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1.
An extreme rainfall event on August 9, 2009, which was close to setting a world record for 48-h accumulated rainfall, induced the Xiaolin deep-seated landslide, which was located in southwestern Taiwan and had volume of 27.6?×?10 6?m 3, and caused the formation of a landslide dam. The landslide dam burst in a very short time, and little information remained afterward. We reconstructed the process of formation and failure of the Xiaolin landslide dam and also inferred the area of the impoundment and topographic changes. A 5?×?5-m digital elevation model, the recorded water stage of the Qishan River, and data from field investigation were used for analysis. The spectral magnitude of the seismic signals induced by the Xiaolin landslide and flooding due to failure of the landslide dam were analyzed to estimate the timing of the dam breach and the peak discharge of the subsequent flood. The Xiaolin landslide dam failure resulted from overtopping. We verified the longevity of the Xiaolin landslide dam at about 2 h relying on seismic signals and water level records. In addition, the inundated area, volume of the impoundment behind the Xiaolin landslide dam, and peak discharge of the flood were estimated at 92.3 ha, 19.5?×?10 6?m 3, and 17?×?10 3?m 3/s, respectively. The mean velocity of the flood-recession wave front due to the dam blockage was estimated at 28 km/h, and the peak flooding velocity after failure of the dam was estimated at 23 km/h. The Xiaolin landslide provides an invaluable opportunity for understanding the mechanism of deep-seated landslides and flooding processes following a landslide dam failure. 相似文献
2.
Glacial lakes represent a threat for the populations of the Andes and numerous disastrous glacial lake outburst floods (GLOFs) occurred as a result of sudden dam failures or dam overtoppings triggered by landslides such as rock/ice avalanches into the lake. This paper investigates a landslide-triggered GLOF process chain that occurred on February 23, 2020, in the Cordillera Vilcabamba in the Peruvian Andes. An initial slide at the SW slope of Nevado Salkantay evolved into a rock/ice avalanche. The frontal part of this avalanche impacted the moraine-dammed Lake Salkantaycocha, triggering a displacement wave which overtopped and surficially eroded the dam. Dam overtopping resulted in a far-reaching GLOF causing fatalities and people missing in the valley downstream. We analyze the situations before and after the event as well as the dynamics of the upper portion of the GLOF process chain, based on field investigations, remotely sensed data, meteorological data and a computer simulation with a two-phase flow model. Comparison of pre- and post-event field photographs helped us to estimate the initial landslide volume of 1–2 million m3. Meteorological data suggest rainfall and/or melting/thawing processes as possible causes of the landslide. The simulation reveals that the landslide into the lake created a displacement wave of 27 m height. The GLOF peak discharge at the dam reached almost 10,000 m3/s. However, due to the high freeboard, less than 10% of the lake volume drained, and the lake level increased by 10–15 m, since the volume of landslide material deposited in the lake (roughly 1.3 million m3) was much larger than the volume of released water (57,000 m3, according to the simulation). The model results show a good fit with the observations, including the travel time to the uppermost village. The findings of this study serve as a contribution to the understanding of landslide-triggered GLOFs in changing high-mountain regions. 相似文献
3.
An Ms 6.5 earthquake shocked the Ludian County, Yunnan Province, China, on 3 August 2014 and triggered the Hongshiyan landslide dam. The dam, with a height of 83 m and a lake capacity of 260?×?10 6 m 3, threatened more than 10,000 people. A unique feature of this landslide dam was that it formed between a man-made dam and a hydropower plant. An existing drainage tunnel connecting the lake and the hydropower plant became a natural drainage conduit for the landslide dam, which played an important role in the mitigation of the landslide dam risks. This paper reports a quantitative risk assessment for the Hongshiyan landslide dam considering both engineering and non-engineering risk mitigation measures. The risk assessment is divided into three stages according to the implementation of two engineering measures: construction of a diversion channel and excavation of a branch drainage tunnel. The dam breaching hydrographs, flood zones, population at risk, and likely fatalities in each of the three stages are analysed. The optimum evacuation strategy in each stage is also studied based on the principle of minimum total consequence. It is found that the diversion channel decreases the dam breaching peak discharge and the associated risks significantly. The branch drainage tunnel prevent the landslide dam from overtopping failure in non-flooded period; however, the landslide dam may fail by overtopping in a future flood if the inflow rate is larger than the outflow rate through the drainage tunnels, resulting in serious losses of lives and properties. The dam breaching risks in all the three stages could be largely reduced by the optimal evacuation decision, which shows that timely evacuation is vital to save life and properties. The study provides a scientific basis for decision making in landslide dam risk management. 相似文献
4.
At 00:30 (local time) on the 10th September 2003 a joint and foliation defined wedge of material with an estimated volume of 7–12×10 6 m 3 slid into the narrow Tsatichhu River Valley, in Jarrey Geog, Lhuentse, eastern Bhutan. The Tsatichhu River, a north–easterly flowing tributary of the Kurichuu River, was completely blocked by the landslide. During its movement, the landslide transitioned into a rock avalanche that travelled 580 m across the valley before colliding with the opposite valley wall. The flow then moved down valley, travelling a total distance of some 700 m. The rock avalanche was accompanied by an intense wind blast that caused substantial damage to the heavily forested valley slopes. The resulting geomorphologically-typical rock-avalanche dam deposit created a dam that impounded a water volume of 4–7×10 6 m 3 at lake full level. This lake was released by catastrophic collapse of the landslide, which occurred at 16:20 (local time) on 10th July 2004, after reported smaller failures of the saturated downstream face. The dam failure released a flood wave that had a peak discharge of 5900 m 3 s −1 at the Kurichhu Hydropower Plant 35 km downstream. 相似文献
5.
The failure of a lava dam 165,000 yr ago produced the largest known flood on the Colorado River in Grand Canyon. The Hyaloclastite Dam was up to 366 m high, and geochemical evidence linked this structure to outburst-flood deposits that occurred for 32 km downstream. Using the Hyaloclastite outburst-flood deposits as paleostage indicators, we used dam-failure and unsteady flow modeling to estimate a peak discharge and flow hydrograph. Failure of the Hyaloclastite Dam released a maximum 11 × 10 9 m 3 of water in 31 h. Peak discharges, estimated from uncertainty in channel geometry, dam height, and hydraulic characteristics, ranged from 2.3 to 5.3 × 10 5 m 3 s −1 for the Hyaloclastite outburst flood. This discharge is an order of magnitude greater than the largest known discharge on the Colorado River (1.4 × 10 4 m 3 s −1) and the largest peak discharge resulting from failure of a constructed dam in the USA (6.5 × 10 4 m 3 s −1). Moreover, the Hyaloclastite outburst flood is the oldest documented Quaternary flood and one of the largest to have occurred in the continental USA. The peak discharge for this flood ranks in the top 30 floods (>10 5 m 3 s −1) known worldwide and in the top ten largest floods in North America. 相似文献
6.
The study presents natural hazards in Slovenia's karst, focusing on flooding in karst poljes. A specific study was done on the flood dynamics of two typical and connected karst poljes (Cerknica and Planina) of the Classical Karst region. In the case of particularly extreme hydrological conditions in the autumn of 2008, detailed analyses of the recharge-discharge regime and the interrelationship of flooding on the two poljes were done. Daily precipitation, discharge, and water level values from several monitoring sites were analyzed and cross-correlated, and additional hydrological analyses were done using a digital elevation model in order to acquire water level increase and decrease intensity, flood water volumes, and the extent of flooding and to understand the conditions controlling karst flooding. The results reveal that the hydrological functioning of the studied karst poljes is influenced by the hydrogeological and temporary hydrological conditions in the catchment area. The response of the binary karst system (i.e., the influence of autogenic and allogenic recharge) is especially distinct. The study shows that during extremely intense recharge, the reactions of karst aquifer systems to precipitation are as rapid as the response of surface waters (the water level of Cerknica Lake increased with an intensity of 38-63 cm/day or 55 m3/s respectively) while retention capacities are negligible. In contrast to flash floods, floods in karst areas may last from several weeks to several months. For the observed period a three-dimensional simulation of the flooding was made. At the maximum recorded water level, the volume of water on the Cerknica polje was 51 million m 3, and 26 million m 3 on the Planina polje. The maximum extent of flooding on the Cerknica polje was 23 km 2 and on the Planina polje 9.5 km 2. On the basis of the study, information was provided regarding future hazard mitigation. However, the study demonstrated that a sufficiently dense monitoring network is necessary to predict the occurrence and duration of floods with greater certainty. 相似文献
7.
Landslides and rock avalanches triggered by the 2008 Wenchuan Earthquake produced 257 landslide dams, mainly situated along
the eastern boundary of the Qinghai-Tibet Plateau where rivers descend approximately 3,000 m into the Sichuan Basin. The largest
of these dams blocked the Tongkou River (a tributary of the Fujiang River) at Tangjiashan. The blockage, consisting of 2.04 × 10 7 m 3 of landslide debris, impounded a lake with a projected maximum volume of 3.15 × 10 8 m 3, potentially inundating 8.92 km 2 of terrain. Its creation during the rainy season and the possibility of an uncontrolled release posed a serious, impending
threat to at least 1.3 million people downstream that could add substantially to the total of 69,200 individuals directly
killed by the earthquake. Risk assessment of the blockage indicated that it was unlikely to collapse suddenly, and that eventual
overtopping could be mitigated by notching the structure in order to create an engineered breach and achieve safe drainage
of the lake. In addition to the installation of monitoring and warning instrumentation, for emergency planning we estimated
several outburst scenarios equivalent to 20, 25, 33, and 50% of the dam failing suddenly, creating, respectively, 3.35, 3.84,
4.22, and 4.65 km 2 of flooded area, and overbank water depths of 4.6, 5.1, 5.7, and 6.2 m, respectively, in Mianyang, the second largest city
in Sichuan Province, 48 km downstream from the blockage. Based on these scenarios, recommendations and plans for excavating
a sluiceway, draining the lake, and downstream evacuation were proposed and later were implemented successfully, with the
blockage breached by overtopping on June 10, less than a month after dam emplacement. The peak discharge of the release only
slightly exceeded the flood of record at Mianyang City. No lives were lost, and significant property damage was avoided. Post-breaching
evaluation reveals how future similar mitigation can be improved. Although initial breach erosion was slow, later erosion
was judged uncontrollably rapid; increased slope of the engineered channel and adoption of a compound, trapezoid–triangular
cross-section can be considered, as can other measures to control the rate of breach incision. Evacuees from Mianyang City
spent an unnecessarily long time (12 days) in temporary settlements; more precise risk management planning can reduce this
time in the future. 相似文献
8.
The risk analysis of reservoir regulation in the flood season is crucial and provides the valuable information for reservoir flood control, safety operation, and decision making, especially under climate change. The purpose of this study is to propose a framework for reasonably estimating the variation of reservoir regulation risk including the dam extreme risk and the overtopping risk during the flood season under climate change. The framework consists of an integrated diagnostic system for detecting the climate abrupt change time, a copula function-based bivariate statistical approach for modeling the dependence between the flood peak and flood volume, a Monte Carlo simulation for generating numerous random flood peak–volume pairs, and a risk calculation model for routing the design flood hydrographs to obtain the frequency curve of the maximum water level reached in front of dam and evaluating the reservoir regulation risk. The methodology was implemented in the Chengbihe reservoir in south China by using the 55-year (1963–2017) hydrometeorological data, including temperature, evaporation, precipitation, and streamflow, in the flood season. Results show that the hydrometeorological series during the flood season changed abruptly in 1992 and the entire data can be divided into two periods (1963–1992 and 1993–2017). The dam extreme risk and overtopping risk during the two periods are assessed, respectively, and a comparison analysis is made based on different flood limit water-level schemes (185.00–188.50 m). It demonstrates that both the dam extreme risk and the dam overtopping risk increase under the influence of climate change. The dam extreme risk increases by 22.91–95.03%, while the climate change-induced increase in the dam overtopping risk is between 38.62 and 123.59%, which indicates that the dam overtopping risk is more sensitive to climate change than the dam extreme risk. The risk evaluations in the study are of great significance in the safety operation and risk management of reservoirs under future climate change. 相似文献
9.
The Wenchuan earthquake triggered many landslides and numerous avalanches and created 100 odd quake lakes. The quake lakes
may be removed or preserved. The removal strategy was applied to several large landslide dams, which were dangerous because
massive amounts of water pooled up in the quake lakes. The dams could eventually fail under the action of dam outburst flooding,
potentially endangering the lives of people in the downstream reaches. This paper studied the stability of landslide dams
and the development of knickpoints by field investigations and experiments, and analyzing satellite images. The study concluded
that if landslide dams were preserved, they would develop into knickpoints and act as a primary control of riverbed incision
and, thus, reduce the potential of new landslide. The stability of landslide dams depends mainly on the development of the
step-pool system and stream power of the flood flow. If a landslide dam consists of many boulders, a step-pool system may
develop on the spillway channel of the dam, which would maximize the resistance, consume most of the flow energy and consequently
protect the dam from incision. The development degree of the step-pool system is represented by a parameter S
p, which was measured with a specially designed instrument. A preservation ratio of landslide dams is defined as the ratio
of preserved height after flood scouring to the original height of the dam. For streams with peak flood discharge lower than
30 m 3/s, the preservation ratio is linearly proportional to S
p. For rivers with a peak flood discharge higher than 30 m 3/s (30–30,000 m 3/s), the minimum S
p value for stable channel increases with log p, in which p is the unit stream power. For a landslide dam with a poorly developed step-pool system, S
p is smaller than the minimum value and the outburst flood incises the spillway channel and causes failure of the dam. For
preserved landslide dams, sediment deposits in the quake lakes. A landslide dam may develop into a knickpoint if it is stabilized
by long-term action of the flow. Large knickpoints can totally change the fluvial processes and river morphology. Uplift of
the Qinghai–Tibetan Plateau has caused extensive channel bed incision along almost all rivers. For many rivers, the incision
has been partly controlled by knickpoints. Upstream reaches of a knickpoint have a new and unchanging base level. This brings
about a transition from degradation to aggradation and from vertical bed evolution to horizontal fluvial process. Multiple
and unstable channels are prominent in the reaches, upstream of the knickpoints. If hundreds of landslide dams occurred simultaneously
on a reach of a mountain river, the potential energy of bank failure and the slope erosion would be greatly reduced and sediment
yield from the watershed may be reduced to nearly zero. The quake lakes may be preserved long term and become beautiful landscapes.
Streams with long-term unfilled quake lakes have good aquatic ecology. 相似文献
10.
Landslide dam failure can trigger catastrophic flooding in the downstream. However, field observation of such flooding is
rarely available, while laboratory experimental studies are sparse. The mechanism of landslide dam failure and the flood has
so far remained insufficiently understood. Here, we present an experimental investigation of landslide dam failure and the
flood. A total of 28 runs of experiments are carried out in a flume of 80 m × 1.2 m × 0.8 m, with differing inflow discharge,
dam composition, dam geometry, and initial breach dimension. An array of twelve automatic water-level probes is deployed to
measure the stage hydrographs along the flume, and the video recording of the dam failure processes facilitates an estimation
of the widening of initial breach. Under the present experimental conditions with dams composed of homogeneous materials,
landslide dam failure is primarily caused by erosion of overtopping flow, and lateral mass collapse is also considerable during
the cause of breach widening. Cohesive clay may act to mitigate the seepage through the dam and thus its subsidence and appreciably
modulate the dam failure process and the flood. However, the impacts of clay may be readily overwhelmed by a large inflow
discharge and initial breach. Gravels in the dam may appreciably depress the rate of the dam failure process and thus modify
the flood. The present work provides new experimental data set for testing mathematical models of the flood flow due to landslide
dam failure. 相似文献
11.
The moraine dam of the Tam Pokhari glacial lake breached on 3 September 1998 and caused a catastrophic flood in the downstream
areas. To learn from the event, a field survey was conducted. The survey team found that a landslide, which is considered
to be responsible for the outburst flood, occurred in the northeast-facing slope of the moraine dam. The dam internal structure
played a crucial role in forming a landslide that triggered the excess overflow and finally the breach of the dam. The internal
structure of the dam was made of alternating layers of finer and coarser sediments inclining at 30° downstream and layers
are truncated in the upslope direction by a huge pile of unconsolidated and structureless moraine materials. Since the upstream
slope angle of the dam i.e., 40° is larger than the angle of repose i.e. 35° of sediments, the increased pore water pressure
in the dam triggered a landslide. The rainfall and seismological activities of that particular day, which hit the record high,
were crucial in triggering the failure. It is estimated that the dam’s north and northeast-facing slopes completely slid involving
about 30,000 m 3 of sediment mass of unconsolidated moraine materials above the shear plane. A slope stability analysis was also performed.
The calculated safety factor was 0.85, and the calculated slip circle agreed with the shear plane marked in the dam. About
18 million cubic metres of water was swiftly released due to the sudden breach of the moraine dam. 相似文献
12.
The summit crater of Mt Ruapehu volcano normally hosts a 15.4-ha warm lake, whose water has been repeatedly wholly or partly
ejected by explosive and extrusive eruptions. Some of the larger eruptions have modified the lake outlet by burying it under
unconsolidated tephra (volcanic ash and blocks), creating a dam-break flood hazard independently of the occurrence of an eruption.
Eruptions in 1995 and 1996 followed this sequence; a break-out flood was anticipated and a warning system was installed to
mitigate the risk from this event and subsequent lahars in the same catchment. The 11-year filling time allowed much planning
and rehearsal. The warning system involved manual inspections of dam integrity, and seepage and lake-level monitoring to constrain
the likely failure window, and telemetered instruments including a tripwire and geophones to detect breaching of the dam and
propagation of the outbreak flood. The dam-collapse sequence, captured by a time-lapse camera, involved a series of retrogressing
landslides initiated and accelerated by seepage forces and toe scour when the lake was 1.1 m below overtopping. The barrier
failed in two phases on 18th March, 2007, beginning at 09:55 (NZST), with rapid retreat of one of the erosion scarps on the
downstream slope of the eastern barrier, initiated by internal erosion. Headward retrogression of the scarp into the barrier
formed an initial breach in the dam, after which increasing outflow led to erosion and undercutting of the wider downstream
toe of the western barrier. A final, larger dam breach occurred between 11:21 and 11:22 as slope instability caused retrogressive
failure of the remaining barrier. Five-hundred meters downstream of the dam, a large landslide was reactivated by toe scour
during the flood, contributing about a million cubic meters of solid material to the volumetric bulking of the outflow, which
reached the coast, 215 km away, 17 h later. The success of the planning and warning system allowed the whole event to occur
with little damage to infrastructure and without causing injury. 相似文献
13.
The debris flow, which was triggered in the Wenjia Gully on August 13, 2010, is an extreme example of mass movement events, which occurred after the Wenchuan earthquake of May 12, 2008. This Earthquake triggered in the Wenjia Gully the second largest co-seismic landslide, which can be classified as a rockslide-debris avalanche. A lot of loose sediments was deposited in the basin. In the main so called Deposition Area II of this landslide, with a volume of 30?×?10 6?m 3, flash floods can easily trigger debris flows because of the steep bottom slope and the relative small grain sizes of the sediments. The largest debris flow of August 13, 2010 destroyed the most downstream dam in the catchment during a heavy rain storm. The debris flow with a peak discharge of 1,530?m 3/s and a total volume of 3.1?×?10 6?m 3 caused the death of 7 persons, 5 persons were missing, 39 persons were injured and 479 houses buried. After three rainy seasons, only 16?% of the landslide-debris deposition was taken away by 5 large-scale debris flow events. Since the threshold for rainfall triggered debris flows in the Wenjia Gully and other catchments drastically decreased after the Wenchuan Earthquake, new catastrophic events are expected in the future during the rainy season. 相似文献
14.
2015年以来珠江流域西江暴雨洪水频发,平均每年发生1~2场编号洪水,其中2017年发生3场编号洪水。利用中国洪水预报系统分析2015年至2019年西江7次编号洪水梧州站的洪水组成、传播时间及影响预报精度的因素,以了解西江流域暴雨洪水及其变化规律,积累洪水预报经验,为今后西江梧州站洪水预测预报提供参考。 相似文献
15.
Canyon Creek drains a 79 km 2 watershed in northwestern Washington State. Extensive logging occurred from the mid-1960s to 1980s, which resulted in numerous
slope instabilities and a several order of magnitude increase in sediment supply to the creek. On November 9, 1989, a hyperconcentrated
flow with a peak discharge of 450 m 3/s destroyed one house on the fan. A forensic investigation of the event suggests that a temporary landslide dam may have
formed at two coalescing earthflows about 4 km above the fan apex. The 1989 hyperconcentrated flow caused significant aggradation
on the fan. One year later to the day, a significant flood occurred, which ran over the aggraded fan surface from the 1989
event. This latter event destroyed four more homes mostly through bank erosion and rendered a section of county road impassable.
FLDWAV, a flood routing model capable of simulating unsteady flow conditions, was used to model landslide dam breaches for
a number of different dam heights at the earthflows. Modeling results were then combined with historic air photograph interpretation,
dendrochronology, and eyewitness accounts to construct a frequency–magnitude relationship for hyperconcentrated flows at Canyon
Creek. FLDWAV results were combined with a hyperconcentrated flow runout model (FLO-2D) on the fan to estimate maximum flow
depth and flow velocity for the design event, a 500-year return period with a predicted peak discharge of 710 m 3/s. A large range of mitigation measures were reviewed, but it was concluded that buy-outs would be the most effective risk
reduction measure. Property acquisition commenced in 2004. 相似文献
16.
The breach of landslide dam often causes significant disaster in the inundated area; the prediction of breach hydrograph is in high demand for the dam breach risk evaluation. In this study, according to the model tests and Tangjiashan landslide dam breach case, the surface erosion accompanied by intermittent mass failure is known as the key breaching mechanism for landslide dam due to overtopping failure. The downstream slope angle would gradually decrease during the dam-breaching process, whereas a planar wedge failure occurs when the breach slopes at the dam crest and downstream breach channel fail. Based on the breach mechanism, a numerical model for landslide dam breach due to overtopping is developed to simulate the coupling process of water and soil. The model focuses on the breach morphology evolution during the breaching for the sake of the improvement of breach hydrograph prediction. Furthermore, the model can handle one- and two-sided breach, as well as incomplete and base erosion at the vertical direction. The case study of Tangjiashan landslide dam-breaching feedback analysis testifies the rationality of the present model with the relative errors less than 10% for peak discharge, final breach widths, and time to peak. The sensitivity analysis indicates that the final breach depth and soil erodibility affect the breach flow prediction of the landslide dam significantly, whereas the one- or two-sided breach mode is less sensitive. 相似文献
17.
In this work, a two-dimensional fourth-order Boussinesq-type numerical model is applied to estimate the impact of landslide-generated
waves in dam reservoirs. This numerical model has recently been extended for simulating subaerial landslides. The extended
model is validated using available three-dimensional experimental data, and a good agreement is obtained. The numerical model
is then employed to investigate the impact of landslide-generated waves in two real cases, the Maku and Shafa-Roud dam reservoirs
in the northwestern and the north of Iran, respectively. Generated wave heights, wave run-up, maximum wave height above dam
crest, and dam overtopping volume have been estimated for each case. The amplitude of generated waves about 18 and 31 m and
the volume of dam overtopping up to 80,000 m 3 emphasize the importance of the estimation of the landslide-generated waves in dam sites. 相似文献
18.
Large-volume debris flow events are defined when the volume of solid materials exceeds 1 million m 3. Traditional engineering measures, such as check dams, diversion channels, and flumes, are effective for normal debris flow
control but are not sufficient to control large-volume debris flows. Experiments were conducted with an artificial step-pool
system on the new Wenjiagou Gully to mitigate large-volume debris flows. The old Wenjiagou Gully was buried by 81.6 million
m 3 of loose solid material created by a landslide that was triggered by the Wenchuan earthquake on May 12, 2008. The new gully
was formed during the scouring process caused by debris flows in 2008. Large-volume debris flows were initiated by rainstorm
flood with high kinetic energy. The artificial step-pool system was constructed with huge and big boulders on the new Wenjiagou
Gully in 2009. The step-pool system dissipated flow energy in steps and hydraulic jumps. Analysis proved that the step-pool
system dissipated two-third of the kinetic energy of flow; thus, the critical discharge for triggering debris flow increased
threefold. Due to the step-pool system maximized the flow resistance and protected the bed sediment and banks from erosion,
the rainstorm floods in 2009 did not trigger debris flows. In 2010, the step-pool system was replaced with 20 check dams.
Huge boulders were broken into small pieces of diameter less than 0.5 m and were used as building materials for the 20 dams.
Without the protection of the step-pool system, a rainstorm flood scoured the base of the dams and caused failures for all
of the 20 check dams in August 2010. The flow incised the gully bed by 50 m. The loose bank materials slid into the flow mixed
with water and formed a large-volume debris flow with a volume of 4.5 million m 3. Many houses were buried by the debris flow, and 12 people were killed. Comparison of the two strategies proved that energy
dissipation structures are necessary for controlling large-volume debris flows. Check dams, if they are stable, may reduce
the potential of bank failures and control debris flows. The step-pool system dissipates flow energy and control gully bed
incision and bank failure. A combination of check dams and step-pool systems may be the most effective for mitigating debris
flows. 相似文献
19.
As streamflow is non-stationary due to climate change and human activities, adapting reservoir operation in the changing environment is of significant importance. Specifically, the flood limited water level (FLWL) needs to be re-established to ensure flood safety when the reservoir inflow is altered. The aims of this study are: (1) to clarify the relationship between the FLWL and streamflow when statistical parameters of the flood peak and volume vary through time and (2) to re-establish the FLWL when the reservoir inflow changes under the non-stationary condition. The adaptive FLWL is derived based on flood routing of non-stationary design floods, and the flood risk probability is then estimated. With China’s Three Gorges Reservoir (TGR) as a case study, the changing pattern of FLWL is quantified when statistical parameters (i.e., mean, \( C_{\text{V}} \) and \( C_{\text{S}} \)) of design floods have a linear temporal trend. The results indicate that the FLWL is sensitive with design floods, i.e., (1) means of design flood peak, 3-day volume, 7-day volume, 15-day volume and 30-day volume yearly decrease by 33 m 3/s, 0.008, 0.021, 0.482 and 0.905 billion m 3, respectively, (2) when the non-stationary design flood is used, the cumulative flood risk probability of the reservoir water level exceeding 175.0 m during 2011–2030 decreases from 1.98 to 1.82% with the conventional FLWL scheme and (3) the FLWL of the TGR could be re-set without increasing the flood risk probability, and the FLWL would increase about 4.7 m by 2030 in this non-stationary streamflow scenario. These findings are helpful to derive the FLWL in a changing environment. 相似文献
20.
On October 30, 2016, a seismic event and its aftershocks produced diffuse landslides along the SP 209 road in the Nera River Gorge (Central Italy). Due to the steep slopes and the outcropping of highly fractured and bedded limestone, several rockfalls were triggered, of which the main event occurred on the slope of Mount Sasso Pizzuto. The seismic shock acted on a rock wedge that, after an initial slide, developed into a rockfall. The debris accumulation blocked the SP 209 road and dammed the Nera River, forming a small lake. The river discharge was around 3.6 m 3/s; the water overtopped the dam and flooded the road. By a preliminary topographic survey, we estimated that the debris accumulation covers an area of about 16,500 m 2, while the volume is around 70,000 m 3. The maximum volume occupied by the pre-existing talus mobilized by the rockfall is about 20% of the total volume. Besides blocking the road, the rockfall damaged a bridge severely, while, downstream of the dam, the water flow caused erosion of a road embankment. A rockfall protection gallery, a few hundred meters downstream of the dam, was damaged during the event. Other elastic nets and rigid barriers were not sufficient to protect the road from single-block rockfalls, with volumes around 1–2 m 3. Considering the geological and geomorphological conditions, as well as the high seismicity and the socioeconomic importance of the area, a review of the entire rockfall protection systems is required to ensure protection of critical infrastructure and local communities. 相似文献
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