Modeling flooding extent from Hurricane Floyd in the coastal plains of North Carolina

Abstract

In this article two modeling approaches were developed based on the use of US Geological Survey digital elevation model (DEM) data. These models were utilized to delineate the extent of flooding induced by precipitation from Hurricane Floyd in a portion of Pitt County, North Carolina. The patterns of flood extent derived from the two models were compared to the extent of flooding indicated on a digital aerial photograph taken two days after peak flood levels had been reached. In addition, floodplain boundaries based on Federal Emergency Management Agency Q3 maps were compared to the extent of flooding on the aerial photo. Actual emergency response operations undertaken through the Pitt County Emergency Operations Center during the flood event are described, and are used to provide a context for evaluating the potential utility of these models. The flood extents produced by the modeling methods performed well at representing the actual extent of the flooding.     

Optimisation patterns for the process of a planned evacuation in the event of a flood

ABSTRACT

The main purpose of the article is to develop an optimisation pattern for the process of a preventive evacuation of people from flood-risk areas (at the first sign of a flood), aimed at mitigating the negative effects of the flood performed through the application of modern computer tools. It has been assumed that the use of both GIS tools and apps for vehicle traffic modelling (the research includes the use of a method developed by the authors) in emergency procedures implemented in response to a flood may increase the efficiency of the anti-flood campaign (here: the evacuation of residents from flooded areas), and thus, it may also minimise the negative effects of the flooding itself. The article distinguishes 14 stages of research, which were chiefly completed by means of the following methods: distance-based accessibility, cumulative accessibility, the Enhanced Two-Step Floating Catchment Area Method (E2SFCA) and the Two-Step Floating Catchment Area Method (2SFCA), the vehicle routing method, algorithms by Dinitz, Edmonds-Karp, and Ford-Fulkerson, and a comparative method applied to draw a comparison between the actual state of affairs and the optimum condition determined by the aforementioned methods.     

Floods on opposite German borders

Abstract

The Rhine and the Oder rivers have many similarities. Both are subject to comparable hydroclimate regimes, are flood prone, are international waterways and have been extensively modified by humans over many hundreds of years. Yet the recent history of flooding on the German sections of these rivers is distinctively different. Most communities along the Rhine seem to take floods in stride whereas along the Oder they have been highly disruptive. The disruption has provided a mechanism for helping to integrate disparate parts of the newly reunified German states emergency management system and has highlighted continuing differences between Polish and German flood experiences.     

Improving flood warnings in Europe: a research and policy agenda

Abstract

Warnings and emergency planning for flooding are based on the reality that no matter how thorough our investigations and flood prevention efforts through engineered structural works or land use management, some risk will always remain. This paper examines recent experience with flood warnings in the UK and continental Europe. It combines this experience with an overview of the relevant literature to identify lessons for incorporation into policy, and problem areas which would most obviously benefit from additional research. Throughout, the emphasis is on the non-engineering aspects of warning systems. Results indicate that much is being achieved in terms of the detail of warning design, but the broader issues seem to be largely ignored by both the research literature and practice. First among these broader issues is the failure, by those charged with warning system development and operation, to conceptualise the warning task as one based explicitly on the needs of those at risk. Making this happen will require the development of processes to build the necessary culture of cooperation and learning among the many organisations involved.     

Flood disaster monitoring and evaluation in China

Abstract

China frequently experiences natural disasters, of which flooding is the most serious. How to monitor and control natural disasters, assess damage, and provide relief is the most urgent problem for the Chinese government and disaster experts. A national integrated system using remote sensing, geographic information systems, the Global Positioning System, and other technology for monitoring and evaluating flood disasters has been assembled and tried out for 3 years. The system has played an important role in flood mitigation during the trial and has become a key part of the flood management system at China's National Flood Control Headquarters. This paper presents an overview of the system and its use in China.     

Flood management in Canada at the crossroads

Abstract

Although Canadian flood management efforts have gained worldwide recognition, flood damages continue to increase. The current practice for preventing, responding to and recovering from floods in Canada is described by focusing attention on the 1997 Red River and 1996 Saguenay River floods. A set of cultures is identified that contribute to the trend of increasing flood damages. These include a culture of conflict, a culture of land development, a culture that impeded native people from easily implementing flood management programs, a culture of institutional fragmentation and a culture of dependency. These foster an inevitable cycle of increasing flood damages. The potential of recent proposals made by Emergency Preparedness Canada and the Insurance Bureau of Canada to address these cultures is assessed. While these documents represent significant progress, they continue to adopt an intermittent project rather an ongoing program perspective, fail to identify the need to adopt specific initiatives tailored for aboriginal communities, and ignore the need to enhance the operational capacity of relevant public and private participants. Addressing these requirements will further reduce future losses and vulnerability.     

Local perception of infrequent,extreme upland flash flooding: prisoners of experience?

The United Kingdom has experienced several exceptional summer flash floods in recent years and there is growing concern about the frequency of such events and the preparedness of the population. This paper uses a case study of the upper Ryedale flash flood (2005) and questionnaire and interview data to assess local perceptions of upland flash flooding. Experience of a major flash flood may not be associated with increased flood risk perception. Despite local residents’ awareness of a trend towards wetter summers and more frequent heavy rainfall, the poor maintenance of rivers was more frequently thought to be a more significant factor influencing local flood risk than climate change. Such findings have important implications for the potential success of contemporary national flood policies, which have put greater emphasis on public responsibility for responding to flooding. This study recommends, therefore, the use of fresh participatory approaches to redistribute and raise awareness of locally‐held flood knowledge.     

Risk factors for driving into flooded roads

Motor vehicle-related deaths account for more than half of all flood fatalities in the United States, but to date, very little is known about the risk factors associated with why people drive into flooded roads. Using data from survey questionnaires administered in Denver, CO, and Austin, TX, this paper suggests that people who do not take warnings seriously are more likely to drive through flooded roads, as are people aged 18–35, and those that do not know that motor vehicles are involved in more than half of all flood fatalities. In Denver, people who have not experienced a flood previously and those who do not know they live in flood-prone areas are also more likely to drive into flooded roads.     

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.     

Have flood mortality qualitative characteristics changed during the last decades? The case study of Greece

Despite the dramatic increase in recorded flood events in Greece in the last decades, recent findings show that related mortality does not show a corresponding rise. This work develops and studies a database of flood-related fatalities to investigate qualitative changes in flood mortality in the country between 1960 and 2010. Observations show a shift in the circumstances under which fatal incidents occurred and in the demographics of the victims. In particular, indoor fatalities and cases in urban environments gradually decrease in favour of incidents occurring outdoors, in rural settings, mostly using motor vehicles. The number of fatalities per flood event show a decline, indicating that multiple-fatality incidents are gradually disappearing and that advances in protection have an impact on mortality. The increase in the use of vehicles, the improvements in the structural integrity of buildings and the advances in early warning and civil protection practices are found to influence mortality both in qualitative and in quantitative terms.     

The 1934 floods in Tabriz, N. W. Iran

The disastrous floods of July 1934 in Tabriz are examined in the context of the history of floodinginthe city, which is crossed by a dry stream bed liable to sudden Inundation by mountain torrents from the southeast. Few details of past events have survived, suggesting that relatively little significance has been attached to them. Typically, flood dykes were inadequately maintained. This neglect, combined with a radical alteration in urban topography after 1925, when broad straight avenues were constructed through the old heart of the city, led to serious losses from flooding twice in 1929 and again in 1934. Enhanced perception of the flood risk finally found expression in the adoption of large scale engineering measures to mitigate future events, including strengthening protective dykes and widening the river channel through the city. These works have reduced vulnerability to flooding from river overflow. No long-term detrimental Impact of the 1934 flood has been observed. Some of the physical and social parameters that have influenced the vulnerability of Tabrizinthe past continue to be present both there and elsewhere in Iran, and they may be characteristic also of other regions with comparable natural environments or in a similar stage of socio-economic development.     

Risk factors for driving into flooded roads

Motor vehicle-related deaths account for more than half of all flood fatalities in the United States, but to date, very little is known about the risk factors associated with why people drive into flooded roads. Using data from survey questionnaires administered in Denver, CO, and Austin, TX, this paper suggests that people who do not take warnings seriously are more likely to drive through flooded roads, as are people aged 18–35, and those that do not know that motor vehicles are involved in more than half of all flood fatalities. In Denver, people who have not experienced a flood previously and those who do not know they live in flood-prone areas are also more likely to drive into flooded roads.     

Flood insurance and floodplain management: the US experience

Abstract

With over six million buildings located within the boundaries of the 100-yr floodplain, flood losses across the United States are widespread (88% of US counties experienced at least one flood disaster during the second half of the twentieth century). To deal with this problem, the federal government provides flood insurance through the National Flood Insurance Program, which was initiated by Congress in 1968 and amended significantly in 1969, 1973, and 1994. This article describes the US approach to flood insurance and notes a number of problems that have limited its effectiveness. Flood hazard identification is incomplete, and methods used are flawed. Mitigation has failed to contain increasing exposure to property damage in floods and coastal storms, and it has failed to markedly reduce exposure to loss of older buildings located in flood hazard areas. Market penetration of flood insurance is low, in spite of mandatory purchase requirements for new construction and the availability of subsidized insurance rates for older buildings located in flood-hazard areas. These problems, although serious, can be remedied through a variety of actions taken by governments at the federal, state, and local level.     

Urban riverbank residents’ evaluation of flood evacuation policies in Winnipeg, Manitoba, Canada

The results of a discrete choice experiment (DCE) as a part of a survey among the urban riverbank residents on the Red River in Winnipeg, Manitoba, Canada, indicated that the risk of over-dike flooding, set at 2 ft above the 1997 flood water level, was a significant determinant of both voluntary and mandatory evacuation, compared to those set at the 1996 or 1997 levels. Mandatory evacuation was more preferred over voluntary evacuation when the likelihood of flooding was at its most severe, and the opposite relationship was the case when the likelihood was low. The notification time for evacuation, suggested as 1, 2, and 4 days, proved to be an insignificant attribute, whereas the respondents indicated significant preference for full flood compensation over an offer of either 80% or 90% flood relief, irrespective of the alternatives of voluntary or mandatory evacuation.     

The consequences and policy implications of urban encroachment into flood-risk areas: the case of Ibadan

Urban encroachment on floodplains has exacerbated flood disasters owing to the reduction in the floodplain’s capacity to mitigate flooding, thereby bringing more settlements and people at flood risk. This study examined the consequences and policy implications of urban encroachment into Ibadan’s flood-risk areas. The survey-based study relied on primary and secondary data, with multistage sampling procedures selecting 15% of the flood-affected buildings in 2011, from which a structured questionnaire was administered to 402 households. The study revealed that the institutional arrangements with respect to responsibilities, regulations and control of urban floodplains were fragmented and non-participatory. At least 62% of all the affected buildings encroached into the statutory setbacks to rivers. Household property lost/damaged included domestic goods (75%), domestic animals and pets (60%), working instruments/machines (31%), the source of domestic water (34%) and vehicles (29%). Strong direct correlations were found between the urban and peri-urban communities in (1) the number of damaged/lost property and (2) the number of households that suffered health-related challenges. The paper recommends that the overall co-ordination of flood management activities be entrusted to an institution that can assume responsibility for legal, technical, administrative and financial matters related to urban planning and flood-risk management.     

Mapping social vulnerability to flood hazard in Norfolk,England

In this paper, we present a method to assess social vulnerability through the creation of an Open Source Vulnerability Index (OS-VI). The OS-VI provides context to environmental hazards and allows NGOs and local agencies to better tailor services and provide targeted pre-emptive vulnerability reduction and resilience-building programmes. A deductive indicator-based approach is utilised to incorporate a wide range of vulnerability indicators known to influence vulnerability. Unlike many vulnerability indices, the OS-VI incorporates flood risk as well as the loss of capabilities and the importance of key services (health facilities and food stores) through the measurement of accessibility when determining an area's level of social vulnerability. The index was developed using open-source mapping and analysis software and is composed completely of open-source data from national data sets. The OS-VI was designed at the national level, with data for all proxy indicators available across the entirety of England and Wales. For this paper, a case study is presented concerned with one English county, Norfolk.

Highlights

• We produce an open-source vulnerability index.

• Accessibility to health care found to be severely affected by flooding.

• High vulnerability areas found to be disproportionately impacted by flooding.

• Urban extent of an area found to increase its level of vulnerability.

• Flood affected areas more likely to be composed of elderly, sick and poor.

     

Urbanisation and flood vulnerability in the peri-urban interface of Mexico City

Chronic flooding in the Chalco valley, state of Mexico, Mexico, is the outcome of past and present socio‐environmental changes which have taken place in Mexico City's south‐eastern peri‐urban interface. This flooding is the result of a complex interaction between urbanisation in an ex‐lacustrine area, permanent ecological deterioration and ground subsidence, poor sanitation and inadequate policy responses. Far from solving the flooding problem, short‐term policy responses have created increasingly unsafe conditions for current residents. A socio‐historical analysis of disasters reveals the importance of taking into consideration particular social actors and institutions in hazard generation and flood vulnerability over time. This paper analyses three aspects of this flooding: first, the importance of approaching floods from a socio‐historical perspective; second, the relation between urbanisation, former policies and flood risk generation; and third, current policy responses to and the failure in the risk management of La Compañía Canal.     

Flash flood mitigation: recommendations for research and applications

Abstract

New technologies promise reduced flash flood losses. However, real-time observations with vast multi-sensor networks, more precise mapping capabilities using remote sensing and GIS, quicker hydrological and meteorological models, and increasing forecast lead times have not reduced losses. In November, 1999, 35 researchers from nine countries met in Ravello, Italy at a NATO sponsored Advanced Study Institute, to discuss these issues and to develop a research agenda that incorporates the various components required to cope with flash floods. The key recommendations from the Institute were: (1) greater emphasis on increasing understanding of the social processes involved in flash flood warning, particularly in the response phases, and (2) the need to reduce vulnerability in sustainable ways compatible with long-term economic and social goals. The relationship between hydrometeorology and social science is seen as critical to advancing our abilities to cope with flash floods.     

Changes in transport accessibility as a result of flooding: a case study of the Mazovia Province (Eastern Poland)

This paper presents the results of research investigating the impact of flooding on the temporal aspect of transport accessibility at national, regional and local levels in the Mazovia Province – an administrative region in Poland. For the purposes of this study the authors measured the theoretical journey times by private transport between settlement units for two variants: journeys made under normal circumstances, that is, without a flood; and journeys made during a flood event, which would necessitate diversions to avoid flooded road sections. This allowed the theoretical journey time differences to be calculated. It was assumed that vehicles move at the highest permissible speed along routes allowing the shortest travel times. The methods of accessibility assessment employed in this paper are based on distance measurements and use isochrones and a cumulative approach. Analysis carried out by the authors has shown that for interregional, intraregional and local journeys, the flooding of a part of the Mazovia region results in changes in travel times, but their absolute and relative magnitudes vary widely. It was found that in the case of national scale journeys the majority of relative journey time increases were no greater than three times the normal duration, while on a local scale they do not exceed 75%. For areas with a high risk of flooding there should be obligatory analyses of changes in transport accessibility; this would facilitate effective flood risk management. Appropriate traffic management in crisis situations would facilitate emergency and rescue services and help inhabitants and any other persons in flooded areas.