Magnitude Of Extreme Rainfall Research Articles

Sustainable flood control strategies under extreme rainfall: Allocation of flood drainage rights in the middle and lower reaches of the yellow river based on a new decision-making framework

Climate change has exacerbated the frequency and magnitude of extreme rainfall, which has led to the perpetuation of flooding as a hazard to humans and society. China has begun to consider introducing Flood drainage rights (FDR), a sustainable flood control measure, into non-engineering measures as a complement to engineering measures for flood control. FDR represent the right of regions to discharge regional floodwaters caused by extreme rainfall into the river, and are the primary means of controlling the amount of floodwaters from regions when regional flood capacity is exceeded. However, existing studies on quantitative FDR allocation still have limitations, and some previous methods have resulted in allocation schemes that are not entirely reasonable and fair because they do not comprehensively consider the influencing factors of FDR or the allocation method is unreasonable. This paper explores the impact of flooding on rural and agricultural areas. We incorporate the factors of agricultural economy and security and construct a system of the allocation indicators of FDR composed of five principles: Natural Environmental Endowment, General Economic and Social Development, Agricultural Economy and Security, Macro policy regulation, and Respect for Historical Background. Second, considering the influence of expert judgment and data of different time nodes on the allocation of FDR, we introduce the concepts of expert weight and time weight into the allocation model of FDR, and construct a new set of framework for the allocation of FDR, i.e., "[(expert weight + subjective weight)+(time weight + objective weight)]+decision making model ". To reduce the loss of information during the transformation of subjective judgments, we also introduced triangular fuzzy numbers for the transformation between expert judgments and numbers. Finally, we take the five provinces in the middle and lower reaches of the Yellow River as an example. Using the data from 2010 to 2021, we obtain the final allocation scheme (proportion) of FDR as Henan (33.26%) > Shaanxi (23.08%) > Inner Mongolia (21.31%) > Shanxi (14.44%) > Shandong (7.91%). On this basis, this paper utilizes sensitivity analysis and comparative validation to demonstrate the rationality and effectiveness of the method, and identifies several indicators that have a greater impact on the results of the allocation of FDR. FDR can form part of a set of integrated flood management system together with flood control projects, which greatly alleviates the drainage conflicts arising from flooding caused by extreme precipitation. Under extreme rainfall conditions, FDR improves drainage efficiency and minimizes the overall damage caused by flooding in the watershed. This study can contribute to the sustainable development of the watershed and provide a reference for the promotion and utilization of sustainable flood control measures.

Extreme Rainfall Events over Accra, Ghana, in Recent Years

This study examines the recent changes in extreme rainfall events over Accra, Ghana. For this study, an extreme rainfall event is defined as a day with rainfall equal to or exceeding the 1980–2019 95th percentile. Knowing extreme rainfall events help to identify the years with the likelihood of rainfall-related disasters in Accra. In addition, it helps to identify the years with the likelihood of drought or severe dryness which are critical for the livelihoods and economic activities of the people. The study used rainfall data from rain gauge for Accra and satellite-derived winds at the 850 hPa level over southern Ghana from 1980 to 2019. It compares these climatic parameters for both pre-2000 and post-2000 to find out the changes that have occurred throughout the study period. Results show that the frequency and magnitude of extreme rainfall have generally increased during the post-2000 period than during the pre-2000 period, causing increases in mortalities and damages to properties. Seasonally, extreme rainfall events were most intense in July during the pre-2000 period but have changed to June during the post-2000 period. Notably, more intense rainfall events have also occurred during post-2000 winter than pre-2000 winter, consistent with increased warming in the study area. Monthly mean meridional winds at the 850 hPa level were stronger (weaker) in the northerly (southerly) direction during the pre-2000 period but have changed to be stronger (weaker) in the southerly (northerly) direction during the post-2000 period.

Extreme rainfall events in Amazonia: The Madeira river basin

Monitoring and understanding the behavior of precipitation is a major challenge of the hydrological cycle and a key issue with respect to the corresponding impact and assessment of risk management in watersheds, notably in the Amazon region. This work investigates the frequency of extreme rainfall events in the largest Amazon sub-basin, the Madeira river basin, using information from the CHIRPS product dataset (Climate Hazards Group Infrared Precipitation with Station) acquired at a spatial degree resolution of 0.05° in a daily basis. Images from 1981 to 2017 were used, spanning a historical time series period of 36 years. Subsequently, these data were analyzed by applying the Gumbel distribution, with trend estimates determined by the Mann-Kendal test at the 95% confidence level. The historical time series revealed that the average maximum rainfall of 1 day, examined throughout the basin, showed variations ranging from approximately 30 to 300 mm. day−1. It should be noted that there is a substantial influence of the El Niño/La Niña climatic phenomenon in the studied region. In addition, the results of the trend assessment showed a reduction in the magnitude of extreme rainfall in regions without vegetation cover in the study area accordingly to the scale of observation of the water balance.

The Challenges of Water Management and Governance in Cities

Combined impacts of sea-level rise, river flooding, increased frequency and magnitude of extreme rainfall, heatwaves, water scarcity, water pollution, ageing or lacking infrastructures for water, wastewater and solid waste in rapidly urbanising regions in the world call for improved water management and governance capacity in cities to accelerate the transition to water-wise cities. The sixteen contributions to this Special Issue create further awareness and present solutions on integrated approaches, advanced water management practices and water governance strategies. It is concluded that cities require a long-term strategy and a multilevel water governance approach. Research has shown how important it is to involve the civil society and private parties early on in this process to create success. Collaboration among cities and regions by sharing best practices for rapid implementation are crucial to cope with nearly all Sustainable Development Goals.

Spatiotemporal trends in extreme rainfall and temperature indices over Upper Tapi Basin, India

The flood risk across the globe is intensified due to global warming and subsequent increase in extreme temperature and precipitation. The long-term trends in extreme rainfall (1944–2013) and temperature (1969–2012) indices have been investigated at annual, seasonal, and monthly time scales using nonparametric Mann-Kendall (MK), modified Mann-Kendall (MMK), and Sen’s slope estimator tests. The extreme rainfall and temperature indices, recommended by the Expert Team on Climate Change Detection Monitoring Indices (ETCCDMI), have been analyzed at finer spatial scales for trend detection. The results of trend analyses indicate decreasing trend in annual total rainfall, significant decreasing trend in rainy days, and increasing trend in rainfall intensity over the basin. The seasonal rainfall has been found to decrease for all the seasons except postmonsoon, which could affect the rain-fed agriculture in the basin. The 1- and 5-day annual maximum rainfalls exhibit mixed trends, wherein part of the basin experiences increasing trend, while other parts experience a decreasing trend. The increase in dry spells and concurrent decrease in wet spells are also observed over the basin. The extreme temperature indices revealed increasing trends in hottest and coldest days, while decreasing trends in coldest night are found over most parts of the basin. Further, the diurnal temperature range is also found to increase due to warming tendency in maximum temperature (T max) at a faster rate compared to the minimum temperature (T min). The increase in frequency and magnitude of extreme rainfall in the basin has been attributed to the increasing trend in maximum and minimum temperatures, reducing forest cover, rapid pace of urbanization, increase in human population, and thereby increase in the aerosol content in the atmosphere. The findings of the present study would significantly help in sustainable water resource planning, better decision-making for policy framework, and setting up infrastructure against flood disasters in Upper Tapi Basin, India.

Future extreme rainfall change projections in the north of Iran

ABSTRACTFuture changes in extreme rainfall arising from climate change may have a significant influence on flood and water erosion control and management strategies to a great extent. The maximum daily rainfall time series were projected for 2020–2049 using six general climate models and two scenarios through artificial neural networks for 22 stations across the north of Iran. The results indicate a reduction of between −3.0 and −0.2% in maximum rainfall for the selected stations and five out of six of the general climate models. The changes in the frequency and magnitude of extreme rainfall were then investigated by fitting a generalized extreme value distribution to the historical (from 1981 to 2010) and projected maximum rainfall. The location parameter of the generalized extreme value distribution fitted to the projected maximum rainfall does not show a significant change while the scale and shape parameters exhibit significant changes compared to the historical period. Estimating the 2, 50 and 100 year return periods showed that the maximum rainfall will have a reduction in the probability of large amounts across the region compared with the base period while the number of extraordinary extreme events may show growth. As a region vulnerable to flash floods and water erosion due to rainfall characteristics and land use change from forest to agriculture, the results may send an alarm to define long term and effective strategies for future flood control management in the region.

Implications of changes in seasonal and annual extreme rainfall

Future projections from climate models and recent observations show a worldwide increase in both the frequency and intensity of heavy rainfall, coinciding with widespread flooding and landslides in Europe. It is estimated, using regional frequency analysis, that the magnitude of extreme rainfall has increased two‐fold over parts of the UK since the 1960s. Intensities previously experienced, on average, every 25 years now occur at 6 year intervals; a consequence of both increased event frequency and changes in seasonality. These climatic changes may be explained by persistent atmospheric circulation anomalies and have huge economic and social implications in terms of increased flooding.