Geosciences

Research

20 pages, 13271 KiB

Open AccessArticle

Interdisciplinary Design of Vital Infrastructure to Reduce Flood Risk in Tokyo’s Edogawa Ward

by Supriya Krishnan, Jiabiao Lin, Johannes Simanjuntak, Fransje Hooimeijer, Jeremy Bricker, Maayan Daniel and Yuka Yoshida

Geosciences 2019, 9(8), 357; https://doi.org/10.3390/geosciences9080357 - 13 Aug 2019

Cited by 6 | Viewed by 5385

Abstract

Engineering for flood resilience of dense coastal regions often neglects the resultant impact on urban design quality. Vital subsurface infrastructure such as hydraulic systems, water networks, civil construction, transport, energy supply and soil systems are especially important in shaping the urban environment and [...] Read more.

Engineering for flood resilience of dense coastal regions often neglects the resultant impact on urban design quality. Vital subsurface infrastructure such as hydraulic systems, water networks, civil construction, transport, energy supply and soil systems are especially important in shaping the urban environment and integrating resilience. However, the complexity and resource intensive nature of these engineering domains make it a challenge to incorporate them into design measures. In the process of planning, this impedes proactive collaboration between the design and engineering communities. This study presents a collaborative design engineering exercise undertaken to find spatial solutions to flood-prone Edogawa ward in Tokyo, Japan. The team included urbanists, hydraulic engineers, water resource managers, and landscape architects. Hydraulic engineering solutions were combined with spatial planning methods to deliver two alternative strategies for the chosen site. Each alternative was then evaluated for its urban design quality and effectiveness in reducing flood risk. The exercise highlighted that successful design requires comprehensive interdisciplinary collaboration to arrive at a sustainable bargain between hard and soft measures. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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19 pages, 17122 KiB

Open AccessArticle

Understanding Community-Level Flooding Awareness in Remote Coastal Towns in Northern Chile through Community Mapping

by Carlota Cubelos, A. H. T. Shyam Kularathna, Ven Paolo Bruno Valenzuela, Nikolaos Iliopoulos, Marco Quiroz, Ramon Yavar, Pedro Henriquez, Gonzalo Bacigalupe, Motoharu Onuki, Takahito Mikami, Rodrigo Cienfuegos, Rafael Aranguiz and Miguel Esteban

Geosciences 2019, 9(7), 279; https://doi.org/10.3390/geosciences9070279 - 26 Jun 2019

Cited by 14 | Viewed by 6468

Abstract

In 2015 and 2017 unusual ocean and atmospheric conditions produced many years’ worth of rainfall in short periods over Northern Chile’s Atacama Desert, resulting in catastrophic flooding in the town of Chañaral. However, the town is not only at risk of fluvial flooding, [...] Read more.

In 2015 and 2017 unusual ocean and atmospheric conditions produced many years’ worth of rainfall in short periods over Northern Chile’s Atacama Desert, resulting in catastrophic flooding in the town of Chañaral. However, the town is not only at risk of fluvial flooding, it is also at risk of tsunamis. Through a community mapping exercise, the authors attempted to establish the level of community awareness about tsunamis, and contrasted it with that of other types of water-related hazards facing the town (namely that of flooding due to high intensity rain). This was then compared with the results of field surveys and tsunami hazard simulations, indicating than overall the community appears to have better awareness than authorities about the threat posed by these types of events. The authors thus concluded that in cases when the community has a high level of hazard awareness (which in the case of Chile was the result of traditional knowledge being transmitted from previous generations) it would be advantageous to include them in discussions on how to improve disaster resilience. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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36 pages, 10445 KiB

Open AccessArticle

Role of Trapped Air on the Tsunami-Induced Transient Loads and Response of Coastal Bridges

by Denis Istrati and Ian Buckle

Geosciences 2019, 9(4), 191; https://doi.org/10.3390/geosciences9040191 - 25 Apr 2019

Cited by 47 | Viewed by 5158

Abstract

In response to the extensive damage of coastal bridges sustained in recent tsunamis, this paper describes an investigation into tsunami-induced effects on two common bridge types, an open-girder deck with cross-frames and one with solid diaphragms. To this end, large-scale (1:5) physical models [...] Read more.

In response to the extensive damage of coastal bridges sustained in recent tsunamis, this paper describes an investigation into tsunami-induced effects on two common bridge types, an open-girder deck with cross-frames and one with solid diaphragms. To this end, large-scale (1:5) physical models with realistic structural members and elastomeric bearings were constructed and tested under a range of unbroken solitary waves and more realistic tsunami-like transient bores. The flexible bearings allowed the superstructure to rotate and translate vertically, thus simulating the wave–structure interaction during the tsunami inundation. Detailed analysis of the experimental data revealed that for both bridge types the resistance mechanism and transient structural response is characterized by a short-duration phase that introduces the maximum overturning moment, upward movement, and rotation of the deck, and a longer-duration phase that introduces significant uplift forces but small moment and rotation due to the fact that the wave is approaching the point of rotation. In the former phase the uplift is resisted mainly by the elastomeric bearings and columns offshore of the center of gravity of the superstructure (C.G.), maximizing their uplift demand. In the latter phase the total uplift is distributed more equally to all the bearings, which tends to maximize the uplift demand in the structural members close to the C.G. The air-entrapment in the chambers of the bridge with diaphragms modifies the wave–structure interaction, introducing (a) a different pattern and magnitude of wave pressures on the superstructure due to the cushioning effect; (b) a 39% average and 148% maximum increase in the total uplift forces; and (c) a 32% average increase of the overturning moment, which has not been discussed in previous studies. Deciphering the exact effect of the trapped air on the total uplift forces is challenging because, although the air consistently increases the quasi-static component of the force, it has an inconsistent and complex effect on the slamming component, which can either increase or decrease. Interestingly, the air also has a complex effect on the uplift demand in the offshore bearings and columns, which can decrease or increase even more than the total deck uplift, and an inconsistent effect on the uplift force of different structural components introduced by the same wave. These are major findings because they demonstrate that the current approach of investigating the effect of trapped air only on the total uplift is insufficient. Last but not least, the study reveals the existence of significant differences in the effects introduced by solitary waves and transient bores, especially when air is trapped beneath the deck; it also provides practical guidance to engineers, who are advised to design the elastomeric bearings offshore of the C.G. for at least 60% and 50% of the total induced uplift force, respectively, for a bridge with cross-frames and one with diaphragms, instead of distributing the total uplift equally to all bearings. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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32 pages, 14760 KiB

Open AccessArticle

Sentinel-1 for Monitoring Land Subsidence of Coastal Cities in Africa Using PSInSAR: A Methodology Based on the Integration of SNAP and StaMPS

by Fabio Cian, José Manuel Delgado Blasco and Lorenzo Carrera

Geosciences 2019, 9(3), 124; https://doi.org/10.3390/geosciences9030124 - 12 Mar 2019

Cited by 58 | Viewed by 11907

Abstract

The sub-Saharan African coast is experiencing fast-growing urbanization, particularly around major cities. This threatens the equilibrium of the socio-ecosystems where they are located and on which they depend: underground water resources are exploited with a disregard for sustainability; land is reclaimed from wetlands [...] Read more.

The sub-Saharan African coast is experiencing fast-growing urbanization, particularly around major cities. This threatens the equilibrium of the socio-ecosystems where they are located and on which they depend: underground water resources are exploited with a disregard for sustainability; land is reclaimed from wetlands or lagoons; built-up areas, both formal and informal, grow without adequate urban planning. Together, all these forces can result in land surface deformation, subsidence or even uplift, which can increase risk within these already fragile socio-ecosystems. In particular, in the case of land subsidence, the risk of urban flooding can increase significantly, also considering the contribution of sea level rise driven by climate change. Monitoring such fast-changing environments is crucial to be able to identify key risks and plan adaptation responses to mitigate current and future flood risks. Persistent scatterer interferometry (PSI) with synthetic aperture radar (SAR) is a powerful tool to monitor land deformation with high precision using relatively low-cost technology, also thanks to the open access data of Sentinel-1, which provides global observations every 6 days at 20-m ground resolution. In this paper, we demonstrate how it is possible to monitor land subsidence in urban coastal areas by means of permanent scatterer interferometry and Sentinel-1, exploiting an automatic procedure based on an integration of the Sentinel Application Platform (SNAP) and the Stanford Method for Persistent Scatterers (StaMPS). We present the results of PSI analysis over the cities of Banjul (the Gambia) and Lagos (Nigeria) showing a comparison of results obtained with TerraSAR-X, Constellation of Small Satellites for the Mediterranean Basin Observation (COSMO-SkyMed) and Environmental Satellite advanced synthetic aperture radar (Envisat-ASAR) data. The methodology allows us to highlight areas of high land deformation, information that is useful for urban development, disaster risk management and climate adaptation planning. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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25 pages, 22717 KiB

Open AccessArticle

Modelling Coastal Flood Propagation under Sea Level Rise: A Case Study in Maria, Eastern Canada

by David Didier, Marion Bandet, Pascal Bernatchez and Dany Dumont

Geosciences 2019, 9(2), 76; https://doi.org/10.3390/geosciences9020076 - 2 Feb 2019

Cited by 9 | Viewed by 6188

Abstract

Coastal management often relies on large-scale flood mapping to produce sea level rise assessments where the storm-related surge is considered as the most important hazard. Nearshore dynamics and overland flow are also key parameters in coastal flood mapping, but increase the model complexity. [...] Read more.

Coastal management often relies on large-scale flood mapping to produce sea level rise assessments where the storm-related surge is considered as the most important hazard. Nearshore dynamics and overland flow are also key parameters in coastal flood mapping, but increase the model complexity. Avoiding flood propagation processes using a static flood mapping is less computer-intensive, but generally leads to overestimation of the flood zone, especially in defended urban backshore. For low-lying communities, sea level rise poses a certain threat, but its consequences are not only due to a static water level. In this paper, the numerical process-based model XBeach is used in 2D hydrodynamic mode (surfbeat) to reproduce an observed historical flood in Maria (eastern Canada). The main goal is to assess the impacts of a future storm of the same magnitude in the horizon 2100 according to an increase in sea level rise. The model is first validated from in situ observations of waves and water levels observed on the lower foreshore. Based on field observations of a flood extent in 2010, the simulated flooded area was also validated given a good fit (59%) with the actual observed flood. Results indicate that the 2010 storm-induced surge generated overwash processes on multiple areas and net landward sediment transport and accumulation (washover lobes). The flood was caused by relatively small nearshore waves (H_s < 1 m), but despite small water depth (>1.2 m), high flow velocities occurred in the main street (U > 2 m/s) prior to draining in the salt marsh. The impact of sea level rise on the low-lying coastal community of Maria could induce a larger flood area in 2100, deeper floodwater, and higher flow velocities, resulting in higher hazard for the population. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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16 pages, 6236 KiB

Open AccessArticle

Comparative Analysis of Tsunami Recovery Strategies in Small Communities in Japan and Chile

by Ven Paolo Bruno Valenzuela, Ratnayakage Sameera Maduranga Samarasekara, A.H.T. Shyam Kularathna, G. Carlota Cubelos Perez, Furukawa Norikazu, Richard Nathan Crichton, Marco Quiroz, Ramon Yavar, Ikeda Izumi, Rafael Aranguiz, Onuki Motoharu and Miguel Esteban

Geosciences 2019, 9(1), 26; https://doi.org/10.3390/geosciences9010026 - 7 Jan 2019

Cited by 11 | Viewed by 5780

Abstract

The Sendai Framework for Disaster Risk Reduction emphasizes the need to rebuild better after a disaster to ensure that the at-risk communities can withstand a similar or stronger shock in the future. In the present work, the authors analyzed the reconstruction paths through [...] Read more.

The Sendai Framework for Disaster Risk Reduction emphasizes the need to rebuild better after a disaster to ensure that the at-risk communities can withstand a similar or stronger shock in the future. In the present work, the authors analyzed the reconstruction paths through a comparative analysis of the perspective of a community in Japan and another in Chile, and their respective local governments. While both countries are at risk to tsunamis, they follow different reconstruction philosophies. Data was gathered through key informant interviews of community members and local government officials, by adapting and modifying the Building Resilience to Adapt to Climate Extremes and Disasters (BRACED) 3As framework to a tsunami scenario. The 3As represent anticipatory, adaptive, and absorptive capacities as well as transformative capacities and respondents were asked to rate this according to their perspectives. It was found that while both communities perceive that much is to be done in recovery, Kirikiri has a more holistic and similar perspective of the recovery with their government officials as compared to Dichato. This shows that community reconstruction and recovery from a disaster requires a holistic participation and understanding. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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15 pages, 9776 KiB

Open AccessArticle

Unsteady Seepage Behavior of an Earthfill Dam During Drought-Flood Cycles

by Ziyang Li, Wei Ye, Miroslav Marence and Jeremy D. Bricker

Geosciences 2019, 9(1), 17; https://doi.org/10.3390/geosciences9010017 - 28 Dec 2018

Cited by 16 | Viewed by 4254

Abstract

Climate change with extreme hydrological conditions, such as drought and flood, bring new challenges to seepage behavior and the stability of earthfill dams. Taking a drought-stricken earthfill dam of China as an example, the influence of drought-flood cycles on dam seepage behavior is [...] Read more.

Climate change with extreme hydrological conditions, such as drought and flood, bring new challenges to seepage behavior and the stability of earthfill dams. Taking a drought-stricken earthfill dam of China as an example, the influence of drought-flood cycles on dam seepage behavior is analyzed. This paper includes a clay sample laboratory experiment and an unsteady finite element method seepage simulation of the mentioned dam. Results show that severe drought causes cracks on the surface of the clay soil sample. Long-term drought causes deeper cracks and induces a sharp increase of suction pressure, indicating that the cracks would become channels for rain infiltration into the dam during subsequent rainfall, increasing the potential for internal erosion and decreasing dam stability. Measures to prevent infiltration on the dam slope surface are investigated, for the prevention of deep crack formation during long lasting droughts. Unsteady seepage indicators including instantaneous phreatic lines, equipotential lines and pore pressure gradient in the dam, are calculated and analyzed under two assumed conditions with different reservoir water level fluctuations. Results show that when the water level changes rapidly, the phreatic line is curved and constantly changing. As water level rises, equipotential lines shift upstream, and the pore pressure gradient in the dam’s main body is larger than that of steady seepage. Furthermore, the faster the water level rises, the larger the pore pressure gradient is. This may cause internal erosion. Furthermore, the case of a cracked upstream slope is modelled via an equivalent permeability coefficient, which shows that the pore pressure gradient in the zone beneath the cracks increases by 5.9% at the maximum water level; this could exacerbate internal erosion. In addition, results are in agreement with prior literature that rapid drawdown of the reservoir water level is detrimental to the stability of the upstream slope based on embankment slope stability as calculated by the Simplified Bishop Method. It is concluded that fluctuations of reservoir water level should be strictly controlled during drought-flood cycles; both the drawdown rate and the fill rate must be regulated to avoid the internal erosion of earthfill dams. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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22 pages, 11079 KiB

Open AccessArticle

Comparison of Implicit and Explicit Vegetation Representations in SWAN Hindcasting Wave Dissipation by Coastal Wetlands in Chesapeake Bay

by Christophe Baron-Hyppolite, Christopher H. Lashley, Juan Garzon, Tyler Miesse, Celso Ferreira and Jeremy D. Bricker

Geosciences 2019, 9(1), 8; https://doi.org/10.3390/geosciences9010008 - 24 Dec 2018

Cited by 20 | Viewed by 4129

Abstract

Assessing the accuracy of nearshore numerical models—such as SWAN—is important to ensure their effectiveness in representing physical processes and predicting flood hazards. In particular, for application to coastal wetlands, it is important that the model accurately represents wave attenuation by vegetation. In SWAN, [...] Read more.

Assessing the accuracy of nearshore numerical models—such as SWAN—is important to ensure their effectiveness in representing physical processes and predicting flood hazards. In particular, for application to coastal wetlands, it is important that the model accurately represents wave attenuation by vegetation. In SWAN, vegetation might be implemented either implicitly, using an enhanced bottom friction; or explicitly represented as drag on an immersed body. While previous studies suggest that the implicit representation underestimates dissipation, field data has only recently been used to assess fully submerged vegetation. Therefore, the present study investigates the performance of both the implicit and explicit representations of vegetation in SWAN in simulating wave attenuation over a natural emergent marsh. The wave and flow modules within Delft3D are used to create an open-ocean model to simulate offshore wave conditions. The domain is then decomposed to simulate nearshore processes and provide the boundary conditions necessary to run a standalone SWAN model. Here, the implicit and explicit representations of vegetation are finally assessed. Results show that treating vegetation simply as enhanced bottom roughness (implicitly) under-represents the complexity of wave-vegetation interaction and, consequently, underestimates wave energy dissipation (error > 30%). The explicit vegetation representation, however, shows good agreement with field data (error < 20%). Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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16 pages, 7529 KiB

Open AccessArticle

Emergency Flood Control: Practice-Oriented Test Series for the Use of Sandbag Replacement Systems

by Christopher Massolle, Lena Lankenau and Bärbel Koppe

Geosciences 2018, 8(12), 482; https://doi.org/10.3390/geosciences8120482 - 13 Dec 2018

Cited by 4 | Viewed by 6044

Abstract

In operational flood defense, it is common practice to use sandbag systems. However, their installation is time-consuming as well as material- and labor-intensive. Sandbag replacement systems (SBRSs) can be installed in significantly shorter time and with less effort. However, owing to the lack [...] Read more.

In operational flood defense, it is common practice to use sandbag systems. However, their installation is time-consuming as well as material- and labor-intensive. Sandbag replacement systems (SBRSs) can be installed in significantly shorter time and with less effort. However, owing to the lack of confidence in their functionality, they are only used to a limited extent. Testing and certifying such innovative systems according to defined criteria is supportive in promoting their use in flood defense. In order to test SBRSs and as a first step toward systematic tests, the Institute for Hydraulic and Coastal Engineering of the Bremen University of Applied Sciences, Germany (IWA) has set up a test facility in which defined test series can be carried out with different SBRSs on an underlying surface of turf. The focus of the test series is on installation time, possible water head, system stability, and seepage rates when in use. A conventional sandbag dam was used as reference in order to compare the test results with the different SBRSs. Test series show that damming with SBRSs has a clear advantage over the use of sandbags in terms of the time it takes to put them in place and comparable values of seepage rates and water heads. In order to professionally promote the spread of SBRSs in operational flood protection, it is recommended to introduce the certification of SBRSs, since they are technical systems whose functional capability must be proven before their use in an emergency. Together with existing international certification schemes, the test series that were carried out deliver a basis for developing a specific testing scheme for SBRSs. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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16 pages, 3997 KiB

Open AccessArticle

The Severe 2013–14 Winter Storms in the Historical Evolution of Cantabrian (Northern Spain) Beach-Dune Systems

by Julio Garrote, Aurora Díaz-Álvarez, Hélio V. Nganhane and Guillermina Garzón Heydt

Geosciences 2018, 8(12), 459; https://doi.org/10.3390/geosciences8120459 - 5 Dec 2018

Cited by 12 | Viewed by 2640

Abstract

The 2013–14 winter storms were the most energetic storms in the European Atlantic on record since at least 1948. They caused intense erosive processes along the coast, similar to those described previously in places such as the United Kingdom and France. In this [...] Read more.

The 2013–14 winter storms were the most energetic storms in the European Atlantic on record since at least 1948. They caused intense erosive processes along the coast, similar to those described previously in places such as the United Kingdom and France. In this study, an analysis is conducted of the historical evolution (1956–2017) of four dune systems in the region of Cantabria (northern Spain) and their response to such storms. The analysis uses aerial images (from 1956, 2002, 2010, 2014, and 2017) implemented in ArcGIS, and the Digital Shoreline Analysis System (DSAS) model for the estimation of a series of statistical parameters relative to the historical behavior of the shoreline. The DSAS model allows a geometric structure to be calculated that is flexible and can be adapted to the morphological conditions of the coast. The results obtained from the model for the entire historical period and the pre-storm analysis show clear variability in the evolution of the dune systems, while the post-storm analysis yields homogeneous results that indicate significant erosion, with no signs of recovery. The limited time elapsed since the 2013–14 winter storm clustering and the high interannual energy variability of the subsequent winters seem to be behind the absence of evidence of dune system recovery and even the increase in the erosion processes observed in some cases. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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16 pages, 1948 KiB

Open AccessArticle

Survey Tool for Rapid Assessment of Socio-Economic Vulnerability of Fishing Communities in Vietnam to Climate Change

by John Erick Avelino, Richard Nathan Crichton, Ven Paolo Valenzuela, Merenchi Galappaththige Nipuni Odara, Michael Adrian Triguero Padilla, Nguyen Kiet, Dang Hoang Anh, Pham Cam Van, Ho Dac Bao, Nguyen Hoang Phuong Thao, Mai Thi Yen Linh, Pham Thi Phuoc Hoai, Nguyen Danh Thao, Motoharu Onuki and Miguel Esteban

Geosciences 2018, 8(12), 452; https://doi.org/10.3390/geosciences8120452 - 3 Dec 2018

Cited by 11 | Viewed by 4672

Abstract

Climate change will likely affect the effectiveness of future management of coastal ecosystems, impacting communities that reside within the coastal area. In order to formulate appropriate adaptation counter-measures it is important to understand the actual vulnerability of the communities that depend on these [...] Read more.

Climate change will likely affect the effectiveness of future management of coastal ecosystems, impacting communities that reside within the coastal area. In order to formulate appropriate adaptation counter-measures it is important to understand the actual vulnerability of the communities that depend on these ecosystems. The present research proposes a tool for assessing the vulnerability of coastal communities to climate change by combining survey results with secondary and observed data available from national and local governments. The study focused on fisheries, given that they constitute the source of livelihood for many communities in developing countries such as Vietnam. The results showed that two coastal wards in Binh Thuan province, Vietnam, are highly vulnerable to the impacts of climate change, mainly because of their dependence on fisheries and the topography of the area. The seasonality of their source of livelihood affects the adaptive capacity of residents, making it less likely that they will be able to successfully adapt to changes in fishery resources that could be brought about by climate change. The results also showed that the communities are particularly vulnerable to sea level rise, given that they are both located in the immediate vicinity of the sea and are particularly low in elevation. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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10 pages, 1441 KiB

Open AccessArticle

Contributions to Coastal Flooding Events in Southeast of Vietnam and their link with Global Mean Sea Level Rise

by Luis Pedro Melo de Almeida, Rafael Almar, Benoit Meyssignac and Nguyen Trung Viet

Geosciences 2018, 8(12), 437; https://doi.org/10.3390/geosciences8120437 - 26 Nov 2018

Cited by 14 | Viewed by 3567

Abstract

This work analyzes the components of the total water level (TWL) that cause flooding in a tropical coastal area (Nha Trang beach, Southeast of Vietnam), and examines their link with global mean sea level rise (GMSLR). Interactions between the wave induced run-up (R) [...] Read more.

This work analyzes the components of the total water level (TWL) that cause flooding in a tropical coastal area (Nha Trang beach, Southeast of Vietnam), and examines their link with global mean sea level rise (GMSLR). Interactions between the wave induced run-up (R) and astronomical tide (AT) were responsible for 43% of the 35 flooding events identified between 1993 and 2015. Most of these events (97%) took place during the winter monsoon season, when long-lasting extreme R and positive non-tidal residual (NTR) are likely to occur. Removal of the GMSLR trend from the NTR was found to affect the flood occurrence of 17% of these events, while the trend in wave height did not have any detectable impact. Our research highlights the direct connection between global climate changes and coastal flooding events. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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19 pages, 10420 KiB

Open AccessArticle

Field Survey of 2018 Typhoon Jebi in Japan: Lessons for Disaster Risk Management

by Tomoyuki Takabatake, Martin Mäll, Miguel Esteban, Ryota Nakamura, Thit Oo Kyaw, Hidenori Ishii, Justin Joseph Valdez, Yuta Nishida, Fuma Noya and Tomoya Shibayama

Geosciences 2018, 8(11), 412; https://doi.org/10.3390/geosciences8110412 - 9 Nov 2018

Cited by 32 | Viewed by 9415

Abstract

Typhoon Jebi struck Japan on the 4 September 2018, damaging and inundating many coastal areas along Osaka Bay due to the high winds, a storm surge, and wind driven waves. In order to understand the various damage mechanisms, the authors conducted a field [...] Read more.

Typhoon Jebi struck Japan on the 4 September 2018, damaging and inundating many coastal areas along Osaka Bay due to the high winds, a storm surge, and wind driven waves. In order to understand the various damage mechanisms, the authors conducted a field survey two days after the typhoon made landfall, measuring inundation heights and depths at several locations in Hyogo Prefecture. The survey results showed that 0.18–1.27 m inundation depths were caused by Typhoon Jebi. As parts of the survey, local residents were interviewed about the flooding, and a questionnaire survey regarding awareness of typhoons and storm surges, and their response to the typhoon was distributed. The authors also mapped the location of some of the containers that were displaced by the storm surge, aiming to provide information to validate future simulation models of container displacement. Finally, some interesting characteristics of the storm surge are summarized, such as possible overtopping at what had initially been thought to be a low risk area (Suzukaze town), and lessons learnt in terms of disaster risk management are discussed. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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26 pages, 16021 KiB

Open AccessArticle

Hydrodynamic and Debris-Damming Failure of Bridge Decks and Piers in Steady Flow

by Kevin Oudenbroek, Nader Naderi, Jeremy D. Bricker, Yuguang Yang, Cor Van der Veen, Wim Uijttewaal, Shuji Moriguchi and Sebastiaan N. Jonkman

Geosciences 2018, 8(11), 409; https://doi.org/10.3390/geosciences8110409 - 9 Nov 2018

Cited by 29 | Viewed by 7427

Abstract

In countries with steep rivers, such as Japan and the United States, bridges fail on an annual basis. Bridges on spread footings are especially susceptible to failure by hydrodynamic loading, often exacerbated by debris damming. Here, such failures are investigated via small scale [...] Read more.

In countries with steep rivers, such as Japan and the United States, bridges fail on an annual basis. Bridges on spread footings are especially susceptible to failure by hydrodynamic loading, often exacerbated by debris damming. Here, such failures are investigated via small scale model laboratory experiments and full scale numerical simulations. In the laboratory, lift and drag forces and overturning moment on bridge decks, piers, and deck-pier systems, are measured and compared with threshold of failure criteria used in design guidelines. Effects of debris on lift, drag, and moment, as well as three-dimensional effects, are quantified. Via numerical simulations, flow patterns and free surface behaviour responsible for these forces are investigated, and described in a framework as a function of the water depth, flow speed, deck clearance, and girder height. Results show that current guidelines are non-conservative in some cases. Importantly, failure of both decks and piers can be prevented by strengthening pier-deck connections, or by streamlining decks. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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9 pages, 6745 KiB

Open AccessArticle

Stability of Individuals during Urban Inundations: What Should We Learn from Field Observations?

by Hubert Chanson and Richard Brown

Geosciences 2018, 8(9), 341; https://doi.org/10.3390/geosciences8090341 - 10 Sep 2018

Cited by 18 | Viewed by 4071

Abstract

The flooding of urbanized areas constitutes a major hazard to populations and infrastructure. Flood flows during urban inundations have been studied only recently and the real-life impact of fluid flows on individuals is not well understood. The stability of individuals in floodwaters is [...] Read more.

The flooding of urbanized areas constitutes a major hazard to populations and infrastructure. Flood flows during urban inundations have been studied only recently and the real-life impact of fluid flows on individuals is not well understood. The stability of individuals in floodwaters is re-assessed based upon the re-analysis of detailed field measurements during a major flood event. The results emphasized that hydrodynamic instabilities, linked to local topographic effects and debris, constitute major real-world hazards. A comparison between a number of flow conditions deemed unsafe for individuals, along with guidelines, suggests that many recommendations are over-optimistic and unsafe in real floodwaters and natural disasters. A series of more conservative guidelines is proposed, particularity relevant to flood events. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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Review

Jump to: Research, Other

25 pages, 4706 KiB

Open AccessReview

Coastal Flood Modeling Challenges in Defended Urban Backshores

by Timu W. Gallien, Nikos Kalligeris, Marie-Pierre C. Delisle, Bo-Xiang Tang, Joseph T. D. Lucey and Maria A. Winters

Geosciences 2018, 8(12), 450; https://doi.org/10.3390/geosciences8120450 - 1 Dec 2018

Cited by 54 | Viewed by 7071

Abstract

Coastal flooding is a significant and increasing hazard. There are multiple drivers including rising coastal water levels, more intense hydrologic inputs, shoaling groundwater and urbanization. Accurate coastal flood event prediction poses numerous challenges: representing boundary conditions, depicting terrain and hydraulic infrastructure, integrating spatially [...] Read more.

Coastal flooding is a significant and increasing hazard. There are multiple drivers including rising coastal water levels, more intense hydrologic inputs, shoaling groundwater and urbanization. Accurate coastal flood event prediction poses numerous challenges: representing boundary conditions, depicting terrain and hydraulic infrastructure, integrating spatially and temporally variable overtopping flows, routing overland flows and incorporating hydrologic signals. Tremendous advances in geospatial data quality, numerical modeling and overtopping estimation have significantly improved flood prediction; however, risk assessments do not typically consider the co-occurrence of multiple flooding pathways. Compound flooding refers to the combined effects of marine and hydrologic processes. Alternatively, multiple flooding source–receptor pathways (e.g., groundwater–surface water, overtopping–overflow, surface–sewer flow) may simultaneously amplify coastal hazard and vulnerability. Currently, there is no integrated framework considering compound and multi-pathway flooding processes in a unified approach. State-of-the-art urban coastal flood modeling methods and research directions critical to developing an integrated framework for explicitly resolving multiple flooding pathways are presented. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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Other

Jump to: Research, Review

22 pages, 5982 KiB

Open AccessConcept Paper

Risk-Based Early Warning System for Pluvial Flash Floods: Approaches and Foundations

by Julian Hofmann and Holger Schüttrumpf

Geosciences 2019, 9(3), 127; https://doi.org/10.3390/geosciences9030127 - 14 Mar 2019

Cited by 34 | Viewed by 13288

Abstract

In times of increasing weather extremes and expanding vulnerable cities, a significant risk to civilian security is posed by heavy rainfall induced flash floods. In contrast to river floods, pluvial flash floods can occur anytime, anywhere and vary enormously due to both terrain [...] Read more.

In times of increasing weather extremes and expanding vulnerable cities, a significant risk to civilian security is posed by heavy rainfall induced flash floods. In contrast to river floods, pluvial flash floods can occur anytime, anywhere and vary enormously due to both terrain and climate factors. Current early warning systems (EWS) are based largely on measuring rainfall intensity or monitoring water levels, whereby the real danger due to urban torrential floods is just as insufficiently considered as the vulnerability of the physical infrastructure. For this reason, this article presents a concept for a risk-based EWS as one integral component of a multi-functional pluvial flood information system (MPFIS). Taking both the pluvial flood hazard as well as the damage potential into account, the EWS identifies the urban areas particularly affected by a forecasted heavy rainfall event and issues object-precise warnings in real-time. Further, the MPFIS performs a georeferenced documentation of occurred events as well as a systematic risk analysis, which at the same time forms the foundation of the proposed EWS. Based on a case study in the German city of Aachen and the event of 29 May 2018, the operation principle of the integrated information system is illustrated. Full article

(This article belongs to the Special Issue River, Urban, and Coastal Flood Risk)

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