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PubMed2005

An analysis of the causes and circumstances of flood disaster deaths.

The objective of this paper is to investigate and to improve understanding of the causes and circumstances of flood disaster deaths. A standardised method of classifying flood deaths is proposed and the difficulties associated with comparing and assessing existing information on flood deaths are discussed. Thirteen flood cases from Europe and the United States, resulting in 247 flood disaster fatalities, were analysed and taken as indicative of flood disaster deaths. Approximately two-thirds of the deaths occurred through drowning. Thus, a substantial number of flood disaster fatalities are not related to drowning. Furthermore, males are highly vulnerable to dying in floods and unnecessary risk-taking behaviour contributes significantly to flood disaster deaths. Based on these results, recommendations are made to prevent loss of life in floods. To provide a more solid basis for the formulation of prevention strategies, better systematic recording of flood fatalities is suggested, especially those caused by different types of floods in all countries.

Adolescent↗
PubMed2000

Sesbania herbacea-Rhizobium huautlense Nodulation in Flooded Soils and Comparative Characterization of S. herbacea-Nodulating Rhizobia in Different Environments.

The nodulation of S. herbacea was compared under flooded and non-flooded conditions in two different soils. One soil was from a flooded field in Sierra de Huautla, the native habitat of this legume, while the other soil was from a well-drained field in Cuernavaca, where rhizobia were found to nodulate the introduced S. herbacea plants. Nodulation of the plants was completely eliminated by flooding in the Cuernavaca soil, whereas nodules were obtained in the same soil under non-flooded conditions. In contrast, nodules were formed in Huautla soil under both flooded and non-flooded conditions. Most isolates, except isolate HS2, from Huautla soil and water were identified as R. huautlense by colony morphology, growth rate, PCR-RFLP of 16S rRNA genes, MLEE, cellular plasmid contents, and RFLP of nifH and nodDAB genes. Isolate HS2 was identified as Mesorhizobium sp. Isolates from Cuernavaca soil were different from R. huautlense in many aspects and were classified into five rDNA types within the genera Mesorhizobium, Rhizobium, and Sinorhizobium by PCR-RFLP of 16S rRNA genes. R. huautlense is a water Rhizobium species. Growth by denitrification under oxygen limitation or with ethanol was observed for R. huautlense bacteria but not for the isolates from Cuernavaca. In an interstrain nodulation competitive assay under both flooded and non-flooded conditions, R. huautlense strain S02 completely inhibited the nodulation of Mesorhizobium sp. Sn2, an isolate from Cuernavaca. From these results, we conclude that R. huautlense has the unique ability to nodulate S. herbacea not only in flooded soils, but in non-flooded soils as well.

Journal Article↗
PubMed2002

Parasite communities of freshwater fish under flood conditions.

The parasite communities of the freshwater fish species roach ( Rutilus rutilus), bitterling ( Rhodeus sericeus amarus) and perch ( Perca fluviatilis) were investigated during a major flood. Differences in parasite community structure due to changes in the host environment were expected. We therefore tested for differences in parasite species abundance and diversity as a consequence of the flood. Potential changes in parasite community structure due to seasonal influences were also considered. We found differences in the composition of parasite species and the proportion of ecto- and endoparasites in the three host species. The parasite community of roach was richer in species than those of perch and bitterling. Roach harboured more ectoparasite than endoparasite species. Parasite communities of both perch and bitterling were richer in endoparasite species and had a lower number of ectoparasite species. Parasite communities of the three different host species responded in different ways to environmental change. Considering all parasite species, no effect of either season or flood was found on the species diversity in either perch or bitterling. The flood caused an increase in the parasite species diversity in roach. For roach and perch, higher parasite abundance were found before the flood compared to after flood. However, no difference was found between the different seasons after the flood. By contrast, bitterling had the highest parasite abundance in the season after the flood. When analysing ecto- and endoparasites separately, a decrease in ectoparasite abundance was found in roach and perch, probably related to the flood, and due mainly to a decrease in monogenean species. A significant increase in the abundance of endoparasites was found in perch. In bitterling, the post-flood increase in ectoparasites was due to a high abundance of Gyrodactylus spp. We conclude that the parasite communities of the three fish species responded in different ways to the flood. This may be due to changes in the host life history strategy or in the immune response in conditions of stress.

Animals↗
PubMed1996

Long- and short-term flooding effects on survival and sink-source relationships of swamp-adapted tree species.

About 95% of swamp tupelo (Nyssa sylvatica var. biflora (Walt.) Sarg.) and sweetgum (Liquidambar styraciflua L.) seedlings survived continuous root flooding for more than two years, whereas none of the swamp chestnut oak (Quercus michauxii Nutt.) and cherrybark oak (Q. falcata var. pagodifolia Ell.) seedlings survived one year of flooding. Death of oak seedlings occurred in phases associated with periods of major vegetative growth, e.g., after bud burst in spring, after summer stem elongation, and during the winter deciduous stage, suggesting that stored reserves and sources were inadequate to maintain the seedlings when vegetative sinks were forming. Additional evidence that flooding induced a source deficiency in oak was that leaves of flooded oak were 65 to 75% smaller than leaves of nonflooded oak. Flooded swamp tupelo seedlings had a normal leaf size and patchy stomatal opening compared with nonflooded seedlings. Flooding caused increases in alcohol dehydrogenase (ADH) specific activity in taproot cambial tissues and increases in starch concentrations of swamp tupelo seedlings that were reversed when seedlings were removed from flooding. Flooding had little effect on soluble sugar concentrations in swamp tupelo or sweetgum. In the long-term flood-dry-flood treatment, in which all species had survivors, upper canopy leaf photosynthetic rates were higher in all species during the dry period than in nonflooded controls, whereas their starch and soluble sugars concentrations were similar to those of nonflooded controls. Based on seedling survival and the sink-source relationships, the order of flood tolerance was: swamp tupelo > sweetgum > swamp chestnut oak > cherrybark oak.

Journal Article↗
PubMed1999

Flood tolerance of four tropical tree species.

Many seasonally flooded habitats in the tropics are dominated by one or a few tree species. We tested the hypothesis that the inability to tolerate flooding restricts most species from becoming established in flood-prone habitats. We compared morphological and physiological responses to flooding in seedlings of Prioria copaifera Griseb., a species that forms monodominant stands in seasonally flooded habitats, and in three species confined to flood-free sites; namely, Calophyllum longifolium Willd., Virola surinamensis Aubl. and Gustavia superba (H.B.K.) Berg. Flooding reduced photosynthesis at Day 45 in all species by 10-30%. By Day 90, photosynthesis returned to the control rate in Prioria, but not in the other species. Flooding reduced stomatal conductance by 25-35% in all species except Calophyllum, and it reduced leaf area growth by 44% in Virola, but not in the other species. All species survived 90 days of flooding without mortality, leaf chlorosis, leaf necrosis, or leaf abscission. Flooding reduced root:shoot ratio significantly in Gustavia and Calophyllum, but not in the other species, and it reduced maximum root depth by 29% in Prioria, but by 61% or more in the species from flood-free habitats.

Journal Article↗
PubMed2004

Flooding, root temperature, physiology and growth of two Annona species.

The effects of root zone temperature (RZT) and flooding on physiology and growth of Annona glabra L. (pond apple) and A. muricata L. (soursop) were investigated. Trees planted in containers were exposed to RZTs of 5, 10, 20, 25 or 35 degrees C in controlled root temperature chambers. Trees at each RZT were either non-flooded (control) or continuously flooded. There were four replications over time for each treatment combination. Pond apple was more flood-tolerant than soursop. A combination of flooding and RZTs of 5 and 10 degrees C resulted in tree mortality of both species by Week 4. Only trees that appeared to develop morphological adaptations survived continuous flooding. In both species, net CO2 assimilation (A) decreased to nearly zero within 1 week following exposure to RZTs of 5 or 10 degrees C and became consistently negative over the remaining experimental period. Flooding reduced leaf chlorophyll index (measured with a SPAD meter), A and plant growth, and increased root electrolyte leakage from soursop. Optimum growth occurred at RZTs of 25 to 35 degrees C for non-flooded pond apple trees and at 20 to 25 degrees C for flooded trees. Soursop exhibited maximum growth at RZTs of 35 degrees C under non-flooded conditions and at 25 degrees C under flooded conditions.

Annona↗
PubMed2002

Reinforcing flood-risk estimation.

Flood-frequency estimation is inherently uncertain. The practitioner applies a combination of gauged data, scientific method and hydrological judgement to derive a flood-frequency curve for a particular site. The resulting estimate can be thought fully satisfactory only if it is broadly consistent with all that is reliably known about the flood-frequency behaviour of the river. The paper takes as its main theme the search for information to strengthen a flood-risk estimate made from peak flows alone. Extra information comes in many forms, including documentary and monumental records of historical floods, and palaeological markers. Meteorological information is also useful, although rainfall rarity is difficult to assess objectively and can be a notoriously unreliable indicator of flood rarity. On highly permeable catchments, groundwater levels present additional data. Other types of information are relevant to judging hydrological similarity when the flood-frequency estimate derives from data pooled across several catchments. After highlighting information sources, the paper explores a second theme: that of consistency in flood-risk estimates. Following publication of the Flood estimation handbook, studies of flood risk are now using digital catchment data. Automated calculation methods allow estimates by standard methods to be mapped basin-wide, revealing anomalies at special sites such as river confluences. Such mapping presents collateral information of a new character. Can this be used to achieve flood-risk estimates that are coherent throughout a river basin?

Climate↗
PubMed2002

Ecological response to and management of increased flooding caused by climate change.

River channels and their flood plains are among the most naturally dynamic ecosystems on earth, in large part due to periodic flooding. The components of a river's natural flood regime (magnitude, frequency, duration and timing of peak flows) interact to maintain great habitat heterogeneity and to promote high species diversity and ecosystem productivity. Flood regimes vary within and among rivers, depending on catchment size, geology and regional hydroclimatology. Geographic variation in contemporary flood regimes results in river-to-river variation in ecosystem structure, and therefore in potential river ecosystem response to increased future flooding. The greater the deviation in flood regime from contemporary or recent historical conditions, the greater the expected ecological alteration. Ecological response will also depend on how extensively humans have altered natural river dynamics through land-use practices. Examples of human-caused changes in flood regime (e.g. urbanization, agricultural practices) provide analogues to explore the ecological implications of region-specific climate change. In many settings where humans have severely modified rivers (e.g. through leveeing), more frequent larger floods will work to re-establish connections with severed flood-plain and riparian wetlands in human-dominated river valleys. Developing and implementing non-structural flood-management policies based on ecological principles can benefit river ecosystems, as well as human society.

Climate↗
PubMed1991

Public perception of the risks of floods: implications for communication.

Floods in the U.S. kill an average of 162 people each year and cause $3.4 billion in property damage. Flood control programs have been successful in lowering, but not eliminating, the risks to lives and property. Since the late 1960s, the federal government has emphasized flood insurance as a primary tool for improving location and flood-proofing decisions, as well as for reimbursing flood losses. Since only 12.7% of houses in flood plain areas are covered by flood insurance, the program has been ineffective. We interviewed people living in three communities that had recently been flooded. Most people had little knowledge of the cause of floods or what could be done to prevent damage. People who work and who are better educated know more and are more likely to have flood insurance. Current government publications about flood risks are not likely to be understood by those at risk. There is little effective communication about the nature and magnitude of the risks and what individuals can do to protect their lives and property and lower their financial risks. The risk management program should both emphasize communication and enforcement of the current law requiring people at risk who hold federally funded loans to be insured.

Communication↗
PubMed2002

Flooding influences ovipositional and feeding behavior of the rice water weevil (Coleoptera: Curculionidae).

The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is the most destructive insect pest of rice in the United States. As part of an effort to develop strategies to manage this pest, the ovipositional and feeding habits of L. oryzophilus on rice plants subjected to different flooding treatments were characterized in greenhouse studies. Presence and depth of flood had a direct influence on the ovipositional behavior of weevils in no-choice studies. More eggs were found in flooded plants than in unflooded plants. Moreover, plants flooded to a depth of 5.1 cm received more eggs than plants flooded to depths of 1.3 or 10.2 cm. Presence and depth of flood influenced both the proportion of females that oviposited in plants and the number of eggs laid by those females that did oviposit. In choice studies, female weevils showed a marked ovipositional preference for plants flooded to a depth of 10.2 cm over unflooded plants and plants flooded to a depth of 1.3 cm. In separate choice experiments, adult rice water weevils fed more on flooded plants than on unflooded plants. In a third set of experiments, flooded plants were taller and had higher concentrations of 10 of 13 plant nutrients than unflooded plants. Thus, flooding may influence rice water weevil behavior both directly, by acting as a stimulus for feeding or oviposition, and indirectly, by inducing changes in the suitability of rice plants for feeding or oviposition. These data suggest that it may be possible to manipulate populations of weevils in rice by changing water management practices.

Animals↗
PubMed2006

The health effects of flooding: Social research results from England and Wales.

This paper presents interview survey data by social scientists using established health measures on the health effects of flooding for residents in 30 locations in England and Wales. Firstly, it examines the extent to which flooded residents reported suffering physical and psychological health effects during and after the event. Secondly, it explores the issue of whether these effects were long-lasting by comparisons with the general population and with those at risk but not flooded. In the study, about two thirds of the flood victims were found to have scores on the General Health Questionnaire-12 scale indicative of mental health problems (scores of 4+) at their worst time after flooding. The evidence of the study also suggests that some flood victims suffered long term mental health effects as a result of their experience of flooding. The study examines the influence of a wide range of factors: characteristics of the flood event, types of property, and socio-demographic and the intervening factors such as the extent of family or community support that may explain the health effects of flooding. It finds that a complex set of social and other factors are involved and that some factors susceptible to human intervention such as having adequate flood insurance cover are important factors in the stress experienced by flood victims.

Adolescent↗
PubMed2000

Wet-to-dry ratio of lung tissue and surfactant outwash after one-lung flooding.

Unilateral flooding of the lung after intubation with a double-lumen tube enables intraoperative sonography of the lung tissue. The flooding restricts the pulmonary blood stream of the flooded lung in a relevant degree and thus reduces the right-to-left shunt volume. The deficient perfusion of the lung tissue during the flooded phase might cause capillary permeability disorders and secondary oedema development. This can be determined by examination of extravascular lung water (EVLW) after draining and reventilation of the flooded lung. Although one-time unilateral lung flooding must be distinguished from bronchopulmonary lavage, it is interesting to study the effects of flooding on the surfactant system. The wet-to-dry ratio of the lung tissues of 13 female pigs was ascertained at different times following one-lung flooding (1 to 11 weeks). A trend towards an increased wet-to-dry ratio in the previously flooded lung was found only in the tissue samples taken 1 h after reventilation. After only 24 h, the two lungs no longer differed in their wet-to-dry ratio. In six pigs, the phospholipid content of the drained flooding liquid was determined. It was shown that the surfactant loss caused by flooding was maximally 47% of the calculated surfactant pool of the respective lung.

Animals↗
PubMed2005

Partial flooding enhances aeration in adventitious roots of black willow (Salix nigra) cuttings.

Black willow (Salix nigra) cuttings are used for streambank stabilization where they are subjected to a range of soil moisture conditions including flooding. Flooding has been shown to adversely impact cutting performance, and improved understanding of natural adaptations to flooding might suggest handling and planting techniques to enhance success. However, data assessing the root aeration in adventitious roots that are developed on cuttings of woody species are scant. In addition, it appears that no data are available regarding aeration of the root system under partially flooded conditions. This experiment was designed to examine the effects of continuous flooding (CF) and partial flooding (PF) on aerenchyma formation and radial oxygen loss (ROL) in black willow cuttings. Photosynthetic and growth responses to these conditions were also investigated. Under laboratory condition, replicated potted cuttings were subjected to three treatments: no flooding (control, C), CF, and PF. Water was maintained above the soil surface in CF and at 10 cm depth in PF. Results indicated that after the 28-d treatments, root porosity ranged between 28.6% and 33.0% for the CF and C plants but was greater for the PF plants (39.2% for the drained and 37.2% for the flooded portions). A similar response pattern was found for ROL. In addition, CF treatment led to decreases in final root biomass and root/shoot ratio. Neither CF nor PF had any detectable adverse effects on plant gas exchange or photosystem II functioning. Our results indicated that S. nigra cuttings exhibited avoidance mechanisms in response to flooding, especially the partially flooded condition which is the most common occurrence in riparian systems.

Oxygen↗
PubMedDate not supplied

Communication and health protection issues arising from a flooding emergency.

OBJECTIVE: To identify and describe the key communication and health protection issues surrounding a flooding emergency. METHODS: A telephone questionnaire was used to assess health and safety information sources, information recalled, and behavioral responses among residents of the town of Feilding, New Zealand following a major flood in February 2004. This was supplemented by key informant interviews and a newspaper content analysis. RESULTS: A total of 154 adult residents were surveyed (76% of those successfully contacted and eligible). Of the respondents, 79% recalled being provided with health and safety information from authorities. The major sources were: radio (41%), pamphlets (23%), and newspapers (20%). The regional newspaper had extensive coverage of this flooding emergency but "health" only was mentioned in 46 (7%) of the 664 flood-related articles. Of those who recalled receiving information from authorities, most (89%) perceived that it was adequate. Nevertheless, 18% actively sought out information (mainly about water safety and availability). In the post-flood period, 73% of all respondents boiled water; however, only 4% maintained boiling water or bottled water use for the necessary nine-week period. Some forms of emergency preparations did not change substantially from before the flood, compared to four months afterwards (e.g., having a radio with batteries increased from 62% to 68%). Perceived health concerns around the flooding were low, though 59% were concerned about the risk of water contamination. Actual self-reported, health consequences from the flood were rare, as only two (1%) people out of 154 reported flood-related health problems. CONCLUSIONS: Health and safety information generally was communicated successfully and was regarded as appropriate by the population of this flood-affected town. Nevertheless, there are further improvements needed in the emergency response by both residents and authorities.

Adult↗
PubMed2003

Using NOAA AVHRR data to assess flood damage in China.

The article used two NOAA-14 Advanced Very High Resolution Radiometer (AVHRR) datasets to assess flood damage in the middle and lower reaches of China's Changjiang River (Yangtze River) in 1998. As the AVHRR is an optical sensor, it cannot penetrate the clouds that frequently cover the land during the flood season, and this technology is greatly limited in flood monitoring. However the widely used normalized difference vegetation index (NDVI) can be used to monitor flooding, since water has a much lower NDVI value than other surface features. Though many factors other than flooding (e.g. atmospheric conditions, different sun-target-satellite angles, and cloud) can change NDVI values, inundated areas can be distinguished from other types of ground cover by changes in the NDVI value before and after the flood after eliminating the effects of other factors on NDVI. AVHRR data from 26 May and 22 August, 1998 were selected to represent the ground conditions before and after flooding. After accurate geometric correction by collecting GCPs, and atmospheric and angular corrections by using the 6S code, NDVI values for both days and their differences were calculated for cloud-free pixels. The difference in the NDVI values between these two times, together with the NDVI values and a land-use map, were used to identify inundated areas and to assess the area lost to the flood. The results show a total of 358,867 ha, with 207,556 ha of cultivated fields (paddy and non-irrigated field) inundated during the flood of 1998 in the middle and lower reaches of the Changjiang River Catchment; comparing with the reported total of 321,000 and 197,000 ha, respectively. The discrimination accuracy of this method was tested by comparing the results from two nearly simultaneous sets of remote-sensing data (NOAA's AVHRR data from 10 September, 1998, and JERS-1 synthetic aperture radar (SAR) data from 11 September, 1998, with a lag of about 18.5 hr) over a representative flooded region in the study area. The results showed that 67.26% of the total area identified as inundated using the NOAA data was also identified as inundated using the SAR data.

Atmosphere↗
PubMed2003

No upward trends in the occurrence of extreme floods in central Europe.

Extreme river floods have been a substantial natural hazard in Europe over the past centuries, and radiative effects of recent anthropogenic changes in atmospheric composition are expected to cause climate changes, especially enhancement of the hydrological cycle, leading to an increased flood risk. For the past few decades, however, observations from Europe do not show a clear increase in flood occurrence rate. Here we present longer-term records of winter and summer floods in two of the largest rivers in central Europe, the Elbe and Oder rivers. For the past 80 to 150 yr, we find a decrease in winter flood occurrence in both rivers, while summer floods show no trend, consistent with trends in extreme precipitation occurrence. The reduction in winter flood occurrence can partly be attributed to fewer events of strong freezing-following such events, breaking river ice at the end of the winter may function as a water barrier and enhance floods severely. Additionally, we detect significant long-term changes in flood occurrence rates in the sixteenth to nineteenth centuries, and conclude that reductions in river length, construction of reservoirs and deforestation have had minor effects on flood frequency.

Journal Article↗
PubMed1995

Physiological, morphological and anatomical responses of Fraxinus mandshurica seedlings to flooding.

Two-year-old Fraxinus mandshurica Rupr. var. japonica Maxim. seedlings were flooded to 8 cm above soil level for 70 days. The flooding treatment altered the growth, morphology, stem anatomy and ethylene production of the seedlings. Although flooding did not affect height growth, it stimulated diameter growth of the submerged stems by increasing both the number and size of wood fibers produced; however, the thickness of the cell walls of the wood fibers was reduced by flooding. In response to the flooding treatment, the seedlings formed abundant hyperhydric tissues, originating from the vicinity of lenticels on the surface of the flooded stems, and adventitious roots, which grew through the hyperhydric tissues. Aerenchyma tissues were observed in the bark of the adventitious roots. The flooding treatment did not affect dry weight increment of leaves and stems, but it reduced the total dry weight increment of the root system even though it promoted adventitious root formation. Flooding also enhanced ethylene production in the submerged portions of stems. The potential roles of flood-induced ethylene in cambial growth and adventitious root formation in flooded plants are discussed.

Journal Article↗
PubMedDate not supplied

Mortality from flash floods: a review of national weather service reports, 1969-81.

Of all weather-related disasters that occur in the United States, floods are the main cause of death, and most flood-related deaths are attributed to flash floods. Whenever a weather-related disaster involves 30 or more deaths or more than $100 million in property damage, the National Weather Service (NWS) forms a survey team to investigate the disaster and write a report of findings. All NWS survey reports on flash floods issued during 1969-81 were reviewed to determine the mortality resulting from such floods, the effect of warnings on mortality, and the circumstances contributing to death. A total of 1,185 deaths were associated with 32 flash floods, an average of 37 deaths per flash flood. The highest average number of deaths per event was associated with the four flash floods in which dams broke after heavy rains. Although there were 18 flash floods in 1977-81 and only 14 in 1969-76, the number of deaths was 2 1/2 times greater during the earlier period. More than twice as many deaths were associated with flash floods for which the survey team considered the warnings inadequate than with those with warnings considered adequate. Ninety-three percent of the deaths were due to drowning and 42 percent of these drownings were car related. The other drownings occurred in homes, at campsites, or when persons were crossing bridges and streams. The need for monitoring dams during periods of heavy rainfall is highlighted.

Disasters↗