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PubMed2001

Photosynthetic light response of flooded cherrybark oak (Quercus pagoda) seedlings grown in two light regimes.

Two-year-old cherrybark oak (Quercus pagoda Raf.) seedlings raised in full or partial (27%) sunlight were flooded for 30 days to study the effects of light availability and root inundation on photosynthetic light response. Compared with seedlings receiving full sunlight, seedlings receiving partial sunlight developed leaves with 90% greater blade area, 26% less mass per unit volume, and 35% lower nitrogen (N) concentration per unit area, leading to a 15% reduction in leaf photosynthetic capacity when carbon exchange rates were based on blade area. However, when carbon exchange rates were based on leaf mass, leaves acclimated to partial sunlight exhibited a 15% greater photosynthetic capacity realized primarily through an increased initial slope of the photosynthetic light response (A/PPFD) curve and increased net photosynthesis at leaf saturation (Amax). Short-term flooding increased leaf mass per unit area more than 19%, reduced foliar N concentrations per unit dry mass by 19%, and initiated reductions in Amax and apparent quantum yield (phi) of seedlings in both light regimes. Greatest impairment of Amax (56% area basis, 65% mass basis) and phi (40%) were observed in leaves receiving full sunlight, and the declines were concomitant with a 35% decrease in chlorophyll concentration. Flooding also depressed instantaneous photosynthetic N-use efficiency (PPNUE) such that Amax decreased 54%, and the initial slope of PPNUE/PPFD curves decreased 33 and 50% for leaves acclimated to partial and full sunlight, respectively. The A/PPFD patterns indicated that the magnitude of flood-induced inhibition of the photosynthetic mechanism of cherrybark oak seedlings is determined partly by the light environment.

Light↗
PubMed1989

Adventitious roots, leaf abscission and nutrient status of flooded Gmelina and Tectona seedlings.

When flooded, seedlings of Gmelina arborea Roxb. produced more adventitious roots, had lower foliar Mn concentrations and lost fewer leaves than seedlings of Tectona grandis L.f. Severing the adventitious roots produced by flooded Gmelina seedlings increased leaf Mn concentration and leaf abscission and reduced whole-plant dry matter production. Flooded Gmelina cuttings, which do not produce adventitious roots, abscised few leaves until foliar concentrations of Mn and Fe had risen substantially above those of unflooded cuttings, at which time most leaves were shed. The results indicate that the development of adventitious roots in flooded seedlings of Gmelina suppressed uptake of Mn thereby minimizing leaf abscission.

Journal Article↗
PubMed2006

Infectious diseases of severe weather-related and flood-related natural disasters.

PURPOSE OF REVIEW: The present review will focus on some of the possible infectious disease consequences of disastrous natural phenomena and severe weather, with a particular emphasis on infections associated with floods and the destruction of infrastructure. RECENT FINDINGS: The risk of infectious diseases after weather or flood-related natural disasters is often specific to the event itself and is dependent on a number of factors, including the endemicity of specific pathogens in the affected region before the disaster, the type of disaster itself, the impact of the disaster on water and sanitation systems, the availability of shelter, the congregating of displaced persons, the functionality of the surviving public health infrastructure, the availability of healthcare services, and the rapidity, extent, and sustainability of the response after the disaster. Weather events and floods may also impact disease vectors and animal hosts in a complex system. SUMMARY: Weather or flood-related natural disasters may be associated with an increased risk of soft tissue, respiratory, diarrheal, and vector-borne infectious diseases among survivors and responders.

Communicable Disease Control↗
PubMed2002

Estuarine flooding and managed retreat.

The concentration of industrial, residential and agricultural activity on the lowlands surrounding our estuaries has led to an increasing problem of flood risk in these areas. However, flood hazards have been, in large part, the result of past human interference in the estuary system and as such may be reduced by more enlightened management. This paper examines the problems of flood risk and discusses some of the research that has been conducted into its alleviation. In particular, it concentrates attention on the programme of 'managed retreat' in the UK, which attempts to restore previously reclaimed areas in order to reduce flooding and other hazards of the estuarine system.

Conservation of Natural Resources↗
PubMed2002

Vulnerability to flooding: health and social dimensions.

This paper presents research results on the impacts that floods can have on the people affected, thus complementing the existing data on the monetary losses liable to occur in flood events. Both datasets should be used when deciding on investment in flood defence measures. We report on research on the vulnerability of flood-affected communities to adverse health effects, and the development of an index of community vulnerability based on extensive focus-group research and secondary-source census data.

Disasters↗
PubMed2002

How can we learn to live with rivers? The findings of the Institution of Civil Engineers Presidential Commission on flood-risk management.

In the wake of the floods of 1998 and 2000 the Government invited the Institution of Civil Engineers (ICE) to carry out a technical review of flood-risk management in England and Wales and to consider the most appropriate approaches to flood-risk management for the 21st century. The findings of this Commission are published in the ICE report Learning to live with rivers. Further information on the Commission and its work is available at www.icenet.org.uk/presidential.htm. This paper provides an introduction to the need for such a review and the scope of the Commission's work. A summary of the findings of the Commission are presented along with key recommendations for improved flood-risk management in the future.

Advisory Committees↗
PubMed2005

The east coast Big Flood, 31 January-1 February 1953: a summary of the human disaster.

The Big Flood was the worst natural disaster to befall Britain during the twentieth century, and the scale of its human impact was due to the lack of adequate disaster preparedness. The 307 deaths on land were caused by drowning or from the effects of exposure. Two-thirds occurred in four clusters along the shoreline and mainly comprised inhabitants of post-war prefabricated buildings, bungalows and chalets, with the highest mortality among the elderly. The emergency response was spontaneous and community led, with the main search and rescue completed before central government became involved. No individuals or agencies were blamed for the neglected state of the flood defences or the absence of warnings, along with the post-war shortage of adequate housing, which were the main causes of vulnerability. The media played a limited role, and television was in its infancy. Mental health impacts were either self-limiting or failed to be articulated in a society recovering from the Second World War. The major mitigating factors included the empathetic response of people, locally and nationally, as well as the availability of armed forces personnel based in East Anglia, whose actions played a decisive part in the battle against the sea. The major legacies of the Big Flood were a coastal flood forecasting system, a more scientific approach to sea defences and the building of the Thames barrier.

Computer Simulation↗
PubMed2006

Subglacial floods beneath ice sheets.

Subglacial floods (jökulhlaups) are well documented as occurring beneath present day glaciers and ice caps. In addition, it is known that massive floods have occurred from ice-dammed lakes proximal to the Laurentide ice sheet during the last ice age, and it has been suggested that at least one such flood below the waning ice sheet was responsible for a dramatic cooling event some 8000 years ago. We propose that drainage of lakes from beneath ice sheets will generally occur in a time-periodic fashion, and that such floods can be of severe magnitude. Such hydraulic eruptions are likely to have caused severe climatic disturbances in the past, and may well do so in the future.

Journal Article↗
PubMed1995

Export of Abscisic Acid, 1-Aminocyclopropane-1-Carboxylic Acid, Phosphate, and Nitrate from Roots to Shoots of Flooded Tomato Plants (Accounting for Effects of Xylem Sap Flow Rate on Concentration and Delivery).

We determined whether root stress alters the output of physiologically active messages passing from roots to shoots in the transpiration stream. Concentrations were not good measures of output. This was because changes in volume flow of xylem sap caused either by sampling procedures or by effects of root stress on rates of whole-plant transpiration modified concentrations simply by dilution. Thus, delivery rate (concentration x sap flow rate) was preferred to concentration as a measure of solute output from roots. To demonstrate these points, 1-aminocyclopropane-1-carboxylic acid (ACC), abscisic acid, phosphate, nitrate, and pH were measured in xylem sap of flooded and well-drained tomato (Lycopersicon esculentum Mill., cv Ailsa Craig) plants expressed at various rates from pressurized detopped roots. Concentrations decreased as sap flow rates were increased. However, dilution of solutes was often less than proportional to flow, especially in flooded plants. Thus, sap flowing through detopped roots at whole-plant transpiration rates was used to estimate solute delivery rates in intact plants. On this basis, delivery of ACC from roots to shoots was 3.1-fold greater in plants flooded for 24 h than in well-drained plants, and delivery of phosphate was 2.3-fold greater. Delivery rates of abscisic acid and nitrate in flooded plants were only 11 and 7%, respectively, of those in well-drained plants.

Journal Article↗
PubMed1980

Growth Responses and Adaptations of Fraxinus pennsylvanica Seedlings to Flooding.

Flooding induced several physiological and morphological changes in Fraxinus pennsylvanica seedlings, with stomatal closure among the earliest responses. Subsequent changes included: reduction in dry weight increment of roots, stems, and leaves; formation of hypertrophied lenticels and production of adventitious roots on submerged portions of the stem above the soil line; leaf necrosis; and leaf abscission. After 15 days of stomatal closure as a result of flooding, stomata began to reopen progressively until stomatal aperture was similar in flooded and unflooded plants. Adventitious roots began to form at about the time stomatal reopening began. As more adventitious roots formed, elongated, and branched, the stomata opened further. The formation of adventitious roots was an important adaptation for flooding tolerance as shown by the high efficiency of adventitious roots in absorption of water and in high correlation between the production of adventitious roots and stomatal reopening.

Journal Article↗
PubMed1983

Effects of soil flooding on leaf gas exchange of tomato plants.

Carbon dioxide and water vapor exchange of tomato (Lycopersicon esculentum Mill. cv Rheinlands Ruhm) leaves were measured before and after 24 h of soil flooding to characterize both stomatal and nonstomatal responses to the stress. Leaf epidermal conductance to water vapor decreased by 47% after flooding, accompanied by an increase in the sensitivity of stomata to changes in CO(2) concentration. Assimilation rates under ambient conditions fell by 27%, and the inhibition could not be overcome by elevated CO(2) partial pressures. Stomatal conductance limited the assimilation rate to approximately the same degree both before and after flooding. The reduction in photosynthetic capacity was not due to a decrease in apparent quantum yield or to an increase in photorespiration. The results were analyzed according to a recent model of photosynthesis, and possible mechanisms underlying the flooding effect are discussed.

Journal Article↗
PubMed2003

Constructing vulnerability: the historical, natural and social generation of flooding in metropolitan Manila.

Flooding is not a recent hazard in the Philippines but one that has occurred throughout the recorded history of the archipelago. On the one hand, it is related to a wider global ecological crisis to do with climatic change and rising sea levels but on the other hand, it is also the effect of more localised human activities. A whole range of socio-economic factors such as land use practices, living standards and policy responses are increasingly influencing the frequency of natural hazards such as floods and the corresponding occurrence of disasters. In particular, the reason why flooding has come to pose such a pervasive risk to the residents of metropolitan Manila has its basis in a complex mix of inter-relating factors that emphasise how the nature of vulnerability is constructed through the lack of mutuality between environment and human activity over time. This paper examines three aspects of this flooding: first, the importance of an historical approach in understanding how hazards are generated; second, the degree of interplay between environment and society in creating risk; and third, the manner in which vulnerability is a complex construction.

Climate↗
PubMed2006

About bridges and bonds: community responses to the 2000 floods in Mabalane district, Mozambique.

Massive floods hit Mozambique in 2000.1 Many of the affected regions benefited from external aid. This paper investigates how the floods impacted on two communities in the interior of the Limpopo Valley, which did not receive significant assistance during the event and in the immediate aftermath. Drawing on the livelihood approach, it focuses on the role of two types of local resources: knowledge and social capital. The paper shows that the scale of the 2000 floods surpassed the response capacity of these resources and looks at how wealth and gender influenced access by households to the local support mechanisms that enhance survival and recovery. It appears that the floods mainly affected wealthier households, as these more frequently lost houses and cattle. The paper points to the importance of ploughs and cattle for local support mechanisms, which, in turn, most likely reduced the capacities of communities to recover from the disaster.

Disasters↗
PubMed2006

Chlorine spot treatment of flooded tube wells, an efficacy trial.

AIMS: To evaluate the water quality of recently flooded tube wells in Bangladesh and the effect of spot chlorination on improving bacteriological quality. METHODS AND RESULTS: The study team identified and tested water samples from 127 tube wells that were flooded within the preceding 4 weeks. Twenty-six of the tube wells with the highest concentration of thermotolerant coliform bacteria were randomly assigned to spot chlorination vs control. On initial screening, water samples from 56 recently inundated tube wells (44%) were contaminated with thermotolerant coliforms. Among the 13 wells randomized to chlorination, there was no change in the proportion of water samples that had no detectable thermotolerant coliform bacteria immediately before chlorine treatment (n = 4, 23%) and 60 min following chlorine treatment (n = 4, 23%). Similarly, there was no difference in the proportion of water samples that had no detectable thermotolerant coliforms between chlorine spot treated and control tube wells 7-18 days later (31 vs 23%P = 0.66). CONCLUSIONS: Spot chlorine treatment of inundated tube wells in Bangladesh three to 6 weeks after the flooding did not improve drinking water quality. SIGNIFICANCE AND IMPACT OF THE STUDY: Unless modified methods improve effectiveness, resources should not be spent promoting spot chlorination of flooded tube wells.

Bangladesh↗
PubMed1990

Application of polar-orbiting, meteorological satellite data to detect flooding of Rift Valley Fever virus vector mosquito habitats in Kenya.

Measurements of green-leaf vegetation dynamics recorded by the advanced very high resolution radiometer instruments onboard National Oceanic and Atmospheric Administration satellites 7 and 9 were used to derive ground moisture and rainfall patterns in Kenya and monitor resultant flooding of mosquito larval habitats (dambos) likely to support Rift Valley Fever virus vector mosquitoes (Aedes and Culex spp.). Satellite-derived data from mid-1981 to December 1988 have been analysed with corresponding rainfall, flooding and vector population data as they relate to Rift Valley Fever virus ecology. Single (7 x 7 km) and multiple grid-cell image analysis (200 x 300 km) in small localized areas and large geographical regions, respectively, of vegetation data were used to quantify the potential for flooding of mosquito breeding habitats. The ability to detect accurately parameters, such as ground moisture, that determine flooding could provide local officials with sufficient warning to allow for implementation of specific mosquito control measures before a disease outbreak.

Animals↗
PubMed1997

Dust-mite-allergen concentrations in asthmatics' bedrooms in the Quad Cities (Illinois, USA) after the Mississippi River floods of 1993.

This study aimed to measure allergens from Dermatophagoides farinae and D. pteronyssinus and to examine possible relationships of these mite allergens with flooding and other housing factors. A total of 313 dust samples were collected from the bedrooms of 57 asthmatics in 45 homes in the Quad Cities (Illinois, USA) and analyzed by ELISA for the presence of the D. farinae and D. pteronyssinus allergens. Twenty of these homes had some flooding in the last 12 months due to the Mississippi River floods of 1993 and/or other factors. The log-transformed least-squares means of allergens collected were 28 ng/m2 for the D. farinae allergen and 26 ng/m2 for the D. pteronyssinus allergen. D. farinae allergen levels were significantly higher in homes located in the valley, in homes during the summer months, in homes with furred or feathered pets, in homes which had not been flooded in the last year, and in homes where rugs had been steam-cleaned in the last 12 months. D. pteronyssinus allergen levels were significantly higher in homes located in the valley, in homes during April and July-September, in homes with furred or feathered pets, and in homes with no dehumidifier.

Allergens↗
PubMed1995

ENSO and disaster: droughts, floods and El Niño/Southern Oscillation warm events.

The connection between El Niño/Southern Oscillation (ENSO) events and precipitation and temperature variability worldwide is increasingly well understood. ENSO has been linked to droughts and flooding in some regions. This paper uses the disaster history database of the U.S. Agency for International Development's Office of U.S. Foreign Disaster Assistance to examine the link between ENSO events and droughts or floods of sufficient magnitude to trigger international disasters. Worldwide, disasters triggered by droughts are twice as frequent during year two of ENSO warm events than during other years. No such relationship is apparent in the case of flood disasters. Drought disasters occur during year two of ENSO warm events significantly more frequently than in other years in Southern Africa and Southeast Asia. No regional pattern emerges from a comparable analysis of flood disasters. Those places likely to be affected by ENSO-triggered droughts can take proactive measures to mitigate the impacts.

Atmosphere↗
PubMed2000

Microbiology of flooded rice paddies.

Flooded rice paddies are one of the major biogenic sources of atmospheric methane. Apart from this contribution to the 'greenhouse' effect, rice paddy soil represents a suitable model system to study fundamental aspects of microbial ecology, such as diversity, structure, and dynamics of microbial communities as well as structure-function relationships between microbial groups. Flooded rice paddy soil can be considered as a system with three compartments (oxic surface soil, anoxic bulk soil, and rhizosphere) characterized by different physio-chemical conditions. After flooding, oxygen is rapidly depleted in the bulk soil. Anaerobic microorganisms, such as fermentative bacteria and methanogenic archaea, predominate within the microbial community, and thus methane is the final product of anaerobic degradation of organic matter. In the surface soil and the rhizosphere well-defined microscale chemical gradients can be measured. The oxygen profile seems to govern gradients of other electron acceptors (e.g., nitrate, iron(III), and sulfate) and reduced compounds (e.g., ammonium, iron(II), and sulfide). These gradients provide information about the activity and spatial distribution of functional groups of microorganisms. This review presents the current knowledge about the highly complex microbiology of flooded rice paddies. In Section 2 we describe the predominant microbial groups and their function with particular regard to bacterial populations utilizing polysaccharides and simple sugars, and to the methanogenic archaea. Section 3 describes the spatial and temporal development of microscale chemical gradients measured in experimentally defined model systems, including gradients of oxygen and dissolved and solid-phase iron(III) and iron(II). In Section 4, the results of measurements of microscale gradients of oxygen, pH, nitrate-nitrite, and methane in natural rice fields and natural rice soil cores taken to the laboratory will be presented. Finally, perspectives of future research are discussed (Section 5).

Archaea↗