International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 09 Issue: 03 | Mar 2022 www.irjet.net p-ISSN: 2395-0072 © 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 1859 Challenges in global flood hazard mapping Hayder Al Hudaib 1, Richard P. Ray2 1 Ph.D. Student, Széchenyi István University, Department of Transportation Infrastructure, and Water Resources Engineering Egyetem tér 1, 9026 Győr, Hungary 2 Professor, Széchenyi István University, Department of Structural and Geotechnical Engineering Egyetem tér 1, 9026 Győr, Hungary ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - Global flood hazard assessment and resilience implementation have become increasingly important in the last decade. The heightened impact has been due to anthropogenic developments changing the natural flow regime of rivers through dam construction or the increasing risk of flooding on a global and national scale due to climate change and land use/cover changes. Such a global impact requires a global response and those efforts have produced methods to assess global flood hazards through simulation of natural and human activities. Implementation of this scale of assessment however is quite challenging on both the analysis and the implementation side. Analysis requires global hydro- meteorological datasets that are applied to regional watershed models. Additional information on hydraulic behavior, control structures, flood defense, and risk exposure are also required. The most recent effort to model at this scale is the global flood awareness system (GloFAS) combined with re-analysis of global data sources such as ERA5 river discharge datasets (1979-2020). While there are many apparent limitations, the future looks promising for the development of large regional hydrological models and the development of global data sources focused on global flood simulation. Getting beyond the limitations in the availability of real-time observed datasets will require international initiatives through collecting and improving the temporal and spatial resolution of hydro-meteorological datasets, and other challenges that affect the efficiency in simulating and forecasting flood events. Finally, we highlight limitations, opportunities, and suggestions in the short and long term for future developments. Key Words: Global flood awareness system (GloFAS), satellite images, flood mapping, reanalysis dataset, flood risk. 1. INTRODUCTION Water is vital to life. Increasing or decreasing water resources represents the main challenge for life and human security. A major threat to water resources comes from extreme climate events such as floods, drought, hurricanes, etc., from natural or human activities. These threats are further amplified by global climate change due to greenhouse gases and carbon cycle emissions from fossil fuel combustion, land use cover changes, and other activities [1]. Floods may be classified as urban flash floods, coastal, riverine, fluvial, pluvial, dam failure, and storm surges. Of course, extreme flood events are becoming more frequent and challenging due to climate change [2]. In summary, weather and extreme climate have had significant impacts on social, ecological, and economic networks across most regions of the world [3]. Flood events in Europe, such as the 2002 Elbe floods, and the 2007 UK floods, are considered national crises and are estimated to have caused around 15 and 6.5 billion euros of damage, respectively [3]. Early Warning Systems (EWS) has developed and widely adopted in recent years to predict the probability of floods and reduce their hazard impact. Cooperation between authorities and countries through early warning, information, and data sharing is particularly important for transboundary river basins to facilitate water resources management, especially in flood season, and coordinate actions [4]. The main challenge in hydrological studies is to estimate past, present, and future hydrological conditions in rivers around the world [5]. The limitation of hydro-meteorological observations represents a major barrier to our ability to provide monitoring and early warnings of hydrological extreme hazards, such as floods and droughts. Global flood modeling for large-scale catchment river basins requires unique models and assistance tools such as Geographic Information System (GIS) and Remote Sensing (RS) techniques. The European Flood Awareness System (EFAS) provides operational flood prediction data sets for major European rivers as a part of the Copernicus Emergency Management Services. Flood hazard maps are produced by using mathematical models to simulate the physical state of river basins and predict flood levels. These are very useful tools to show the probability of occurrence, magnitude, and flood footprint extent as well as potential consequences over a certain area. Results can provide a supporting tool for decision-makers to enhance land use planning and disaster risk management. Long-term global river discharge re-analysis datasets were produced as part of the Global Flood Awareness System (GloFAS) jointly developed by the European Commission and the European Centre for Medium-Range Weather Forecasts (ECMWF). Numerous international agencies are gathering and refining the spatial and temporal resolution of satellite data to produce better flood maps. With the aid of advanced numerical weather prediction (NWP) models, they generate re-analysis datasets for the land, ocean, and atmospheric variables that serve as a key starting point.