Suchergebnisse

Abstract. The increasing number and severity of floods, driven by phenomena such as urbanization, deforestation, subsidence and climate change, create a growing need for accurate and timely flood maps. In this paper we present and evaluate a method to create deterministic and probabilistic flood maps from Twitter messages that mention locations of flooding. A deterministic flood map created for the December 2015 flood in the city of York (UK) showed good performance (F(2) =  0.69; a statistic ranging from 0 to 1, with 1 expressing a perfect fit with validation data). The probabilistic flood maps we created showed that, in the York case study, the uncertainty in flood extent was mainly induced by errors in the precise locations of flood observations as derived from Twitter data. Errors in the terrain elevation data or in the parameters of the applied algorithm contributed less to flood extent uncertainty. Although these maps tended to overestimate the actual probability of flooding, they gave a reasonable representation of flood extent uncertainty in the area. This study illustrates that inherently uncertain data from social media can be used to derive information about flooding.

The study assessed the extent of typhoon Ulysses flooding and the flood risk management interventions of heavily affected households in Isabela Province. A total of 3,000 respondents were selected through quota sampling technique in four municipalities, namely Cabagan, San Pablo, Sto. Tomas, and Santa Maria. Microsoft Excel and open source GIS software were used in the processing and analysis of data. Results show that in Cabagan, about 3,380 hectares of land were submerged to flood, including about 1,925.56 hectares of cornfields and 407.96 hectares of rice fields. In Santa Maria, about 16.04 percent (245.39has.) of its total land area has been flooded with the cornfields (991.10has), which contributed to the largest area flooded, followed by rice fields and grasslands with 546.76 and 193.72 hectares, respectively. In Sto. Tomas, about 2,724.7 hectares have been flooded, including 1,363.53 hectares of cornfields and 836.65 hectares of rice fields. In San Pablo, the total area flooded was 321.4 hectares. Cornfields represent the largest area flooded (244.8has.) followed by the built-up areas (33.1has.). Based on the survey respondents, the top three interventions made before the onset of widespread flooding were: stay alert on MDRRMC's notice and media news, buy emergency kits, and store food. In relation to the provision of immediate help from the government and non-government organizations, all participants received relief goods, cash aid, clothing, and beddings. In contrast, few received hygiene kits, agricultural inputs (seeds for sowing, seedlings, and fertilizers), and home reconstruction materials. However, there is a need to improve the government's response to the calamity.

The study assessed the extent of typhoon Ulysses flooding and the flood risk management interventions of heavily affected households in Isabela Province. A total of 3,000 respondents were selected through quota sampling technique in four municipalities, namely Cabagan, San Pablo, Sto. Tomas, and Santa Maria. Microsoft Excel and open source GIS software were used in the processing and analysis of data. Results show that in Cabagan, about 3,380 hectares of land were submerged to flood, including about 1,925.56 hectares of cornfields and 407.96 hectares of rice fields. In Santa Maria, about 16.04 percent (245.39has.) of its total land area has been flooded with the cornfields (991.10has), which contributed to the largest area flooded, followed by rice fields and grasslands with 546.76 and 193.72 hectares, respectively. In Sto. Tomas, about 2,724.7 hectares have been flooded, including 1,363.53 hectares of cornfields and 836.65 hectares of rice fields. In San Pablo, the total area flooded was 321.4 hectares. Cornfields represent the largest area flooded (244.8has.) followed by the built-up areas (33.1has.). Based on the survey respondents, the top three interventions made before the onset of widespread flooding were: stay alert on MDRRMC's notice and media news, buy emergency kits, and store food. In relation to the provision of immediate help from the government and non-government organizations, all participants received relief goods, cash aid, clothing, and beddings. In contrast, few received hygiene kits, agricultural inputs (seeds for sowing, seedlings, and fertilizers), and home reconstruction materials. However, there is a need to improve the government's response to the calamity.

A letter report issued by the General Accounting Office with an abstract that begins "The Federal Emergency Management Agency (FEMA) run National Flood Insurance Program (NFIP) has combined flood hazard mitigation efforts and insurance to protect homeowners against losses from floods. The program provides an incentive for communities to adopt floodplain management ordinances to mitigate the effect of flooding upon new or existing structures. Virtually all communities in the country with flood-prone areas now participate in the NFIP, and over four million U.S. households have flood insurance. Nevertheless, the President's proposed budget for 2003 characterizes the NFIP as "moderately effective," because many at-risk properties remain uninsured. The proposed budget establishes a goal to increase flood insurance policies in force by five percent in 2003 and would increase funding for flood zone mapping activities to better identify at-risk properties. Although the assessment and goal described in the proposed budget apply to the entire NFIP, the success of a particular component of the program--the mandatory purchase requirement--has been the subject of debate for many years. The federal bank regulators overseeing lending institutions that hold or service mortgages on properties that must have flood insurance believe that there is a high level of compliance. However, others have questioned whether the requirements are being met. The different types of evidence collected by bank regulators and government-sponsored enterprises on the one hand, and FEMA on the other, are the bases for their opposing perspectives on lender noncompliance with flood insurance purchase requirements. Federal organizations overseeing lenders use bank examinations and loan portfolio reviews to examine a nonstatistical sample of loans for compliance. These organizations uncovered few significant violations, leading them to believe that lenders are complying with flood insurance purchase requirements. In contrast, FEMA relies on its own noncompliance estimates from data it generates itself, from other entities, limited studies it conducted, and anecdotal evidence from public officials and others with knowledge of the program to gauge noncompliance. These data indicate that lenders are not adequately complying with the requirements. GAO's analysis of readily available data does not suggest a major noncompliance problem at loan origination in highly flood-prone areas. Property-specific data on mortgages, flood zone determinations, and flood insurance policies--compiled at loan origination and at various points during the life of the loan--would be needed to fully measure compliance. These data are needed to ensure that homeowners purchase, maintain, and do not terminate required flood insurance."

Cover -- Title -- Copyright -- Contents -- Contributors -- Section 1 Monitoring and Modeling Flood Processes and Hazards -- Chapter 1 - Earth Observation for Flood Applications: Progress and Perspectives -- 1 - Motivation of this book -- 2 - Summary of content -- 2.1 - Section 1: Monitoring and modeling flood processes and hazards -- 2.2 - Section 2: Estimating flood exposure, damage, and risk -- 2.3 - Section 3: Emerging applications and challenges -- Chapter 2 - An Automatic System for Near-Real Time Flood Extent and Duration Mapping Based on Multi-Sensor Satellite Data -- 1 - Introduction -- 2 - Satellite-based multi-sensor flood mapping system -- 2.1 - NRT Flood extent mapping -- 2.1.1 - Auxiliary datasets -- 2.1.2 - TerraSAR-X Flood Service -- 2.1.3 - Sentinel-1 Flood Service -- 2.1.4 - Sentinel-2/Landsat-8 Flood Service -- 2.2 - Flood duration mapping -- 2.2.1 - Backward Flood Duration -- 2.2.2 - Total Flood Duration -- 2.2.3 - Flood duration quality layer -- 3 - Results -- 3.1 - Study area and dataset -- 3.2 - Flood extent masks -- 3.3 - Flood duration products -- 4 - Conclusion -- List of acronyms -- References -- Chapter 3 - Flood Mapping with Passive Microwave Remote Sensing: Current Capabilities and Directions for Future Development -- 1 - Introduction -- 1.1 - Microwave flood mapping for sovereign risk transfer -- 1.2 - Managing flood map ambiguities in applications -- 2 - Methods for passive microwave remote sensing for flood mapping -- 2.1 - Estimating flooded fraction -- 2.2 - Downscaling flooded fraction to map flooding -- 3 - Current capabilities -- 3.1 - Microwave flood mapping verification examples -- 3.2 - Microwave flood mapping uncertainties and limitations -- 3.2.1 - Flooded fraction noise and minimum detectability threshold -- 3.2.2 - Urban areas -- 3.2.3 - Flash false positives -- 3.2.4 - Flood duration.

Abstract. Coastal flooding related to marine extreme events has severe socioeconomic impacts, and even though the latter are projected to increase under the changing climate, there is a clear deficit of information and predictive capacity related to coastal flood mapping. The present contribution reports on efforts towards a new methodology for mapping coastal flood hazard at European scale, combining (i) the contribution of waves to the total water level; (ii) improved inundation modeling; and (iii) an open, physics-based framework which can be constantly upgraded, whenever new and more accurate data become available. Four inundation approaches of gradually increasing complexity and computational costs were evaluated in terms of their applicability to large-scale coastal flooding mapping: static inundation (SM); a semi-dynamic method, considering the water volume discharge over the dykes (VD); the flood intensity index approach (Iw); and the model LISFLOOD-FP (LFP). A validation test performed against observed flood extents during the Xynthia storm event showed that SM and VD can lead to an overestimation of flood extents by 232 and 209 %, while Iw and LFP showed satisfactory predictive skill. Application at pan-European scale for the present-day 100-year event confirmed that static approaches can overestimate flood extents by 56 % compared to LFP; however, Iw can deliver results of reasonable accuracy in cases when reduced computational costs are a priority. Moreover, omitting the wave contribution in the extreme total water level (TWL) can result in a  ∼  60 % underestimation of the flooded area. The present findings have implications for impact assessment studies, since combination of the estimated inundation maps with population exposure maps revealed differences in the estimated number of people affected within the 20–70 % range.

Abstract. Fluvial flood events are a major threat to people and
infrastructure. Typically, flood hazard is driven by hydrologic or river
routing and floodplain flow processes. Since they are often simulated by
different models, coupling these models may be a viable way to increase the
integration of different physical drivers of simulated inundation estimates. To facilitate coupling different models and integrating across flood hazard processes, we here present GLOFRIM 2.0, a globally applicable framework for integrated hydrologic–hydrodynamic modelling. We then tested the hypothesis that smart model coupling can advance inundation modelling in the Amazon and Ganges basins. By means of GLOFRIM, we coupled the global hydrologic model PCR-GLOBWB with the hydrodynamic models CaMa-Flood and LISFLOOD-FP. Results show that replacing the kinematic wave approximation of the hydrologic model with the local inertia equation of CaMa-Flood greatly enhances accuracy of peak discharge simulations as expressed by an increase in the Nash–Sutcliffe efficiency (NSE) from 0.48 to 0.71. Flood maps obtained with LISFLOOD-FP improved representation of observed flood extent (critical success index C=0.46), compared to downscaled products of PCR-GLOBWB and CaMa-Flood (C=0.30 and C=0.25, respectively). Results confirm that model coupling can indeed be a viable way forward towards more integrated flood simulations. However, results also suggest that the accuracy of coupled models still largely depends on the model forcing. Hence, further efforts must be undertaken to improve the magnitude and timing of simulated runoff. In addition, flood risk is, particularly in delta areas, driven by coastal processes. A more holistic representation of flood processes in delta areas, for example by incorporating a tide and surge model, must therefore be a next development step of GLOFRIM, making even more physically robust estimates possible for adequate flood risk management practices.

Remote sensing of Arctic water bodies is an essential method for monitoring the dynamics of frozen ground. Thaw lake change provides insight into the state of permafrost. In the vast Arctic and sub-Arctic areas capturing changes in lake extent is assisted by satellite data. In particular, active microwave sensors can be used in a straightforward manner for water body classifications. This study uses the pan-Siberian datasets that are provided under the ESA STSE-ALANIS methane project. Surface water classifications in 10-day intervals have been produced using Envisat ASAR (Advanced Synthetic Aperture Radar) operating in wide swath mode. The high temporal frequency of these data allows an investigation of surface hydrology on an intra-annual basis. The current study applies a post-processing algorithm to the ALANIS products in order to investigate changes in surface inundation across the Yamalo-Nenets Autonomous District over the summer period of 2007. Multiple areas are found to exhibit changes in surface inundation. Strong seasonal variations occur in areas where previous investigations determined disappearing lakes. Spring floods associated with the depletion of snow-cover and melt waters as well as floodplain dynamics can be identified. On the Yamal peninsula, these changes occur most dominantly in the west; an area subject to anthropogenic land-use change. Changes in water body extent for each hot spot of seasonal variations are quantified and discussed. ; European Space Agency (ESA) Support to Science Element (STSE) programme (ESRIN) ; the European Union FP7-ENV ; Austrian Science Fund (FWF)

Abstract. Floods affect more people than any other natural hazard; thus flood warning and disaster management are of utmost importance. However, the operational hydrological forecasts do not provide information about affected areas and impact but only discharge and water levels at gauges. We show that a simple hydrodynamic model operating with readily available data is able to provide highly localized information on the expected flood extent and impacts, with simulation times enabling operational flood warning. We demonstrate that such an impact forecast would have indicated the deadly potential of the 2021 flood in western Germany with sufficient lead time.

Flooding is one of the most catastrophic events among the wide spectrum of natural disasters that impact human communities. The identification of flood-prone areas and the probability of occurrence, or estimated return period, of flood events are fundamental to proper planning for flood management and minimi-zation of the social and economic costs of flood damage. In this study, 2D flood models of the Mert River, which flows into the Black Sea at Samsun in north-central Turkey, were developed. Based on the flood modeling results, flood extent, flood depth and flood hazard maps for the river were produced and they showed that the study area is particularly flood prone, as evidenced by catastrophic flooding in 2012. Specifically, the estimated 100-, 500- and 1000-year peak discharges would affect 184 ha, 262 ha and 304 ha, respectively, of the 1200 ha study area. Hazard ratings for the areas expected to be affected are shown in the flood hazard maps generated. The results of this research can be used by local government agencies in Samsun for the development of policies, strategies and actions that would help minimize the social and economic impacts of flooding, especially adjacent to the downstream sections where there is intensive development on the flood plain.

Abstract. This research proposes a methodology that leverages non-authoritative data to augment flood extent mapping and the evaluation of transportation infrastructure. The novelty of this approach is the application of freely available, non-authoritative data and its integration with established data and methods. Crowdsourced photos and volunteered geographic data are fused together using a geostatistical interpolation to create an estimation of flood damage in New York City following Hurricane Sandy. This damage assessment is utilized to augment an authoritative storm surge map as well as to create a road damage map for the affected region.

Abstract. Flood risk communication with the general public and the population at risk is getting increasingly important for flood risk management, especially as a precautionary measure. This is also underlined by the EU Flood Directive. The flood related authorities therefore have to develop adjusted information tools which meet the demands of different user groups. This article presents the formative evaluation of flood hazard maps and web mapping services according to the specific requirements and needs of the general public using the dynamic-transactional approach as a theoretical framework. The evaluation was done by a mixture of different methods; an analysis of existing tools, a creative workshop with experts and laymen and an online survey. The currently existing flood hazard maps or web mapping services or web GIS still lack a good balance between simplicity and complexity with adequate readability and usability for the public. Well designed and associative maps (e.g. using blue colours for water depths) which can be compared with past local flood events and which can create empathy in viewers, can help to raise awareness, to heighten the activity and knowledge level or can lead to further information seeking. Concerning web mapping services, a linkage between general flood information like flood extents of different scenarios and corresponding water depths and real time information like gauge levels is an important demand by users. Gauge levels of these scenarios are easier to understand than the scientifically correct return periods or annualities. The recently developed Bavarian web mapping service tries to integrate these requirements.