22 research outputs found
Developing a method to include flood defenses explicitly in flood hazard maps based on limited available information
No full textFlooding is one of the most damaging natural disasters worldwide, and presents a signi_cant risk for a large amount of the global population. For the development of ood disaster management strategies, policy makers make use of ood hazard maps to inform investment strategies to reduce risk. In many current ood hazard mapping methods, the role of embankments is either implicit or completely unaccounted for. However, these defense systems can play a key role in both the _nal extent of the inundation as well as in the development of the inundation. Limitations in available data are often the reason for the lack of explicit implementation of embankments. The goal of this study is the development of a method that can explicitly include the e_ects of ood defenses in a ood hazard map based on limited available data. Next, this has been tested for a low-lying riverine area and the Tisa river basin in Serbia was selected as a case study area for this purpose. First, an idealized approach has been followed to better understand the model behavior using settings resembling this river. Finally, the method has been applied with a more realistic river schematization. To develop a method for a more explicit inclusion of ood defenses, an understanding of the di_erent current approaches has been generated based on a literature review. On the scale of global ood maps, the failure probabilities of ood defenses are not used. Only with post-processing, certain areas are considered protected by removing inundation from the maps. Many studies of ood hazard mapping use the so-called bathtub approximation. Hereby is assumed that the complete oodplain will ood and that the inundation depth is found by extrapolating the water surface level outside of the embankments to the area inside of the embankments. The inuences of the ood defenses on the inundation are not included. Regional ood hazard maps are still made without ood defenses in many cases. While the improved resolution allows for more detailed maps, the lack of available data still limits the implementation of ood defenses. Flood mapping methods exist that include failure probabilities for ood defenses but these require large amounts of data that is not available everywhere. An idealized model based on the Tisa river characteristics is used to test a ood mapping method which includes explicitly the presence and potential failure of embankments. Based upon data on the river geometry, hydraulics as well as land-use in the oodplains, a model schematization has been set up with the SOBEK software. The embankments were simpli_ed to a crown height for the purpose of overow and an estimated failure probability. The breaching of the levee is simulated according to the Verheij-vdKnaap breach growth model. The estimation of the failure probabilities was based on historical failure rates of a comparable ood defense system along the Elbe River. The levees were schematized into segments based on the maximum breach width of the breaching model…Civil Engineering | Hydraulic Engineerin
Defend or raise? Optimising flood risk reduction strategies
No full textFlood risk reduction can be provided by interventions such as raising land or constructing flood defences. This paper introduces an approach to optimise the selection of risk reduction strategies. It expands existing economic optimization approaches for flood defences, by introducing (largely) analytical formulations to include the effects of approaches to mitigate flood consequences. The method considers the size of the protected area and associated damages, the costs and dimensioning of interventions and the likelihood of flooding. It is applied in several practical cases. Within the context of this economic model, we conclude that a system of flood defences is more economical than a landfill for larger areas. Fills are preferred for small areas and/or for low costs. A combination of strategies is preferred when the value protected by the flood defence is low compared to the value protected by the fill, or when the high value development is relatively small in size. The sensitivity of outcomes to the choice of the main input parameters is presented, as well as implications of the results and selection of strategies in developing and developed countries. Overall, this approach supports decision makers in developing effective strategies to manage and reduce flood risk.Hydraulic Structures and Flood Ris
HYDRAULIC BOUNDARY CONDITIONS AND THE DEVELOPMENT OF STRUCTURE GEOMETRY FOR THE INNER HARBOR NAVIGATION CANAL SURGE BARRIER PROJECT, NEW ORLEANS, LOUISIANA, USA
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Mapping mangrove opportunities with open access data: A case study for Bangladesh
No full textMangroves protect coastal areas against hazards like storms or cyclones by attenuating waves and currents, and by trapping floating debris during extreme events. Bangladesh is a very vulnerable country to floods and cyclones, and part of its coastal system is thus being upgraded to a higher safety standard. These upgrades include embankment reinforcement and mangrove afforestation schemes seawards of the embankments. To further strengthen the implementation of combined green–grey infrastructure in future programs, identifying potential mangrove development sites near the polder systems is a necessary first step. We thus developed a tool to systematically identify mangrove sites throughout the coastal area based on open access data. This method identi-fies potential sites for mangrove development based on their distance from existing mangrove patches and suggests the required technique to implement the vegetation depending on the rate of coastline change. Our method showed that approximately 600 km of the coastal stretches placed seawards of embankments are within 10 km of existing mangroves, and could thus be potential sites for mangrove establishment. Out of those 600 km, we identified 140 km of coastline where the land-wards polders are particularly vulnerable to flooding. The sites with highest restoration potential and priority are located in Galachipa, Hatiya, Bhola, Manpura, Khangona, and Boro Moheshkhali. More detailed data collection and local assessments are recommended prior to executing mangrove afforestation schemes. Nevertheless, this method could serve as a useful systematic tool for feasi-bility studies that identify mangrove opportunities in data-scarce areas and help to prioritize data collection at the sites of highest interest.</p
Modelling the seasonal dynamics of SPM with a simple algorithm for the buffering of fines in a sandy seabed
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An idealized meteorological-hydrodynamic model for exploring extreme storm surge statistics in the North Sea in an alternative way
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