Suchergebnisse

With increasing flood risk due to climate change and socioeconomic trends, governments are under pressure to continue implementing flood protection measures, such as dikes, to reduce flood risk. However, research suggests that a sole focus on government-funded flood protection leads to an adverse increase in exposure as people and economic activities tend to concentrate in protected areas. Moreover, governmental flood protection can reduce the incentive for autonomous adaptation by local households, which paradoxically results in more severe consequences if an extreme flood event occurs. This phenomenon is often referred to as the 'safe development paradox' or 'levee effect' and is generally not accounted for in existing flood risk models used to assess developments in future flood risk under climate change. In this study we assess the impact of extreme flood events for the European Union using a large-scale agent-based model (ABM). We quantify how the safe development paradox affects (1) population growth and the increase in exposed property values, (2) the reduction in investments to flood-proof buildings as public protection increases, and (3) the increase in potential damage should a flood occur. For this analysis, we apply an ABM that integrates the dynamic behaviour of governments and residents into a large-scale flood risk assessment framework, in which we include estimates of changing population growth. We find that the impact of extreme flood events increases considerably when governments provide high protection levels, especially in large metropolitan areas. Moreover, we demonstrate how policy that stimulates the flood-proofing of buildings can largely counteract the effects of the safe development paradox.

This article investigates media coverage of 19th and early 20th century river activism and its effect on federal policy to control the Mississippi River. The U.S. Army Corps of Engineers' "levees-only" policy—which joined disparate navigation and flood control interests—is largely blamed for the Great Flood of 1927, called the largest peacetime disaster in American history. River activists organized annual conventions, and later, professional lobbies organized media campaigns up and down the Mississippi River to sway public opinion and pressure Congress to fund flood control and river navigation projects. Annual river conventions drew thousands of delegates such as plantation owners, shippers, bankers, chambers of commerce, governors, congressmen, mayors and cabinet members with interests on the Mississippi River. Public pressure on Congress successfully captured millions of federal dollars to protect property, drain swamps for development, subsidize local levee districts and influence river policy.

Two-way interactions and feedback between hydrological and social processes in settled floodplains determine the complex human-flood system and change vulnerability over time. To focus on the dynamic role of individual and governmental decision making on flood-risk management, we developed and implemented a coupled agent-based and hydraulic modelling framework. Within this framework, household agents are located in a floodplain protected by a levee system. Individual behaviour is based on Protection Motivation Theory and includes the options to (1) not react to flood risk; (2) implement individual flood protection measures; or (3) file a complaint to the government. The government decides about reinforcing the levee system, compromising between a cost-benefit analysis and filed complaints from households. We found that individual decision making can significantly influence flood risk. In addition, the coupled agent-based and hydraulic modelling framework approach captures commonly observed socio-hydrological dynamics, namely levee and adaptation effects. It provides an explanatory tool for assessing spatial and temporal dynamics of flood risk in a socio-hydrological system.

This article investigates media coverage of 19th and early 20th century river activism and its effect on federal policy to control the Mississippi River. The U.S. Army Corps of Engineers' "levees-only" policy - which joined disparate navigation and flood control interests - is largely blamed for the Great Flood of 1927, called the largest peacetime disaster in American history. River activists organized annual conventions, and later, professional lobbies organized media campaigns up and down the Mississippi River to sway public opinion and pressure Congress to fund flood control and river navigation projects. Annual river conventions drew thousands of delegates such as plantation owners, shippers, bankers, chambers of commerce, governors, congressmen, mayors and cabinet members with interests on the Mississippi River. Public pressure on Congress successfully captured millions of federal dollars to protect property, drain swamps for development, subsidize local levee districts and influence river policy.

Abstract. Floods caused by levee breaching pose disastrous risks to the lower reaches and the flood flow zones of rivers. Thus, a comprehensive assessment of flow and sediment transport during floods must be performed to mitigate flood disasters. Given that the flow state becomes relatively more complex and the range of the submerged area becomes more extensive after a levee breach, this paper established a flow and sediment model by using two-dimensional shallow water equations (SWEs) to explore the breach development process and the flow and sediment transport in a curved bed after a levee breach due to overtopping. A three-element weighted essentially non-oscillatory Roe scheme was adopted for the discretization of SWEs. In addition, a non-equilibrium total-load sediment transport model was established to simulate the scour depth development process of the breach. A stable equilibrium of the breach was established based on flow shear force and soil shear strength. The lateral widening of the breach was simulated by the scouring-collapse lateral widening mode. These simulations, together with the levee breach experiment conducted in the laboratory, demonstrate the validity of the flow and sediment transport process established in this paper. The effects of water head in and out of the watercourse, the flow rate, the levee sediment grading, and other variables during levee breaching were also analyzed. The mathematical model calculation provided a number of physical quantities, such as flow rate and flow state at the breach, that are difficult to measure by using the current laboratory facilities. The results of this research provide fundamental data for developing measures that can reduce casualties and asset loss due to floods caused by levee breaching.

Abstract. Levee-breach-induced flooding occurs occasionally but always
causes considerable losses. A serious flood event occurred due to the
collapse of a 15 m long levee section in Qianbujing Creek, Shanghai, China,
during Typhoon Fitow in October 2013. Heavy rainfall associated with the typhoon
intensified the flood severity (extent and depth). This study investigates
the flood evolution to understand the dynamic nature of flooding and the
compound effect using a well-established 2D hydro-inundation model
(FloodMap) to reconstruct this typical event. This model coupled urban
hydrological processes with flood inundation for high-resolution flood
modeling, which has been applied in a number of different environments, and
FloodMap is now the mainstream numerical simulation model used for flood
scenarios. Our simulation results provide a comprehensive view of the
spatial patterns of the flood evolution. The worst-hit areas are predicted
to be low-lying settlements and farmland. Temporal evaluations suggest that
the most critical time for flooding prevention is in the early
1–3 h after dike failure. In low-elevation areas,
temporary drainage measures and flood defenses are equally important. The
validation of the model demonstrates the reliability of the approach.

This report summarizes the results of a cultural resources survey by Gray & Pape, Inc. of an approximately 14.8-hectare (36.6-acre) property in Fort Bend County, Texas, planned for a bank stabilization project on behalf of their client, Berg-Oliver Associates, Inc. The goals of the survey were to determine if the proposed project would affect any previously identified archaeological sites as defined by Section 106 of the National Historic Preservation Act of 1966, as amended (36 CFR 800), and to establish whether or not previously unidentified buried archaeological resources were located within the project's Area of Potential Effect. Portions of the project are on property owned by Fort Bend County Municipal Utility District Number 121, political subdivisions of the state, as such, a Texas Antiquities Permit (Permit Number 8734) was required prior to the commencement of fieldwork. All fieldwork and reporting activities were completed with reference to state (the Antiquities Code of Texas) and federal guidelines. Prior to fieldwork mobilization, a background literature and site file search were conducted to identify the presence of recorded sites and previous cultural resource surveys within or near the project area. The search indicated that no previously identified archaeological sites, cemeteries, historic markers, or National Register properties are located within the project area. The same research identified that eight previous cultural resource surveys had been conducted within the study radius of the project area, one of which overlapped with the current project area. In addition, 14 previously recorded archaeological sites are located within the study radius, none of which are located within or immediately adjacent to the current project area. Field investigations were carried out in two mobilizations in January and December 2019 and consisted of a combination of pedestrian survey and subsurface testing, resulting in the excavation of 32 shovel tests. Five planned tests were left unexcavated due to inundation, and eight planned tests were left unexcavated due to significant surface disturbance. All shovel tests were negative for cultural resource material and no historic-age resources were identified during survey. After a revised scope of work was submitted to the Texas Historical Commission, investigation of deeply buried soils took place tandem with construction by regular monitoring of construction excavation. When the construction schedule allowed, traditional deep testing, by means of mechanical excavation, was carried out in five of six areas anticipated to have deep impacts from the proposed bank stabilization project. A total of 22 trenches were excavated. No buried features or deeply buried paleosols were encountered. Gray & Pape, Inc. archaeologists are of the opinion that the shovel test survey and deep testing completed within the Area of Potential Effects has adequately assessed the potential for surface and near surface intact, significant cultural resources, as well as determining the potential for deeply buried resources or paleosols. No artifacts or cultural features were encountered during the course of the survey, and no new archaeological sites were identified. No negative impacts on any previously identified sites are anticipated from the proposed project. Based on these results, Gray & Pape, Inc. recommends that no further cultural work be required and that the project be cleared to proceed as planned. As required under the provisions of Texas Antiquities Code Permit 8734, all project records are housed at the Center for Archaeological Studies at Texas State University, San Marcos, Texas.

Floods can be managed at the collective and individual level. Knowing the interaction between measures taken at both scales can help design more efficient flood risk management policies. Here, we combine the data collected during a survey of 331 inhabitants of flood-prone areas in the South of France and spatial databases to empirically examine the interaction between individual adaptation measures and three types of collective management tools: a national insurance scheme, dikes, and zoning instruments. In line with the levee effect hypothesis, we found that dike protection reduces the probability to have or take individual adaptation measures and that this effect could be mitigated by zoning instruments. Moreover, we found that the national insurance scheme does not crowd out individual adaptation.

Floods can be managed at the collective and individual level. Knowing the interaction between measures taken at both scales can help design more efficient flood risk management policies. Here, we combine the data collected during a survey of 331 inhabitants of flood-prone areas in the South of France and spatial databases to empirically examine the interaction between individual adaptation measures and three types of collective management tools: a national insurance scheme, dikes, and zoning instruments. In line with the levee effect hypothesis, we found that dike protection reduces the probability to have or take individual adaptation measures and that this effect could be mitigated by zoning instruments. Moreover, we found that the national insurance scheme does not crowd out individual adaptation.

Floods can be managed at the collective and individual level. Knowing the interaction between measures taken at both scales can help design more efficient flood risk management policies. Here, we combine the data collected during a survey of 331 inhabitants of flood-prone areas in the South of France and spatial databases to empirically examine the interaction between individual adaptation measures and three types of collective management tools: a national insurance scheme, dikes, and zoning instruments. In line with the levee effect hypothesis, we found that dike protection reduces the probability to have or take individual adaptation measures and that this effect could be mitigated by zoning instruments. Moreover, we found that the national insurance scheme does not crowd out individual adaptation.

Floods can be managed at the collective and individual level. Knowing the interaction between measures taken at both scales can help design more efficient flood risk management policies. Here, we combine the data collected during a survey of 331 inhabitants of flood-prone areas in the South of France and spatial databases to empirically examine the interaction between individual adaptation measures and three types of collective management tools: a national insurance scheme, dikes, and zoning instruments. In line with the levee effect hypothesis, we found that dike protection reduces the probability to have or take individual adaptation measures and that this effect could be mitigated by zoning instruments. Moreover, we found that the national insurance scheme does not crowd out individual adaptation.

With increasing flood risk due to climate change and socioeconomic trends, governments are under pressure to continue implementing flood protection measures, such as dikes, to reduce flood risk. However, research suggests that a sole focus on government-funded flood protection leads to an adverse increase in exposure as people and economic activities tend to concentrate in protected areas. Moreover, governmental flood protection can reduce the incentive for autonomous adaptation by local households, which paradoxically results in more severe consequences if an extreme flood event occurs. This phenomenon is often referred to as the 'safe development paradox' or 'levee effect' and is generally not accounted for in existing flood risk models used to assess developments in future flood risk under climate change. In this study we assess the impact of extreme flood events for the European Union using a large-scale agent-based model (ABM). We quantify how the safe development paradox affects (1) population growth and the increase in exposed property values, (2) the reduction in investments to flood-proof buildings as public protection increases, and (3) the increase in potential damage should a flood occur. For this analysis, we apply an ABM that integrates the dynamic behaviour of governments and residents into a large-scale flood risk assessment framework, in which we include estimates of changing population growth. We find that the impact of extreme flood events increases considerably when governments provide high protection levels, especially in large metropolitan areas. Moreover, we demonstrate how policy that stimulates the flood-proofing of buildings can largely counteract the effects of the safe development paradox.