37,177 research outputs found
Long-term strategies for flood risk management: scenario definition and strategic alternative design
No full textThis report reviews some mainstream existing methods of scenario development and use, as well as experiences with the design and assessment of strategic alternatives for flood risk management. Next, a procedure and methods are proposed and discussed. Thirdly, the procedure and methods are tried on the Schelde Estuary and the Thames Estuary and, finally, conclusions are draw
FLOOD EASEMENTS
No full textWe examine the efficiency of current flood risk allocation and the use of flood easements as a means of reallocating flood risk and reducing total flood damages in large river floodplains. Changes in agricultural floodplain land use and levels of crop insurance coverage as the risk of flooding changes are simulated using mathematical programming. The net benefits of flood easements to a portion of the Lagrange Reach of the Illinois River region are then simulated. Our results indicate that flood easements may provide positive net benefits. This positive result stems primarily from the decreased risk of flooding for non-inundated agricultural levee districts, rather than from reduced municipal flood damages. Our results are robust to changes in the estimated dollar damages, yet extremely sensitive to changes in hydrological estimates.Resource /Energy Economics and Policy,
Environmental Determinants of Housing Prices: The Impact of Flood Zone Status
No full textThis study examines the valuation of homes located within 100-year flood plains. Utilizing a database of 29,887 property transactions in Alachua County, Florida, the results of this investigation suggest that comparable characteristic homes located within a flood zone sell, on average, for less than homes located outside flood zones. Interestingly, the price differential is less than the present value of future flood insurance premiums. In addition, the price differential is shown to have increased since passage of the National Flood Insurance Reform Act of 1994. Finally, it appears that property tax assessors have slightly over-assessed properties located in flood zones relative to those in other areas. The large database and the lengthy period of analysis (1980–1997) are much broader than that of previous research efforts.
Flood damage, vulnerability and risk perception - challenges for flood damage research
No full textThe current state-of-the-art in flood damage analysis mainly focuses on the economic evaluation of tangible flood effects. It is contended in this discussion paper that important economic, social and ecological aspects of flood-related vulnerabilities are neglected. It is a challenge for flood research to develop a wider perspective for flood damage evaluation. --Flood damage analysis,flood vulnerability,risk perception,cost-benefit analysis,integrated assessment
Hydrologic versus geomorphic drivers of trends in flood hazard
No full textThis work was partially supported by a NERC studentship to LJSFlooding is a major hazard to lives and infrastructure, but trends in flood hazard are poorly understood. The capacity of river channels to convey flood flows is typically assumed to be stationary, so changes in flood frequency are thought to be driven primarily by trends in streamflow. We have developed new methods for separately quantifying how trends in both streamflow and channel capacity have affected flood frequency at gauging sites across the USA. Flood frequency was generally nonstationary, with increasing flood hazard at a statistically significant majority of sites. Channel capacity driven changes in flood hazard were smaller, but more numerous, than those driven by streamflow. Our results demonstrate that accurately quantifying changes in flood hazard requires accounting separately for trends in both streamflow and channel capacity. They also show that channel capacity trends may have unforeseen consequences for flood management and for estimating flood insurance costs.Peer reviewe
Applications of statistics in flood frequency analysis
No full textEstimation of the probability of occurrence of future flood events at one
or more locations across a river system is frequently required for the design of
bridges, culverts, spillways, dams and other engineering works. This study
investigates some of the statistical aspects for estimating the flood frequency
distribution at a single site and on regional basis.
It is demonstrated that generalized logistic (GL) distribution has many
properties well suited for the modelling of flood frequency data. The GL
distribution performs better than the other commonly recommended flood frequency
distributions in terms of several key properties. Specifically, it is capable of
reproducing almost the same degree of skewness typically present in observed
flood data. It appears to be more robust to the presence of extreme outliers in the
upper tail of the distribution. It has a relatively simpler mathematical form. Thus all
the well known methods of parameter estimation can be easily implemented.
It is shown that the method of probability weighted moments (PWM)
using the conventionally recommended plotting position substantially effects the
estimation of the shape parameter of the generalized extreme value (GEV)
distribution by relocating the annual maximum flood series. A location invariant
plotting position is introduced to use in estimating, by the method of PWM, the
parameters of the GEV and the GL distributions.
Tests based on empirical distribution function (EDF) statistics are
proposed to assess the goodness of fit of the flood frequency distributions. A
modified EDF test is derived that gives greater emphasis to the upper tail of a
distribution which is more important for flood frequency prediction. Significance
points are derived for the GEV and GL distributions when the parameters are to be
estimated from the sample data by the method of PWMs. The critical points are
considerably smaller than for the case where the parameters of a distribution are
assumed to be specified. Approximate formulae over the whole range of the
distribution for these tests are also developed which can be used for regional
assessment of GEV and GL models based on all the annual maximum series
simultaneously in a hydrological region.
In order to pool at-site flood data across a region into a single series for
regional analysis, the effect of standardization by at-site mean on the estimation of
the regional shape parameter of the GEV distribution is examined. Our simulation
study based on various synthetic regions reveals that the standardization by the at-site
mean underestimates the shape parameter of the GEV by about 30% of its true
value and also contributes to the separation of skewness of observed and simulated
floods. A two parameter standardization by the at-site estimates of location and
scale parameters is proposed. It does not distort the shape of the flood frequency
data in the pooling process. Therefore, it offers significantly improved estimate of
the shape parameter, allows pooling data with heterogeneous coefficients of
variation and helps to explain the separation of skewness effect.
Regions on the basis of flood statistics L-CV and USKEW are derived
for Scotland and North England. Only about 50% of the basins could be correctly
identified as belonging to these regions by a set of seven catchment characteristics.
The alternative approach of grouping basins solely on the basis of physical
properties is preferable. Six physically homogeneous groups of basins are
identified by WARD's multivariate clustering algorithm using the same seven
characteristics. These regions have hydrological homogeneity in addition to their
physical homogeneity. Dimensionless regional flood frequency curves are produced
by fitting GEV and GL distributions for each region. The GEV regional growth
curves imply a larger return period for a given magnitude flood. When floods are
described by GL model the respective return periods are considerably smaller
An analysis of the determinants of flood damages
No full textIn this paper we analyze mortality caused by 2,194 large flood events between 1985 and 2008 in 108 countries. Unlike previous studies that looked at natural-disaster mortality, we find that year-to-year changes in income and institutional determinants of vulnerability do not affect flood mortality directly. Income and institutions influence mortality only indirectly, through their impact on the intensity and frequency of floods. Population exposure affects the number of deaths both directly and indirectly. Higher population exposure results in more deaths once the flood has occurred, but it is associated with smaller floods. In developing countries it also reduces the count of floods.Natural Disasters, Floods, Mortality, Adaptation, Climate Change, Environmental Economics and Policy, International Development, Land Economics/Use, Risk and Uncertainty, Q54,
Flood perception and mitigation: The role of severity, agency, and experience in the purchase of flood protection, and the communication of flood information
No full textProtection of human life and property from flooding is a strategic priority in
the UK. We examine how to encourage home owners to protect themselves and their
residences. A model of factors that influence the decision to buy flood
protection devices is tested using survey data from 2,109 home owners. The
results showed that the majority of respondents have not purchased domestic
flood protection (N=1,732; 82.1%). Purchase of flood protection devices was
influenced by age; perceived seriousness; and beliefs about, and trust in, the
role of regulators in managing flooding. In younger respondents, the perceived
seriousness of the dangers of flooding acted as precursors and barriers to
action depending on individual sense of responsibility and agency. The second
part of the study examined responsiveness to information. Information about
flooding alone was insufficient to promote behavioural change, particularly
among people who have not experienced a flood or who believe that they are not
in a flood zone. Implications for understanding flood protection, managing
agency issues, and flood communication campaigns are discussed
Flood Mapping and Flood Dynamics of the Mekong Delta: ENVISAT-ASAR-WSM Based Time Series Analyses
No full textSatellite remote sensing is a valuable tool for monitoring flooding. Microwave sensors are especially appropriate instruments, as they allow the differentiation of inundated from non-inundated areas, regardless of levels of solar illumination or frequency of cloud cover in regions experiencing substantial rainy seasons. In the current study we present the longest synthetic aperture radar-based time series of flood and inundation information derived for the Mekong Delta that has been analyzed for this region so far. We employed overall 60 Envisat ASAR Wide Swath Mode data sets at a spatial resolution of 150 meters acquired during the years 2007–2011 to facilitate a thorough understanding of the flood regime in the Mekong Delta. The Mekong Delta in southern Vietnam comprises 13 provinces and is home to 18 million inhabitants. Extreme dry seasons from late December to May and wet seasons from June to December characterize people’s rural life. In this study, we show which areas of the delta are frequently affected by floods and which regions remain dry all year round. Furthermore, we present which areas are flooded at which frequency and elucidate the patterns of flood progression over the course of the rainy season. In this context, we also examine the impact of dykes on floodwater emergence and assess the relationship between retrieved flood occurrence patterns and land use. In addition, the advantages and shortcomings of ENVISAT ASAR WSM based flood mapping arediscussed. The results contribute to a comprehensive understanding of Mekong Delta flood dynamics in an environment where the flow regime is influenced by the Mekong River, overland water-flow, anthropogenic floodwater control, as well as the tides
The Cork City Flood of November 2009 : lessons for flood risk management and climate change adaptation at the urban scale
No full textFlood hazards are a pressing challenge in several Irish and European cities and their impacts seem likely to intensify as climate change brings sea level rise, changes in storm patterns and increases in rainfall. Drawing on the example of Cork City and the November 2009 flood in particular, this paper evaluates contemporary policy and decision-making responses to flood hazards to determine whether they are sufficient to address current and future flood risks and vulnerabilities. It is clear that current policy and practice remains heavily influenced by a risk management paradigm that emphasises physical exposure and largely ignores socio-economic vulnerability. Floods and the losses they induce are seen as identical while engineering and technological fixes are viewed as the optimal means of reducing future flood losses. This framing of flood hazards is shaped by several influences including the historic evolution of flood policy and current institutional structures. The November 2009 flood highlights the limits of current policy and practice. Recent changes in national and European policy may also prove to be ineffective in facilitating effective adaptation and further changes in policy and practice are likely to be required
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