scholarly journals An Alternative Algorithm for Simulating Flash Flood

2021 ◽  
Vol 930 (1) ◽  
pp. 012076
Author(s):  
M F Khaldirian ◽  
A P Rahardjo ◽  
D Luknanto ◽  
R D R Sondi
Keyword(s):  
Numerical Modeling ◽  
Debris Flow ◽  
Coordinate System ◽  
Flash Flood ◽  
Front Propagation ◽  
Bed Elevation ◽  
Forward Difference ◽  
Lagrangian Coordinate ◽  
The Galerkin Method ◽  
Sediment Mixture

Abstract Most of the approaches in numerical modeling techniques are based on the Eulerian coordinate system. This approach faces difficulty in simulating flash flood front propagation. This paper shows an alternative method that implements a numerical modeling technique based on the Lagrangian coordinate system to simulate the water of debris flow. As for the interaction with the riverbed, the simulation uses an Eulerian coordinate system. The method uses the conservative and momentum equations of water and sediment mixture in the Lagrangian form. Source terms represent deposition and erosion. The riverbed in the Eulerian coordinate system interacts with the flow of the mixture. At every step, the algorithm evaluates the relative position of moving nodes of the flow part to the fixed nodes of the riverbed. Computation of advancing velocity and depth uses the riverbed elevation, slope data, and the bed elevation change computation uses the erosion or deposition data of the flow on the moving nodes. Spatial discretization is implementing the Galerkin method. Furthermore, temporal discretization is implementing the forward difference scheme. Test runs show that the algorithm can simulate downward, upward, and reflected backward 1-D flow cases. Two-D model tests and comparisons with SIMLAR software show that the algorithm works in simulating debris flow.

scholarly journals A quasi-Lagrangian coordinate system based on high resolution tracer observations: implementation for the Antarctic polar vortex

2008 ◽  
Vol 8 (4) ◽  
pp. 16123-16173 ◽  
Author(s):  
E. V. Ivanova ◽  
C. M. Volk ◽  
O. Riediger ◽  
H. Klein ◽  
N. M. Sitnikov ◽  
...  
Keyword(s):  
High Resolution ◽  
Coordinate System ◽  
Vortex Core ◽  
Polar Vortex ◽  
Mixing Ratio ◽  
Lagrangian Coordinate ◽  
Antarctic Polar Vortex ◽  
The Antarctic ◽  
Lagrangian Coordinate System

Abstract. In order to quantitatively analyse the chemical and dynamical evolution of the polar vortex it has proven extremely useful to work with coordinate systems that follow the vortex flow. We propose here a two-dimensional quasi-Lagrangian coordinate system {χi, Δχi}, based on the mixing ratio of a long-lived stratospheric trace gas i, and its systematic use with i = N2O, in order to describe the structure of a well-developed Antarctic polar vortex. In the coordinate system {χi, Δχi} the mixing ratio χi is the vertical coordinate and Δχi = χi(Θ)−χivort(Θ) is the meridional coordinate (χivort(Θ) being a vertical reference profile in the vortex core). The quasi-Lagrangian coordinates {χi, Δχi} persist for much longer time than standard isentropic coordinates, potential temperature Θ and equivalent latitude φe, do not require explicit reference to geographic space, and can be derived directly from high-resolution in situ measurements. They are therefore well-suited for studying the evolution of the Antarctic polar vortex throughout the polar winter with respect to the relevant chemical and microphysical processes. By using the introduced coordinate system {χN2O, ΔχN2O} we analyze the well-developed Antarctic vortex investigated during the APE-GAIA (Airborne Polar Experiment – Geophysica Aircraft in Antarctica – 1999) campaign (Carli et al., 2000). A criterion, which uses the local in-situ measurements of χi=χi(Θ) and attributes the inner vortex edge to a rapid change (δ-step) in the meridional profile of the mixing ratio χi, is developed to determine the (Antarctic) inner vortex edge. In turn, we suggest that the outer vortex edge of a well-developed Antarctic vortex can be attributed to the position of a local minimum of the χH2O gradient in the polar vortex area. For a well-developed Antarctic vortex, the ΔχN2O-parametrization of tracer-tracer relationships allows to distinguish the tracer inter-relationships in the vortex core, vortex boundary region and surf zone and to examine their meridional variation throughout these regions. This is illustrated by analyzing the tracer-tracer relationships χi : χN2O obtained from the in-situ data of the APE-GAIA campaign for i = CFC-11, CFC-12, H-1211 and SF6. A number of solitary anomalous points in the CFC-11 : N2O correlation, observed in the Antarctic vortex core, are interpreted in terms of small-scale cross-isentropic dispersion.

scholarly journals Characteristics and Prevention of the Debris Flows following Wenchuan Earthquake in Jushui River Basin, An County, China

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Yonggang Ge ◽  
Jianqiang Zhang ◽  
Xiaojun Guo
Keyword(s):  
Debris Flow ◽  
Wenchuan Earthquake ◽  
River Basin ◽  
Debris Flows ◽  
Flash Flood ◽  
River Channel ◽  
Hazard Identification ◽  
Control Mode ◽  
Potential Hazard ◽  
Prevention Measures

After analysing the catastrophic debris flows on August 18, 2012, and on July 9, 2013, in Jushui River basin, An County, the Wenchuan Earthquake seriously striken areas, it was found that they were characterized by the clay soil content of 0.1~1.2%, the density of 1.68~2.03 t/m3, the discharges of 62.2 m3/s to 552.5 m3/s, and the sediment delivery modulus of 1.0~9.4 × 104 m3/km2. Due to intense rainstorm, many large debris flows produced hazard chain, involved in flash flood, debris flow, dammed lake, and outburst flood, and rose Jushui River channel about 1~4 m as well as amplified flood. The hazards and losses mainly originated from the burying and scouring of debris flows, flood inundating, and river channel rise. The prevention of debris flows is facing the intractable problems including potential hazard identification, overstandard debris flow control, control constructions destructing, and river channel rapid rise. Therefore, the prevention measures for the basin, including hazard identification and risk assessment, inhabitants relocating, monitoring and alarming network establishing, emergency plans founding, and river channel renovating, and the integrated control mode for watershed based on regulating the process of debris flow discharge, were recommended for mitigation.

scholarly journals Debris-flow velocities and superelevation in a curved laboratory channel

2015 ◽  
Vol 52 (3) ◽  
pp. 305-317 ◽  
Author(s):  
Christian Scheidl ◽  
Brian W. McArdell ◽  
Dieter Rickenmann
Keyword(s):  
Debris Flow ◽  
Flow Velocity ◽  
Correction Factor ◽  
Debris Flows ◽  
Laboratory Experiments ◽  
Flow Conditions ◽  
Vortex Equation ◽  
Flow Surface ◽  
Sediment Mixture ◽  
Sediment Mixtures

The vortex equation is often used to estimate the front velocity of debris flows using the lateral slope of the flow surface through a channel bend of a given radius. Here we report on laboratory experiments evaluating the application of the vortex equation to channelized debris flows. Systematic laboratory experiments were conducted in a 8 m long laboratory flume with a roughened bed, semi-circular cross section (top width 17 cm), and two different bend radii (1.0 and 1.5 m) with a common bend angle of 60°, and two channel inclinations (15° and 20°). Four sediment mixtures were used with systematic variations in the amount of fine sediment. In the experiments, 12 kg of water-saturated debris were released in a dam-break fashion, and multiple experiments were conducted to verify the repeatability for a given sediment mixture. Data are available for 69 experimental releases at a channel inclination of 20° and 16 releases at an inclination of 15°. Flow velocity was determined with high-speed video, and flow depth and the lateral inclination of the flow surface (superelevation) were measured using laser sensors. In general, the results from an individual sediment mixture are repeatable. We found that the channel slope as well as centerline radius have a significant influence on the correction factor k used in the vortex equation. Relatively coarse-grained sediment mixtures have larger superelevation angles than finer-grained mixtures. We found a statistically significant relation between the correction factor and Froude number. Correction factors of 1 < k < 5 were found for supercritical flow conditions. However, for subcritical flow conditions the correction factor shows a larger value as a function of the Froude number, which leads to an adaption of the forced vortex formula considering active and passive earth pressures. Finally, based on our experimental results, we present a forced vortex equation for debris-flow velocity estimation without a correction factor.

Review of Research Related to Sediment Disaster Mitigation

2007 ◽  
Vol 2 (1) ◽  
pp. 11-18 ◽  
Author(s):  
Shinji Egashira ◽  
Keyword(s):  
Flow Characteristics ◽  
Disaster Mitigation ◽  
Annual Number ◽  
Erosion And Deposition ◽  
Sediment Erosion ◽  
Bed Elevation ◽  
Numerical Predictions ◽  
Sediment Research ◽  
Sediment Mixture ◽  
Structural Methods

The annual number of deaths resulting from landslides and debris flow in Japan over the past 40 years has shown a decreasing tendency as corresponding countermeasures are implemented. The countermeasures constituted of structural and non-structural methods are introduced, focusing on their phenomenological function to clear up roles of sediment research on them. In addition, governing equations which are employed currently in numerical predictions are shown, including formulas for bed shear stress and sediment erosion and deposition in order to illustrate differences between the flow of water and sediment mixture in steep areas and the flow of usually observed floods in rivers. It is recommended that equations which are able to distinguish rapid changes of flow characteristics due to internal solid type friction, sediment erosion and deposition and the corresponding changes of bed elevation should be applied in the numerical computations.

An Evaluation of Flash Flood and Debris Flow Guidance in Gangwon Province in Korea

2016 ◽  
Vol 12 (4) ◽  
pp. 85-96
Author(s):  
Byung In Yu ◽  
◽  
Byung Sik Kim ◽  
Suck Ho Lee ◽  
◽  
...  
Keyword(s):  
Debris Flow ◽  
Flash Flood

scholarly journals Parameterization of a numerical 2-D debris flow model with entrainment: a case study of the Faucon catchment, Southern French Alps

2012 ◽  
Vol 12 (10) ◽  
pp. 3075-3090 ◽  
Author(s):  
H. Y. Hussin ◽  
B. Quan Luna ◽  
C. J. van Westen ◽  
M. Christen ◽  
J.-P. Malet ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Debris Flow ◽  
Debris Flows ◽  
Source Area ◽  
European Alps ◽  
Actual Process ◽  
French Alps ◽  
Modeling Software ◽  
Entrainment Process

Abstract. The occurrence of debris flows has been recorded for more than a century in the European Alps, accounting for the risk to settlements and other human infrastructure that have led to death, building damage and traffic disruptions. One of the difficulties in the quantitative hazard assessment of debris flows is estimating the run-out behavior, which includes the run-out distance and the related hazard intensities like the height and velocity of a debris flow. In addition, as observed in the French Alps, the process of entrainment of material during the run-out can be 10–50 times in volume with respect to the initially mobilized mass triggered at the source area. The entrainment process is evidently an important factor that can further determine the magnitude and intensity of debris flows. Research on numerical modeling of debris flow entrainment is still ongoing and involves some difficulties. This is partly due to our lack of knowledge of the actual process of the uptake and incorporation of material and due the effect of entrainment on the final behavior of a debris flow. Therefore, it is important to model the effects of this key erosional process on the formation of run-outs and related intensities. In this study we analyzed a debris flow with high entrainment rates that occurred in 2003 at the Faucon catchment in the Barcelonnette Basin (Southern French Alps). The historic event was back-analyzed using the Voellmy rheology and an entrainment model imbedded in the RAMMS 2-D numerical modeling software. A sensitivity analysis of the rheological and entrainment parameters was carried out and the effects of modeling with entrainment on the debris flow run-out, height and velocity were assessed.

Forced Vibration Analysis of Spinning Disks Subjected to Transverse Loads

2015 ◽  
Vol 15 (03) ◽  
pp. 1450049 ◽  
Author(s):  
Hamed Norouzi ◽  
Davood Younesian
Keyword(s):  
Coordinate System ◽  
Forced Vibration ◽  
Natural Frequencies ◽  
Rotating Disk ◽  
Transverse Load ◽  
Solution Technique ◽  
Rotating Speed ◽  
Stationary Coordinate System ◽  
Forced Vibration Analysis ◽  
The Galerkin Method

Forced vibration of a rotating disk subjected to a stationary transverse load is studied in this paper. Time and frequency responses are obtained and effects of the rotating speed on the natural frequencies are evaluated. Finite element method (FEM) is employed as the solution technique and natural frequencies are obtained for different speeds. Forced vibration is then considered and disk responses are determined using the Galerkin method. The solution is determined in two different coordinate systems. In the first one, the disk is assumed to be rotating in an inertial coordinate system, while in the second coordinate system, a rotating peripheral force is applied on a stationary disk. The objective here in this paper is to compare the two modeling scenarios and is to find limiting range of the rotational speed for employing the stationary coordinate system.

scholarly journals Venezuelan debris flow and flash flood disaster of 1999 studied

Eos ◽  
2001 ◽  
Vol 82 (47) ◽  
pp. 572-572 ◽  
Author(s):  
M. C. Larsen ◽  
G. F. Wieczorek ◽  
L. S. Eaton ◽  
B. A. Morgan ◽  
H. Torres-Sierra
Keyword(s):  
Debris Flow ◽  
Flash Flood ◽  
Flood Disaster

scholarly journals Flash flood and debris flow in the Harihara River, Kyushu, Japan

2000 ◽  
Vol 22 ◽  
Author(s):  
N. Gurung ◽  
A. Rahman ◽  
Y. Iwao
Keyword(s):  
Debris Flow ◽  
Heavy Rainfall ◽  
Flash Flood ◽  
Soil Mass ◽  
Field Investigation ◽  
Great Loss ◽  
Electrical Survey ◽  
Main Factors ◽  
Hidden Fault

The flash flood and debris flow after a heavy rainfall wiped out a village of southern Japan on the tragic midnight of 10 July 1997, and a great loss of property and lives took place in this ill-fated incident. After the heavy rainfall, the debris flow induced by a sudden flash flood took 21 lives in Southern Kyushu. Detailed field investigation, in situ survey, electrical survey, and hydrogeological analyses were conducted to find out the triggering factors of the disaster. The main factors of this disaster were a hidden fault and the perched groundwater. Moving soil mass downhill into the agricultural pond had triggered the flash flood. The details of sequential disaster events as perceived from the observation and analyses are presented in this paper.

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