The influence of spring floods on small mammal communities in the Nemunas River Delta, Lithuania

The influence of the annual spring floods on small mammal communities was studied in the Nemunas River Delta, SW Lithuania. The aim of the investigation was to compare the diversity of small mammals inhabiting spring-flooded meadows, meadows not subjected to flooding and spring-flooded forest in years characterized by differing heights and durations of spring flood. In the years of the high flood, the number of species and diversity index were higher, while index of dominance was less than in the years of low flood. Significantly, the highest proportions of Apodemus agrarius were recorded in spring-flooded meadows in years of high flood (41.7%), while Microtus oeconomus occurred in the highest proportions in spring-flooded meadows in years of low flood (66.8%) and in meadows not subjected to flooding (47.1%). In non-flooded areas, M. Oeconomus is not expelled by the floods and outcompetes other species. After high levels of flooding, during the process of re-population, the voles may be outcompeted by A. agrarius. In the absence of dominant species, greater opportunities existed for the establishment of more species (13 species in flooded meadows). Micromys minutus accounted for up to 19.5–30.1% in the years of high flood. We concluded that the annual spring floods in the Nemunas Delta had no long-term negative effects, the number of small mammal species and their abundance had been restored in just a few months. The worst consequences of the high flood were recorded in forest habitat. Spring floods, and especially the higher floods, are natural environmental agents, maintaining the high diversity of small mammals in meadows and reed-beds.     

基于土地利用变化情景的城市暴雨洪涝灾害风险评估——以深圳市茅洲河流域为例

近年来频发的暴雨洪涝成为威胁城市可持续发展的主要灾害类型,而土地利用变化改变了区域原有的景观结构和水文过程,是城市暴雨洪涝灾害风险加剧的重要诱因,定量探讨土地利用变化对暴雨洪涝灾害及其风险影响具有重要意义。以深圳市茅洲河流域为例,基于CLUE-S模型、SCS模型及等体积淹没算法等,对12种暴雨洪涝致灾-土地利用承灾情景下的城市暴雨洪涝灾害风险进行定量模拟。研究结果显示,相同土地利用空间格局下城市暴雨洪涝灾害随暴雨致灾危险性增加风险加剧显著;在同等致灾危险性水平下随建设用地面积增加,中等风险和高风险区面积均呈现较为明显的增加趋势,中、高风险区面积与建设用地面积的增加率表现出较高的协同变化特征;以50年遇危险性水平为例,随着建设用地面积由基期的15368.85hm~2增加至近期16076.07hm~2和远期16750.89hm~2,高风险区面积由254.07hm~2增加至276.48hm~2和286.2hm~2。由此可见,尽管暴雨强度的增加是城市暴雨洪涝灾害风险加剧的根本诱因,但是以建设用地面积增加为表征的土地利用变化对暴雨洪涝灾害风险的影响不容忽视。     

The relevance of fire frequency for the floodplain vegetation of the Okavango Delta, Botswana

The study investigates the relevance of fire frequency for the floodplain vegetation of the Okavango Delta in Botswana, considering species composition, species richness, vegetation structure and tree density. Based on flood and fire frequency data derived from a series of satellite images, active and drying floodplains were separated and study plots were selected with fire frequencies up to ten burns between 1989 and 2003. Both for drying and active floodplains, no typical species assemblage could be associated with fire frequency. On drying floodplains, fire frequency showed no effect on species composition, but rather on vegetation structure. While small woody species showed higher cover values on high fire frequency, large trees showed significantly lower cover values on high fire frequency. For active floodplains, a significant response to fire frequency, both positively and negatively could be determined for specific species. But as almost none of these species appear at low or high frequency only, no differences in species composition could be associated with fire frequency. Rather flood frequency and specific annual flood cycles could be described as the determining factors for the vegetation on active floodplains.     

西南地区农业洪涝等级指标构建及时空分布特征

利用西南农业区341个气象站1961—2010年的逐日降水量资料,结合灰色关联分析,以重庆市单站洪涝指标为原型,对该指标降水量临界值进行幅度为-50～+50 mm、步长为1 mm的增减,得到该区域各省份相对应的101个洪涝指标,并结合基于各洪涝指标计算得出的洪涝发生强度与农作物洪涝实际受灾程度的相关性、指标与历史洪涝灾害记录的吻合性以及分省指标的可比性,确定了各省农业洪涝等级指标,同时,分析了该区域农业洪涝灾害的时空分布特征.结果表明： 构建的云南指标为原指标+16 mm,贵州指标为原指标+30 mm,四川-重庆指标为原指标+40 mm,指标定义的洪涝指数与各省份受灾率的相关系数分别为0.314（P<0.05）、0.553（P<0.01）和0.305（P<0.05）,指标与历史灾害记录的吻合性较高.1961—2010年,云南、贵州、四川-重庆洪涝发生较严重的年代分别为20世纪80年代、20世纪90年代、20世纪80年代和21世纪初,洪涝多发区分别位于云南西南和东南部、贵州西南部和四川盆地的西部和东北部.     

A reconstruction of flood events using scarred trees in the Tatra Mountains, Poland

In this paper we reconstructed flood events in a small mountain stream (6.6 km long, elevation 1100–1950 m a.s.l.) in the Dolina Waksmundzka Valley in the Tatra Mountains in the Western Carpathians. This reconstruction was based on cross-dated flood scars found in Norway spruce trees growing along stream banks. The scars were most likely formed by woody debris and stones transported during flood events. Reconstructed flood years were then compared with climatic records collected at the nearest meteorological station.Fifty-eight scars were cross-dated indicating 17 years with flood events in the period between 1928 and 2005. The large number of reconstructed flood events proves that the Potok Waksmundzki stream discharge can be highly variable. The high mid-summer rainfall (approximately 300 mm or more per month) peaks in June, July, August and this period coincides with some of the flood scar formation. The high winter and spring precipitation (December–May) does not seem to induce floods. The rate of snow melting seems to be more important. The highest number of scars (33%) was formed in dormant season of 1957/1958. In April and May 1958 there was an unusually large difference between mean monthly temperatures, the highest recorded in the twentieth century. This probably led to an abnormally rapid snow melt. No one single climatic factor can be held responsible for all flood events. Intensive mid-summer rainfall as well as rapid snow melting may induce floods in the Dolina Waksmundzka Valley. Cross-dated scars have enabled past flood events to be detected, which are otherwise invisible from climatic data alone.     

The effects of a record flood on the aquatic vegetation of the Upper Mississippi River System: some preliminary findings

During 1993 the Upper Mississippi River System experienced floods of exceptional magnitude and duration, especially at its more downstream reaches. The flood had widespread effects on the vegetation. Submerged species such as Potamogeton pectinatus significantly decreased in abundance, especially at sites with more severe flooding. However, many species were able to regenerate in 1994 from seeds or storage organs. Emergent species such as Scirpus fluviatilis were similarly affected, but in the upstream reaches were able to regrow in the autumn following the flood and at many sites showed exceptionally high productivity in the following year, probably due to nutrient-rich sediment deposition by the flood. Many tree species were very severely impacted, although Acer saccharinum and Populus deltoides have shown some seedling regeneration on newly deposited sediment beneath stands of mature trees, which would have out-shaded the seedlings if they had not been killed by the flood.     

Monitoring trends in the extent of major floods in the lower reach of Songkhram River Basin, Northeastern Thailand

This study analyzes trends in the extent of major floods in the lower reach of Songkhram River Basin, one of the most important areas for aquatic biological production in the Lower Mekong River Basin. We first classified the time series Landsat imagery acquired at a 2-year interval between 2000 and 2006 using the unsupervised classification method. We then analyzed the extent of major floods through the image matrix analysis on seasonal land cover map pairs. Additionally, we estimated flood volumes and discharge rates for each time series. We finally analyzed the extent of land uses that were affected by major flood events. Accuracy assessment showed that the extent of major floods was accurately mapped. Analysis of trends of major floods revealed that there was a considerable variation in the extent through 2006, with the flood decreasing since 2002. Analysis of flood risk areas based on the 2000–2004 data showed that about 3.04% of the study areas was at high risk of being flooded. Between 2000 and 2006, about 5.5% of the study area that are classified as agriculture and built-up land uses was affected by major floods. Our estimates on flood volumes and discharge rates are consistent with the data from other studies. Overall findings suggest that accurate mapping of major floods and flood risk areas using space and time dependent data can be important for developing protocols for flash flood early warning and flood risk management and mitigation. Output GIS maps and data combined with crude assumptions about water flow will serve as the baseline data to estimate the amount of water that flows in and out of the basin. Further research should focus on integration of social science research to evaluate the socio-economic impacts of major floods and identifying coping strategies of affected communities.     

Emergency situations in the Republic of Ingushetia and the prevention of their epidemiological consequences

Information on the sanitary and epidemiological situation and water supply in the Republic of Ingushetia during the period before and after the emergency situation (high flood) is presented. The results of epidemiological observations on the territory of the Republic of Ingushetia for the period of June 22 to the end of the year 2002 indicate that no considerable rise in infectious morbidity, as well as outbreaks of natural focal infections, was noted. This suggests that, in spite of the complicated sanitary and epidemiological situation before the emergency situation (due to the vicinity of the conflict in the Chechen Republic, the intensive migration of the population and the presence of a large of refugees on the territory of the Republic of Ingushetia) and its sharp deterioration caused by the high flood, the timely realization of a complex of sanitary and prophylactic measures made it possible to avoid the wide spread of infectious diseases.     

Mapping ecosystem services: The supply and demand of flood regulation services in Europe

Ecosystem services (ES) feature highly distinctive spatial and temporal patterns of distribution, quantity, and flows. The flow of ecosystem goods and services to beneficiaries plays a decisive role in the valuation of ES and the successful implementation of the ES concept in environmental planning. This is particularly relevant to regulating services where demands emerge often spatially separated from supply. However, spatial patterns of both supply and demand are rarely incorporated in ES assessments on continental scales. In this paper, we present an ES modeling approach with low data demand, fit to be employed in scenario analysis and on multiple scales. We analyze flood regulation services at a European scale by explicitly addressing the spatial distribution of ES demand. A flood regulation supply indicator is developed based on scenario runs with a hydrological model in representative river catchments, incorporating detailed information on land, cover, land use and management. Land use sensitive flood damage estimates in the European Union (EU) are employed to develop a spatial indicator for flood regulation demand. Findings are transferred to the EU territory to create a map of the current supply of flood regulation and the potential supply under conditions of natural vegetation. Regions with a high capacity to provide flood regulation are mainly characterized by large patches of natural vegetation or extensive agriculture. The main factor limiting supply on a continental scale is a low water holding capacity of the soil. Flood regulation demand is highest in central Europe, at the foothills of the Alps and upstream of agglomerations. We were able to identify areas with a high potential capacity to provide flood regulation in conjunction with land use modifications. When combined with spatial patterns of current supply and demand, we could identify priority areas for investments in ES flood regulation supply through conservation and land use planning. We found that only in a fraction of the EU river catchments exhibiting a high demand, significant increases in flood regulation supply are achievable by means of land use modifications.     

Organization of the workers of the State Sanitary and Epidemiologic Services of the Stavropol Territory in the period of eradication of the consequences of the flood in urban and rural regions of the Territory in 2002

As the result of high flood occurring during the period of June 21-22, 2002, in the Stavropol Territory, 65 settlements were affected. About 200,000 inhabitants found themselves lacking centralized drinking water supply. From the very first days of the emergency situation the state sanitary and epidemiological service took a complex of measures aimed at the liquidation of the medico-sanitary consequences of the high flood, the prevention of the appearance of mass infectious diseases among the affected population. As the result of these measures, the appearance of the outbreaks of acute enteric infections, viral hepatitis A aggravations in malaria and other infectious diseases could be prevented.     

Effects of macrophyte complexity and hydrometric level on fish assemblages in a Neotropical floodplain

Habitat heterogeneity provided by aquatic macrophytes and water level variations (flood pulse) are essential factors in structuring fish assemblages. This study aimed to describe the fish species that prefers macrophytes covered areas and to evaluate how macrophytes complexities and a flood pulse influence the structure of fish assemblages and selected attributes (viz. fish species density, species richness and evenness). Sampling was performed with seining nets in five floodplain lakes associated with the Baía River, before (November to December 2011) and after (February to July 2012) a flood, considering different degrees of macrophyte complexity (Absent, intermediate, and high). A total of 48 fish species was recorded, with Characiformes the most dominant. Eight species were indicators of high complexities (seven before the flood and only one after). Significant differences among the different degrees of macrophyte complexity and before and after the flood were found for assemblage structure, species density and richness. Fish assemblage attributes were high in higher habitat heterogeneity provided by macrophytes, but all before the flood. Nevertheless, macrophyte stands with high and intermediate complexity were less affected by the flood, suggesting that the structure propitiated by macrophytes favors the persistence of the fish assemblage in floodplain lakes. Therefore, any action towards conservation of fish assemblages in macrophytes should consider dam operation upstream, to ensure seasonality of flood pulses.     

长三角城市群城市洪涝韧性与生态系统服务的耦合协调关系

厘清城市洪涝韧性与生态系统服务之间耦合协调关系,可为城市防洪减灾和生态文明建设提供重要决策参考。综合运用基于麻雀算法的投影寻踪模型、InVEST模型和耦合协调度模型,在分析2000-2020年长三角城市群的城市洪涝韧性与水源涵养、水质净化、土壤保持和气候调节四种生态系统服务时空格局基础上,尝试探索两者耦合协调关系及其时空演变特征。研究发现:(1)长三角城市群的城市洪涝韧性水平呈现"N"型增加趋势,并呈现"上海>江苏>浙江>安徽"的空间格局,表明经济水平越高的城市展现出更强的洪涝韧性,经济是影响城市洪涝韧性波动的主要因素,而自然韧性成为城市洪涝韧性提升的关键短板;(2)生态系统服务存在显著的空间异质性,高植被覆盖的南部地区提供了更高的生态系统服务,从时间维度看其空间分布是稳定的,水源涵养和水质净化服务总体呈向好趋势,土壤保持服务整体呈现倒"N"型增加,气候调节服务呈现微弱的下降趋势;(3)城市洪涝韧性与生态系统服务的耦合协调度在研究期内较为稳定,且与生态系统服务的时空变化趋于一致,呈现"南高北低、由西南向东北逐渐减弱"的趋势,生态系统服务较高的城市,表现出更好的耦合协调性,且随着生态系统服务的增加而改善。因此,长三角城市群有必要从提高生态系统服务功能的角度出发,因地制宜、分类施策,促进城市洪涝韧性与生态系统服务的协调发展。     

Floating vegetation mats on a floodplain billabong in the Northern Territory of Australia

The floristics and physical structure of a floating mat of vegetation in the Finniss River area of the Northern Territory are described. During the dry season floating mats contain green productive vegetation when the adjacent flood plains are dry and many of the plants are withered. At this time insects are more abundant on the mats than on the adjacent flood plain. Some flood plain vertebrates appear to concentrate their activity on floating mats during the dry season. During the period 1963 to 1978 the area of floating mat in the Finniss River study area was greatly reduced, probably as a result of high densities of feral water buffalo (Bubalis bubalus).(Present address: c/o 38 Hardy Terrace, East Ivanhoe, Victoria 3079).(Present address: c/o 38 Hardy Terrace, East Ivanhoe, Victoria 3079).     

The effects of the flood cycle on the diversity and composition of the phytoplankton community of a seasonally flooded Ramsar wetland in Bangladesh

Freshwater wetlands in Bangladesh are strongly influenced by the monsoons and the annual flood cycle has measurable impacts on the abiotic and biotic components of these ecosystems. The northeastern Haor Basin of Bangladesh is particularly rich in seasonally flooded freshwater wetlands that support a wide diversity of flora and fauna. These wetlands are of great importance to the local economy due to the abundance of rich floodplain fisheries. Little is known about the phytoplankton communities of these wetlands that are known to be linked with zooplankton and fish productivity. We investigated the seasonal variation in the diversity and abundance of phytoplankton assemblages in Tanguar Haor, a Ramsar wetland in northeastern Bangladesh during the period of inundation (June–December). A total of 107 genera of phytoplankton representing five classes were recorded. Blooms of Microcystis dominated the phytoplankton community throughout the study period but were particularly acute during the early part of the high water period. Among the Bacillariophyceae, Melosira was the most dominant, reaching bloom proportions early in the high water period. Factor analysis of physicochemical variables separated the flood cycle into four distinct periods: early high water, mid high water, late high water and low water periods. Phase of the flood cycle, nutrient availability, the physicochemical variables combined with the dominance of Microcystis seemed to be important in controlling the abundance, diversity and dynamics of the phytoplankton genera. The abundance of genera of desmids and some Bacillariophyceae is indicative of the relatively unpolluted conditions of Tanguar Haor.     

湖泊型流域洪涝灾害经济损失多情景模拟——以南四湖流域为例

洪涝灾害情景模拟与损失预估对湖泊型流域防洪减灾和可持续发展具有重要意义。以我国典型的湖泊型流域南四湖流域为例,利用CA-Markov模型预测2030年三种用地情景,采用P-III型概率曲线构建10、20、50、100 a四个重现期强降雨情景,得到12种组合情景;通过InVEST模型和等体积淹没法量化不同情景的径流和淹没深度;在各产业GDP空间预测的基础上计算12种情景的洪涝直接经济损失。结果表明:(1) CA-Markov模型在南四湖流域的土地利用模拟精度较高,三种用地情景的各地类变化显著;(2)用地变化对流域洪涝灾害的影响显著,其中城镇发展情景下洪涝灾害风险最大,而生态保护情景风险最低;(3)暴雨强度会明显增加各用地情景的经济损失,但增幅在50 a重现期后有所减缓;生态保护情景的经济损失最少,介于97.39-128.81亿元之间,与其他情景相比,该情景可在一定程度上减少洪灾损失。为此,在气候变化背景下湖泊型流域可持续发展应充分考虑土地利用变化对洪涝灾害风险的影响,合理扩张城镇建设用地,优化布局生态用地,充分发挥国土空间规划在防洪减灾方面的作用。     

Prevention of acute enteric infections and viral hepatitis A in the Stavropol Territory in connection with a natural disaster

Materials on the organization and realization of prophylactic measures with respect to acute enteric infections (AEI) and viral hepatitis A (VHA) at the period of the liquidation of medico-sanitary consequences of the high flood are presented. As shown in these materials, the epidemiological surveillance on AEI and VHA in the areas affected by the emergency situation included the effective system of monitoring on these diseases. On the basis of monitoring optimum decisions were taken and concrete prophylactic measures were realized. This made it possible to detect the foci of infectious diseases in due time and efficiently liquidate them, as well as to prevent the development of the epidemiological consequences of the high flood.     

The ecology of the Kafue lechwe population of Zambia before the operation of hydro-electric dams on the Kafue River

Aerial surveys from 1970 onwards suggest a stable Kafue lechwe population of 94 000±9% on the Kafue Flats. The present distribution shows a contraction in dry and wet season range in comparison with 1953/54. Sex ratios of populations on both the North and South banks of the Kafue river do not differ significantly from unity. North bank males have a higher survival rate than South bank males. Survival curves for males and females on the South bank show the same pattern. For both the 1971 and 1972 breeding seasons 73% of South bank females older than 1½ years are expected to have bred successfully. The peaks of conceptions for both seasons are from mid-December to mid-March, suggesting a main lambing period from mid-July until mid-October. Present sex ratio, age structure, reproductive status and the reproductive cycle have been compared with 1961/62 data. Variation in physical condition, based on monthly measurements of the kidney fat percentage, dressing-out percentage and live weight, although influenced by the physiological demands of rut and pregnancy, is correlated with the availability of flood-plain grazing. The lowest values of condition parameters are found during the period of maximum flood, after the end of the rains (April/May), until the receding flood makes flood-plain grazing available, usually in early June. A high level of tuberculosis, lungworm infection and many other pathogens amongst the South bank population are reported. Animals from the North bank are thought to be in better physical condition. The Kafue Gorge dam, completed in 1971, and the Iteshi-teshi dam, at present under construction, will prolong the high flood period in wet years and prevent most flooding in dry years, both of these effects will reduce the carrying capacity of the flood plain for lechwe and a large reduction of the size of the population is expected to result from the operation of the dams.     

洪水对大凌河河流浮游细菌群落的影响

洪水是一种突发性强、破坏力大的自然灾害,它不仅造成巨大的经济损失,而且对生态环境也有严重危害。在地球生物化学过程中起重要作用的微生物是否也受到影响值得深入研究。2012年采集了洪水暴发前后辽宁省锦州段大凌河表层水样,利用DGGE技术,结合PCA和RDA分析研究了洪水对河流表层水中细菌群落的影响。结果表明:(1)洪水发生前后河流表层水中的细菌群落发生了改变:洪水发生前河流中细菌群落结构与河段所处的自然环境有很大的相关性,而洪水发生后这一现象消失。(2)洪水发生前,影响细菌群落结构的主要环境因素是pH和盐度,而洪水发生后,影响细菌群落结构的主要环境因素是总磷。这一研究结果提示洪水通过改变河流表层水环境特性对其中的细菌群落进行重塑。     

Aquatic ecosystem responses to fire and flood size in the Okavango Delta: observations from the seasonal floodplains

The frequency of fires in the Okavango Delta seasonal floodplains peaked at an intermediate frequency of flooding. Floodplains are commonly burnt every 3–5 years. This study showed fundamental changes in ecosystem properties due to burning. A burnt seasonal floodplain in the aquatic phase had oxygen levels well above saturation, 100–200%, while the levels in the un-burnt control site were below saturation and, at night, could decline to 10–40% saturation. The total phosphorous and total nitrogen concentrations were similar on both floodplains but considerably enriched relative to inflowing water, due to nutrient release from the flooded soil-sediment and animal droppings. Zooplankton biomass was very high in both systems although the abundance of fish fry was ten times higher on the un-burnt floodplain. In a low flood year the un-burnt floodplain water had high nutrient levels, primary production, methane emission, and subsequent uptake of methane in biota, as well as a high zooplankton biomass. The very high flood the following year showed the opposite with much lower production at all levels owing primarily to greater dilution of nutrients. The abundance of fish, however, was much higher during the high flood year. Macrophytes and litter provide direct shelter for fish fry but also promote low oxygen levels when decaying. Large flooded areas result in high fish production by removing obstacles related to congestion. This interplay between hydroperiod and fire may be crucial for the maintenance of high biological productivity both in the aquatic and terrestrial phases in a very nutrient poor wetland landscape. Understanding these interactions is crucial for optimal management.     

Effects of a natural flood disturbance on species richness and beta diversity of stream benthic diatom communities

Natural hydrological disturbances in streams may reduce biomass and species richness and change community composition within streams. Disturbances can also affect beta diversity among streams if their effects are species specific or vary across sites. We investigated the effect of a natural flood on species richness, community composition and among-streams beta diversity of benthic diatoms (total community and three functional groups: low profile, high profile and motile) of seven streams in New Zealand. Sampling occurred shortly before, 10 days after and 40 days after the flood. Species richness of the total diatom community did not change after the flood. The high-profile group was the only one whose species richness declined after the flood, whereas species richness of the low-profile group increased. Community composition changed after the flood, mostly as a result of species replacement rather than richness differences over time. Finally, among-streams beta diversity did not change after the flood, suggesting that variation in species composition of benthic diatoms among streams may be maintained in the face of flood disturbances.