Search

Flooding is Aotearoa-New Zealand's most frequent natural hazard, and there is high confidence that climate change is making extreme rainfall events more frequent and intense. Additionally, there are significant development pressures which could both increase the number of people and assets at risk and the flood hazard. To date, there is no publicly available consistent approach to accurately determine flood risk on a national scale, nor for how this may be changing; although there is a growing legislative requirement to provide quality information over multiple spatial scales. This paper draws on empirical data to gain insights on how to best manage changing flood risks in Aotearoa-New Zealand from the perspective of centrally organised entities. Findings confirm the need for a nationally consistent approach to flood risk management, better understanding of Aotearoa's communities and their vulnerability to floods, equitable access to quality information and decision-support tools, and better understanding of the economic impacts on differing communities, regions and places. The paper concludes that to achieve a flood-resilient Aotearoa, flood governance needs to be reconfigured to achieve national consistency in flood risk management whilst enabling targeted variability at the local scale. [ABSTRACT FROM AUTHOR]

Mismanaged plastic waste (MPW) and urban flooding are typically considered distinct environmental challenges. However, there are notable links between growing quantities of MPW and the rising incidence of floods in cities. A majority of people now live in cities, especially along coastlines and in estuaries where residents are both vulnerable to flooding and significant sources of plastic waste. Predicted increases in the frequency and severity of heavy rainfall associated with anthropogenic climate change coincide with rising global quantities of MPW, much of which is discharged into water bodies and the sea. Given the urgent and expanding nature of these issues, understanding impacts of urban floods on solid waste management and vice versa is crucial. Social-ecological systems (SES) thinking calls for a holistic approach to the relationships and interactions between human actors and environmental systems which can result in dynamic and emergent outcomes. In this review paper, we make a first step towards better understanding of the interactions between urban flooding and MPW by synthesizing emerging quantitative and qualitative research on particular aspects of such interactions. More research is needed which explicitly focuses on and elaborates the nature of these interactions, and also to consider potential relations across scales (from global to local) and over both long and short timeframes. We conclude that an SES approach can make visible novel possibilities for interventions which are context specific and sensitive to the interactions between urban floods and MPW. This article is categorized under: Science of Water > Water and Environmental Change Human Water > Water Governance Engineering Water > Planning Water [ABSTRACT FROM AUTHOR]

The present research study aims to analyze flood frequency to relate flood magnitudes with corresponding return periods. These estimates are crucial for the development of flood-preventive hydrological infrastructures and flood plain zoning, etc. Basin-wide high intensity of rainfall and high discharge from the upper riparian region during monsoon months creates flooding in the middle and lower reaches of the Ghagra River basin. Therefore, the flood estimates for three gauging sites situated on the mainstream of the Ghagra River viz., Elginbridge, Ayodhya, and Turtipar, have been comprehended using the Gumbel distribution (Extreme Value Type I) method and the Log-Pearson Type III distribution method. Flood estimates are calculated for 1.01, 1.05, 1.11, 1.25, 2, 5, 10, 20, 50, 100, 200, and 500 years return periods considering flood time series of 50 years to reduce estimation uncertainty. The findings of flood frequency analysis (FFA) revealed that the probability of occurrence of the flood is more than 80% at all three sites because Ghagra River can carry around 7800 to 9000 m3/s of water discharge without posing a high risk of levee break. The upper and lower limits of discharge carrying capacity depend on the river's desiltation process. Hence, the flood occurs almost every year in the basin; its only variation is its severity. The rainfall-runoff relationship is estimated by integrating a simple linear model and for rainfall trend analysis Mann-Kendall is applied. Linear regression analysis-based rainfall-runoff relationship outcomes revealed a significant relationship with a positive correlation coefficient i.e., 0.2722 for Elginbridge, 0.39624 for Ayodhya, and 0.4844 for Turtipar gauging site in the monsoon season but other factors like a high amount of water discharge from dams in upper riparian regions, etc. are also responsible for flooding in the middle and lower reaches. The Mann-Kendall trend analysis shows a decrease in annual average rainfall and rainfall in the monsoon season. Discharge variability indicates the direct relationship between flood fury and changes in climatic patterns in recent decades. This paper identifies that future research is needed to better inform the policy planners who strive to design sustainable infrastructure. [ABSTRACT FROM AUTHOR]

The Albanian agriculture sector is deeply affected by climate change. To cope with climate change, it is necessary to understand its consequences. The views of agriculture extension service experts are crucial in improving farmers' understanding and resilience, especially when farming practices are poorly adapted to the changing climate. This paper analyses the risks from climate change and the adaptive capacity of farmers based on an expert evaluation survey. The respondents identified prolongation of drought durations, rising temperatures, above-average occurrences of floods, pre-seasonal rainfall and frost as primary risks during recent years. Extension experts view a high (negative) impact from climate change through processes such as increased plant diseases occurrence, increased exposure to rodents, harmful insects and pests for plants and livestock, as well as forest and pasture degradation. The paper also provides experts' opinions on the policy implications, such as considerations about adaptation strategies towards climate change. [ABSTRACT FROM AUTHOR]

• An LRFD framework for embankments considering climate change effects is established. • Additional partial factors are introduced to account for the climate change effects. • Non-stationary maximum flood depth is developed using a peak-over-threshold method. • Embankment reliability is evaluated against overtopping and slope failure. • The proposed framework can serve as a reference for future code design. Riverine floods have become increasingly prevalent on a global scale, posing significant risks to infrastructure systems and communities. The escalating impacts of climate change associated with the increase in rainfall intensities and frequencies necessitate the improvement of the existing design methodologies to account for the non-stationary climate change effects to ensure that the reliability is above the target level and mitigate future flood disasters. This paper presents a novel LRFD approach for river embankments subjected to extreme rainfall under non-stationary climate change effects. This approach introduces an additional partial factor to account for the effects of climate change. Precipitation and temperature projections are collected from various climate models considering several cases of emission scenarios. An integrated hydrological and hydraulic modeling of the analyzed river is carried out to estimate the associated time-variant river discharge and water surface elevation. The non-stationary extreme value associated with the maximum flood level is leveraged using the peak-over-threshold approach. The embankment reliability and the corresponding most probable points are evaluated using limit states associated with overtopping and slope failures. Based on the estimated and target reliability indexes, the design point for each random variable is assessed considering the cases with and without climate change effects. Finally, the partial factors associated with climate change effects are determined. As an illustrative example, the proposed framework is applied to the Ashida River in Fukuyama city of Japan. [ABSTRACT FROM AUTHOR]

In this paper, three case studies are analyzed in Uruguay at the basin level, to identify the factors that favor the flood phenomenon. Transformations in land use and eventually climate change are considered. Over a 30-year period, land use modifications were evaluated using a Geographic Information System, and the variability of rainfall and river levels was analyzed. The three basins show completely different behavior from their land use change, and show increasing trends in rainfall over the period analyzed. It is evident that land use change is one of the most influential factors in the increase of flooding in urban areas. These transformations are mostly related to the exploitation of soil for the generation of commodities for export and generate modifications in the agrarian territories in Uruguay. [ABSTRACT FROM AUTHOR]

• Exploring the urban inundation response law based on designed rainstorms by coupled hydrodynamic and rainfall-tracking model. • Source tracking analysis method is novelty proposed to excavate the response law of the connectivity among source areas to characteristics of rainstorms. • The analysis of source areas contribution further illustrates the reason why the study area would undergo inundation damage when the precipitation exceeds 100 mm. • The study is helpful to further understand the response law of inundation and relationship among source areas to characteristics of rainstorms, provide novel insights for constructing integrated flooding intervention practices. Extreme stormwater and high-impervious area, caused by climate change and high-urbanization, are widely considered as the essential factors for causing urban flood. Understanding the response law of urban inundation to characteristics of rainstorms is helpful to implement integrated flood mitigation measures. Therefore, this paper is focused on exploring the urban inundation response law based on designed rainstorms by coupled hydrodynamic and rainfall-tracking model. Pilot area of Guyuan sponge city, which is divided into 5 source areas, is adopted to conduct 36 types of rainfall scenario simulations with the combination of different rainfall amounts and durations as well as peak coefficients. Inundation analysis methods is used to obtain the relationship between maximum inundation maps and characteristics of rainstorms, and source tracking analysis method is novelty proposed to excavate the response law of the connectivity among source areas to characteristics of rainstorms. First, Results of inundation analysis reveal that rainfall amount, duration and peak value are the first, second and third critical rainstorm characteristics that determine the severity of disasters, the variation of inundation volume are 140 %, 30 % and 4.2 % when precipitation and duration as well as peak value double. Second, the inundation area that water depth more than 0.5 m increases quickly is the major reason that inundation volume varies with 2 times as the increasing of precipitation; the transferring runoff volume between source areas and land use reaches 0–6 % and 0–10 % of inundation volume. Third, SA 1 and 2 are the critical sub-areas to manage the runoff, when precipitation equals to 200 mm, SA 1 contributes 19.5–33.7 % of inundation volume in SA 2, and SA 2 contributes 28–30 % of inundation volume in SA 3. The study is helpful to further understand the response law of inundation and relationship among source areas to characteristics of rainstorms, provide novel insights for constructing integrated flooding intervention practices. [ABSTRACT FROM AUTHOR]

• The extent of flooding in China is greater than in any other country. • Nearly 66% of China's landmass is submerged by flooding. • Financial toll of flooding accounts for approximately 1.42% of the annual GDP. • Various forms of climatic change contribute to flooding. The extent of flooding in China is more significant than in any other country. Our research reveals that approximately 66 % of China's landmass is submerged by flooding, affecting about 50 % of the population. Furthermore, the financial toll of flooding now accounts for approximately 1.42 % of the annual gross domestic product (GDP), which is almost 40 times higher than the corresponding figure for the United States. We have observed that Zhengzhou city in Henan province, which faced a devastating flood in 2021, received a significant amount of rainfall, specifically a total of 552.5 mm within a 24-hour period. The floods in Henan province in 2021 caused considerable damage, including impacting nearly 15 million people, resulting in almost 400 deaths, damaging over 10,000 square kilometers of agricultural land, causing almost $19 billion in economic losses, and leading to the collapse of over 35,000 households and damage to various properties. In a similar manner, the significant flooding that occurred in southern China in 2020 impacted approximately 7.1 million individuals across eight provinces and resulted in 54 fatalities, the collapse of 6,700 houses, and incurred a direct economic loss of US$3.33 billion. We found that rainstorms have significantly increased to 10 % in the last 60 years in China. In this paper, we delved into exploring the existing published articles, reports, and government and authoritative legal texts to analyze the causes and impacts of flooding in China's flood-prone regions and potential mitigation strategies to reduce the repercussions of distressing flood events. We believe this study will help policymakers by providing new insights while formulating policy to reduce the loss caused by high-level flooding. [ABSTRACT FROM AUTHOR]

The paper presents a summary analysis of the phenomena of the degradation of earth dams by the action of changing climate conditions in the eastern part of Romania. Climate change over the last 30 years has led to hydrological risks in the hydrographic network, represented by rapid, frequent flash floods over short periods of time. The floods are due to the uneven distribution of rainfall over the year. The floods are concentrated in a short time and have a very high intensity. This is a major cause of the degradation of dams. Most damage occurs due to floods associated with structural faults, mechanical faults, or hydraulic faults. This situation is confirmed by the events that have taken place over the last 30 years at a series of earth dams in Suceava county (eg. Crujana, Grănicești, Horodnic etc.). The destructive actions were manifested by structural degradations to the dam body, to the large water drain, to the bottom emptying, to the drainage system, etc. In order to prevent adverse events, the term "safety" of hydrotechnical constructions must be taken into account at all stages of the design, execution and operation work. In order to prevent possible accidents that could occur through a dam failure, tests and models shall be carried out in specialized programs. [ABSTRACT FROM AUTHOR]

Our paper reviews recent progress in the study and understanding of observed trends in extreme rainfall events in the Metropolitan Area of São Paulo (MASP). These are discussed in relation to hydrometeorological hazards that trigger natural disasters, such as flash floods, landslides, and droughts, that affect the population and local economies. A review of the most updated literature on rainfall and extremes in the MASP shows a significant increase in the total volume of rainy-season rainfall during the last seven decades. While there were practically no days with heavy rain (more than 50 mm) in the 1950s, these days have been occurring two to five times a year in the last 10 years. This, together with the inappropriate occupation of risky areas, such as slopes and banks of watercourses, leads to inundation, flooding, and landslides. Changes in extremes can be partly due to natural climate variability but can also be related to global warming and/or urbanization. There is ample evidence of an increasing risk of rainfall-related hazards in theMASP. This is particularly so for landslides in vulnerable areas. Exposure will continue to lead to risk increases. This calls for significant improvement in climate and disaster risk reduction and management efforts in theMASP region. [ABSTRACT FROM AUTHOR]

Extreme Flood events due to climate change have been hit Semarang City several times. The disaster usually occurs because of the development of flood protection generally does not include climate change factors on the design flood. The paper was appointed to characterize rainfall run-off with 10 years of historical data from three rain gauge stations likely Wolo, Brumbung, and Maritim. The analytical showed annual rainfall and maximum daily rainfall tends to increase on average 2.139 mm per year, the number of rainy days tends to decrease two days per year. The future Intensity Duration Frequency (IDF) is needed to anticipate global temperature increases more than 2 degrees. Whereas the analysis for drainage capacity showed by the intensity return period of rainfall for 2, 5, 10, 25, 50, 100 years were 81.656 mm/ hour, 104.262 mm/hour,116.00 mm/hour, 126.511 mm/hour, 132.773 mm/hour, 138.030 mm/hour. With the findings, it is expected to develop a flood control system, simply considering the impact of climate change. Hence, the research is successful to predict the flood in a small catchment, with historical data only. The result contributed to one frame that it should take into account the necessity of flood mitigation, including the climate change impact. [ABSTRACT FROM AUTHOR]

Compound floods due to intense rainfall and storm surges in coastal areas have shown an increasing trend in some parts of the world, and many studies suggested a strong link with climate change. Yet, such link has not been fully explored and quantitively assessed. In this paper, we demonstrate the development and application of a nonstationary framework to determining different compound scenarios, where individual drivers and their interactions have altered under climate change. The framework has been applied to one of the most flood-prone areas: the Ho Chi Minh City of Vietnam, to help analyze the present and future compound flood risks in both the dry and wet seasons driven by the joint effect from heavy inland rainfall and high skew surge. Over the period of 1980–2017, the two drivers are found to be significantly correlated in March and April, corresponding to the transition from dry-to-wet seasons. We also find that the commonly-used traditional multivariate statistical models underestimate the flood magnitudes for both the current (represented by 2020) and future (represented by 2050) scenarios, when compared with the results produced by the nonstationary methods. In addition, the results reveal that the dry season is expected to receive more floods triggered by the increased intensity and frequency of rainfall extremes, with the magnitude reaching a similar level to that of the wet season. This is in line with the climate projections under RCP4.5 and 8.5 scenarios although the duration of dry spells is expected to increase and the total annual rainfall to decrease in Vietnam. The simulated flood inundations indicate remarkable increases in flood magnitude and extension, especially at the locations identified as low risk by the stationary models. • A nonstationary framework for quantifying compound flood driven by time-varying factors and dependency under climate change. • Compound floods in March in Ho Chi Minh City driven by increased interaction between rainfall and skew surge. • Averaged rainfall in the wet season in Ho Chi Minh City decreased but the occurrence of extremes increased. • Sea level rise is the main factor triggering the increase of compound flood overcompensating for decreased rainfall. • Traditional stationary method underestimates the compound flood depth in both current (2020) and future (2050) scenarios. [ABSTRACT FROM AUTHOR]

In order to estimate possible changes in the flood regime in the mountainous regions of Slovakia, a simple physically-based concept for climate change-induced changes in extreme 5-day precipitation totals is proposed in the paper. It utilizes regionally downscaled scenarios of the long-term monthly means of the air temperature, specific air humidity and precipitation projected for Central Slovakia by two regional (RCM) and two global circulation models (GCM). A simplified physically-based model for the calculation of short-term precipitation totals over the course of changing air temperatures, which is used to drive a conceptual rainfall-runoff model, was proposed. In the paper a case study of this approach in the upper Hron river basin in Central Slovakia is presented. From the 1981-2010 period, 20 events of the basin's most extreme average of 5-day precipitation totals were selected. Only events with continual precipitation during 5 days were considered. These 5-day precipitation totals were modified according to the RCM and GCM-based scenarios for the future time horizons of 2025, 2050 and 2075. For modelling runoff under changed 5-day precipitation totals, a conceptual rainfall-runoff model developed at the Slovak University of Technology was used. Changes in extreme mean daily discharges due to climate change were compared with the original flood events and discussed. [ABSTRACT FROM AUTHOR]

Climate change scenario shows that areas with bimodal rainfall pattern and major river basins including the Rufiji basin are anticipated to receive an increase of rainfall intensity by 5% to 45%, with a decrease of raining seasons. This incident is expected to upsurge the frequency and magnitude of extreme flood events and cause serious devastations to vulnerable communities. This paper examined the progression of factors causing community vulnerability to flood disasters as basis for developing appropriate flood risk reduction strategies. Data collection methods involved household survey, focus group discussions, in-depth interviews, remote sensing and hydrological analysis. The household survey and hydrological data were analysed using Statistical Packages for Social Science and Trend Analysis software. Data from focus group discussion and interviews were triangulated with community during participatory discussions. Results showed high degree of community vulnerability to flood impacts extending from geographical, social, economic, political and environmental factors. The catchment delineation model showed that the community is geographically located in flood hazardous areas because the river networks flow into the study area. Also, severity of flood impacts was locally related by the recent influx of cattle in the area which has contributed to land degradation, increased runoff and siltation of the Rufiji river. Furthermore, lack of access to social services such as education, health, water and sanitation facilities were found to largely reduce socioeconomic abilities while illuminating underlying vulnerabilities of study communities to flood impacts. The findings suggested combining underlying and immediate factors in reducing future community vulnerability to flood disasters. [ABSTRACT FROM AUTHOR]

The Monsoonal North West (MNW) region of Australia faces a number of challenges adapting to anthropogenic climate change. These have the potential to impact on a range of industries, including agricultural, pastoral, mining and tourism. However future changes to rainfall regimes remain uncertain due to the inability of Global Climate Models to adequately capture the tropical weather/climate processes that are known to be important for this region. Compounding this is the brevity of the instrumental rainfall record for the MNW, which is unlikely to represent the full range of climatic variability. One avenue for addressing this issue (the focus of this paper) is to identify sources of paleoclimate information that can be used to reconstruct a plausible pre-instrumental rainfall history for the MNW. Adopting this approach we find that, even in the absence of local sources of paleoclimate data at a suitable temporal resolution, remote paleoclimate records can resolve 25% of the annual variability observed in the instrumental rainfall record. Importantly, the 507-year rainfall reconstruction developed using the remote proxies displays longer and more intense wet and dry periods than observed during the most recent ~ 100 years. For example, the maximum number of consecutive years of below (above) average rainfall is 90% (40%) higher in the rainfall reconstruction than during the instrumental period. Further, implications for flood and drought risk are studied via a simple GR1A rainfall runoff model, which again highlights the likelihood of extremes greater than that observed in the limited instrumental record, consistent with previous paleoclimate studies elsewhere in Australia. Importantly, this research can assist in informing climate related risks to infrastructure, agriculture and mining, and the method can readily be applied to other regions in the MNW and beyond. [ABSTRACT FROM AUTHOR]

Sewer flooding, urban surface water flooding and wet weather pollution are recognised as significant problems in the UK and elsewhere in the world, and changes in extreme rainfall arising as a consequence of climate change are likely to exacerbate these problems. This paper reports on new approaches to estimate potential future rainfall intensity changes over the UK at temporal and spatial scales that impact on urban drainage systems. The research (part of UK Water Industry Research's programme of climate change related projects) has produced estimates of rainfall intensity change over different parts of the UK using a climate analogue approach and a very high-resolution (1·5 km) climate model developed by the UK Met Office. The new estimates produced are, in general, higher than existing UK climate change allowances for rainfall intensity. Sewer flooding volumes, flooding frequency and frequency of pollution events are also investigated for one location; indicating that these incidents and flood volumes are also likely to increase in the future. [ABSTRACT FROM AUTHOR]

• Future rainfall and sea level rise are predicted. • Impact of sea level rise and future rainfall change on compound flooding is assessed. • Changes in depth, extent, and duration of floods under climate change are analyzed. Flood disasters in coastal cities are generally caused by the combined effect of typhoon rainfall, storm surge and other factors. Coastal cities will face more severe compound flooding under climate change. Although some studies have analyzed compound flooding under climate change, there is a lack of research considering the combined effect of sea level rise (SLR) and future rainfall changes, especially lack of the jacking effect of SLR on the volume and duration of compound flooding. This paper investigates the impact of future rainfall changes and SLR on compound flood risk, via a case study of a coastal city, Haikou, China. Future rainfall in Haikou is obtained by bias correction of rainfall from five global climate models (GCMs) in CMIP5. The SLR in 2050 and 2090 is predicted according to IPCC. Then, a 1D/2D hydrological-hydrodynamic model for dynamic simulation of surface runoff is applied to simulate compound flooding. Results show that both future rainfall changes and SLR will lead to the increase of flood extent, flood depth and flood duration. But future rainfall changes will have a greater impact on flood, and the combined effect of future rainfall changes and SLR on flood is greater than the sum of their individual effects. The individual effects of SLR and future rainfall changes would increase flood depth in 10.6 % and 32.1 % of the study area, respectively, while their combined effect would increase this proportion to 34.9 %. Also, the jacking effect of SLR on compound flooding will lead to an increase in flood volume, but it presents a nonlinear relationship that gradually slows down with the increase of SLR. A SLR of 0.3 m and 0.63 m will lead to a 2.34 % and 3.22 % increase in flood volume, respectively. And the jacking effect of SLR is more obvious when future rainfall changes are considered, which will lead to a sharp increase in the duration of compound flooding. Moreover, water storage facilities and tidal gates are effective ways to reduce the impact of climate change on compound flooding. [ABSTRACT FROM AUTHOR]

Studies of climate change from both natural science and social science disciplines are increasingly turning their focus to the issue of extreme events. Extreme heat waves, storms, droughts, and coastal inundations pose a disproportionate risk to human life, livelihood, and capital across the world. In the Global South, including Africa, much of the adverse impacts come from hydroclimate extremes as people with limited means are often highly vulnerable to climate shocks. The focus of this review paper will be on hydroclimate extremes in Africa. This paper will consider observations and modeling studies of heat extremes, drought, and flooding from heavy rainfall, along with observations and modeling studies of extreme streamflow events in major rivers and extremes of lake level. This being said, observations of trends in extreme events need to be situated in a context of understanding regional hydroclimate variability. There is tremendous diversity and variability in the hydroclimate of Africa and many extreme events, especially of precipitation and streamflow are associated with patterns of natural variability on a range of time scales. [ABSTRACT FROM AUTHOR]

Recently developed methodologies such as climate reanalysis make it possible to create a historical record of climate systems. This paper proposes a methodology called Hydrological Retrospective (HR), which essentially simulates large rainfall datasets, using this as input into hydrological models to develop a record of past hydrology, making it possible to analyze past floods and droughts. We developed a methodology for the Amazon basin, where studies have shown an increase in the intensity and frequency of hydrological extreme events in recent decades. We used eight large precipitation datasets (more than 30 years) as input for a large scale hydrological and hydrodynamic model (MGB-IPH). HR products were then validated against several in situ discharge gauges controlling the main Amazon sub-basins, focusing on maximum and minimum events. For the most accurate HR, based on performance metrics, we performed a forecast skill of HR to detect floods and droughts, comparing the results with in-situ observations. A statistical temporal series trend was performed for intensity of seasonal floods and droughts in the entire Amazon basin. Results indicate that HR could represent most past extreme events well, compared with in-situ observed data, and was consistent with many events reported in literature. Because of their flow duration, some minor regional events were not reported in literature but were captured by HR. To represent past regional hydrology and seasonal hydrological extreme events, we believe it is feasible to use some large precipitation datasets such as i) climate reanalysis, which is mainly based on a land surface component, and ii) datasets based on merged products. A significant upward trend in intensity was seen in maximum annual discharge (related to floods) in western and northwestern regions and for minimum annual discharge (related to droughts) in south and central-south regions of the Amazon basin. Because of the global coverage of rainfall datasets, this methodology can be transferred to other regions for better estimation of future hydrological behavior and its impact on society. [ABSTRACT FROM AUTHOR]

Changes in extreme precipitation should be one of the primary impacts of climate change (CC) in urban areas. To assess these impacts, rainfall data from climate models are commonly used. The main goal of this paper is to report on the state of knowledge and recent works on the study of CC impacts with a focus on urban areas, in order to produce an integrated review of various approaches to which future studies can then be compared or constructed. Model output statistics (MOS) methods are increasingly used in the literature to study the impacts of CC in urban settings. A review of previous works highlights the non-stationarity nature of future climate data, underscoring the need to revise urban drainage system design criteria. A comparison of these studies is made difficult, however, by the numerous sources of uncertainty arising from a plethora of assumptions, scenarios, and modeling options. All the methods used do, however, predict increased extreme precipitation in the future, suggesting potential risks of combined sewer overflow frequencies, flooding, and back-up in existing sewer systems in urban areas. Future studies must quantify more accurately the different sources of uncertainty by improving downscaling and correction methods. New research is necessary to improve the data validation process, an aspect that is seldom reported in the literature. Finally, the potential application of non-stationarity conditions into generalized extreme value (GEV) distribution should be assessed more closely, which will require close collaboration between engineers, hydrologists, statisticians, and climatologists, thus contributing to the ongoing reflection on this issue of social concern. [ABSTRACT FROM AUTHOR]

Climate change has become an increasing global concern, where more frequent, long lasting and severe weather extremes affect water resources around the world. Freshwater/groundwater resources in Bangladesh are one of the most important aspects of the country, which in future will be significantly affected. Global warming has been affecting the characteristics of drinking water level in many ways. The predicted changing environmental conditions suggest that we should be particularly concerned about the over use of groundwater and its withdrawal. In Bangladesh and nearby countries the effect of climate change has been studied but the nature of relationships between renewable freshwater/groundwater resources, temperature, rainfall and flood affected areas (AA) have not been examined in the manner done in this paper. This article examines the relationships between freshwater/groundwater level in terms of temperature changes, rainfall levels and flood AA during the period of 1962-2015. The quantile regressions show the three variables affect the fresh water levels with varying levels of significance (1, 5, 7 and 10% for example). This study uniquely examines the results from two modelling tools namely, STATA and EVIEWS; and confirms the similarity of the results. Freshwater/groundwater resources are negatively affected by temperature changes, rainfall levels and positively affected by flood affected area coverage -flood allows stagnant water filtration to groundwater over time. Temperature causes evaporation of stored water and rainfall causes runoff in early stages but in flood conditions the effect is positive and this is shown by the quantile regression results. [ABSTRACT FROM AUTHOR]

• Adverse impacts of sea-level rises are not limited to a landward shift in shoreline. • Shallow groundwater can impact inland infrastructure kilometers from the coastline. • About 2/3 of the stormdrain length is subject to seawater & groundwater intrusion. • Coastal stressors can increase flood magnitude, frequency, and duration. • Compound flooding volume increases up to 6 times by a 2 m sea-level rise. Low-lying coastal areas are susceptible to multiple types of flooding from marine, subsurface, and surface sources. The co-occurrence of a rainfall event with high sea level, which raises coastal groundwater tables conjointly, may result in a compound flooding event, which could be much more widespread and dangerous than that of an individual flooding source. Focusing on Imperial Beach as a low-elevation coastal community in California, this paper provides a generalized methodology to determine the vulnerability of coastal stormdrain systems to compound seawater, groundwater, and stormwater flooding under a changing climate. Although marine inundation by itself is expected to flood only 7% of the study area by 2100 under the most pessimistic scenario (i.e. 2 m rise), our results show that more than 20% of the study area's subterranean stormdrain system is already at the risk of subsurface flooding at current sea levels. While marine inundation is a concern near the coastline as sea level rises, the results show that seawater intrusion into the stormdrain system can impact areas kilometers away from the coastline. The consequences of sea-level rise (SLR) can be exacerbated by an under-resourced stormdrain system, caused by groundwater infiltration through system defects. As such, by a 2 m rise in current sea-level, the flooding volume may double in an ideal system (i.e., no defects) while this ratio can increase six fold in a slightly defective stormdrain system (with 0.25 % porosity systemwide). The continuous simulations of the stormdrain system performance indicate that flood events will be more destructive and frequent under these circumstances. [ABSTRACT FROM AUTHOR]

Abstract: Climate change and rainfall variability poses serious risks to rainfed farming communities in the semi-dry agro-ecological zones of Zimbabwe. Its impacts include erratic and unpredictable seasonal rainfall, floods and cyclones. These impacts are more magnified in marginal rainfed agricultural areas characterized by low and erratic precipitation leading to low and unpredictable levels of crop production. Adaptation to these impacts is increasingly being advocated as a more sustainable response that enhances livelihoods. Through an examination of key debates from climate-science scholars, this paper examines the social research and action priorities that can be pursued in order to build the resilience of rural communities who rely on rainfed agriculture for their livelihoods. The paper examines the nature of adaptation processes and subsequently identifies research themes, action priorities and approaches that can generate more robust responses to climate change at various levels. The study found out that despite the weaknesses identified in Zimbabwean water and agricultural policies, there are a number of specific actions that researchers, policy-makers and communities can take to enhance adaptation capacity. Systematic assessment of rural risk and vulnerability and participatory identification of possible solutions can enable the rural poor to get better access to options, assets and the services they require to improve their livelihoods. This also enables the identification and improvement of more adaptation options that the farmers themselves have already been trying out for many years. [Copyright &y& Elsevier]

Climate change modelling has improved significantly in recent years and the impact of climate change on flooding in the UK and internationally has become an area of increased importance. Flooding in the UK occurs for a range of reasons; this paper examines some of the predicted changes related to rainfall processes. The different types of rainfall in the UK can be categorised into groups such as frontal, orographic and convective, and combinations of these. Notable flooding events in the UK in recent years have been caused by different types of rainfall; Boscastle in 2004 and the widespread autumn 2000 floods being examples of quite different rainfall processes. Predicting how different types of flood-producing rainfall will change in the future climate presents researchers with major challenges, including that of spatial scale and uncertainty in the predictions. This paper highlights some of these challenges and looks at areas where future research could be focused. [ABSTRACT FROM AUTHOR]

The eastern United States is vulnerable to flooding from tropical cyclone rainfall. Understanding how both the frequency and intensity of this rainfall will change in the future climate is a major challenge. One promising approach is the dynamical downscaling of relatively coarse general circulation model results using higher-resolution regional climate models (RCMs). In this paper, we examine the frequency of landfalling tropical cyclones and associated rainfall properties over the eastern United States using Zetac, an 18-km resolution RCM designed for modeling Atlantic tropical cyclone activity. Simulations of 1980-2006 tropical cyclone frequency and rainfall intensity for the months of August-October are compared against results from previous studies and observation-based datasets. The 1980-2006 control simulations are then compared against results from three future climate scenarios: CMIP3/A1B (late twenty-first century) and CMIP5/RCP4.5 (early and late twenty-first century). In CMIP5 early and late twenty-first century projections, the frequency of occurrence of post-landfall tropical cyclones shows little net change over much of the eastern U.S. despite a decrease in frequency over the ocean. This reflects a greater landfalling fraction in CMIP5 projections, which is not seen in CMIP3-based projections. Average tropical cyclone rain rates over land within 500 km of the storm center increase by 8-17 % in the future climate projections relative to control. This is at least as much as expected from the Clausius-Clapeyron relation, which links a warmer atmosphere to greater atmospheric water vapor content. Over land, the percent enhancement of area-averaged rain rates from a given tropical cyclone in the warmer climate is greater for larger averaging radius (300-500 km) than near the storm, particularly for the CMIP3 projections. Although this study does not focus on attribution, the findings are broadly consistent with historical tropical cyclone rainfall changes documented in a recent observational study. The results may have important implications for future flood risks from tropical cyclones. [ABSTRACT FROM AUTHOR]

ABSTRACT Heavy rain events or rainstorms of various scales often occur in Hong Kong from April to September. In extremes cases, they lead to serious landslides and flash floods resulting in loss of life, and damage to property and infrastructure. With climate change, extreme rain events are projected to be more frequent and more intense in this region. A system to gauge and label the severity of rainstorms would be useful for identifying and communicating extreme conditions in warning and disaster prevention operations. In parallel, a better understanding of the characteristics of rainstorms would also be important for impact assessments and engineering design purposes. This paper formulates a practical framework to index the magnitude and severity of rainstorms in Hong Kong. An index termed as the Severity Index combining the magnitude of different rainstorm attributes is devised for quantifying the overall severity of rainstorms. This index is flexible to allow tuning for specific applications. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents compilation of geological and geoarchaeological data, based on excavations at the Saqqara necropolis, to denote climate variability in Egypt during the late Old Kingdom (around 2200 BC). A change in climate in that time was expressed firstly by aridification and low floods of the Nile, but also by occasional heavy rainfalls in northern Egypt. Low Nile floods were probably a consequence of decreased summer precipitation in the Ethiopian Highlands that resulted in catastrophically low discharges into the Blue Nile drainage basin. These weaker summer monsoons in Ethiopia and gradual aridification in Egypt that started about 5000 cal BP, were coincident with a southward progressing shifting of the summer Intertropical Convergence Zone in Africa. Simultaneous intensive rainfalls resulted in wide-spread sheet-flood accumulations, attested by archaeological evidence in northern Egypt. These rainfalls could be triggered by the North Atlantic Oscillation. Both these reasons caused a rapid collapse of the Old Kingdom at about 4200 cal BP. [Copyright &y& Elsevier]

Climate change and modification of the urban environment increase the frequency and the negative effects of flooding, increasing the interest of researchers and practitioners in this topic. Usually, flood frequency analysis in urban areas is indirectly carried out by adopting advanced hydraulic models to simulate long historical rainfall series or design storms. However, their results are affected by a level of uncertainty which has been extensively investigated in recent years. A major source of uncertainty inherent to hydraulic model results is linked to the imperfect knowledge of the rainfall input data both in time and space. Several studies show that hydrological modelling in urban areas requires rainfall data with fine resolution in time and space. The present paper analyses the effect of rainfall knowledge on urban flood modelling results. A mathematical model of urban flooding propagation was applied to a real case study and the maximum efficiency conditions for the model and the uncertainty affecting the results were evaluated by means of generalised likelihood uncertainty estimation (GLUE) analysis. The added value provided by the adoption of finer temporal and spatial resolution of the rainfall was assessed. [ABSTRACT FROM AUTHOR]

In comparison with drylands elsewhere, the unpredictability of rainfall in central Australia is globally distinctive. The transformative rhythms of arid Australia reflect extremes of climatic conditions rather than seasons, and are characterized by irregular pulses of productivity that punctuate long periods of drought. These decadal-scale dynamics are only now beginning to be understood. Further complications in predicting and managing the biological processes within these landscapes arise from the vast spatial extent of arid and semi-arid communities, and increasing recognition of the heterogeneities that drive the formation of patterns across multiple scales. In 2010 and 2011 flooding rains broke long-standing rainfall records and triggered an anticipated greening of the typically dry red landscapes of central Australia. These unusual climatic events provided an unparalleled opportunity to test ideas about productivity and function, bottom-up versus top-down effects, and differential responses of biota that reflect landscape connections and heterogeneity. Migrations of species outside their known ranges, irruptions of rodents and redistribution of resources are just a few of the novel observations that were reported. The transformation of the landscape also presented land managers with challenges stemming from the influx of invasive species that trigger novel ecological interactions and processes. The papers presented in this special issue describe how ecologists and managers responded to the unprecedented rainfall events, key lessons that we have learnt, and practical recommendations on how to improve conservation outcomes for the fragile inland environment into the future. [ABSTRACT FROM AUTHOR]

This paper assesses future climate changes over East and South Asia using a regional climate model (RegCM4) with a 50 km spatial resolution. To evaluate the model performance, RegCM4 is driven with 'perfect boundary forcing' from the reanalysis data during 1970-1999 to simulate the present day climate. The model performs well in reproducing not only the mean climate and seasonality but also most of the chosen indicators of climate extremes. Future climate changes are evaluated based on two experiments driven with boundary forcing from the European-Hamburg general climate model (ECHAM5), one for the present (1970-1999) and one for the SRES A1B future scenario (2070-2099). The model predicts an annual temperature increase of about 3°-5° (smaller over the ocean and larger over the land), and an increase of annual precipitation over most of China north of 30°N and a decrease or little change in the rest of China, India and Indochina. For temperature-related extreme indicators in the future, the model predicts a generally longer growing season, more hot days in summer, and less frost days in winter. For precipitation-related extremes, the number of days with more than 10 mm of rainfall is predicted to increase north of 30°N and decrease in the south, and the maximum five-day rainfall amount and daily intensity will increase across the whole model domain. In addition, the maximum number of consecutive dry days is predicted to increase over most of the model domain, south of 40°N. Most of the Yangtze River Basin in China stands out as 'hotspots' of extreme precipitation changes, with the strongest increases of daily rain intensity, maximum five-day rain amount, and the number of consecutive dry days, suggesting increased risks of both floods and droughts. [ABSTRACT FROM AUTHOR]

This paper provides a synoptic view of extreme monsoon floods on all the nine large rivers of South Asia and their association with the excess (above-normal) monsoon rainfall periods. Annual maximum flood series for 18 gauging stations spread over four countries (India, Pakistan, Bangladesh and Nepal) and long-term monsoon rainfall data were analyzed to ascertain whether the extreme floods were clustered in time and whether they coincided with multi-decade excess monsoon rainfall epochs at the basin level. Simple techniques, such as the Cramer's t-test, regression and Mann-Kendall (MK) tests and Hurst method were used to evaluate the trends and patterns of the flood and rainfall series. MK test reveals absence of any long-term tendency in all the series. However, the Cramer's t test and Hurst-Mandelbrot rescaled range statistic provide evidence that both rainfall and flood time series are persistent. Using the Cramer's t-test the excess monsoon epochs for each basin were identified. The excess monsoon periods for different basins were found to be highly asynchronous with respect to duration as well as the beginning and end. Three main conclusions readily emerge from the analyses. Extreme floods (>90th percentile) in South Asia show a tendency to cluster in time. About three-fourth of the extreme floods have occurred during the excess monsoon periods between ~1840 and 2000 AD, implying a noteworthy link between the two. The frequency of large floods was higher during the post-1940 period in general and during three decades (1940s, 1950s and 1980s) in particular. [ABSTRACT FROM AUTHOR]

Abstract: Although spate irrigation systems are risk-prone, they can be an important component for livelihood security in semi-arid areas. Spate uses water (flood water), which upstream users often do not require, as rainfall during these periods is more than sufficient. The use of this flood water for spate irrigation is therefore a good opportunity to convert water with a low opportunity cost to high value water. As more rivers are closing, due to socio-economic and climate changes, spate irrigation may become increasingly relevant in semi-arid areas. Spate irrigation systems pose institutional and technical challenges: collective action is challenged by complex upstream–downstream interactions between users within the system, and the high labour demands for regular reconstruction of temporary diversion weirs and intake structures. This paper describes a spate irrigation system in Makanya village, Tanzania that emerged in response to increased upstream water use. We use three of the four dimensions (hydrological, hydraulic and sociological) of spate irrigation proposed by to assess the Makanya spate irrigation system. The Makanya spate irrigation system has an organisational structure that is similar to the canal irrigation (furrow) committees located upstream, and effectively deals with the institutional demands of managing water in spate irrigation systems. Water allocation is reminiscent to the water sharing arrangements existing in the full irrigation system, which previously was in place at the site and in the high- and midlands of the Makanya catchment and therefore set this system apart from the traditional spate irrigation practice elsewhere. Technically, a major challenge is the reconstruction of the head works after each flood. Another aspect is the changes in the river bed. Flash floods carry sediments that deposit on the fields, raising the elevation of the irrigated land every year and making it increasingly difficult for the river water to enter the plots. Improving system efficiency through modernisation of the diversion and distribution structures in this case is not feasible due to the huge amounts of sediments delivered to the system each year. Instead investments in conjunctive use of groundwater could be the solution because it involves a relatively small intervention, minimises the physical disturbance of the system, and therefore is likely to respect the existing locally developed water management arrangements. [Copyright &y& Elsevier]

This paper describes work to improve the understanding of the broad range of factors affecting the occurrence of postfire flooding, with emphasis on an event that occurred in the Alpine Shire, Victoria, Australia, in 2003. Analysis and mesoscale modeling of the conditions surrounding the event suggests that the drivers of the extreme rainfall event were above-average precipitable water in the atmosphere, significant values of CAPE, producing strong updrafts within the thunderstorm capable of supporting large quantities of suspended water droplets, and thunderstorm cell regeneration in the same area. However, atmospheric instability was further enhanced by anabatic breezes, above-average boundary layer moisture, and increased surface heating resulting from reduced surface albedo and soil moisture of the recently burned fire surface. Flash flooding resulted, due to 1) the storm cells likely being pulse wet microbursts, 2) cell regeneration over the same area (very little horizontal movement), and 3) the small catchment size. It is likely that a further contributor to the observed flash flood was the reduced infiltration often observed in recently burned catchments; these factors will be explored in a subsequent hydrologic study. It is intended that the mechanisms elucidated in this study will assist in emergency preparedness in the Alpine Shire. Given the warmer conditions expected with near-term anthropogenic climate change for the Alpine Shire, and the concomitant increase in fires, this causal relationship, even for a relatively rare event, has implications for emergency managers and Alpine Shire residents. [ABSTRACT FROM AUTHOR]

This paper describes a study of the potential effects of climate change on the design and performance of sewer storage tanks. A long-term synthetic rainfall time-series has been derived based on the IPPC medium-high emission scenario for a case study in London. Results indicate a 35% increase in the number of storm events that cause filling of the tank and a 57% increase in the average volume of storage required. A method to estimate the required future storage volume for any given return period has been developed and described. Indications are that significantly larger storage volumes will be required to maintain the same level of flood protection. [ABSTRACT FROM AUTHOR]

Taking the role of frames into account may significantly add to the tools that have been developed for communication and learning on complex risks and benefits. As part of a larger multidisciplinary study into climate-related forms of sense-making this paper explores which frames are used by the citizens of Western European countries and, in particular, the Netherlands. Three recent multi-national public opinion surveys were analysed to examine beliefs about climate change in the context of beliefs about energy technology and concerns about other environmental issues, such as natural disasters. It appeared that many citizens had only vague ideas about the energy situation and that these do not constitute an unequivocal frame for climate issues. In contrast, the results suggest that the long-lasting rainfall and severe floods in Central Europe have had a significant impact. Climate change was often framed in a way that articulates its associations with rain- and river-based problems. This result is extremely important for risk communication, because especially in the Netherlands with its vulnerable coastal zones climate change may produce many more consequences than rain- and river-based problems only [ABSTRACT FROM AUTHOR]

In terms of the effects of future climate change upon society, some of the most important parameters to estimate are associated with changing risks of extreme rainfall events, both floods and droughts. However, such aspects of the climate system are hard to estimate well using general circulation models (GCMs)—in particular, for a small mountainous landmass such as New Zealand. This paper describes a downscaling technique using broad-scale changes simulated by GCMs to select past analogs of future climate. The analog samples are assumed to represent an unbiased sample of future rainfall and are used to develop detailed descriptions of rainfall statistics using hidden semi-Markov models of rainfall breakpoint information. Such models are used to simulate long synthetic rainfall time series for comparison with the historical record. Results for three New Zealand sites show overall increases in rainfall with climate change, brought about largely by an increased frequency of rainfall events rather than an increase in rainfall intensity. There was little evidence for significant increases in high-intensity short-duration rainfalls at any site. Such results suggest that, although regional increases of rainfall are consistent with expected future climate changes, it may be that circulation changes, rather than temperature (and vapor pressure) changes, will be the more important determinant of future rainfall distributions, at least for the coming few decades. [ABSTRACT FROM AUTHOR]

This paper describes the use of numerical weather and climate models for predicting severe rainfall anomalies over the Yangtze River Basin (YRB) from several days to several months in advance. Such predictions are extremely valuable, allowing time for proactive flood protection measures to be taken. Specifically, the dynamical climate prediction system (IAP DCP-II), developed by the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP), is applied to YRB rainfall prediction and flood planning. IAP DCP-II employs ensemble prediction with dynamically conditioned perturbations to reduce the uncertainty associated with seasonal climate prediction. IAP DCP-II was shown to successfully predict seasonal YRB summer flooding events based on a 15-year (1980–1994) hindcast experiment and the real-time prediction of two summer flooding events (1999 and 2001). Finally, challenges and opportunities for applying seasonal dynamical forecasting to flood management problems in the YRB are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Under enhanced greenhouse conditions, climate models suggest an increase in rainfall intensities in the northern Hemisphere. Major flood events in the UK during autumn 2000 and central Europe in August 2002, have focussed attention on the dramatic impacts these changes may have on many sectors of society. In the companion paper [Fowler et al., J. Hydrol. (2004) this issue], we suggested that the HadRM3H model may be used with some confidence to estimate extreme rainfall distributions, showing good predictive skill in estimating statistical properties of extreme rainfall during the baseline period, 1961–1990. In this study, we use results from the future integration of HadRM3H (following the IPCC SRES scenario A2 for 2070–2100) to assess possible changes in extreme rainfall across the UK using two methods: regional frequency analysis and individual grid box analysis. Results indicate that for short duration events (1–2 days), event magnitude at a given return period will increase by 10% across the UK. For longer duration events (5–10 days), event magnitudes at given return periods show large increases in Scotland (up to +30%), with greater relative change at higher return periods (25–50 years). In the rest of the UK, there are small increases in the magnitude of more frequent events (up to +10%) but reductions at higher return periods (up to -20%). These results provide information to alter design storm depths to examine climate change impacts on various structures. The uncertainty bounds of the estimated changes and a ‘scaling’ methodology are additionally detailed. This allows the estimation of changes for the 2020s, 2050s and 2080s, and gives some confidence in the use of these estimates in impact studies. [Copyright &y& Elsevier]

Climate change is affecting the frequency and intensity of rainfall extreme events worldwide. Despite the growing global awareness, developing flood resilient cities has proven to be a major challenge. This paper investigates the application of an event-based scalable Flood Resilience Index (FRI) for assessing climate change adaptation. Flood resilience is represented by three dimensions: physical, social and economic. A household climate adaptation is adopted consisting of a combination of a flood-proof gate with an indoor tank and a submersible pump system implemented in all houses. The climate related impact under a high-emission scenario (RCP8.5) is analysed for Munich with the CRCM5 Large-Ensemble. Results show that for Munich extreme heavy rainfall events are increasing. The FRI can successfully identify households and districts which: a) are mostly affected by heavy rainfall, b) benefit the most from the climate adaptation, and c) are the most resilient. For the most severe future scenario investigated the climate adaptation measure was able to improve 57% of all affected buildings within Maxvorstadt to an FRI equal to 1.0 during the event and recovery phase. • We assess climate change adaptation (CCA) via a scalable Flood Resilience Index (FRI). • The FRI can identify the most resilient households and districts. • A household CCA consists of flood-proof gate with an indoor tank and pump system. • The CCA was able to improve 57% of all affected buildings to an FRI equal to 1.0. [ABSTRACT FROM AUTHOR]