Study region: The study focuses on Kerala, a state in the southwest of India. Kerala is composed of 14 districts, each characterised by variations in topography, climate, and land use patterns. Study focus: This review critically analyses the literature on flood risk assessment (FRA) in Kerala, particularly after the devastating 2018 floods. Kerala has experienced sporadic floods in the 21st century, caused by localized heavy rainfall, rapid urbanization and improper management of water resources. The 2018 Kerala Floods was one of the most catastrophic recent floods. Nearly all 14 districts were affected, over 480 people lost their lives, and more than a million were displaced. Anthropogenic factors, such as encroachment on wetlands, sand mining in riverbeds, and inadequate drainage systems in urban areas, have worsened the impact of floods. Despite the long history of flooding, flood management in Kerala has struggled to keep pace with the increasing magnitude and frequency of these events. Factors such as outdated infrastructure, uncoordinated dam management, and poor urban planning have exacerbated the impacts of floods. Against this backdrop, this review on flood risk assessment (FRA) in Kerala evaluates and synthesises existing methodologies to improve understanding of current state-of-the-art FRA in Kerala and provide a foundation for more effective flood management strategies. New hydrological insights for the region: The review identifies that research conducted after the 2018 floods can be categorised into three broad methodological themes: Remote Sensing and Geographic Information Systems (GIS), Predictive Modeling (including hydrological and hydraulic simulations), and Analytical Approaches (such as machine learning, statistical methods, and multi-criteria decision-making). The spatial focus of the studies reveals significant disparities, with Allapuzha being the most extensively studied district and Thiruvananthapuram receiving minimal attention. The review identifies critical gaps in the literature, including challenges in translating mitigation strategies, urban flooding stemming from poor land use planning, insufficient integration of various flood sources, and limited research on compound extreme events. Highlighting the urgency of translating the quantification of hazard to mitigation and the integration of climate change projections, the article provides avenues for further research for FRA in Kerala.

Emergency responders in coastal cities are anticipated to provide effective evacuation of at-risk populations during the preparedness and response phases of coastal floods due to land-falling storms or cyclones. However, existing contingency plans primarily focus on the evacuation of the general public rather than special arrangement for elderly populations who constitute a large proportion of flood fatalities. Here we present a system-level methodology to elaborate citywide coastal flood evacuation plans for optimal deployment of shelters and effective transfer of elderly people with special needs. We conduct a comparative analysis between Shanghai and New York City, which are both among the most exposed coastal cities to storm-induced flooding but represent two distinct institutional systems of emergency operation. The results show marked disparities in evacuation patterns for elderly residents in the two cities. Storm flood evacuation is more challenging in Shanghai due to insufficient provision of shelter capacity (~230,000). Implementing risk-informed and strategic planning could not only meet the potentially huge demand of vulnerable elderly (~520,000) but also improve the overall efficiency of evacuee transfer by a factor of 3. Our work provides new insights into operational emergency evacuation decisions and informs flood management policy development for major coastal cities globally.

This study investigates the impact of struts and a central tower on the aerodynamics and aeroacoustics of Darrieus Vertical Axis Wind Turbines (VAWTs) at chord-based Reynolds numbers of 8.12 × 104. A 2-bladed H-Darrieus VAWT is used, featuring a 1.5m diameter, a solidity of 0.1 and a blade cross-section of symmetrical NACA 0021. The turbine design is kept simple and straight-bladed which is essential for isolating and analyzing the specific effects of struts and a tower. The high-fidelity Lattice Boltzmann Method (LBM) in PowerFLOW 6-2020 and the mid-fidelity Lifting Line Free Vortex Wake (LLFVW) method in QBlade 2.0 are employed, with the mid-fidelity method providing a faster analytical tool for insights into the turbine performance. Firstly, both the LLFVW (mid-fidelity) and LBM (high-fidelity) methods effectively capture the general trends observed in VAWT power performance. However, the former predicts mean thrust values that are approximately 10% higher, and mean torque values that are approximately 19% higher, in comparison to the latter. Subsequently, the former predicts lower streamwise wake velocities relative to those predicted by the latter. These differences increase in configurations that include struts and a tower (to 30% - 31%). Secondly, the presence of struts and a tower leads to a reduction in both mean power (by 15% to 55%) and thrust (by 3% to 3.6%), with a further small decrease observed when doubling the tower diameter (power and thrust both by 0.5% to 3%). The struts predominantly affect the spanwise distribution of blade loading, while the tower impacts the azimuthal variation of blade loading. Additionally, the addition of struts and a tower reduces low-frequency noise (50-200 Hz) while increasing high-frequency noise (> 300 Hz). The observed decrease in mean blade loading results in reduced low-frequency noise, while the increase in high-frequency noise is ascribed to the increased intensity of BWI/BVI leading to higher unsteady loading fluctuations on blades.

Hydrological hazards (“hydro-hazards”) are defined as extreme events associated with the occurrence, movement and distribution of water, specifically resulting in floods and droughts. As a result of global climate change these hazards are expected to change in the future, with areas of the globe becoming “hotspots” for the intensification of these extremes. This paper is the first global review of the state- of-the-art research on hotspots for floods and drought. The work follows a systematic literature review of published research, and analyses and categorizes the results of 122 published papers after a methodical screening process. The analysis highlighted the geographical areas where increasing hazards are anticipated (e.g., Europe for both floods and droughts), and those areas of the globe where no significant research has been published (e.g., Russia). The methods used to undertake the research are analyzed and new trends identified. Potential avenues for future research are highlighted, including the incorporation of uncertainty analyses into hydro-hazard assessments, the consideration of multi-hazards and their interconnections, and finally the consideration of dynamic vulnerability and exposure in conjunction with changing hydro-hazards to understanding future risk.