Suchergebnisse

On January 9, 2018, a series of debris flows killed 23 people and caused over a $1 billion in economic losses in Montecito, Santa Barbara County, California. The debris flows followed a classic pattern in mountainous areas of southern California: A large wildfire (the 2017 Thomas Fire) burned the headwaters of streams draining the Transverse Ranges southward to the Pacific. A cell of intense rain fell on hydrophobic soils in the burn area, generating debris flows that propagated downstream, affecting areas along the stream channels. The 2018 Montecito debris flows raise compelling questions about the role of scientific information in decision making generally, and specifically how hazardous areas along rivers and streams are mapped, how land use is regulated in these zones, and how best to respond in emergency situations. We analyze the evolution of urban development in these flood hazard areas since the beginning of the 20th century, the recovery planning strategies that the local government adopted after the event, and the role of post-fire debris flow maps in environmental planning. We highlight the importance of exposure as a key element to reduce risk.

International audience ; In France, sirens have been the principal tool designated to alert the population in the case of danger. However, their efficacity has not been objectively tested. Using a geographical information system, questionnaires, and surveys, we analyzed (1) the spatial distribution of the siren network in relation to the covered population, the hazards threatening different areas, and the actual number of disasters that have occurred in the past, (2) the political dilemma of activating sirens, and (3) the population's trust in sirens, as well as its understanding of expected behavior in the case of an emergency. Results show that, with a few exceptions, siren coverage in France is primarily determined by population density, not by the expected hazards or the cumulative number of past disasters. Sirens are also rarely used by the authorities. However, surveyed members of the population identify sirens as the most effective alert system over other alternatives such as cell-phone-based alerting tools. In a "mock" emergency most members of the public did not know how to respond in the case of an emergency, and even most of those who correctly identified the appropriate response prior to the exercise did not react upon later hearing the siren. To improve the effectiveness of the French siren network, we recommend (1) relocating sirens to optimize their efficiency, (2) complementing the sound of sirens with a clear and unified message, (3) reorganizing the competencies to activate siren alerts, and finally (4) improving public education on different alert tools and expected behavior during an emergency.

International audience ; In France, sirens have been the principal tool designated to alert the population in the case of danger. However, their efficacity has not been objectively tested. Using a geographical information system, questionnaires, and surveys, we analyzed (1) the spatial distribution of the siren network in relation to the covered population, the hazards threatening different areas, and the actual number of disasters that have occurred in the past, (2) the political dilemma of activating sirens, and (3) the population's trust in sirens, as well as its understanding of expected behavior in the case of an emergency. Results show that, with a few exceptions, siren coverage in France is primarily determined by population density, not by the expected hazards or the cumulative number of past disasters. Sirens are also rarely used by the authorities. However, surveyed members of the population identify sirens as the most effective alert system over other alternatives such as cell-phone-based alerting tools. In a "mock" emergency most members of the public did not know how to respond in the case of an emergency, and even most of those who correctly identified the appropriate response prior to the exercise did not react upon later hearing the siren. To improve the effectiveness of the French siren network, we recommend (1) relocating sirens to optimize their efficiency, (2) complementing the sound of sirens with a clear and unified message, (3) reorganizing the competencies to activate siren alerts, and finally (4) improving public education on different alert tools and expected behavior during an emergency.

International audience ; In France, sirens have been the principal tool designated to alert the population in the case of danger. However, their efficacity has not been objectively tested. Using a geographical information system, questionnaires, and surveys, we analyzed (1) the spatial distribution of the siren network in relation to the covered population, the hazards threatening different areas, and the actual number of disasters that have occurred in the past, (2) the political dilemma of activating sirens, and (3) the population's trust in sirens, as well as its understanding of expected behavior in the case of an emergency. Results show that, with a few exceptions, siren coverage in France is primarily determined by population density, not by the expected hazards or the cumulative number of past disasters. Sirens are also rarely used by the authorities. However, surveyed members of the population identify sirens as the most effective alert system over other alternatives such as cell-phone-based alerting tools. In a "mock" emergency most members of the public did not know how to respond in the case of an emergency, and even most of those who correctly identified the appropriate response prior to the exercise did not react upon later hearing the siren. To improve the effectiveness of the French siren network, we recommend (1) relocating sirens to optimize their efficiency, (2) complementing the sound of sirens with a clear and unified message, (3) reorganizing the competencies to activate siren alerts, and finally (4) improving public education on different alert tools and expected behavior during an emergency.

International audience ; In France, sirens have been the principal tool designated to alert the population in the case of danger. However, their efficacity has not been objectively tested. Using a geographical information system, questionnaires, and surveys, we analyzed (1) the spatial distribution of the siren network in relation to the covered population, the hazards threatening different areas, and the actual number of disasters that have occurred in the past, (2) the political dilemma of activating sirens, and (3) the population's trust in sirens, as well as its understanding of expected behavior in the case of an emergency. Results show that, with a few exceptions, siren coverage in France is primarily determined by population density, not by the expected hazards or the cumulative number of past disasters. Sirens are also rarely used by the authorities. However, surveyed members of the population identify sirens as the most effective alert system over other alternatives such as cell-phone-based alerting tools. In a "mock" emergency most members of the public did not know how to respond in the case of an emergency, and even most of those who correctly identified the appropriate response prior to the exercise did not react upon later hearing the siren. To improve the effectiveness of the French siren network, we recommend (1) relocating sirens to optimize their efficiency, (2) complementing the sound of sirens with a clear and unified message, (3) reorganizing the competencies to activate siren alerts, and finally (4) improving public education on different alert tools and expected behavior during an emergency.

Intro -- Foreword -- Acknowledgments -- Contents -- Biographies -- List of Figures -- Chapter 1: Introduction -- References -- Part I: Big River Basins -- Chapter 2: Managing Floods in Large River Basins in the USA: The Mississippi River -- 2.1 Introduction -- 2.1.1 The Mississippi River Basin -- 2.1.2 Flood Risk Management in the Mississippi: History and Governance -- 2.2 The 2011 Mississippi River Flood: What Worked -- 2.3 Land-Use Conflicts in Floodways of the Mississippi River System -- 2.3.1 Introduction -- 2.3.2 The Birds Point: New Madrid Floodway -- 2.3.3 The Atchafalaya Floodway System -- 2.3.4 Risk Perception and Implications for Floodway Operation -- 2.3.5 Conclusion -- 2.4 Mississippi River Navigation System: A Major Contributor to Flooding -- 2.4.1 Introduction -- 2.4.2 The Upper Mississippi River Navigation System -- 2.4.3 River Training Structures in the Middle Mississippi River -- 2.4.4 Scientific Consensus Regarding Effects of River Training Structures and the Agency Response -- 2.4.5 Conclusion and Recommendations -- 2.5 Floodplains: Meeting the Needs of People and Nature -- References -- Chapter 3: Managing Floods in Large River Basins in the USA: The Sacramento River -- 3.1 Introduction -- 3.1.1 The Sacramento River Basin -- 3.1.2 The Sacramento Valley: A Highly Engineered System -- 3.1.3 Flood Risk Management in California: Governance System -- 3.2 Managing Floods in the California Central Valley -- 3.2.1 State Plan of Flood Control -- 3.2.2 Standard Levee Design -- 3.2.3 Heightened Protection for Urban Areas -- 3.2.4 National Flood Insurance Program -- 3.2.5 The Flood of 1986 -- 3.2.6 The Flood of 1997 -- 3.2.7 2003 Paterno Decision -- 3.3 The Central Valley Flood Protection Plan -- 3.3.1 Central Valley Flood Protection Plan -- 3.3.2 Handbook for Local Communities -- 3.3.3 Building Code -- 3.3.4 Flood Risk Notification.

International audience ; Although hydraulic infrastructure such as levees remain important for flood risk management in the USA, France, and Quebec (Canada), there is increasing emphasis on nonstructural measures, such as regulatory flood maps, to reduce exposure and vulnerability, for example, preventing people from building in high hazard areas. One key concept related to areas protected by levees is that of "residual risk", that is, the risk from floods greater than the design standard of the levees (levee overtopping) and from levee breach. In this article,we review the legislative framework for regulatory flood maps in the USA, France, and Quebec (Canada) and compare how residual risk behind protective structures is taken into account (or not) in regulatory flood maps. We find big differences in how the USA, France and Canada manage residual risk behind the levees. While in France the area behind levees is part of the regulatory flood prone area, and land use restrictions, building codes, emergency measures and risk communication are mandatory, in the USA the area behind levees is only shown as part of the regulatory flood prone area if the levee is not accredited. In Quebec, regulatory flood maps in general follow the French approach with a few exceptions. ; Bien que les infrastructures hydrauliques telles que les digues restent importantes pour la gestion des risques d'inondation aux États-Unis, en France et au Québec (Canada), l'accent est de plus en plus mis sur les mesures non structurelles, telles que les cartes réglementaires des inondations, pour réduire l'exposition et la vulnérabilité, par exemple en empêchant les personnes de construire dans des zones à haut risque. Un concept clé lié aux zones protégées par des digues est celui de «risque résiduel», c'est-à-dire le risque d'inondations pour des événements qui dépassent le niveau de conception des digues (débordement de digues) et de rupture de digues. Dans cet article, nous passons en revue le cadre législatif des cartes d'inondation ...

International audience ; Although hydraulic infrastructure such as levees remain important for flood risk management in the USA, France, and Quebec (Canada), there is increasing emphasis on nonstructural measures, such as regulatory flood maps, to reduce exposure and vulnerability, for example, preventing people from building in high hazard areas. One key concept related to areas protected by levees is that of "residual risk", that is, the risk from floods greater than the design standard of the levees (levee overtopping) and from levee breach. In this article,we review the legislative framework for regulatory flood maps in the USA, France, and Quebec (Canada) and compare how residual risk behind protective structures is taken into account (or not) in regulatory flood maps. We find big differences in how the USA, France and Canada manage residual risk behind the levees. While in France the area behind levees is part of the regulatory flood prone area, and land use restrictions, building codes, emergency measures and risk communication are mandatory, in the USA the area behind levees is only shown as part of the regulatory flood prone area if the levee is not accredited. In Quebec, regulatory flood maps in general follow the French approach with a few exceptions. ; Bien que les infrastructures hydrauliques telles que les digues restent importantes pour la gestion des risques d'inondation aux États-Unis, en France et au Québec (Canada), l'accent est de plus en plus mis sur les mesures non structurelles, telles que les cartes réglementaires des inondations, pour réduire l'exposition et la vulnérabilité, par exemple en empêchant les personnes de construire dans des zones à haut risque. Un concept clé lié aux zones protégées par des digues est celui de «risque résiduel», c'est-à-dire le risque d'inondations pour des événements qui dépassent le niveau de conception des digues (débordement de digues) et de rupture de digues. Dans cet article, nous passons en revue le cadre législatif des cartes d'inondation réglementaires aux États-Unis, en France et au Québec (Canada) et comparons la prise en compte (ou non) du risque résiduel derrière les ouvrages de protection dans les cartes d'inondation réglementaires. Nous constatons de grandes différences dans la manière dont les États-Unis, la France et le Canada gèrent le risque résiduel derrière les digues. Alors qu'en France, la zone derrière les digues fait partie de la zone inondable réglementaire et que les restrictions d'utilisation des sols, les codes de construction, les mesures d'urgence et la communication des risques sont obligatoires, aux États-Unis, la zone derrière les digues n'est indiquée comme faisant partie de la zone inondable réglementaire que si la digue n'est pas accréditée. Au Québec, les cartes d'inondation réglementaires suivent en général l'approche française à quelques exceptions près.

Abstract. In France, sirens have been the principal tool designated to alert the population in the case of danger. However, their efficacity has not been objectively tested. Using a geographical information system, questionnaires, and surveys, we analyzed (1) the spatial distribution of the siren network in relation to the covered population, the hazards threatening different areas, and the actual number of disasters that have occurred in the past, (2) the political dilemma of activating sirens, and (3) the population's trust in sirens, as well as its understanding of expected behavior in the case of an emergency. Results show that, with a few exceptions, siren coverage in France is primarily determined by population density, not by the expected hazards or the cumulative number of past disasters. Sirens are also rarely used by the authorities. However, surveyed members of the population identify sirens as the most effective alert system over other alternatives such as cell-phone-based alerting tools. In a "mock" emergency most members of the public did not know how to respond in the case of an emergency, and even most of those who correctly identified the appropriate response prior to the exercise did not react upon later hearing the siren. To improve the effectiveness of the French siren network, we recommend (1) relocating sirens to optimize their efficiency, (2) complementing the sound of sirens with a clear and unified message, (3) reorganizing the competencies to activate siren alerts, and finally (4) improving public education on different alert tools and expected behavior during an emergency.

International audience ; Although hydraulic infrastructure such as levees remain important for flood risk management in the USA, France, and Quebec (Canada), there is increasing emphasis on non-structural measures, such as regulatory flood maps, to reduce exposure and vulnerability, e.g., preventing people from building in high hazard areas. One key concept related to areas protected by levees is that of "residual risk", i.e., the risk from floods greater than the design standard of the levees (levee overtopping), and from levee breach. In this article, we review the legislative framework for regulatory flood maps in the US, France, and Quebec (Canada), compare restrictions on land use within the designated high-hazard zones, and compare how residual risk behind protective structures is taken into account (or not) in regulatory flood maps. Comparing the Flood Insurance Rate Maps (FIRMs) in the USA with the "Plans de Prévention du Risque d'Inondations" (PPRi) in France and the "Cartes de Zones Inondables" in Quebec, we find big differences in how the USA, France and Canada manage residual risk behind the levees.

International audience ; Although hydraulic infrastructure such as levees remain important for flood risk management in the USA, France, and Quebec (Canada), there is increasing emphasis on non-structural measures, such as regulatory flood maps, to reduce exposure and vulnerability, e.g., preventing people from building in high hazard areas. One key concept related to areas protected by levees is that of "residual risk", i.e., the risk from floods greater than the design standard of the levees (levee overtopping), and from levee breach. In this article, we review the legislative framework for regulatory flood maps in the US, France, and Quebec (Canada), compare restrictions on land use within the designated high-hazard zones, and compare how residual risk behind protective structures is taken into account (or not) in regulatory flood maps. Comparing the Flood Insurance Rate Maps (FIRMs) in the USA with the "Plans de Prévention du Risque d'Inondations" (PPRi) in France and the "Cartes de Zones Inondables" in Quebec, we find big differences in how the USA, France and Canada manage residual risk behind the levees.

Rivers are the lifeblood of many cities, but flood risk is projected to increase due to urbanisation and climate change. Better floodplain management in and near urban areas is required to produce the New Urban Agenda's 'just, safe, healthy, accessible, affordable, resilient and sustainable cities'. Many jurisdictions are looking to move or keep people out of human-constructed residential 'niches' on hazardous floodplains, but this has proved difficult to achieve. Our historical case studies of colonial societies in ancient Rome, as well as on the Yangtze, Mississippi and Brisbane rivers, show the deep roots of many contemporary flood risk issues, such as failures of risk perception related to recent settlement, the moral hazard of spending on flood defence infrastructure, the creeping nature of floodplain encroachment into 'niches' of perceived protection created by structural interventions, the need for a central, 'whole of river' approach, and the difficulties of implementing this approach locally. These case studies also suggest solutions, including the adoption of Indigenous perspectives, benefits to incentivise local actors and a historical education strategy to increase appetite for more sustainable flood risk mitigation.