scholarly journals Developments in large-scale coastal flood hazard mapping

2016 ◽  
Author(s):  
Michalis I. Vousdoukas ◽  
Evangelos Voukouvalas ◽  
Lorenzo Mentaschi ◽  
Francesco Dottori ◽  
Alessio Giardino ◽  
...  
Keyword(s):  
Large Scale ◽  
Flood Hazard ◽  
Coastal Flooding ◽  
Water Volume ◽  
Hazard Mapping ◽  
Population Exposure ◽  
Storm Event ◽  
Volume Discharge ◽  
Computational Costs ◽  
Coastal Flood

Abstract. Coastal flooding related to marine extreme events has severe socio-economic 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 modelling; 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 for 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 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 affect within the 20–70 % range.

scholarly journals Developments in large-scale coastal flood hazard mapping

2016 ◽  
Vol 16 (8) ◽  
pp. 1841-1853 ◽  
Author(s):  
Michalis I. Vousdoukas ◽  
Evangelos Voukouvalas ◽  
Lorenzo Mentaschi ◽  
Francesco Dottori ◽  
Alessio Giardino ◽  
...  
Keyword(s):  
Water Level ◽  
Large Scale ◽  
Flood Hazard ◽  
Coastal Flooding ◽  
Hazard Mapping ◽  
Volume Discharge ◽  
Total Water ◽  
Computational Costs ◽  
Coastal Flood ◽  
Total Water Level

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.

scholarly journals An integrated framework of coastal flood modelling under the failures of sea dikes: a case study in Shanghai

2021 ◽  
Author(s):  
Qian Ke ◽  
Jiangshan Yin ◽  
Jeremy D. Bricker ◽  
Nicholas Savage ◽  
Erasmo Buonomo ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Flood Hazard ◽  
Discharge Rate ◽  
Coastal Flooding ◽  
Water Volume ◽  
Coastal Flood ◽  
Sea Dikes ◽  
And Sea Level

AbstractClimate change leads to sea level rise worldwide, as well as increases in the intensity and frequency of tropical cyclones (TCs). Storm surge induced by TC’s, together with spring tides, threatens to cause failure of flood defenses, resulting in massive flooding in low-lying coastal areas. However, limited research has been done on the combined effects of the increasing intensity of TCs and sea level rise on the characteristics of coastal flooding due to the failure of sea dikes. This paper investigates the spatial variation of coastal flooding due to the failure of sea dikes subject to past and future TC climatology and sea level rise, via a case study of a low-lying deltaic city- Shanghai, China. Using a hydrodynamic model and a spectral wave model, storm tide and wave parameters were calculated as input for an empirical model of overtopping discharge rate. The results show that the change of storm climatology together with relative sea level rise (RSLR) largely exacerbates the coastal hazard for Shanghai in the future, in which RSLR is likely to have a larger effect than the TC climatology change on future coastal flooding in Shanghai. In addition, the coastal flood hazard will increase to a large extent in terms of the flood water volume for each corresponding given return period. The approach developed in this paper can also be utilized to investigate future flood risk for other low-lying coastal regions.

scholarly journals Coastal Flooding in the Maldives Induced by Mean Sea-Level Rise and Wind-Waves: From Global to Local Coastal Modelling

2021 ◽  
Vol 8 ◽  
Author(s):  
Angel Amores ◽  
Marta Marcos ◽  
Rodrigo Pedreros ◽  
Gonéri Le Cozannet ◽  
Sophie Lecacheux ◽  
...  
Keyword(s):  
Climate Change ◽  
Sea Level Rise ◽  
Sea Level ◽  
Large Scale ◽  
Land Reclamation ◽  
Flood Hazard ◽  
Wind Waves ◽  
Coastal Flooding ◽  
Major Drawback ◽  
Mean Sea Level

The Maldives, with one of the lowest average land elevations above present-day mean sea level, is among the world regions that will be the most impacted by mean sea-level rise and marine extreme events induced by climate change. Yet, the lack of regional and local information on marine drivers is a major drawback that coastal decision-makers face to anticipate the impacts of climate change along the Maldivian coastlines. In this study we focus on wind-waves, the main driver of extremes causing coastal flooding in the region. We dynamically downscale large-scale fields from global wave models, providing a valuable source of climate information along the coastlines with spatial resolution down to 500 m. This dataset serves to characterise the wave climate around the Maldives, with applications in regional development and land reclamation, and is also an essential input for local flood hazard modelling. We illustrate this with a case study of HA Hoarafushi, an atoll island where local topo-bathymetry is available. This island is exposed to the highest incoming waves in the archipelago and recently saw development of an airport island on its reef via land reclamation. Regional waves are propagated toward the shoreline using a phase-resolving model and coastal inundation is simulated under different mean sea-level rise conditions of up to 1 m above present-day mean sea level. The results are represented as risk maps with different hazard levels gathering inundation depth and speed, providing a clear evidence of the impacts of the sea level rise combined with extreme wave events.

scholarly journals A holistic model for coastal flooding using system diagrams and the Source-Pathway-Receptor (SPR) concept

2012 ◽  
Vol 12 (5) ◽  
pp. 1431-1439 ◽  
Author(s):  
S. Narayan ◽  
S. Hanson ◽  
R. J. Nicholls ◽  
D. Clarke ◽  
P. Willems ◽  
...  
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Flood Management ◽  
Coastal Flooding ◽  
System Level ◽  
Holistic Model ◽  
Directional Model ◽  
Coastal Flood ◽  
Systems Model ◽  
Level Analysis

Abstract. Coastal flooding is a problem of increasing relevance in low-lying coastal regions worldwide. In addition to the anticipated increase in likelihood and magnitude of coastal floods due to climate change, there is rapid growth in coastal assets and infrastructure. Sustainable and integrated coastal flood management over large areas and varying coastline types cannot be simply treated as local combinations of flood defences and floodplains. Rather, a system level analysis of floodplains is required to structure the problem as a first step before applying quantitative models. In this paper such a model is developed using system diagrams and the Source-Pathway-Receptor (SPR) concept, to structure our understanding of large and complex coastal flood systems. A graphical systems model is proposed for the assessment of coastal flood systems with regard to individual elements and their topological relationships. Two examples are discussed – a unidirectional model for a large-scale flood system, and a multi-directional model for a smaller-scale system, both based on the Western Scheldt estuary. The models help to develop a comprehensive understanding of system elements and their relationships and provide a holistic overview of the coastal flood system. The approach shows that a system level analysis of floodplains is more effective than simple topographic maps when conveying complex information. The models are shown to be useful as an apriori approach for making the assumptions about flood mechanisms explicit and for informing inputs to numerical models.

scholarly journals A GIS-Based Hydrological Modeling Approach for Rapid Urban Flood Hazard Assessment

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1483
Author(s):  
Qianqian Zhou ◽  
Jiongheng Su ◽  
Karsten Arnbjerg-Nielsen ◽  
Yi Ren ◽  
Jinhua Luo ◽  
...  
Keyword(s):  
Large Scale ◽  
Hydrological Modeling ◽  
Performance Indicator ◽  
Flood Hazard ◽  
Flood Mapping ◽  
Hazard Mapping ◽  
Flood Hazards ◽  
Topographic Wetness Index ◽  
Urban Flood ◽  
Mapping Techniques

Urban floods are detrimental to societies, and flood mapping techniques provide essential support for decision-making on the better management of flood risks. This study presents a GIS-based flood characterization methodology for the rapid and efficient identification of urban flood-prone areas, which is especially relevant for large-scale flood hazards and emergency assessments for data-scarce studies. The results suggested that optimal flood mapping was achieved by adopting the median values of the thresholds for local depression extraction, the topographic wetness index (TWI) and aggregation analyses. This study showed the constraints of the depression extraction and TWI methods and proposed a methodology to improve the performance. A new performance indicator was further introduced to improve the evaluation ability of hazard mapping. It was shown that the developed methodology has a much lower demand on the data and computation efforts in comparison to the traditional two-dimensional models and, meanwhile, provides relatively accurate and robust assessments of flood hazards.

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