Urban flood simulation and integrated flood risk management

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. 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 managemen

Development of Intensity Duration Frequency Curve of the Lower Rio Grande Valley

Section 1: This chapter incorporates extensive information about the concept of Intensity-Duration-Frequency (IDF) curves, their historical development and usage, specific focus on the Lower Rio Grande Valley, and the importance of using a comprehensive 32-year data set from 1990-2022 to develop these curves. Section 2: This chapter provides detailed information about the rigorous comparison of the developed IDF curves with previous ones, where past IDF curves were developed using an empirical formula method. The research presented here employs the Gumbel distribution method, providing a fresh perspective and potentially more accurate predictions of future weather extremes. Section 3: This chapter outlines the process of developing hyetographs and the methodologies used to determine the threshold of hurricanes. It offers insights into how these hyetographs can be used for predicting hurricanes, underscoring the critical importance of this research in contributing to our understanding of extreme weather events, and offering potential strategies for future weather predictions and disaster preparedness

Proceedings of the XXVIIIth TELEMAC User Conference 18-19 October 2022

Hydrodynamic

Sustainability of Rural Water Supply in Sub-Saharan Africa: GIT-Based Studies in East-Central Tanzania

The achievement of sustainable and lasting effects from projects is a significant challenge for donors and the agencies implementing and supporting water supply in developing countries. The current estimations for Sub-Saharan Africa (SSA) suggest that only two out of three water points in rural areas on the continent are functioning at any given time. The region of SSA includes many of the world’s poorest countries, and sustainability of water supply services is vital concerning people without access to safe drinking water. Not surprisingly, many policies and planning decisions are taken without access to adequate data, a situation that increases the risk of inappropriate measures being adopted. The objective of the present study is to address the potential of applying geospatial technology to monitor the sustainability of rural water supply services. It focused on the Wami River Basin in Tanzania due to its diversified use, which benefits a multi-diversity of stakeholders and its role as a vital area for providing water, food and other natural resources. It is in the interest of this study to understanding reasons for “success” and “failure” of water points using Geographic Information Technologies (GIT) based approach to analyse factors of biophysical and human domains that respond to both in time and space. The study analyses the trends in annual and seasonal rainfall time series in the Wami River Basin during 1983–2017 for any significant changes in the patterns and how they affect the access to water supply services in rural areas. First, waterpoint mapping datasets were analysed considering seasonal variation. Later, the study focused on changes in land-use/land-cover patterns upstream and downstream and explored the spatial econometric technique by analysing the impact of land-use/land-cover change on water ecosystem services for domestic use in the basin. Lastly, I provide my vision of the water-food-land nexus giving attention to how it relates to agriculture expansion. I identify trade-offs between and assess the synergies associated with the influence of agriculture intensification and anticipation of water services concerning data availability. The results showed that water points were significantly affected by seasonal changes, both in terms of availability and water quality. There also exists a strong relationship between rural water services and seasons. With a time series of maps, change analysis can reveal the overall development of the land distribution, including the detection of sites of different types of changes. In general, net gain and net loss were observed downstream, indicating that this region was more affected than upstream. I found that all measured land-use/land-cover changes and water point characteristic correlations were statistically significant; therefore, I concluded that land-use/land-cover change affects the water ecosystem in the basin. These findings provide baseline information for decision-makers and stakeholders concerning water supply services for better planning and management decisions in the basin. Furthermore, the approach has contributed to the application of geospatial technologies in rural water supply services and might help pursue sustainability strategies in other basins. The approach based on detailed large-area field data to identify variations in the spatial distribution of the water service supply regarding quality and quantity to a reasonable degree of accuracy. Hence, it presents an excellent opportunity to provide relevant information about water supply services performance in response to spatially and temporally critical importance. However, due to the lack of up-to-date information, it does not cover other essential access aspects concerning the vulnerability of the water services like lack of financial and governance components that play a significant role in the sustainability of rural water supply services. Therefore, more studies should be undertaken to explore the use of Remote Sensing (RS) and Geographic Information Systems (GIS) with different temporal and spatial scales in future research, integrating institutional and socio-economic analyses of environmental sustainability.:Note on the Commencement of the Doctoral Procedure ii Declaration of conformity iii AckAcknowledgements v Abstract vi Zusammenfassung viii 1. Introduction 1 1.1 Background 1 1.2 The Motivation for Research Issues 3 1.3 Objectives of the Study 7 1.4 Description of the Study Area 7 1.5 The Organisation of the Chapters 11 1.6 References 12 2. Seasonal and Annual Rainfall Variability and Their Impact on Rural Water Supply Services in the Wami River Basin 22 2.1 Abstract 22 2.2 Introduction 23 2.3 Methods and Data 24 2.3.1 Statistical Test for Trend Analysis 25 2.3.2 Simple Regression Model 26 2.3.3 Water Point Mapping System 2.4 Results 29 2.4.1 Annual and Seasonal Rainfall Trends Analysis 29 2.4.2 Dry and Wet Seasonal Variation and Use of Water Points 34 2.5 Discussion 43 2.6 Conclusions 45 2.7 References 46 3. Land-Use and Land-Cover (LULC) Change Detection in the Wami River Basin, Tanzania 54 3.1 Abstract 54 3.2 Introduction 55 3.3 Materials and Methods 57 3.3.1 Data Acquisitions and Preparation 57 3.3.2 Classification and Change Detection 58 3.4 Results 59 3.4.1 Accuracy Assessment 59 3.4.2 Upstream Sub-Catchment (Kinyasungwe) 60 3.4.3 Downstream Sub-Catchment (Wami) 65 3.5 Discussion 68 3.6 Conclusions 70 3.7 References 70 4. Impact of Land-Use/Land-Cover Change on Drinking Water Ecosystem Services in Wami River Basin, Tanzania 78 4.1 Abstract 78 4.2 Introduction 79 4.3 Material and Methods 81 4.3.1 Spatial Regression Analysis 81 4.4 Results 83 4.4.1 Accuracy Assessment 83 4.4.2 Kinyasungwe Sub-Catchment 83 4.4.3 Wami Sub-Catchment 89 4.5 Discussion 95 4.6 Conclusion 97 4.7 References 98 5. Water-Food-Land Nexus and Agriculture Expansion: Prospects for Enhancing Water Ecosystem Services in Tanzania 106 5.1 Abstract 106 5.2 Introduction 107 5.3 Nexus Concept and Interlinkage 109 5.4 Exploring Agriculture Expansion and Drinking Water Supply Services Challenges. 112 5.4.1 Agriculture Expansion Challenges. 112 5.4.2 Water Supply Services Challenges. 113 5.5 Trade-off between Agriculture Expansion and Water Ecosystem Services 114 5.6 Synergies and Role of Data to Improve Accountability in Governance for Sustainable Water Ecosystem Services 116 5.7 The Nexus Approach and Synergies based on improved Management Information Systems (MIS) 118 5.8 Monitoring Drought Resilience based on typologies and a composite Nexus Index 119 5.9 Conclusions 120 5.10 References 121 6. Conclusion, Recommendations and Outlook 134 6.1 Conclusion and Recommendations 134 6.2 Outlook 13

Urban impact assessment and emergency response to flooding in Buenos Aires, Argentina.

The determination of urban resilience and community response to flooding are significant aspects of hazard management and disaster risk reduction. Anticipating hazard impacts is vital to the development of flood mitigation strategies and emergency response planning. Argentina is an emerging economy with high flood hazard exposure, and its capital, Buenos Aires, is one of the most affected areas. Inappropriate disaster response could therefore affect food supply chains, telecommunications and transport systems nationwide. Flood risk areas in Buenos Aires City have been geographically identified. However, flood impacts have not been well considered, and the emergency response capacity of the city has not been evaluated. This research examined flood impacts in Buenos Aires on infrastructure lifelines and critical facilities, as well as on the wider commercial and residential built environment under current conditions, and accounting for projected impacts of climate change. Evacuation dynamics were explored through characterising spatiotemporal population exposure, modelling evacuation routes, and analysing emergency service response areas. Analyses of different sea-level rise and storm return interval scenarios showed clear trends in increasing impacts under increasing hazard intensities; these impacts were ameliorated when flood warnings were applied. Spatiotemporal population exposures developed for evacuation analyses showed increasing impacts under increasing sea-level rise scenarios. Dynamic evacuation analyses highlighted inadequacies in current welfare facilities to shelter evacuees, however modelling suggests that shelter and emergency response can both be improved by increasing the number of facilities. This research contributes to the quantification of impacts on the built environment and associated economic losses, and helps inform disaster response and management. The methodological approach presented here provides an analytical framework for flood impact analyses and evacuation dynamics that can inform other flood-exposed cities globally

Paddy and banana cultivation in Sri Lanka : a study analysing the farmers’ constraints in agriculture with focus on Sooriyawewa D.S. division

The farmers in Sooriyawewa D.S. division, situated in the Dry Zone in Sri Lanka, are main cultivators of paddy and banana. The agriculture in the Dry Zone is heavily depending on water from the irrigation schemes. The objective of the study is to investigate the methods used in the paddy and banana cultivation in Sri Lanka with focus on Sooriyawewa D.S. division in order to understand the main constraints that the farmers experience in their agricultural practice. Five paddy and banana farmers in the study area were thus interviewed, with help of an interpreter, to gain a comprehensive picture of the farmers’ situation. A literature study was also performed and in addition, relevant statistics describing the rainfall, the banana and paddy crops cultivated in the region were analysed. The farmers all stated that the water situation was their main concern, in particular for the paddy farmers since paddy cultivation requires a lot of water. Secondly pests and diseases were the main concern for the banana farmers. The farmers had also observed that the rainfall seemed to decrease in amount, seasonality and reliability. The literature study confirmed that the water situation is the paddy farmers’ greatest problem and the statistics indicated that the Yala season (dry season) is getting drier while the Maha season (wet season) is getting wetter. However, the paddy yields are increasing despite the decrease in rainfall during the Yala season. The changes seen in the rainfall pattern indicates that the agriculture in the Dry Zone has to prepare for years with droughts that will be more severe than the droughts in the past