Drought And Flood
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2021 ◽  
Vol 9 ◽  
Author(s):  
Xia Tang ◽  
Qi Feng

It is important to analyze the characteristics of drought and flood change in an arid area over a long timescale for the evolution of the environment. Historical documents were used to reconstruct a drought and flood grade series for the Hexi Corridor from 0 to 1950 AD. The moving average and wavelet transform processing methods were used to determine the temporal evolution characteristics of droughts and floods, as well as the corresponding relationships with climate change and human activities in the Hexi Corridor after 1000 AD. The results showed the occurrence of eight drought phases (370–410 AD, 790–870 AD, 1050–1150 AD, 1260–1340 AD, 1430–1570 AD, 1710–1770 AD, 1800–1890 AD, and 1910–1950 AD), five flood phases (320–360 AD, 1670–710 AD, 1730–1790 AD, 1810–1860 AD, and 1880–1950 AD), and 3 oscillation periods of drought and flood events. Climate change may have been the main factor inducing droughts and floods before 1580 AD, whereas human activities may have increased the frequency of droughts and floods after the 16th century. Therefore, quantifying the impacts of natural factors and human activities on droughts and floods can provide important theoretical guidance for the prevention and reduction of future disasters.


Author(s):  
Manuela Irene Brunner

Abstract Hydrological extremes can be particularly impactful in catchments with high human presence where they are modulated by human intervention such as reservoir regulation. Still, we know little about how reservoir operation affects droughts and floods, particularly at a regional scale. Here, we present a large data set of natural and regulated catchment pairs in the United States and assess how reservoir regulation affects local and regional drought and flood characteristics. Our results show that (1) reservoir regulation affects drought and flood hazard at a local scale by reducing severity (i.e. intensity/magnitude and deficit/volume) but increasing duration; (2) regulation affects regional hazard by reducing spatial flood connectedness (i.e. number of catchments a catchment co-experiences flood events with) in winter and by increasing spatial drought connectedness in summer; (3) the local alleviation effect is only weakly affected by reservoir purpose for both droughts and floods. We conclude that both local and regional flood and drought characteristics are substantially modulated by reservoir regulation, an aspect that should neither be neglected in hazard nor climate impact assessments.


2021 ◽  
Author(s):  
Changqing Ye ◽  
Yi Zou ◽  
Yanhu He ◽  
Youwen Lin ◽  
Dan Li ◽  
...  

Abstract Most studies of temporal and spatial distribution characteristics of droughts and floods analysis were conducted only from the perspective of a single factor (precipitation), while ignoring the impact of the characteristics of the underlying surface on the formation of droughts and floods. Using the daily precipitation data of 88 meteorological stations in Hainan province from 1970 to 2019, the 30m resolution DEM data, land use dataset, etc, the precipitation Z index is used to evaluate the drought and flood levels in Hainan province. The analysis results were revised by underlying surface data to evaluate the spatiotemporal characteristics of the drought and flood area in Hainan province. The drought-prone areas and flood prone areas in Hainan province were divided, and on this basis, the set pair analysis method was used to identify the regions with alternating drought and flood areas in Hainan. The results show that the overall arid area shows an obvious downward trend, while the flood area presents an increasing trend. The drought-prone areas throughout the year are more concentrated in the northeast of Hainan Province, while flood prone areas are mainly distributed in the eastern coastal areas. The regions where drought and flood occur alternately are small but concentrated. The drought and flood prone areas and alternate drought and flood areas before and after the revision by the underlying surface were compared. It can be seen that the overall trend is relatively similar and obvious before and after the revision. The result of drought areas before revision is 20.43 times larger than that after revision. The flood prone areas before revision are 8.50 times larger than that after revision. The alternating drought and flood areas before underlying surface revision in spring and summer are 17.50 times larger than that after revision. Similarly, it is 48.64 times in summer and autumn, and 17.62 times in autumn and winter. Finally, combining climate and underlying surface factors, suggestions are put forward for drought and flood prevention.


Author(s):  
Md Mamun ◽  
Usman Atique ◽  
Ji Yoon Kim ◽  
Kwang-Guk An

Freshwater reservoirs are a crucial source of urban drinking water worldwide; thus, long-term evaluations of critical water quality determinants are essential. We conducted this study in a large drinking water reservoir for 11 years (2010–2020). The variabilities of ambient nutrients and total suspended solids (TSS) throughout the seasonal monsoon-mediated flow regime influenced algal chlorophyll (Chl-a) levels. The study determined the role of the monsoon-mediated flow regime on reservoir water chemistry. The reservoir conditions were mesotrophic to eutrophic based on nitrogen (N) and phosphorus (P) concentrations. An occasional total coliform bacteria (TCB) count of 16,000 MPN per 100 mL was recorded in the reservoir, presenting a significant risk of waterborne diseases among children. A Mann–Kendall test identified a consistent increase in water temperature, conductivity, and chemical oxygen demand (COD) over the study period, limiting a sustainable water supply. The drought and flood regime mediated by the monsoon resulted in large heterogeneities in Chl-a, TCB, TSS, and nutrients (N, P), indicating its role as a key regulator of the ecological functioning of the reservoir. The ambient N:P ratio is a reliable predictor of sestonic Chl-a productivity, and the reservoir was P-limited. Total phosphorus (TP) had a strong negative correlation (R2 = 0.59, p < 0.05) with the outflow from the dam, while both the TSS (R2 = 0.50) and Chl-a (R2 = 0.32, p < 0.05) had a strong positive correlation with the outflow. A seasonal trophic state index revealed oligo-mesotrophic conditions, indicating a limited risk of eutrophication and a positive outcome for long-term management. In conclusion, the Asian monsoon largely controlled the flood and drought conditions and manipulated the flow regime. Exceedingly intensive crop farming in the basin may lead to oligotrophic nutrient enrichment. Although the reservoir water quality was good, we strongly recommend stringent action to alleviate sewage, nutrient, and pollutant inflows to the reservoir.


2021 ◽  
Author(s):  
Hossein Tabari ◽  
Parisa Hosseinzadehtalaei ◽  
Wim Thiery ◽  
Patrick Willems

Eos ◽  
2021 ◽  
Vol 102 ◽  
Author(s):  
Huan Wu ◽  
Dennis Lettenmaier ◽  
Qiuhong Tang ◽  
Philip Ward

A new book presents recent advances in the modeling and remote sensing of droughts and floods of use to emergency response organizations and policy makers on a global scale.


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