scholarly journals What do Biphasic Flow Experiments Reveal On the Variability of Exposure on Alluvial Fans and Which Implications for Risk Assessment Result From This?

2021 ◽  
Author(s):  
Hector Diaz ◽  
Bruno Mazzorana ◽  
Bernhard Gems ◽  
Ivan Rojas ◽  
Nicole Santibañez ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Solid Fraction ◽  
Flood Hazard ◽  
Alluvial Fan ◽  
Water Volume ◽  
Alluvial Fans ◽  
Loading Conditions ◽  
Stream Power ◽  
Convex Shape ◽  
Specific Loading

Abstract Autogenic processes, such as sudden avulsions, unexpected channel migrations and backfilling phenomena, can considerably alter the propagation of sediment-laden flows on alluvial fans. Once the initial and boundary conditions of the hazard scenario with a given return period are determined, the delineation of the associated exposed areas is based on one numerical, essentially deterministic, process simulation, which may not adequately reflect the underlying process variability. By following a ‘similarity-of-process concept’ we generated sediment-laden flows on an experimental alluvial fan. Thereby, we considered an alluvial fan model layout with a curved guiding channel and featuring a convex shape. As loading conditions, we defined a reference, an increased and a reduced level for the released water volume and the predisposed solid fraction. Further, we imposed two different stream power regimes and executed, for each factor combination, eight experimental runs. The associated exposure areas were recorded by video and were mapped in a GIS. We then analyzed exposure data and derived exposure probability maps superposing the footprints of the eight repetitions generated by each experimental loading condition. The patterns of exposure associated with specific loading conditions showed a noticeable variability due to the main effect of the total event volume, the solid fraction and the interactions between them and with the imposed stream power in the feeding channel. Our research highlights that a probabilistic notion of exposure in risk assessment and mitigation needs to be considered. Further, a major challenge consists in adapting numerical codes to better mirror the stochastics of process propagation for more reliable flood hazard and risk assessments.

scholarly journals Enhancing Flood Hazard Estimation Methods on Alluvial Fans Using an Integrated Hydraulic and Geological and Geomorphological Approach

2017 ◽  
Author(s):  
Zeinab Mollaei ◽  
Kamran Davary ◽  
Seyed Majid Hasheminia ◽  
Alireza Faridhosseini ◽  
Yavar Pourmohamad
Keyword(s):  
Flood Hazard ◽  
Alluvial Fan ◽  
Geographical Information ◽  
Estimation Methods ◽  
Alluvial Fans ◽  
Flow Paths ◽  
Integrated Method ◽  
Riverine Floods ◽  
Simple Stochastic Model ◽  
2D Model

Abstract. Due to the uncertainty concerning the location of flow paths on active alluvial fans, alluvial fan floods could be more dangerous than riverine floods. FEMA used a simple stochastic model named FAN in this regard for many years. In the last decade, this model has been criticized as a consequence of developing complex computer models. Instead, more recent hydraulic models with capability of avulsion simulation were recommended. This study was conducted on three alluvial fans located in the northeast and southeast part of Iran using combination of FAN model, FLO-2D model and geomorphological information. Initial stages included three steps: (a) identifying the alluvial fans' landforms, (b) determining the active and inactive areas of alluvial fans, and (c) delineating 100-year flood within these selected areas. This information was used as an input in the mentioned three approaches of: (I) FLO-2D model, (II) geomorphological method, and (III) FAN model. Thereafter, the results of each model were obtained and Geographical Information System (GIS) layers were created and overlaid. Afterwards, using a scoring system, the results were summarized and then the integrated method was compared with the three approaches.

scholarly journals Enhancing flood hazard estimation methods on alluvial fans using an integrated hydraulic, geological and geomorphological approach

2018 ◽  
Vol 18 (4) ◽  
pp. 1159-1171 ◽  
Author(s):  
Zeinab Mollaei ◽  
Kamran Davary ◽  
Seyed Majid Hasheminia ◽  
Alireza Faridhosseini ◽  
Yavar Pourmohamad
Keyword(s):  
Flood Hazard ◽  
Cost Effective ◽  
Developed Countries ◽  
The United States ◽  
Alluvial Fan ◽  
Geographical Information ◽  
Estimation Methods ◽  
Alluvial Fans ◽  
Flood Hazards ◽  
2D Model

Abstract. Due to the uncertainty concerning the location of flow paths on active alluvial fans, alluvial fan floods could be more dangerous than riverine floods. The United States Federal Emergency Management Agency (FEMA) used a simple stochastic model named FAN for this purpose, which has been practiced for many years. In the last decade, this model has been criticized as a consequence of development of more complex computer models. This study was conducted on three alluvial fans located in northeast and southeast Iran using a combination of the FAN model, the hydraulic portion of the FLO-2D model, and geomorphological information. Initial stages included three steps: (a) identifying the alluvial fans' landforms, (b) determining the active and inactive areas of alluvial fans, and (c) delineating 100-year flood within these selected areas. This information was used as an input in the mentioned three approaches of the (i) FLO-2D model, (ii) geomorphological method, and (iii) FAN model. Thereafter, the results of each model were obtained and geographical information system (GIS) layers were created and overlaid. Afterwards, using a scoring system, the results were evaluated and compared. The goal of this research was to introduce a simple but effective solution to estimate the flood hazards. It was concluded that the integrated method proposed in this study is superior at projecting alluvial fan flood hazards with minimum required input data, simplicity, and affordability, which are considered the primary goals of such comprehensive studies. These advantages are more highlighted in underdeveloped and developing countries, which may well lack detailed data and financially cannot support such costly projects. Furthermore, such a highly cost-effective method could be greatly advantageous and pragmatic for developed countries.

scholarly journals A Case Study of Flood Risk Evaluation Based on Emergy Theory and Cloud Model in Anyang Region, China

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 420
Author(s):  
Zening Wu ◽  
Yuhai Cui ◽  
Yuan Guo
Keyword(s):  
Risk Assessment ◽  
Flood Risk ◽  
Flood Control ◽  
Flood Hazard ◽  
Cloud Model ◽  
Flood Disaster ◽  
Assessment System ◽  
Assessment Model ◽  
Flood Risk Assessment ◽  
Emergy Theory

With the progression of climate change, the intensity and frequency of extreme rainfall have increased in many parts of the world, while the continuous acceleration of urbanization has made cities more vulnerable to floods. In order to effectively estimate and assess the risks brought by flood disasters, this paper proposes a regional flood disaster risk assessment model combining emergy theory and the cloud model. The emergy theory can measure many kinds of hazardous factor and convert them into unified solar emergy (sej) for quantification. The cloud model can transform the uncertainty in flood risk assessment into certainty in an appropriate way, making the urban flood risk assessment more accurate and effective. In this study, the flood risk assessment model combines the advantages of the two research methods to establish a natural and social dual flood risk assessment system. Based on this, the risk assessment system of the flood hazard cloud model is established. This model was used in a flood disaster risk assessment, and the risk level was divided into five levels: very low risk, low risk, medium risk, high risk, and very high risk. Flood hazard risk results were obtained by using the entropy weight method and fuzzy transformation method. As an example for the application of this model, this paper focuses on the Anyang region which has a typical continental monsoon climate. The results show that the Anyang region has a serious flood disaster threat. Within this region, Linzhou County and Anyang County have very high levels of risk for flood disaster, while Hua County, Neihuang County, Wenfeng District and Beiguan District have high levels of risk for flood disaster. These areas are the core urban areas and the economic center of local administrative regions, with 70% of the industrial clusters being situated in these regions. Only with the coordinated development of regional flood control planning, economy, and population, and reductions in the uncertainty of existing flood control and drainage facilities can the sustainable, healthy and stable development of the region be maintained.

Reconstructing the Timing of Flash Floods Using 10Be Surface Exposure Dating at Leidy Creek Alluvial Fan and Valley, White Mountains, California–Nevada, USA

2015 ◽  
Vol 83 (1) ◽  
pp. 178-186 ◽  
Author(s):  
Markus Fuchs ◽  
Rebecca Reverman ◽  
Lewis A. Owen ◽  
Kurt L. Frankel
Keyword(s):  
Flash Floods ◽  
Alluvial Fan ◽  
Optically Stimulated Luminescence ◽  
Alluvial Fans ◽  
White Mountains ◽  
The Holocene ◽  
Surface Exposure Dating ◽  
Exposure Dating ◽  
Outburst Floods ◽  
Glacial Lake Outburst Floods

AbstractLarge alluvial fans characterize the piedmonts of the White Mountains, California–Nevada, USA, with large boulders strewn across their surfaces. The boulders are interpreted as flash floods deposits with an unclear trigger for the transport process. Several triggers are possible, including glacial lake outburst floods (GLOFs), thunderstorms or rainfall on snow cover. From a paleoenvironmental perspective, the origin of the flash floods is of fundamental importance. The alluvial fans that flank the White Mountains at Leidy Creek display particularly impressive examples of these deposits. The boulder deposits and the source catchment at Leidy Creek were examined using 10Be terrestrial cosmogenic nuclide (TCN) surface exposure dating to help elucidate their age and origin. All boulders dated on the alluvial fans date to the Holocene. This is in accordance with the geomorphic analyses of the Leidy Creek catchment and its terraces and sediment ridges, which were also dated to the Holocene using optically stimulated luminescence (OSL) and 10Be surface exposure. The results suggest that the boulders on the alluvial fan were deposited by flash floods during thunderstorm events affecting the catchment of the Leidy Creek valley. Paleomonsoonal-induced mid-Holocene flash floods are the most plausible explanation for the discharges needed for these boulder aggradations, but a regional dataset is needed to confirm this explanation.

Eolian and fluvial sedimentation in the southwestern Sinai Mountains, Egypt: a record of flash floods during the late Pleistocene

2012 ◽  
Vol 44 (2) ◽  
pp. 281-299
Author(s):  
Jörg Völkel ◽  
Jörg Grunert ◽  
Matthias Leopold ◽  
Kerstin Hürkamp ◽  
Juliane Huber ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Arid Environment ◽  
Alluvial Fan ◽  
Luminescence Dating ◽  
Alluvial Fans ◽  
Extreme Floods ◽  
Optically Stimulated Luminescence Dating ◽  
Fluvial Sedimentation ◽  
Southwestern Sinai ◽  
The Last Glacial

Wadis emerging from the southwestern Sinai Mountains (Egypt) westwards to the Gulf of Suez are filled by >40 m thick late Pleistocene sediments, which have been subsequently incised to bedrock after the Last Glacial Maximum (LGM). Sedimentation and erosion resulted from changes in the basin's hydrological conditions caused by climate variations. Sediment characteristics indicate distinct processes ranging from high to low energy flow regimes. Airborne material is important as a sediment source. The fills are associated with alluvial fans at wadi mouths at the mountain fronts. Each alluvial fan is associated and physically correlated with the respective sediment fill in its contributing wadi. The alluvial fans have steep gradients and are only a few kilometers long or wide. The alluvial fans converge as they emerge from the adjacent valleys. According to optically stimulated luminescence dating, the initial sediment has an age of ∼45 ka and the sedimentation ends ∼19 ka, i.e., happened mainly during marine isotope stage (MIS) 3 and early MIS 2 formation and initial incision sometime during LGM. As the delivery of sediments in such a hyper-arid environment is by extreme floods, this study indicates an interval of intense fluvial activity, probably related to increased frequency of extreme floods in Southern Sinai. This potentially indicates a paleoclimatic change in this hyper-arid environment.

Flood Hazard Mapping in Alluvial Fans with Computational Modeling

2021 ◽  
Author(s):  
Sofia Melo Vasconcellos ◽  
Masato Kobiyama ◽  
Fernanda Stachowski Dagostin ◽  
Claudia Weber Corseuil ◽  
Vinicius Santana Castiglio
Keyword(s):  
Computational Modeling ◽  
Flood Hazard ◽  
Hazard Mapping ◽  
Alluvial Fans

scholarly journals A framework for global river flood risk assessments

2013 ◽  
Vol 17 (5) ◽  
pp. 1871-1892 ◽  
Author(s):  
H. C. Winsemius ◽  
L. P. H. Van Beek ◽  
B. Jongman ◽  
P. J. Ward ◽  
A. Bouwman
Keyword(s):  
Risk Assessment ◽  
Flood Risk ◽  
Hydrological Model ◽  
Flood Hazard ◽  
Probability Distributions ◽  
Flood Routing ◽  
Risk Assessments ◽  
First Case ◽  
Impact Models ◽  
Damage Estimates

Abstract. There is an increasing need for strategic global assessments of flood risks in current and future conditions. In this paper, we propose a framework for global flood risk assessment for river floods, which can be applied in current conditions, as well as in future conditions due to climate and socio-economic changes. The framework's goal is to establish flood hazard and impact estimates at a high enough resolution to allow for their combination into a risk estimate, which can be used for strategic global flood risk assessments. The framework estimates hazard at a resolution of ~ 1 km2 using global forcing datasets of the current (or in scenario mode, future) climate, a global hydrological model, a global flood-routing model, and more importantly, an inundation downscaling routine. The second component of the framework combines hazard with flood impact models at the same resolution (e.g. damage, affected GDP, and affected population) to establish indicators for flood risk (e.g. annual expected damage, affected GDP, and affected population). The framework has been applied using the global hydrological model PCR-GLOBWB, which includes an optional global flood routing model DynRout, combined with scenarios from the Integrated Model to Assess the Global Environment (IMAGE). We performed downscaling of the hazard probability distributions to 1 km2 resolution with a new downscaling algorithm, applied on Bangladesh as a first case study application area. We demonstrate the risk assessment approach in Bangladesh based on GDP per capita data, population, and land use maps for 2010 and 2050. Validation of the hazard estimates has been performed using the Dartmouth Flood Observatory database. This was done by comparing a high return period flood with the maximum observed extent, as well as by comparing a time series of a single event with Dartmouth imagery of the event. Validation of modelled damage estimates was performed using observed damage estimates from the EM-DAT database and World Bank sources. We discuss and show sensitivities of the estimated risks with regard to the use of different climate input sets, decisions made in the downscaling algorithm, and different approaches to establish impact models.

Multi-level patient-specific modelling of the proximal femur. A promising tool to quantify the effect of osteoporosis treatment

2009 ◽  
Vol 367 (1895) ◽  
pp. 2079-2093 ◽  
Author(s):  
Leen Lenaerts ◽  
G. Harry van Lenthe
Keyword(s):  
Bone Strength ◽  
Material Properties ◽  
Bone Structure ◽  
Structural Information ◽  
Response To Treatment ◽  
Patient Specific ◽  
Loading Conditions ◽  
Femoral Bone ◽  
Fe Modelling ◽  
Specific Loading

Preventing femoral fractures is an important goal in osteoporosis research. In order to evaluate a person's fracture risk and to quantify response to treatment, bone competence is best assessed by bone strength. Finite-element (FE) modelling based on medical imaging is considered a very promising technique for the assessment of in vivo femoral bone strength. Over the past decades, a number of different FE models have been presented focusing on the effect of several methodological aspects, such as mesh type, material properties and loading conditions, on the precision and accuracy of these models. In this paper, a review of this work is presented. We conclude that moderate to good predictions can be made, especially when the models are tuned to specific loading scenarios. However, there is room for improvement when multiple loading conditions need to be evaluated. We hypothesize that including anisotropic material properties is the first target. As a proof of the concept, we demonstrate that the main orientation of the femoral bone structure can be calculated from clinical computed tomography scans. We hypothesize that this structural information can be used to estimate the anisotropic bone material properties, and that in the future this could potentially lead to a greater predictive value of FE models for femoral bone strength.

scholarly journals Hydrogeomorphic processes and torrent control works on a large alluvial fan in the eastern Italian Alps

2010 ◽  
Vol 10 (3) ◽  
pp. 547-558 ◽  
Author(s):  
L. Marchi ◽  
M. Cavalli ◽  
V. D'Agostino
Keyword(s):  
Urban Areas ◽  
Debris Flows ◽  
Land Use Changes ◽  
Integrated Approach ◽  
Alluvial Fan ◽  
Aerial Photographs ◽  
European Alps ◽  
Alluvial Fans ◽  
Economic Activities ◽  
Hazard Management

Abstract. Alluvial fans are often present at the outlet of small drainage basins in alpine valleys; their formation is due to sediment transport associated with flash floods and debris flows. Alluvial fans are preferred sites for human settlements and are frequently crossed by transport routes. In order to reduce the risk for economic activities located on or near the fan and prevent loss of lives due to floods and debris flows, torrent control works have been extensively carried out on many alpine alluvial fans. Hazard management on alluvial fans in alpine regions is dependent upon reliable procedures to evaluate variations in the frequency and severity of hydrogeomorphic processes and the long-term performance of the torrent training works. An integrated approach to the analysis of hydrogeomorphic processes and their interactions with torrent control works has been applied to a large alluvial fan in the southern Carnic Alps (northeastern Italy). Study methods encompass field observations, interpretation of aerial photographs, analysis of historical documents, and numerical modelling of debris flows. The overall performance of control works implemented in the early decades of 20th century was satisfactory, and a reduction of hazardous events was recognised from features observed in the field and in aerial photographs, as well as from the analysis of historical records. The 2-D simulation of debris flows confirms these findings, indicating that debris flow deposition would not affect urban areas or main roads, even in the case of a high-magnitude event. Present issues in the management of the studied alluvial fan are representative of situations frequently found in the European Alps and deal with the need for maintenance of the control structures and the pressures for land use changes aimed at the economic exploitation of the fan surface.

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