Journal of Flood Risk Management最新文献

Groundwater flooding might be triggered by disregarding hydrogeological processes during urban area development. Such flooding might result in public disruption, engineering infrastructure destruction, and general damage to natural and human environments, as in the northern part of Almaty city. A MODFLOW groundwater flow model was used to simulate and quantitatively assess the changes in hydrogeological conditions affecting the groundwater flooding process. A field study of the Akbulak micro-district research site showed that groundwater flooding occurred in its center owing to a water table hillock with a total area of 0.07 km² and groundwater levels ranging from 1.2 to 0.25 m below the ground surface. The MODFLOW simulation suggested that this water table hillock developed from runoff, which, owing to a decrease in natural infiltration across an urbanized area, accumulated in low-elevation areas and infiltrated. This runoff accumulation effect may be up to eight times the annual average precipitation amount. Once in local sub-basins, larger runoff volume infiltrates into an underlying aquifer water table that is already high, might cause groundwater flooding in populated areas. The Almaty scenario simulation confirmed the field observations, suggesting that the clogging of the Karasu-type stream has concentrated runoff to low-elevation areas and is the leading cause of flooding.

Torrent control structures are essential countermeasures against potential losses from flood to debris flow events. The durability of these structures hinges upon several factors, including the structure's design, construction materials and ongoing maintenance as well as the physical pressures they are under. Over the past half-century, a decline in investments allocated to routine maintenance activities, coupled with the natural degradation of these structures, has contributed to a reduction in their protective capacity. In this context, monitoring and maintaining existing structures are essential actions. This study presents a comprehensive proposal for a routine inspection process adopted for torrent control structures along four rivers in North Italy. The results of the first-level inspections consist of a dataset encompassing missing details (e.g., width, length, height, construction age, materials used), present condition of structures and functionality. The further step is to predict the vulnerability of the inspected torrent control structures; so, the Markov chain model is implemented for forecasting their service life, also in function of different maintenance strategies. Furthermore, this study serves as a valuable resource for reinforcing the role of the first-level inspections and ongoing monitoring, which is essential for planning future investments in watershed management, especially in the routine maintenance of torrent control structures.

Regional flood mapping poses computational and spatial heterogeneity challenges, exacerbated by climate change-induced uncertainties. This study focuses on creating a state-wide flood mapping solution with enhanced accuracy and computational speed to support regional flooding hazard analysis and the assessment of climate change, using New Jersey as a case study. The Height Above Nearest Drainage (HAND) framework was employed for large-scale flood mapping. The model was validated against high water marks (HWMs) collected after Hurricane Irene. Based on the National Water Model (NWM), synthetic rating curves in HAND were calibrated by tuning Manning's roughness, aligning the predicted and observed flood depths. The roughness values were generalized across the state from the validated water basins to the ungauged ones, using a multivariate regression with the hydrologic and geographic information. To map the future climate-change-induced flooding, a correlation between NOAA historical precipitation totals and NWM flow data from 2010 to 2020 was established to link precipitation and runoff. This study also invented a novel method for correcting catchment discontinuities, inherent in the HAND model, based on a computer vision scheme, the Sobel filter. The modeling results show that average and worst-case storm events have the potential to increase 10%–50% in the state, where mountain areas and major river banks would be exposed to this impact more significantly.

Climate change urges water managers in low-lying deltas to diversify their flood risk management (FRM) strategies. To reduce residual risks, they increasingly need to incorporate spatial and other measures. This has implications for the boundary judgements made by water authorities, that is, the implicit and explicit decisions about who and what is relevant to include and consider. To understand these implications, we assess the boundary judgements made by a Dutch regional water authority in two diversification-oriented frontrunner projects. We distinguish between three categories of judgements: (1) substantive: the scale, domains, time horizon and solutions that are considered; (2) participation: who is involved, to what extent and when; and (3) planning and decision: the flexibility of responsibilities, financing, planning and decision-making. Our results show that, in both projects, most of the boundary judgements became wider over time as a result of pressure from or interactions with actors from outside the water sector. Hence, despite its ambition to diversify flood risk strategies, the water authority continued to draw boundaries that were too tight to allow for meaningful collaboration with actors outside the water sector. Considering the importance of reconfiguring practices in transforming FRM, we recommend more engaged research into practices.

Rice is a major agricultural crop in Thailand, while paddy fields near river lines are exposed to high flood risk. This study assesses rice exposure and economic flood risk under future climate in the Lower Chao Phraya River Basin, Thailand. To encompass various flood events, this study estimates the frequency of rice economic damage by employing a large ensemble climate projection dataset based on database for Policy Decision making for Future climate change (d4PDF). Results show that, in the 4-K warmer climate, the 100-year exposed cultivation area and duration will increase approximately by 1.2–1.4 and 1.1–1.2 times, respectively. Decreased rice production is evaluated as monetary damage through several fragility curves. The economic damage by the 2011 flooding is estimated as 11.25 billion Thai Baht, while the estimation varies from the fragility curves employed. In the 4 K warmer climate, regardless of the fragility curves, 100-year rice damage is projected to increase by 1.2–1.4 times. The 2011 flooding is larger than all 3000-year simulations in the past climate, whereas extreme events in the 4 K warmer climate showed higher damage than the 2011 flooding, indicating that agricultural damage corresponding to the 2011 flooding may occur more frequently in the future climate.

Reliable flood hazard mapping is crucial for enhancing flood preparedness, especially in poorly gauged and vulnerable areas. Yet, current flood models are either highly detailed and computationally intensive or oversimplified, failing to capture important flow dynamics. Here, we present the Rapid Estimation of FLood EXtent (REFLEX), a hydro-geomorphological model for flood hazard mapping at multiple scales that improves upon the existing Height Above the Nearest Drainage model by constraining flood extent using physically-coherent flood volumes. Input volume is distributed from channel to hillslope cells by using an iterative optimization based on the Manning's equation, bypassing the need for accurate rating curves. The model improves the accuracy of inundation extent in flat areas by accounting for backwater effects, and in coastal zones by extending the calculation boundaries beyond the direct watershed area. REFLEX was tested over five areas with different climatic conditions, including flash-flood prone catchments in Italy and large floodplains in the Zambezi river basin. Results denote skillful representation of flooded areas in the Italian catchments, with critical success index (CSI) up to 0.62. In the African cases, REFLEX produced the best estimates of the flood extent and CSI comparable with two state of the art global inundation models. REFLEX is a competitive flood modelling tool for large scale and high resolution applications thanks to its limited input requirements and computing times two orders of magnitude shorter than equivalent hydraulic simulations.

Integrated flood risk management based on urban policies remains challenging compared with infrastructure due to the unclear risk-reduction effects over time. To consider heterogeneity in social responses to urban planning measures, a previous study developed an agent-based household relocation model under flood risk (AHR-FLOOD) by combining flood-inundation and agent-based relocation models. However, accurate modelling of relocation incentives remains challenging. This study aimed to improve AHR-FLOOD by introducing spatial amenities based on transportation convenience and reflecting their impact on the decision-making processes of agents to analyze the development of different flood risk areas. AHR-FLOOD considering access to public transportation reproduced the spatial characteristics of the actual population and housing prices. The development of low-risk areas reduced flood exposure and resulting flood damage. However, this effect was less clear for low-income individuals, but the development of low-amenity areas had the potential to induce low-income population to move to safe areas. Chain migration was observed as a long-term effect of the spatial amenity policy. This study presents insights into the effect of transportation policies on flood safety for long-term spatial distance management in an agent-based approach with the rigorous modelling and validation of local amenity impact on household relocation choices.

Quantifying flood risk depends on accurate probability estimation, which is challenging due to non-stationarity and the combined effects of multiple factors in a changing environment. The threat of compound flood risks may spread from coastal areas to inland basins, which have received less attention. In this study, a framework based on time-varying copulas was introduced for the treatment of compound flood risk and bivariate design in non-stationary environments. Archimedean copulas were developed to diagnose the non-stationary trends of flood risk. Return periods, average annual reliabilities, and bivariate designs were estimated. Model uncertainty was analyzed by comparing the results for stationary and non-stationary conditions. The case study investigated the extreme rainfall and water level series from the Qinhuai River Basin and the Yangtze River in China. The results showed that marginal distributions and correlations are non-stationary in all bivariate combinations. Ignoring composite effects may lead to inappropriate quantification of flood risk. Excluding non-stationarity may lead to risk over or underestimation. It showed the limitations of the 1-day scale and quantified the uncertainty of non-stationary models. This study provided a flood risk assessment framework in a changing environment and a risk-based design technique, which is essential for climate change adaptation and water management.

Flood risks can stem from various causes and exhibit distinct characteristics that shape the way they are governed. Depending on flood risk characteristics, specific policies are designed and organisations are involved. In Indonesia, like in other regions, organisational divisions are made for coastal floods, fluvial floods and pluvial floods (resulting from tides, rivers and rain, respectively). The Indonesian cities of Manado and Pontianak both face recurring floods. However, the characteristics of and responses to these floods are different, with consequences for distributive, procedural as well as recognition justice in those cities. In line with Fraser, we define recognition justice in relation to three forms of misrecognition: cultural domination, disrespect, and non-recognition, with examples from Manado and Pontianak. We show that the misrecognition of certain types of floods overlaps and interacts with the non-recognition of low-income informal settlements, disrespect and stereotyping of residents of these areas, and a lack of attentiveness to the culture, livelihoods and practices of people who live alongside rivers. In this way, we examine the landscape of recognition justice in the event of flooding in an urban context, drawing on qualitative interview data gathered from the cities of Manado and Pontianak. The following questions are considered: Who experiences misrecognition? By whom is this misrecognition perpetrated? At which level (institutional frameworks or laws, implementation or social practices) and what are the resulting consequences of this misrecognition? Finally, we explore the interactions between different forms of misrecognition, which create a foundation for further distributional and procedural injustices.

The traditional flood hazard assessment system for emergency departments is based on the average hazard index of administrative regions. However, this approach may overlook errors with significant hazards caused by the transition from watershed hazard maps to administrative hazard maps. In our study, we propose an innovative approach that utilizes fuzzy sets to represent flood risk grades, incorporating the upper and lower boundaries of membership variety to effectively indicate higher and lower risks errors, respectively. The introduction of fuzzy set risk grades not only incorporates conventional information but also addresses local risk errors caused by the conversion, enabling Emergency Departments to allocate disaster prevention funds accurately for all risk spots. The fund allocation coefficient, based on fuzzy risk grades, strongly correlates with the proportion of flood-affected populations over time, highlighting the robustness of utilizing fuzzy set risk grades.