Spatiotemporal Characteristics of Droughts and Floods in Shandong Province,China and Their Relationship with Food Loss

Mastering the pattern of food loss caused by droughts and floods aids in planning the layout of agricultural production,determining the scale of drought and flood control projects,and reducing food loss.The Standardized Precipitation Evapotranspiration Index is calculated using monthly meteorological data from 1984 to 2020 in Shandong Province of China and is used to identify the province’s drought and flood characteristics.Then,food losses due to droughts and floods are estimated separately from disaster loss data.Finally,the relationship between drought/flood-related factors and food losses is quantified using methods such as the Pearson correlation coefficient and linear regression.The results show that:1)there is a trend of aridity in Shandong Province,and the drought characteristic variables are increasing yearly while flood duration and severity are decreasing.2)The food losses caused by droughts in Shandong Province are more than those caused by floods,and the area where droughts and floods occur frequently is located in Linyi City.3)The impact of precipitation on food loss due to drought/flood is significant,followed by potential evapotranspiration and temperature.4)The relationship between drought and flood conditions and food losses can be precisely quantified.The accumulated drought duration of one month led to 1.939×10^(4)t of grain loss,and an increase in cumulative flood duration of one month resulted in1.134×10^(4)t of grain loss.If the cumulative drought severity and average drought peak increased by one unit,food loss due to drought will increase by 1.562×10^(4)t and 1.511×10^(6)t,respectively.If the cumulative flood severity and average flood peak increase by one unit,food loss will increase by 8.470×103t and 1.034×10^(6)t,respectively.

Mechanism of the Impact of Floods and Typhoons on the Morphological Evolution of the Yangtze Estuary

In the last two decades,the Yangtze Estuary has undergone significant changes under the influence of reduced sediment inflow and estuary engineering.This study investigates the influence of floods and typhoons on sediment concentration and the morphological evolution of shoals and channels in the Yangtze Estuary.The analysis is conducted through the utilization of topographic data measured pre-and post-flood events and observations of hydro-sedimentary changes during typhoons.By using a generalized estuary mathematical model,this study examines the interplay between varying tidal ranges,tidal divisions,runoff volumes,and regulation projects on the erosion and deposition of shoals and channels in bifurcated estuaries.The results show that due to the implementation of river and waterway regulation projects,the impact of the 2020 flood on the main channel and shoal was significantly less than that of the1998 flood.The swing amplitude of the South Branch main channel decreased.However,local river sections such as the Southern Waterway of Baimao Shoal exhibited erosion.During typhoons,sediment concentration in the 20 cm above the bottom increased significantly and was closely related to wave processes,with a weakened correlation to tidal dynamics.After typhoons,high shoals in South Passage above 0 m were silted up,while the terrain on one side of the tail of Jiuduan Shoal in the downstream deep-water area was generally scoured due to strong wave action.The generalized mathematical model of the bifurcated estuary revealed that M2 tidal component contributed most to the ero sion and deposition evolution of estuary shoals and channels,with floods exhibiting characteristics of sedime ntation on shoals and erosion on channels.With the implementation of a branch rectification project,branch resistance increased,diversion decreased,and the riverbed changed from pre-project erosion to post-project sedimentation,with an increase in erosion in non-project branches.

Variation Characteristics of Droughts and Floods in Deyang Area in the Past 30 years

Based on the data of annual average precipitation in Deyang area and its five stations (Mianzhu, Deyang, Zhongjiang, Shifang and Guanghan) from 1984 to 2013, the annual precipitation anomaly percentage was calculated, and then the flood and drought situation in Deyang area was graded to discuss the variation characteristics of droughts and floods in the past 30 years. The results show that the cycle of droughts and floods in Deyang was about 3-5 a. The precipitation anomaly percentage indicates that the climate in Deyang area of Sichuan tended to be dry slowly in the past 30 years, and Deyang gradually entered a dry and warm period.

The Effect of the Land Use/Cover Changes on the Floods of the Madarsu Basin of Northeastern Iran

In order to understand the effect of the land use/cover change on the hydrologic regime of the Madarsu Basin in Golestan province of Iran, we selected the two floods of June 1964 and June 2003 with equal amount of rainfall but different rate of runoff. For these floods the closest time images of MODIS were selected. On these images we analyzed the land use/cover types and calculated their area and change rate between two floods. We also calculated the Curve Number (CN) for each land use/cover type according to the US Soil Conservation System (SCS) model. The results showed that: the intensity of the peak floods has increased from 1960 to 2002, and the natural lands of forests, rangelands, and bare lands have been decreased from 1960 to 2002. While the agricultural lands showed increase during the same period. The CN value has also increased during the study period causing the decrease of moisture retention capacity of the soil. As a result, despite the equal rainfall, the discharge rate of 2003 flood was about 10 times larger than that of the 1964 flood, which is the direct effect of the land use/cover change from the stable forests and rangelands to the unstable agricultural lands on the both soil moisture retention capacity and run off rate.

The 2020 Summer Floods and 2020/21 Winter Extreme Cold Surges in China and the 2020 Typhoon Season in the Western North Pacific

China experienced significant flooding in the summer of 2020 and multiple extreme cold surges during the winter of 2020/21.Additionally,the 2020 typhoon season had below average activity with especially quiet activity during the first half of the season in the western North Pacific(WNP).Sea surface temperature changes in the Pacific,Indian,and Atlantic Oceans all contributed to the heavy rainfall in China,but the Atlantic and Indian Oceans seem to have played dominant roles.Enhancement and movement of the Siberian High caused a wavier pattern in the jet stream that allowed cold polar air to reach southward,inducing cold surges in China.Large vertical wind shear and low humidity in the WNP were responsible for fewer typhoons in the first half of the typhoon season.Although it is known that global warming can increase the frequency of extreme weather and climate events,its influences on individual events still need to be quantified.Additionally,the extreme cold surge during 16–18 February 2021 in the United States shares similar mechanisms with the winter 2020/21 extreme cold surges in China.

Toward Understanding the Extreme Floods over Yangtze River Valley in June−July 2020:Role of Tropical Oceans

The extreme floods in the Middle/Lower Yangtze River Valley(MLYRV)during June−July 2020 caused more than 170 billion Chinese Yuan direct economic losses.Here,we examine the key features related to this extreme event and explore relative contributions of SST anomalies in different tropical oceans.Our results reveal that the extreme floods over the MLYRV were tightly related to a strong anomalous anticyclone persisting over the western North Pacific,which brought tropical warm moisture northward that converged over the MLYRV.In addition,despite the absence of a strong El Niño in 2019/2020 winter,the mean SST anomaly in the tropical Indian Ocean during June−July 2020 reached its highest value over the last 40 years,and 43%(57%)of it is attributed to the multi-decadal warming trend(interannual variability).Based on the NUIST CFS1.0 model that successfully predicted the wet conditions over the MLYRV in summer 2020 initiated from 1 March 2020(albeit the magnitude of the predicted precipitation was only about one-seventh of the observed),sensitivity experiment results suggest that the warm SST condition in the Indian Ocean played a dominant role in generating the extreme floods,compared to the contributions of SST anomalies in the Maritime Continent,central and eastern equatorial Pacific,and North Atlantic.Furthermore,both the multi-decadal warming trend and the interannual variability of the Indian Ocean SSTs had positive impacts on the extreme floods.Our results imply that the strong multi-decadal warming trend in the Indian Ocean needs to be taken into consideration for the prediction/projection of summer extreme floods over the MLYRV in the future.

Numerical Simulation of the Relationships between the 1998 Yangtze River Valley Floods and SST Anomalies

With the IAP/LASG GOALS model, the relationships between the floods in the Yangtze River valley arid sea surface temperature anomalies (SSTA) in the Pacific and Indian Oceans in 1998 have been studied. The results show that the model can reproduce the heavy rainfall over the Yangtze River valley in the sum-mer of 1998 forced by global observational sea surface temperatures (SST). The model can also reproduce the observed principal features of the subtropical high anomalies over the western Pacific. The experiments with the observed SST in different ocean areas and different periods have been made. By comparing the ef-fects of SSTA of different ocean areas on the floods, it is found that the SSTA in the Indian Ocean are a ma-jor contributor to the floods, and the results also show that the SSTA in the Indian Ocean and the western Pacific have a much closer relationship with the strong anomalies of the subtropical high over the western Pacific than the SSTA in other concerned areas. The study also indicates that the floods and subtropical high anomalies in the summer of 1998 are more controlled by the simultaneous summertime SSTA than by SSTA in the preceding winter and spring seasons.

Increasing Flash Floods in a Drying Climate over Southwest China

In a globally warming world, subtropical regions are generally expected to become drier while the tropics and mid-high latitudes become wetter. In line with this, Southwest China, close to 25°N, is expected to become increasingly prone to drought if annual mean precipitation decreases. However, despite this trend, changes in the temporal distribution of moisture supply might actually result in increased extreme rainfall in the region, whose climate is characterized by distinct dry and wet seasons. Using hourly and daily gauge observations, rainfall intensity changes since 1971 are exalnined for a network of 142 locations in the region. From the analysis, dry season changes are negligible but wet season changes exhibit a significantly strong downward trend [-2.4% （10 yr）^-1], particularly during the past 15 years [-17.7% （10 yr）^-1]. However, the intensity of events during the wettest of 5% hours appears to steadily increase during the whole period [1.4% （10 yr）^-1], tying in with government statistical reports of recent droughts and flooding. If the opposing trends are a consequence of a warming climate, it is reasonable to expect the contradictory trend to continue with an enhanced risk of flash flooding in coming decades in the region concerned.

Flash Floods and Groundwater Recharge Potentials in Arid Land Alluvial Basins, Southern Red Sea Coast, Egypt

Flash flooding is one of the periodic geohazards in the southern Red Sea Coast. However, their freshwaters are the main source of recharging alluvial and fractured aquifers. This paper presents hydrological and geomorphologic classification of Wadi El-Gemal, Wadi Umm El-Abas, Wadi Abu Ghuson and Wadi Lahmi, along the southeastern Red Sea Coast in Egypt. The main goal is to find a relationship of flash floods and groundwater recharge potentials. Satellite imageries and topographic data were analysed via remote sensing and GIS techniques. The main four valleys’ orders range from six to seven. Wadi El-Gemal was the main focus of this study;it is characterized by high stream frequency, low stream density and coarse texture, reflecting influence of highly fractured Precambrian rocks. Most of the wadis have umbrella-shaped catchment areas, due to the influence of NW-SE Najd Fault System and late E-W strike-slip faults. The main wadis were divided into 45 sub-basins. 14 of the studied sub-basins flow into Wadi El-Gemal, 7 flow into Wadi Umm El-Abas, 10 are in Abu Ghuson, and rest of the basins flow into WadiLahmi. A conceptual model was used in this study, showing that most of the sub-basins have high flash flooding and low groundwater recharge potentials. However, only two sub-basins have low potential of flooding and high potential of groundwater recharge, whereas few sub-basins have moderate potential of groundwater recharge as well as flooding. For flash floods beneficiation and mitigation, construction of multifunctional embankment dams is imminent.

PRELIMINARY STUDY ON FLASH FLOODS IN TARIM RIVER BASIN

Flash floods are the important events of the hydrological regime of rivers in arid areas. In the Tarim River, northwestern china, flash flood are being monitored. The observed data and investigation demonstrate the difference in time, place, fraquency and intensity of their occurrences. In this paper two main flash fled are put forward, they are rainstorm flash flood (RFF) and glacier lake outburst flood(GLOF). Two cases of flash flood in the two tributaries of the Tarim River presented in this paper. It analyses and compares the causes and the development of the two kinds of flash floods.Through further discussion about influence of flash floods on the main channel of the Tarirn River, conclusion can be drawn that the greatest flood in record of the main channel come from the GLOF of the upper reaches of the Kunmalik River, especially augmented by great ablation flood. Finally the advantages and disadvantages from flash floods to the environment of the catchment are demonstrated in the paper.

On Fundamentals Predicting Floods-Landslides

Based on the floods landslides commensurability system, the paper presents and discusses the disasters/hazards with comprehensive interaction and erosional processes. However, people are not enough to get their possibility for the sustainability. They have had so many disasters to meet and to control continuously. Finally, the fundamentals should be built up with nonlinear solutions of landsliding problems; the events of geomagnetism anomaly should be considered.

Long-term reconstruction of flash floods in the Qilian Mountains,China,based on dendrogeomorphic methods

In China,flash floods are one of the main natural disasters causing loss of life and damage to infrastructure.The threat of flash floods is exacerbated with climate change and increased human activities,such that the number of disasters has shown a clear upward trend in recent years.However,due to the scarcity of instrumental data or overly short timeseries,we are still lacking critical data to understand spatio-temporal patterns and driving factors of extreme flash floods.This missing knowledge is however crucial for a proper management of these hazards,especially in remote mountain environments.In forested catchments,dendrogeomorphology allows the reconstruction of past process activity based on growth disturbances(GDs)in trees that have been affected by past flash floods.Therefore,in our study,for the first time,we reconstruct past flash floods in the Qilian Mountains,northeast Tibetan Plateau,over past centuries.To this end,we sampled 99 Qinghai spruce(Picea crassifolia)trees affected by flash floods,with a total of 194increment cores,and identified 302 GDs induced by past flash floods.These GDs have been caused by at least 21 flash floods that we are able to reconstruct over the last 170 years.The position of GDs within tree rings and the intra-seasonal dating of past events also allowed discussion of the likely synoptic situations that may have led to the triggering of flash floods in the past.Logistic regression analysis confirms that significant correlation exists between cumulative maximum 5-day August-September precipitation and reconstructed flash floods,which is corresponding to the majority of scars and related tangential rows of traumatic resin ducts(TRDs)found in the latewood portion of growth rings.These results support the idea that abundant precipitation occurring at the end of the summer season and early fall is the key factor driving flash floods in our study area.Our research not only fills the gaps regarding historical flash flood histories in the Qilian Mountains,but also provides a scientific basis for the region's response to climate change and flood prevention and reduction.

Magnitude,Scale,and Dynamics of the 2020 Mei-yu Rains and Floods over China

Large parts of East and South Asia were affected by heavy precipitation and flooding during early summer 2020.This study provides both a statistical and dynamical characterization of rains and floods affecting the Yangtze River Basin(YRB).By aggregating daily and monthly precipitation over river basins across Asia,it is shown that the YRB is one of the areas that was particularly affected.June and July 2020 rainfall was higher than in the previous 20 years,and the YRB experienced anomalously high rainfall across most of its sub-basins.YRB discharge also attained levels not seen since 1998/1999.An automated method detecting the daily position of the East Asian Summer Monsoon Front(EASMF)is applied to show that the anomalously high YRB precipitation was associated with a halted northward progression of the EASMF and prolonged mei-yu conditions over the YRB lasting more than one month.Two 5-day heavy-precipitation episodes(12−16 June and 4−8 July 2020)are selected from this period for dynamical characterization,including Lagrangian trajectory analysis.Particular attention is devoted to the dynamics of the airstreams converging at the EASMF.Both episodes display heavy precipitation and convergence of monsoonal and subtropical air masses.However,clear differences are identified in the upper-level flow pattern,substantially affecting the balance of airmass advection towards the EASMF.This study contextualizes heavy precipitation in Asia in summer 2020 and showcases several analysis tools developed by the authors for the study of such events.

The Trend and Fluctuation of Historical Floods in the Middle Reaches of the Yangtze River

The middle reaches of the Yangtze River are the worst flood area of the whole basin. To study the variation regulation of the fl oods in this area over a long historical period assure improvement in prediction s of floods in the region. The trend of flood occurred frequency has close relat ionship with human activities near the river. By using statistics analysis, the fluctuations for the time series of floods since 1525 are studied. The results show that the main cycle of flood variation can be identified obviously the per iod of 2, 8 and 40 years with exceeding the level of confidence 0.03.

Regional Climate Index for Floods and Droughts Using Canadian Climate Model (CGCM3.1)

The impacts of climate change on the discharge regimes in New Brunswick (Canada) were analyzed, using artificial neural network models. Future climate data were extracted from the Canadian Coupled General Climate Model (CGCM3.1) under the greenhouse gas emission scenarios B1 and A2 defined by the Intergovernmental Panel on Climate Change (IPCC). The climate change fields (temperatures and precipitation) were downscaled using the delta change approach. Using the artificial neural network, future river discharge was predicted for selected hydrometric stations. Then, a frequency analysis was carried out using the Generalized Extreme Value (GEV) distribution function, where the parameters of the distribution were estimated using L-moments method. Depending on the scenario and the time slice used, the increase in low return floods was about 30% and about 15% for higher return floods. Low flows showed increases of about 10% for low return droughts and about 20% for higher return droughts. An important part of the design process using frequency analysis is the estimation of future change in floods or droughts under climate scenarios at a given site and for specific return periods. This was carried out through the development of Regional Climate Index (RCI), linking future floods and droughts to their frequencies under climate scenarios B1 and A2.

Floods and Hydrograms of Floods of Rivers in Arid Zones of the Mediterranean, Case of the Kingdom of Morocco

The Moroccan territory is often exposed to brutal and destructive floods. The latter is triggered by intense rains and sudden duration (rain showers, thunderstorms). The human and material damage caused by these floods has always been very high. The violence of the flood (1000 m3/s) of Oued Ourika on Aug 17, 1995, killed 730 people. The material damage caused by torrential rain only for the years 2008 and 2009 on the road network (roads and civil engineering works) represents more than 2.9 billion dirhams. The development of flood protection studies requires the values of the instantaneous frequency flow of a certain probability and the corresponding flood hydrogram, generally, these values are not available in the watersheds studied. The objective of this study is to propose for the Moroccan territory a method of calculating flood flows and hydrographs of floods for stream and wadis ungauged for the benefit of engineers and planners for possible studies of flood protection. The proposed method is based on the delimitation of homogeneous regions of Moroccan territory (three homogeneous regions). The frequency analysis carried out for these three zones made it possible to identify the climatic parameters necessary to calculate the flood index and consequently the frequency floods. The proposed Galton type flood hydrograph includes three parameters namely the rise time, the shape parameter and the flood index. These latter parameters are easily calculated by the formulas proposed.

A 249-Year Record of Floods at Appleby in Westmorland, UK

An analysis of nearly 250 years of flood records on the river Eden at Appleby-in-Westmorland has enabled a flood frequency relationship to be established. The most severe floods were in the late 18th and early 19th century. With such a long history of flooding, some remedial measures would have been expected but the local people have, to some extent, adapted to the flood hazard by means of temporary and permanent flood proofing methods such as a cemented board across a doorway and removable flood boards. These measures were overwhelmed during the 2015 flood, as were the flood gates installed by the Environment Agency in 1998. A higher level of protection from floods at Appleby is called for.

Extreme Weather and Climate Events and Their Impacts on Island Countries in the Western Pacific: Cyclones, Floods and Droughts

Increases in the frequency of extreme weather and climate events and the severity of their impacts on the natural environment and society have been observed across the globe in recent decades. In addition to natural climate variability and greenhouse-induced climate change, extreme weather and climate events produce the most pronounced impacts. In this paper, the climate of three island countries in the Western Pacific: Fiji, Samoa and Tuvalu, has been analysed. Warming trends in annual average maximum and minimum temperatures since the 1950s have been identified, in line with the global warming trend. We present recent examples of extreme weather and climate events and their impacts on the island countries in the Western Pacific: the 2011 drought in Tuvalu, the 2012 floods in Fiji and a tropical cyclone, Evan, which devastated Samoa and Fiji in December 2012. We also relate occurrences of the extreme weather and climate events to phases of the El Niño-Southern Oscillation (ENSO) phenomenon. The impacts of such natural disasters on the countries are severe and the costs of damage are astronomical. In some cases, climate extremes affect countries to such an extent that governments declare a national state of emergency, as occurred in Tuvalu in 2011 due to the severe drought’s impact on water resources. The projected increase in the frequency of weather and climate extremes is one of the expected consequences of the observed increase in anthropogenic greenhouse gas concentration and will likely have even stronger negative impacts on the natural environment and society in the future. This should be taken into consideration by authorities of Pacific Island Countries and aid donors when developing strategies to adapt to the increasing risk of climate extremes. Here we demonstrate that the modern science of seasonal climate prediction is well developed, with current dynamical climate models being able to provide skilful predictions of regional rainfall two-three months in advance. The dynamic climate model-based forecast products are now disseminated to the National Meteorological Services of 15 island countries in the Western Pacific through a range of web-based information tools. We conclude with confidence that seasonal climate prediction is an effective solution at the regional level to provide governments and local communities of island nations in the Western Pacific with valuable assistance for informed decision making for adaptation to climate variability and change.

A framework of numerical simulation on moraine-dammed glacial lake outburst floods

Glacial outburst floods（GLOFs） in alpine regions tend to be relatively complicated, multi-stage catastrophes, capable of causing significant geomorphologic changes in channel surroundings and posing severe threats to infrastructure and the safety and livelihoods of human communities. GLOF disasters have been observed and potential hazards can be foreseen due to the newly formed glacial lakes or the expansion of existing ones in the Poiqu River Basin in Tibet, China. Here we presented a synthesis of GLOF-related studies including triggering mechanism（s）, dam breach modeling, and flood routing simulation that have been employed to reconstruct or forecast GLOF hydrographs. We provided a framework for probability-based GLOFs simulation and hazard mapping in the Poiqu River Basin according to available knowledge. We also discussed the uncertainties and challenges in the model chains, which may form the basis for further research.

Three Gorges Project Withstanding 2010 Peak Floods

The Three Gorges Project(TGP) on the Yangtze River(YR) is the largest hydro-power project in the world;it is now attracting the world wide attention.Possessing comprehensive utilization benefits mainly for flood control,power generation and navigation improvement,TGP is a vital and important project in harnessing and developing the YR.The Project primarily aims at flood control whose reservoir has a total storage capacity of 39.3 billion m3,22.15 billion m3 of which can be set for flood control.Construction of the project has greatly improved the flood control capacity in the middle and lower sections of the YR.In 2010 TGP has successfully withstood 3 peak floods,especially the one on July 20 with a frequency of once in 20-year,the largest since the construction of TGP.TGP as an eco-environmental project will be beneficial to ecological and environmental protection and low carbon economy and it will accelerate coordination of the economy,society,resources and environment and sustainable development along the valley,as well as the rapid development of Chinese economy.