two case studies of Changsha city in south-central China. In case study I, fluvial flooding was considered on mesoscale and an MCA- based approach was proposed to assess the integrated flood risk of Changsha central city. HEC-RAS 1-D model was used to simulation the inundation characteristics for hazard analysis based on four risk dimensions: economic, social, environmental, and infrastructural risk. For infrastructural dimension, apart for direct damage on road segments, network analysis method was combined with inundation information and macroscopic traffic simulation to evaluate the impact on traffic volume as well as a decrease of road service level. Closeness centrality weighted with a travel time of pre- and after- flood was compared in order to measure the impact on urban accessibility. Integrated risk values were calculated using various weighting criteria sets. Sobol' indices were used as a tool of spatially-explicit global Uncertainty Analysis and Sensitivity Analysis (UA/SA) for damage models. In case study II, an agent-based modeling approach was proposed to simulate the emergency pluvial flood event caused by a short-time rainstorm in local areas of cities aiming at developing an interactive flood emergency management system capable of interpreting the risk and reduction strategy of the pluvial flood. The simulation integrated an inundation model with microscopic traffic simulation. It also reveals that all agents can benefit significantly from both engineering measures and the only pedestrian obtain relatively more benefits from risk warning with high awareness. The method provided potentials in studies on the adaptive emergency management and risk reduction, help both decision-makers and stakeholders to acquire deeper and comprehensive understanding of the flood risk. IV This Ph.D. study has investigated holistic methods and models’ selection in flood risk assessment and management to overcome data deficiency and to achieve the integration of different data. The results of the first case study reveal that the integrated methods have proved to be able to improved flood risk analysis and assessment especially for indirect damage of infrastructural system with network features. The global UA/SA based on Sobol' method and visualization with maps enable to gain the spatial distribution of uncertainty for various factors, the validation of damage models, and deeper and more comprehensive understanding of flood risk. Then based on the integrated risk assessment, functions of spatial planning in flood risk management were discussed, potentially providing guidance and support for decision-making. The results of the second case study denote that agent-based modeling and simulation can be effectively utilized for flood emergency management. Two scenarios focusing on specific risk reduction interventions were designed and compared. Engineering measures by improving capability of the drainage system and the surface permeability of waterlogging areas are the most effective means for damage mitigation. High public risk awareness still has great potential benefits of the in the event of emergencies, which can greatly enhance the effectiveness of the official warning. The agent-based modeling and simulation provided an effective method for analyzing the effectiveness of different strategies for reducing flood risk at the local scale and for supporting urban flood emergency management. The case studies also indicate the significance and necessity of establishing a platform and database to realize full sharing and synergies of spatial information resources for flood risk management, which is a vital issue to manage the urban flood risk and take effective measures correspondingly with responding to emergency extreme flood event. Keywords: urban flood; flood risk assessment; network analysis; flood simulation; flood risk management CONTENTS V CONTENTS ACKNOWLEDGMENT ............................................................................................... I ABSTRACT ............................................................................................................. III CONTENTS .............................................................................................................. V LIST OF FIGURES ................................................................................................... VII LIST OF TABLES ...................................................................................................... IX ABBREVIATIONS ....................................................................................................11 CHAPTER 1: INTRODUCTION ................................................................................... 1 1.1 Background ......................................................................................................................................... 1 1.1.1 Increasing urban flood ...............................................................................................................1 1.1.2 Urban flood in South China ........................................................................................................2 1.1.3 Challenges of Flood Risk Management in China .......................................................................4 1.2 Research objectives, questions and scope ............................................................................... 7 1.2.1 Research objectives ...................................................................................................................7 1.2.2 Research questions ....................................................................................................................8 1.2.3 Research scope ..........................................................................................................................8 1.3 Study area ........................................................................................................................................... 10 1.3.1 Overview of study area ............................................................................................................10 1.3.2 Spatial scales of case studies ...................................................................................................13 1.4 Structure of the dissertation ....................................................................................................... 15 CHAPTER 2: LITERATURE REVIEW ..........................................................................17 2.1 The components