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.     

The performance of the sydney flood warning system, august 1986

During August 1986 Sydney experienced its worst flooding for decades. Some 2,500 properties were flooded and transport was severely disrupted in much of the metropolitan area. The flood provided an opportunity to examine the operation of a warning system in a major Australian city. Pre-existing research into flood warnings was expanded to take advantage of the opportunity.
The warning system is examined in terms of: its impact on flood losses; consumer satisfaction; and inefficiences or breakdowns within the system. Much of the flooded area was not covered by a formal warning system. For the area that was covered, performance could be improved. Problems were experienced with the data collection and transmission network. Warning dissemination was inadequate, and the majority of those surveyed claimed that they did not receive warnings. The actions of householders reduced the flood damage substantially, but this does not appear to be the result of official warnings. Key recommendations concern improving the reliability of the flood detection network and information management.     

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.     

北江大堤洪水风险图信息管理系统中仿真模型的开发研究

“北江大堤洪水风险信息管理系统”中洪水仿真模型的研究, 是根据北江大堤可能出现的溃堤风险,模拟了北江大堤溃决后保护区内洪水的演进过程,模型的计算结果提供的淹没水深、淹没范围、淹没历时以及流速等洪水风险信息, 为北江大堤洪水风险图的绘制提供了依据     

Contextual influences on national level flood risk communication

With high profile flooding events and increasing risk and probable damages of flooding in the future flood risk management (FRM) in England and Wales has undergone substantial changes over the last decade. The contextual influences on flood risk communication in the areas of flood forecasting, warning and response, spatial planning and development control and flood insurance at a national level are investigated in this paper. Research is based on qualitative interviews with 21 representatives of key organisations and activities at a national level of FRM. Drawing on communication theory the research highlights the key contextual features at play: the characteristics of communication flow through organisations, the importance of policy as a communication tool informed and constrained by flood events, organisational agendas, communication approaches and the development of knowledge and technology. The paper describes the influence of clear policy guidance on activities in certain government FRM communication initiatives and the commercial imperative driving the insurance industry activities.     

Contextual influences on national level flood risk communication

With high profile flooding events and increasing risk and probable damages of flooding in the future flood risk management (FRM) in England and Wales has undergone substantial changes over the last decade. The contextual influences on flood risk communication in the areas of flood forecasting, warning and response, spatial planning and development control and flood insurance at a national level are investigated in this paper. Research is based on qualitative interviews with 21 representatives of key organisations and activities at a national level of FRM. Drawing on communication theory the research highlights the key contextual features at play: the characteristics of communication flow through organisations, the importance of policy as a communication tool informed and constrained by flood events, organisational agendas, communication approaches and the development of knowledge and technology. The paper describes the influence of clear policy guidance on activities in certain government FRM communication initiatives and the commercial imperative driving the insurance industry activities.     

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.

     

The effects of flooding on residential property values in three new zealand communities

Research on the effects of natural events on property values has focused primarily on experiences in the United States and has shown that these impacts must be evaluated in the context of both the hydrologic regime and local urban economic situations. It remains unclear if these relationships exist with different flood regimes and under different institutional arrangements. The research reported here analyzes the impacts of flooding on property values in Paeroa, Te Aroha, and Thames, New Zealand. The results indicate different experiences in the three communities, but suggest several common trends. Each community has distinct housing submarkets that exhibit different housing value characteristics, independent of hazardousness, which may either mask or exaggerate flood-related impacts. In addition, initial local impacts of events vary, but eventually differences in flooded and non-flooded properties decrease. Thus, at least over the long term, hazardousness is not a factor in housing value differentials.     

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.     

Coping and adaptation strategies and institutional perceptions of hydrological risk in an urban Amazonian city

This paper investigates coping and adaptation strategies and institutional perceptions of hydrological risk at the local scale in Santarém, an Amazonian city in the state of Pará, Brazil. Methods and tools of analysis encompassed secondary data, field observations, and qualitative techniques (focus-group discussions and in-depth interviews). Stakeholders from affected neighbourhoods describe their means of coping with and adapting to flooding, focusing on purposefulness, type of initiative and investment, risk timing, temporal and spatial scope, and performance. The results comprise an inventory of 16 mostly structural measures. The perceptions of six institutions of general responses to flooding are presented as opinions on actions that reduce the effects of such events, individual strategies and collective community endeavours in at-risk areas, and the activities of the public and private sectors to manage floods. Understanding of coping and adaptation strategies and knowledge of institutional flood risk perceptions can benefit the implementation of risk and disaster reduction policies and practices.     

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.     

Permanent post-disaster housing in honduras: aspects of vulnerability to future disasters

To some degree it is unfair to evaluate a post-disaster housing program as to its effectiveness in decreasing vulnerability and preventing future disasters. As Burton states, "With rare exceptions, administrators and techniques have been trained to cope with disaster rather than to prevent it" [reference (2), p.197]. These were certainly not goals articulated by the agency responsible for constructing housing after Fifi. However, the authors feel that failure to evaluate specific projects by persons knowledgeable of the projects functioning, will only forestall the shift which Cuny calls for, "… from disaster response to disaster mitigation and prevention" [reference (4), p.123). In doing this we hope to add some specific case study data to the growing literature on disaster mitigation and prevention. Disaster vulnerability in Honduras is overwhelmingly related to flooding. More crucial than the materials and construction of housing is the issue of siting. If appropriately sited, houses made of bajarique, wood, or concrete block are able to withstand the heavy rains associated with a hurricane. Regarding the siting of the projects, the Honduras Project clearly has one positive and one negative accomplishment in the cases of Santa Rica and Flores, respectively. San Jose is less clear but is certainly a much safer site than those formerly occupied by the residents, in that there is no danger of flooding. The present site was not flooded during Fifi nor did it experience mudslides. However, the future is not so clear regarding the latter. Within the village proper a large amount of vegetation has been added which will tend to stabilise the soil on the steeper slopes. The streets, however, are seriously eroded and probably can not be maintained for vehicle usage, which does not pose a serious problem to the residents as none possess automobiles or trucks. One large gully bisects the village and receives run-off from the adjacent hills. It has been expanding, which would suggest that the slopes above the village could prove problematic in case of a Fifi-sized storm. Flores is located on a very poor site in reference to prevention and mitigation. It is located in a portion of the Sula Valley which is prone to flooding and, as mentioned before, was inundated by over 2m of water during hurricane Fifi. No prevention techniques were possible by NAEA/HEA and the houses were built on earthen mounds barely adequate to keep water out during the rainy season. The nearby dike which could possibly provide protection is non-functional due to poor maintainance. Given a storm of Fifi's magnitude, or possibly smaller, this site will again be flooded. Santa Rica is clearly well sited concerning flooding: it did not experience flooding during Fifi and is not flood prone. However, houses did experience some wall damage due to earthquakes following and associated with the Guatemalan quake of 1976. Due to the size and nature of the latter much "re-adjustment" occurred in the neighbouring fault system; however, damage to the houses was all superficial. We feel the residents were vocal about their concern due to the severity of the Guatemalan disaster and their lack of experience with concrete block houses. That the two sites (particularly Flores and partially San Jose) are vulnerable to future disasters cannot be considered solely the fault of an outside agency without local knowledge and understanding. In the engineering report issued during the construction it was explicitly stated that in Flores, "Future flooding remains a danger," [reference (6), p.49]. The future residents of Flores had gained access to the land from the National Agrarian Institute and were anxious to receive assistance in building homes. In fact, CARE, which had previously given these people tin roofing for houses, was threatening to take it back since the people had not yet started building. NAEA/HEA were responding to people in a rather desperate situation. But, on the other hand, they were responding to people who had been promised (not given) land by an agency of the Honduran national government which would be cognizant of the potential flooding at this site. Likewise, in San Jose, where mudslides and erosion remain a threat, the land was provided by a local government agency, the municipality. Although our goal in this discussion has not been to establish blame, we feel it imperative to mention the sequence of events that resulted in the questionable siting of Flores and San Jose. It is very easy and often accurate to place blame on outsiders who lack sophistication and knowledge about such matters. In this case local input did not result in post-disaster planning that is actually precautionary. This, we feel, illustrates the extreme complexity of cross-cultural aid, especially in the post-disaster period. It also points to the need for precautionary planning with reference to permanent post-disaster reconstruction.     

The spatial and temporal variability of residential real estate values in response to flooding

A relationship between residential property values and the incidence of flooding is represented, using a case study of two Californian communities that were flooded following a levee break. Analysis of the real estate market before and after the flood shows that the flood was capitalized into housing values, whereby both list and selling prices dropped immediately and have recently begun to recover. However, recovery of the market is not uniform throughout the floodplain. Houses that suffered eighteen inches of water recovered to near pre-flood values in less than one year. In contrast, houses that had approximately ten feet of water in them have not recovered to the same extent, indicating that capitalization and recovery do not occur evenly. These findings suggest that policies and programs should address these spatial and temporal differences in recovery, which are expected to vary with different flood frequencies and magnitudes.     

Urban flooding in Australia: Policy development and implementation

This paper presents a review of Australian urban riverine flooding. By world standards the Australian flood problem is relatively small, though there are pockets of development subject to regular severe inundation. In the past, government response to flooding was ad hoc and characterized by structural adjustments. The 1970s and 1980s, however, have seen a major shift in approach. The new approach emphasizes resource management rather than construction, and consists of the announcement of policies, enactment of enabling legislation, and the introduction of procedures to help ensure that the widest range of flood damage reduction measures are considered. The changes are evident at both the federal and state levels of government.
Though problems remain, particularly at the local government level, where ultimate responsibility for policy implementation generally rests, the authors feel there are good grounds for optimism. Some suggestions for future policy are offered and the importance of public safety is stressed.     

Time needed to evacuate the Netherlands in the event of large-scale flooding: strategies and consequences

On 30 May 2008, the Government of the Netherlands informed the national parliament about the effectiveness of preventive evacuation of coastal and river areas in case of flooding. Analysis of a case study showed that it is impossible to evacuate coastal areas preventively within a 48-hour time span preceding a worst credible scenario flood caused by a storm surge. This fact illustrates the need for alternative evacuation strategies, such as vertical evacuation (evacuating to safe havens, inside the flood zone) or shelter-in-place (hiding), to reduce loss of life and the impact of the evacuation. This paper defines these strategies and demonstrates, by returning to the case study used by the Dutch government, that they require different measures, methods of approach, and crisis management processes. In addition, it addresses the need for flexible and scalable preparation so that after detecting and understanding the threat, authorities and citizens can make decisions about different evacuation strategies.     

Repetitive flood victims and acceptance of FEMA mitigation offers: an analysis with community-system policy implications

Of all natural disasters, flooding causes the greatest amount of economic and social damage. The United States' Federal Emergency Management Agency (FEMA) uses a number of hazard mitigation grant programmes for flood victims, including mitigation offers to relocate permanently repetitive flood loss victims. This study examines factors that help to explain the degree of difficulty repetitive flood loss victims experience when they make decisions about relocating permanently after multiple flood losses. Data are drawn from interviews with FEMA officials and a survey of flood victims from eight repetitive flooding sites. The qualitative and quantitative results show the importance of rational choices by flood victims in their mitigation decisions, as they relate to financial variables, perceptions of future risk, attachments to home and community, and the relationships between repetitive flood loss victims and the local flood management officials who help them. The results offer evidence to suggest the value of a more community-system approach to FEMA relocation practices.     

Health and social impacts of a flood disaster: responding to needs and implications for practice

Carlisle in northwest England suffered its worse floods for more than 180 years in 2005. A study, reported here, was undertaken to assess the health and social impacts of these floods via in‐depth, taped individual and focus‐group interviews with people whose homes had been flooded and with agency workers who helped them. Respondents spoke of physical health ailments, psychological stress, water health‐and‐safety issues related to the floods, and disputes with insurance and construction companies, which they felt had caused and exacerbated psychological health problems. Support workers also suffered from psychological stress. Furthermore, it was found that people had low expectations of a flood and were not prepared. The findings are presented in five sections covering flood risk awareness, water contamination issues, physical health, mental health, and impact on frontline support workers. The discussion focuses on the implications of the findings for policy and practice vis‐à‐vis psychological health provision, contamination issues, training and support for frontline support workers, matters relating to restoration, and preparation for flooding.     

20世纪下半叶新疆洪水灾害的新趋向

受全球气候变暖和当地人类活动加剧的影响,20世纪下半叶以来,尤其80年代以来新疆洪灾在时空分布上,发生了比较明显的变化,呈现出一些新的趋向.这些新趋向突出表现在:与前30年(1950-1979年)相比,洪灾农田受灾面积增大、发生次数增多、直接经济损失明显上升以及洪灾多发区向北疆西部和天山南北麓集中.     

Effects of the 2008 flood on economic performance and food security in Yemen: a simulation analysis

Extreme weather events such as floods and droughts can have devastating consequences for individual well being and economic development, in particular in poor societies with limited availability of coping mechanisms. Combining a dynamic computable general equilibrium model of the Yemeni economy with a household‐level calorie consumption simulation model, this paper assesses the economy‐wide, agricultural and food security effects of the 2008 tropical storm and flash flood that hit the Hadramout and Al‐Mahrah governorates. The estimation results suggest that agricultural value added, farm household incomes and rural food security deteriorated long term in the flood‐affected areas. Due to economic spillover effects, significant income losses and increases in food insecurity also occurred in areas that were unaffected by flooding. This finding suggests that while most relief efforts are typically concentrated in directly affected areas, future efforts should also consider surrounding areas and indirectly affected people.