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At least 73 records · Page 4Linked to original sources
PubMed2005

[Study on a monitoring program regarding leptospirosis in some fore-and-after flood-affected along large rivers in Anhui province].

OBJECTIVE: The study was designed to find out the epidemic characteristics of leptospriosis and to develop effective intervention measures. The effects of floods on leptospriosis in some areas along Yangzi river and Huai river in Anhui province was also analysed. METHODS: Study on serum epidemiology of leptospriosis was carried out from serous samples collected from native residents and animal hosts including isolation of pathogens at different phases (before,middle and after) and different monitoring spots,during the floods. RESULTS: Infection rate with leptospriosis pathogen among native residents was 13.49% during the flood-period,much higher than 2.18% at post-flood (chi2 = 22.78, P < 0.01) stage, in the flood-affected areas along Yangzi river in 1998. The average rates of infection were 2.48% and 5.35% in affected and unaffected areas along Huai river respectively, in 2003. CONCLUSIONS: There was full evidence that floods causing the epidemics of leptospriosis. However, the transmission of leptospriosis among people would depend on affecting factors as scales of floods, lasting time, coincidence between flood happening and epidemic season, immuno-protection level against leptospriosis among people and so on to a great extent. Factors as the magnitude of pathogens carried by various kinds of infectious sources were also important determinants affecting the nature, being epidemic or pandemic of leptospriosis. It was suggested that active surveillance network on the sources of infection and risk factors of leptospriosis should be developed for the control and prevention of the disease, in the flood-hit areas.

Adolescent↗
PubMed2003

Comparing the evidence relevant to impact and flood basalt at times of major mass extinctions.

The five major mass extinctions identified in 1982 by Raup and Sepkoski have expanded to six, with the suggestion that the Permian-Triassic extinction was a double event. Is there a general explanation for great mass extinctions, or can they result from different triggers, or even from internal system instabilities? The two most-discussed candidates for a general extinction mechanism are impacts and flood-basalt eruptions. A compilation of evidence for impact at the times of mass extinctions shows that this cause is abundantly confirmed in the case of the Cretaceous-Tertiary extinction and the late Eocene, which is a time of minor and gradual extinction, but little or no evidence connects other major extinctions to impact. On the other hand, there is a remarkable time correlation between flood basalts and four major extinctions, but no other evidence that flood basalts cause mass extinctions. The evidence for an impact-extinction linkage is strikingly different from that for a connection between flood basalts and extinctions. Flood basalts cover larger areas than craters and their associated thick ejecta blankets, which are thus less likely to be found. Impacts distribute proxies globally at instantaneous time horizons, whereas flood-basalt events are extended in time, and no remote proxies have been recognized. Many global killing mechanisms have been proposed in the case of impacts, but few have been suggested for flood basalts. It is possible that flood basalts are triggered by impact, but it is not obvious how impacts could result from anything other than chance. The hypothesis that impacts are the general cause of mass extinctions has not received supporting evidence, but has not been falsified. The hypothesis that flood basalts are the general cause of mass extinctions is supported by evidence from timing, but is not susceptible to falsification. Other candidates for general extinction causes, especially sea-level changes and system instabilities, would require separate treatment. The question is still very much open.

Disasters↗
PubMed2006

Anti-transpirant activity in xylem sap from flooded tomato (Lycopersicon esculentum Mill.) plants is not due to pH-mediated redistributions of root- or shoot-sourced ABA.

In flooded soils, the rapid effects of decreasing oxygen availability on root metabolic activity are likely to generate many potential chemical signals that may impact on stomatal apertures. Detached leaf transpiration tests showed that filtered xylem sap, collected at realistic flow rates from plants flooded for 2 h and 4 h, contained one or more factors that reduced stomatal apertures. The closure could not be attributed to increased root output of the glucose ester of abscisic acid (ABA-GE), since concentrations and deliveries of ABA conjugates were unaffected by soil flooding. Although xylem sap collected from the shoot base of detopped flooded plants became more alkaline within 2 h of flooding, this rapid pH change of 0.5 units did not alter partitioning of root-sourced ABA sufficiently to prompt a transient increase in xylem ABA delivery. More shoot-sourced ABA was detected in the xylem when excised petiole sections were perfused with pH 7 buffer, compared with pH 6 buffer. Sap collected from the fifth oldest leaf of "intact" well-drained plants and plants flooded for 3 h was more alkaline, by approximately 0.4 pH units, than sap collected from the shoot base. Accordingly, xylem [ABA] was increased 2-fold in sap collected from the fifth oldest petiole compared with the shoot base of flooded plants. However, water loss from transpiring, detached leaves was not reduced when the pH of the feeding solution containing 3-h-flooded [ABA] was increased from 6.7 to 7.1 Thus, the extent of the pH-mediated, shoot-sourced ABA redistribution was not sufficient to raise xylem [ABA] to physiologically active levels. Using a detached epidermis bioassay, significant non-ABA anti-transpirant activity was also detected in xylem sap collected at intervals during the first 24 h of soil flooding.

Abscisic Acid↗
PubMed2004

Public health impacts of floods and chemical contamination.

INTRODUCTION: Flooding accounts for about 40 per cent of all natural disasters that occur worldwide. In 2002-2003 many counties in England experienced severe floods. Floods are particularly important in public health terms as they may have multiple environmental consequences. METHODS: Details of floods reported to Chemical Hazards and Poisons Division, London [CHaPD(L)] were analysed and a literature review was undertaken to identify published reports of flood-related chemical incidents that have had an impact on public health. RESULTS: Epidemiological evidence shows that chemical material may contaminate homes and that in some cases flooding may lead to mobilization of dangerous chemicals from storage or remobilization of chemicals already in the environment, e.g. pesticides. Hazards may be greater when industrial or agricultural land adjoining residential land is affected. Less evidence exists to support the hypothesis that flooding that causes chemical contamination has a clear causal effect on the pattern of morbidity and mortality following these flooding events. CONCLUSION: In the light of this evidence, a checklist/pro forma for public health response to and investigation of flooding events that may result in chemical contamination was needed. This is available from CHaPD(L).

Causality↗
PubMed1999

Seasonal changes in photosynthesis of trees in the flooded forest of the Mapire River.

We studied the flood tolerance of five tree species growing in the flooded forest adjacent to the Mapire river, in SW Venezuela. Mean photosynthetic rate and leaf conductance were 11 &mgr;mol m(-2) s(-1) and 700 mmol m(-2) s(-1), respectively. Xylem water potential ranged from -0.08 to -1.15 MPa. Based on leaf gas exchange as a criterion of tolerance to flooding, two response patterns were identified: (1) decreasing photosynthetic rate with increasing flooding and leaf conductance (Psidium ovatifolium Berg. ex Desc., Campsiandra laurifolia Benth., Symmeria paniculata Benth. and Acosmium nitens (Vog.) Benth); and (2) independence of photosynthesis and leaf conductance from flooding (Eschweilera tenuifolia (Berg.) Miers.). In the first response pattern, declining photosynthetic rate with flooding may be interpreted as a sign of reduced flood tolerance, whereas the second response pattern may indicate increased flood tolerance. An increase in xylem water potential with depth of water column was found for all species (with the possible exception of P. ovatifolium), indicating that flooding does not cause water stress in these trees. Submerged leaves that had been under water for between four days and four months generally had photosynthetic rates and leaf conductances similar to those of aerial leaves, indicating maintenance of photosynthetic capacity under water. Daily positive oscillations in glucan content in submerged leaves of P. ovatifolium and C. laurifolia suggest that submerged leaves do not represent a sink for photosynthates produced by aerial leaves.

Journal Article↗
PubMed2002

Evidence for trends in UK flooding.

Recent major flooding in the UK has raised concern that climate change is causing increases in flood frequency and flood magnitude. This paper considers whether UK flood data provide evidence of increasing trends in fluvial floods. The analysis examines both local and national flood series and investigates the effect of climate variability on trend detection. The results suggest that there have been trends towards more protracted high flows over the last 30-50 years, but that this could be accounted for as part of climatic variation rather than climate change. There is no statistical evidence of a long-term trend in flooding over the last 80-120 years. Thus, although climate change could be influencing floods, direct analysis of flood records does not yet provide proof.

Climate↗
PubMed2006

Impacts of climate change on coastal flood risk in England and Wales: 2030-2100.

Coastal flood risk is a function of the probability of coastal flooding and the consequential damage. Scenarios of potential changes in coastal flood risk due to changes in climate, society and the economy over the twenty-first century have been analysed using a national-scale quantified flood risk analysis methodology. If it is assumed that there will be no adaptation to increasing coastal flood risk, the expected annual damage in England and Wales due to coastal flooding is predicted to increase from the current 0.5 billion pounds to between 1.0 pound and 13.5 billion pounds, depending on the scenario of climate and socio-economic change. The proportion of national flood risk that is attributable to coastal flooding is projected to increase from roughly 50% to between 60 and 70%. Scenarios of adaptation to increasing risk, by construction of coastal dikes or retreat from coastal floodplains, are analysed. These adaptations are shown to be able to reduce coastal flood risk to between 0.2 pounds and 0.8 billion pounds. The capital cost of the associated coastal engineering works is estimated to be between 12 pounds and 40 billion pounds. Non-structural measures to reduce risk can make a major contribution to reducing the cost and environmental impact of engineering measures.

Climate↗
PubMed1996

Stomatal Closure in Flooded Tomato Plants Involves Abscisic Acid and a Chemically Unidentified Anti-Transpirant in Xylem Sap.

We address the question of how soil flooding closes stomata of tomato (Lycopersicon esculentum Mill. cv Ailsa Craig) plants within a few hours in the absence of leaf water deficits. Three hypotheses to explain this were tested, namely that (a) flooding increases abscisic acid (ABA) export in xylem sap from roots, (b) flooding increases ABA synthesis and export from older to younger leaves, and (c) flooding promotes accumulation of ABA within foliage because of reduced export. Hypothesis a was rejected because delivery of ABA from flooded roots in xylem sap decreased. Hypothesis b was rejected because older leaves neither supplied younger leaves with ABA nor influenced their stomata. Limited support was obtained for hypothesis c. Heat girdling of petioles inhibited phloem export and mimicked flooding by decreasing export of [14C]sucrose, increasing bulk ABA, and closing stomata without leaf water deficits. However, in flooded plants bulk leaf ABA did not increase until after stomata began to close. Later, ABA declined, even though stomata remained closed. Commelina communis L. epidermal strip bioassays showed that xylem sap from roots of flooded tomato plants contained an unknown factor that promoted stomatal closure, but it was not ABA. This may be a root-sourced positive message that closes stomata in flooded tomato plants.

Journal Article↗
PubMed2003

The impact of climate variability on flood risk in Poland.

This article examines the role of climatic and hydrological variability in assessing the cumulative risk of flood events in Poland over a T-year period. In a broad sense flood-risk estimation combines a frequency analysis of extreme hydrological phenomena with an evaluation of flood-induced damages. The damage from floods depends on the critical values of the river discharges. The probabilistic flood analysis usually includes an estimation of the expected annual probability of the critical discharge Qcr being exceeded and the equivalent long-term risk of it being exceeded over the next T years. If, however, the process is nonstationary, the T-year risk of flood damage may depend importantly on the variation of hydrological processes. As a possible explanation for the variations observed in snowmelt-induced floods in Polish rivers, this article investigates the possible impact of the North Atlantic Oscillation (NAO) on surface air temperature T and precipitation P. The spatial distribution of the correlation coefficients between NAO and T, as well as NAO and P, show very significant differences in the NAO impact on meteorological variables in various parts of Europe. To assess the implications of NAO variations on spring flood discharges, a simple model of Snow Cover Water Equivalent (SCWE) was applied to selected Polish river catchments. The conclusion of this analysis is that the yearly maximum of SCWE values significantly decreases with increasing NAO. This leads to a temporal redistribution of winter and spring runoff. The question of spring flood characteristics being stationary or nonstationary may therefore be linked with stochastic properties of the NAO index time series.

Journal Article↗
PubMed2006

Insurability and mitigation of flood losses in private households in Germany.

In Germany, flood insurance is provided by private insurers as a supplement to building or contents insurance. This article presents the results of a survey of insurance companies with regard to eligibility conditions for flood insurance changes after August 2002, when a severe flood caused 1.8 billion euro of insured losses in the Elbe and the Danube catchment areas, and the general role of insurance in flood risk management in Germany. Besides insurance coverage, governmental funding and public donations played an important role in loss compensation after the August 2002 flood. Therefore, this article also analyzes flood loss compensation, risk awareness, and mitigation in insured and uninsured private households. Insured households received loss compensation earlier. They also showed slightly better risk awareness and mitigation strategies. Appropriate incentives should be combined with flood insurance in order to strengthen future private flood loss mitigation. However, there is some evidence that the surveyed insurance companies do little to encourage precautionary measures. To overcome this problem, flood hazards and mitigation strategies should be better communicated to both insurance companies and property owners.

Journal Article↗
PubMed2006

Organic phosphorus fractions in organically amended paddy soils in continuously and intermittently flooded conditions.

Soil organic phosphorus (SOP) can greatly contribute to plant-available P and P nutrition. The study was conducted to determine the effects of organic amendments on organic P fractions and microbiological activities in paddy soils. Samples were collected at the Changshu Agro-ecological Experiment Station in Tahu Lake Basin, China, from an experiment that has been performed from 1999 to 2004, on a paddy soil (Gleysols). Treatments consisted of swine manure (SM), wheat straw (WS), swine manure plus wheat straw (SM + WS), and a control (chemical fertilization alone). Organic amendments markedly increased soil total organic phosphorus (TOP) and total organic carbon (TOC), especially in continuously flooded conditions. Based on the fractionation of SOP, organic amendments significantly increased soil labile organic phosphorus (LOP), moderately labile organic phosphorus (MLOP), and moderately stable organic phosphorus (MSOP) compared with the control. For SM and SM + WS treatments, LOP in continuously flooded soils decreased by 30.1 and 36.4%, respectively, compared to intermittently flooded soils. In organically amended soils, continuous flooding showed significantly lower microbial biomass phosphorus (MBP) and alkaline phosphatase activities (APA) than intermittent flooding. In intermittently flooded conditions, incorporating organic amendments into soil resulted in greater P uptake and biomass yield of rice than the control. In the intermittently flooded soils, APA (P < 0.05) and MBP (P < 0.01) were significantly and positively related to TOP, LOP, MLOP, and MSOP, whereas in continuously flooded soils, there was a significant (P < 0.05) negative relationship between MBP, TOP, and MSOP. Based on soil organic P fractions and soil enzymatic and microbiological activities, continuous flooding applied to paddy soils should be avoided, especially when swine manure is incorporated into paddy soil.

Crops, Agricultural↗
PubMed2002

Flood area and damage estimation in Zhejiang, China.

A GIS-based method to estimate flood area and damage is presented in this paper, which is oriented to developing countries like China, where labor is readily available for GIS data collecting, and tools such as, HEC-GeoRAS might not be readily available. At present local authorities in developing countries are often not predisposed to pay for commercial GIS platforms. To calculate flood area, two cases, non-source flood and source flood, are distinguished and a seed-spread algorithm suitable for source-flooding is described. The flood damage estimation is calculated in raster format by overlaying the flood area range with thematic maps and relating this to other socioeconomic data. Several measures used to improve the geometric accuracy and computing efficiency are presented. The management issues related to the application of this method, including the cost-effectiveness of approximate method in practice and supplementing two technical lines (self-programming and adopting commercial GIS software) to each other, are also discussed. The applications show that this approach has practical significance to flood fighting and control in developing countries like China.

China↗
PubMed2006

Arbuscular mycorrhizal colonization and nodulation improve flooding tolerance in Pterocarpus officinalis Jacq. seedlings.

Pterocarpus officinalis (Jacq.) seedlings inoculated with the arbuscular mycorrhizal fungus, Glomus intraradices, and the strain of Bradyrhizobium sp. (UAG 11A) were grown under stem-flooded or nonflooded conditions for 13 weeks after 4 weeks of nonflooded pretreatment under greenhouse conditions. Flooding of P. officinalis seedlings induced several morphological and physiological adaptive mechanisms, including formation of hypertrophied lenticels and aerenchyma tissue and production of adventitious roots on submerged portions of the stem. Flooding also resulted in an increase in collar diameter and leaf, stem, root, and total dry weights, regardless of inoculation. Under flooding, arbuscular mycorrhizas were well developed on root systems and adventitious roots compared with inoculated root systems under nonflooding condition. Arbuscular mycorrhizas made noteworthy contributions to the flood tolerance of P. officinalis seedlings by improving plant growth and P acquisition in leaves. We report in this study the novel occurrence of nodules connected vascularly to the stem and nodule and arbuscular mycorrhizas on adventitious roots of P. officinalis seedlings. Root nodules appeared more efficient fixing N(2) than stem nodules were. Beneficial effect of nodulation in terms of total dry weight and N acquisition in leaves was particularly noted in seedlings growing under flooding conditions. There was no additive effect of arbuscular mycorrhizas and nodulation on plant growth and nutrition in either flooding treatment. The results suggest that the development of adventitious roots, aerenchyma tissue, and hypertrophied lenticels may play a major role in flooded tolerance of P. officinalis symbiosis by increasing oxygen diffusion to the submerged part of the stem and root zone, and therefore contribute to plant growth and nutrition.

Acclimatization↗
PubMed1996

A flooding-induced xyloglucan endo-transglycosylase homolog in maize is responsive to ethylene and associated with aerenchyma.

Development of aerenchyma (soft cortical tissue with large intercellular air spaces) in flooded plants results from cell-wall hydrolysis and eventual cell lysis and is promoted by endogenous ethylene. Despite its adaptive significance, the molecular mechanisms behind aerenchyma development remain unknown. We recently isolated a flooding-induced maize (Zea mays L.) gene (wusl1005[gfu]; abbreviated as 1005) encoding a homolog of xyloglucan endo-transglycosylase (XET), a putative cell-wall-loosening enzyme active during germination, expansion, and fruit softening. XET and related enzymes may also be involved in cell-wall metabolism during flooding-induced aerenchyma development. Under flooding, 1005 mRNA accumulated in root and mesocotyl locations that subsequently exhibited aerenchyma development and reached maximum levels within 12 h of treatment. Aerenchyma development was observed in the same locations by 48 h of treatment. Treatment with the ethylene synthesis inhibitor (aminooxy) acetic acid (AOA), which prevented cortical air space formation under flooding, almost completely inhibited 1005 mRNA accumulation in both organs. AOA treatment had little effect on the accumulation of mRNA encoded by adh1, indicating that it did not cause general suppression of flooding-responsive genes. Additionally, ethylene treatment under aerobic conditions resulted in aerenchyma development as well as induction of 1005 in both organs. These results indicate that 1005 is responsive to ethylene. Treatment with anoxia, which suppresses ethylene accumulation and aerenchyma development, also resulted in 1005 induction. However, in contrast to flooding, AOA treatment under anoxia did not affect 1005 mRNA accumulation, indicating that 1005 is induced via different mechanisms under flooding (hypoxia) and anoxia.

Amino Acid Sequence↗
PubMed1983

Involvement of plant growth substances in the alteration of leaf gas exchange of flooded tomato plants.

Ethylene, abscisic acid, and cytokinins were tested for their ability to either induce or prevent the changes which occur in gas exchange characteristics of tomato (Lycopersicon esculentum Mill. cv. Rheinlands Ruhm) leaves during short-term soil flooding. Ethylene, which increases in the shoots of flooded plants, had no effect on stomatal conductance or photosynthetic capacity of drained plants. Abscisic acid, which also accumulates in the shoots of flooded plants, could reproduce the stomatal behavior of flooded plants when sprayed on the leaves of drained plants. However, photosynthetic capacity of drained plants was unaffected by abscisic acid sprays. Cytokinin export from the roots to the shoots declines in flooded plants. Spray applications of benzyladenine increased stomatal conductance in both flooded and drained plants. In addition, the decline in photosynthetic capacity during flooding was largely prevented by supplementary cytokinin applications. The possible involvement of these growth substances in modifying leaf gas exchange during flooding is discussed.

Journal Article↗
PubMed1997

Institutional arrangements for flood hazard management in Malaysia: an evaluation using the criteria approach.

Institutional aspects of flood hazards significantly affect their outcomes in Malaysia. Institutional arrangements to deal with floods include: legislative activity, organisational structures, attitudes and sub-culture, and policies and instruments. When assessed in terms of four specific criteria, institutional aspects of flood hazards are found to be largely inadequate. Disaster reduction programmes are over-dependent on a reactive approach based largely on technology and not even aimed at floods specifically. Structural flood reduction measures are the predominant management tool and, although the importance of non-structural measures is recognised, thus far they have been under-employed. Current laws and regulations with regard to flood management are also insufficient and both the financial and human resources of flood hazard organisations are generally found to be wanting. Finally, economic efficiency, equity and public accountability issues are not adequately addressed by institutional arrangements for flood hazards.

Attitude↗
PubMed2006

Flooding risks: a comparison of lay people's perceptions and expert's assessments in Switzerland.

Experts on the risk of flooding have developed very detailed maps for different parts of Switzerland that indicate the types of damage possible and the probabilities of adverse events. Four categories of risk severity are defined on the maps, ranging from high risk to no risk. Based on these existing maps, we selected respondents for a mail survey, some from areas high in risk and others from low-risk regions. Respondents answered several questions related to flood risk perception and preparedness. Survey results showed that respondents' risk perceptions were correlated with the experts' risk assessments. Respondents who lived in areas designated "no risk" by the experts had lower perceptions of risk than respondents who lived in areas with higher levels of designated risk. With regard to concrete prevention behavior, no differences between people living in different risk areas were observed. Survey results further suggest that many inhabitants do not know that flooding maps exist for their region. Results suggest that in some regions people overestimate the risks associated with flooding. Consequently, some people are more afraid of flooding than is justified by the facts. Some people show prevention behavior that most likely is superfluous. However, in other regions people underestimate the risks associated with flooding. These people do not show prevention behavior, and they are not well prepared for an adverse event. Furthermore, results suggest that respondents' experiences with flooding are positively related to their perceptions of flood risk. Findings of the present study are in line with the availability heuristic.

Journal Article↗
PubMed2002

The potential impact of flooding on confined animal feeding operations in eastern North Carolina.

Thousands of confined animal feeding operations (CAFOs) have been constructed in eastern North Carolina. The fecal waste pit and spray field waste management systems used by these operations are susceptible to flooding in this low-lying region. To investigate the potential that flood events can lead to environmental dispersion of animal wastes containing numerous biologic and chemical hazards, we compared the geographic coordinates of 2,287 CAFOs permitted by the North Carolina Division of Water Quality (DWQ) with estimates of flooding derived from digital satellite images of eastern North Carolina taken approximately 1 week after Hurricane Floyd dropped as much as 15-20 inches of rain in September 1999. Three cattle, one poultry, and 237 swine operations had geographic coordinates within the satellite-based flooded area. DWQ confirmed 46 operations with breached or flooded fecal waste pits in the same area. Only 20 of these 46 CAFOs were within the satellite-based estimate of the inundated area. CAFOs within the satellite-based flood area were located in 132 census block groups with a population of 171,498 persons in the 2000 census. African Americans were more likely than whites to live in areas with flooded CAFOs according to satellite estimates, but not according to DWQ reports. These areas have high poverty rates and dependence on wells for drinking water. Our analysis suggests that flood events have a significant potential to degrade environmental health because of dispersion of wastes from industrial animal operations in areas with vulnerable populations.

Adult↗