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Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
3
DOI: 10.4408/IJEGE.2011-03.B-001
STUDY ON MORAINE DAM FAILURE AND RESULTING FLOOD/DEBRIS
FLOW HYDROGRAPH DUE TO WAVES OVERTOPPING AND EROSION
R
iPendRa
AWAL, H
aJime
NAKAGAWA, k
enJi
KAWAIKE, y
asuyuki
BABA & H
ao
ZHANG
(*)
(*)
Disaster Prevention Research Institute, Kyoto University, Shimomisu, Yoko-oji, Fushimi-ku, Kyoto 612-8235, Japan
Tel +81-75-611-4394 - Email: ripendra@uh31.dpri.kyoto-u.ac.jp, ripendra@gmail.com
INTRODUCTION
Glacial lake outburst flood (GLOF) is a release
of an enormous amount of stored water in the gla-
cial lake due to failure or breach of ice or moraine
dam. Moraine dam failure and GLOF are phenom-
ena closely related to climate change. These events
may cause floods of great magnitudes, loss of life,
properties and sediment disaster in the downstream
river reaches. Moraine dammed lakes and GLOFs
are common in different glacierized regions of the
world (l
liboutRy
et alii, 1977; H
aebeRli
, 1983;
C
osta
& s
CHusteR
, 1988; y
amada
, 1998; C
laGue
& e
vans
, 2000; R
iCHaRdson
& R
eynolds
, 2000). In
the Himalaya, a study carried out jointly by Inter-
national Centre for Integrated Mountain Develop-
ment (ICIMOD), United Nations Environment Pro-
gramme/Regional Resource Centre for Asia and the
Pacific (UNEP/RRC-AP) and Asia-Pacific Network
for Global Change research (APN) between 1999
and 2003 estimated about 9000 glacial lakes and
more than 200 potentially dangerous glacial lakes
(see Tab. 1) in Bhutan, Nepal, Pakistan and select-
ed basins of China and India (b
aJRaCHaRya
et alii,
2008). Thus monitoring of glaciers, glacial lakes,
installation of early warning systems and different
hazard mitigation measures are required for proper
management of potential GLOF events.
Moraine dams are distinct ridges and mounds of
debris lay down directly by a glacier or pushed up by
it at the point of its greatest progress. Some moraine
ABSTRACT
Glacial lake outburst floods (GLOFs) may cause
floods of great magnitudes, loss of life, properties
and sediment disaster in the downstream river reach-
es. About 80% of GLOFs (based on 20 cases with
known failure mechanisms) were initiated by dis-
placement waves from ice avalanches that collapsed
into the lakes from hanging or calving glaciers and
rock avalanches. Therefore, an integrated model is
essential for the i) prediction of waves generated
by ice/rock avalanche, ii) prediction of outflow hy-
drograph due to waves overtopping and erosion of
moraine dam and iii) flow and sediment routing in the
downstream for flood risk assessment. Toward devel-
opment of an integrated model, this study focuses on
experimental study of moraine dam failure due to
waves overtopping and erosion. Extensive laborato-
ry experiments are carried out by varying size of ice/
rock avalanche, shape of the dam, dam material and
lake water level. The outflow hydrographs produced
by waves overtopping and erosion consist of multi-
ple peaks. For the same falling block and lake water
level, the initial peaks are similar for both triangular
and trapezoidal dams. However, magnitude and tim-
ing of subsequent peaks are different according to
dam shapes and dam materials.
K
ey
words
: GLOF, waves overtopping, erosion, outflow
hydrograph, laboratory experiment
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R. AwAL, H. NAkAGAwA, k. kAwAIkE, Y. BABA & H. ZHANG
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5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
to study overtopping of potential surge waves from ter-
minal moraine that may generate by 43m high ice cliff.
The material comprising most moraine dams is
silty, sandy, bouldery till, with minimal clay content.
Most of the moraine dams are steep sided (some ex-
ceeding 40°). Moraine dams are made of loose, easily
erodible materials that are incorporated in the outburst
flood, commonly resulting in a debris flow immedi-
ately downstream. The instananesos flood discharge
due to GLOF event may be very high compare with
mean annual maximum instantaneous flood discharge
due to rainfall. In Fig. 2 maximum instantaneous flood
discharge in 1985 is due to Dig Tsho GLOF (4
th
Au-
gust, 1985) which is about 2.7 times higher than mean
annual maximum instantaneous flood discharge. There
are two methods to predict probable peak discharge
from potential failure of natural dams. Many empirical
relationships are derived to determine peak discharge
from data set of historic dam failures for landslide,
glacier and moraine dams (C
osta
, 1988; w
aldeR
&
o’C
onnoR
, 1997). However, these empirical relation-
ships are derived from limited number of cases. The
other method employs computer implementation of
dams contain dead glacier ice. A lake formed as a gla-
cier recedes from its terminal moraine is known as
moraine-dammed lake. Moraine dams generally fail
by overtopping and incision. Potentially dangerous
lakes typically require a trigger mechanism to initiate
a flood. The triggering event is most frequently an ice
avalanche from the toe of the retreating glacier which
generates waves that overtop the dam. Failure of dam
slopes, melting of ice cores and piping are other fail-
ure mechanisms which may cause self destruction of
moraine dam. Earthquake is also an external trigger
which may cause settlement of the moraine dam and
lake outburst. About 80% of GLOFs were initiated
by displacement waves from ice avalanches that col-
lapsed into the lakes from hanging or calving glaciers
and rock avalanches (see Fig. 1). NEA (2005) com-
piled thirty three historical GLOF events that occurred
in Nepal and Tibet (China). The causes of failure of
thirteen events were unknown. The cause of failure of
Dig Tsho was mentioned as rock avalanche however
other studies (v
uiCHaRd
& z
immeRmann
, 1987; y
a
-
mada
, 1998) have shown that the failure was due to
ice avalanche. Thus, in this study, the cause of failure
of Dig Tsho is classified as ice avalanche. The main
causes of glacial lake outburst floods are shown in Fig.
1 based on twenty cases of glacial lake outburst floods
(with known failure mechanisms) which occurred in
Nepal and Tibet (China). Ice avalanching is a common
trigger for moraine dam failure because many glaciers
have retreated up steep rock slopes and toes of such
glaciers are heavily crevassed and wet, and thus prone
to failure (C
laGue
& e
vans
, 2000). The volume of ice
avalanche/rock fall may as large as 1/4 to 1/2 of the
lake volume (x
u
& f
enG
, 1994). The recent study of
one of the potentially dangerous glacial lake in Nepal
(Imja Lake) by w
atanabe
et alii (2009) recommended
Fig. 2 - Annual maximum instantaneous flood discharge
at Rabuwa Bazar (90km downstream of Dig Tsho
glacial lake), Dudhkoshi river (A
wAl
, 2008)
Tab. 1 - Summary of glacial lakes and potentially danger-
ous glacial lakes in the Himalaya
Fig. 1 - Causes of glacial lake outburst floods (Based on
20 cases with known failure mechanisms)
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STUDY ON MORAINE DAM FAILURE AND RESULTING FLOOD/DEBRIS FLOW
HYDROGRAPH DUE TO WAVES OVERTOPPING AND EROSION
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
5
landslide/rock avalanche (f
Ritz
et alii, 2004; z
weifel
et alii, 2007). However, very few studies focused
on dam breaking by waveinduced erosional incision
(b
almfoRtH
et alii, 2008; b
almfoRtH
et alii, 2009).
In-depth knowledge of the mechanism of the mo-
raine dam failure by waves overtopping and measured
data are still lacking. Extensive laboratory experi-
ments are carried out to study such triggering event
and failure mechanism by varying size of ice/rock av-
alanche, shape of the dam, dam material and freeboard
between the crest of the dam and lake water level.
EXPERIMENTAL METHOD
The schematic diagram of the flume and other ac-
cessories used in the experiments are shown in the Fig.
4. The rectangular flume of length 500cm, width 30cm
and depth 50cm was used. The shapes of the moraine
dam used in the experiments are trapezoidal with flat
crest and triangular. The crest width of trapezoidal dam
was 10cm. The height of all dams was 15 cm. In gen-
eral, most of moraine dams are steep-sided and narrow
crest, however some moraine dam has wider flat crest.
Rigid dam of wood and mixed silica sand (Mix: 1-6
and Mix: 1- 7) were used to prepare dam in the flume.
The mixed silica sand Mix: 1-6 was prepared by mixing
silica sand S1, S2, S3, S4, S5 and S6 in equal portion.
Similarly, Mix: 1-7 was prepared by mixing silica sand
S1, S2, S3, S4, S5, S6 and S7 in equal portion. The
mean dia. of sediment Mix: 1-7 and Mix: 1-6 were 1mm
and 1.15mm respectively. The grain size distribution of
sediment mixtures are shown in Fig. 5. In general, mo-
raine dams comprise loose, poorly sorted, stratified to
massive sediment deposited directly form glacier ice.
Some moraine dams consist largely of coarse, blocky
and bouldery material with a matrix of sand and gravel
physically based mathematical models. Several re-
searchers have developed physically based models
(f
Read
, 1991; t
akaHasHi
& n
akaGawa
, 1994; a
wal
et
alii 2008). However, most of the models are applicable
for overtopping and erosion of the dam. An integrated
model developed by a
wal
et alii (2008) is applicable
for dam failure due to sliding and overtopping. The
mechanism of moraine dam failure in many cases is
different from simple overtopping due to snow melt or
precipitation. The high amplitude waves generated by
ice/rock avalanche produce rapid erosion of moraine
dam. Thus, the released water from breached moraine
dam will be highly dependent on size, shape and loca-
tion of initiation of ice/rock avalanche, height and speed
of wave generated. However, an integrated model to
predict waves, outflow hydrograph and downstream
flooding for such type of failure mode is still lacking. In
this context, this study has proposed an integrated mod-
el for the i) prediction of waves generated by ice/rock
avalanche, ii) prediction of outflow hydrograph due to
waves overtopping and erosion of moraine dam and iii)
flow and sediment routing in the downstream for flood
risk assessment. The general outline of proposed model
is shown in Fig. 3. Some of the recent studies on gla-
cial lake outburst floods used BREACH model (f
Read
,
1991) to predict outflow hydrograph (b
aJRaCHaRya
et
alii, 2007; w
anG
et alii 2008). However, this model has
limitation to represent batter slopes of dam greater than
11° (d
avies
et alii, 2007) and does not consider waves
overtopping due to ice/rock avalanches.
An experiment on moraine dam failure provides
an opportunity to observe failure mechanisms as the
failure of a moraine-dammed lake has never been
directly witnessed. Most of the experimental stud-
ies are focused on prediction of waves generated by
Fig. 3 - An integrated model to predict glacial lake outburst flood (GLOF) due to waves overtopping and erosion
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R. AwAL, H. NAkAGAwA, k. kAwAIkE, Y. BABA & H. ZHANG
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5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
mixed sediments prepared from silica sand were used.
Ice or rock avalanche is a very complicated physi-
cal phenomenon. However, for simplicity, in this
study block of definite shape was used. A wave was
initiated in the lake by falling a rigid block. The vol-
ume of Block A was 1/8 of the lake volume (L=25 cm,
B=30 cm) and weight was 18.2kg. Similarly, the vol-
ume of Block B was 1/4 of the lake volume (L=50 cm,
B=30 cm) and weight was 33.5 kg. Servo-type water
gauges, WG-1 and WG-2, were used to measure wave
height in the lake at two locations as shown in Fig. 4.
WG-1 and WG-2 are located at 130 cm and 210cm
respectively from end of the flume.
where as other moraine dams consist of silty and sandy
diamicton and sandy gravel (C
laGue
& e
vans
, 2000).
However, details of grain size distribution of most of
moraine dams are unknown. Therefore in this study
Tab. 2 - Summary of experiments
Fig. 4 - Experimental setup
Fig. 5 - Grain size distribution of sediment mixes
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STUDY ON MORAINE DAM FAILURE AND RESULTING FLOOD/DEBRIS FLOW
HYDROGRAPH DUE TO WAVES OVERTOPPING AND EROSION
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
7
Load cell and servo-type water gauge (WG-3)
were used to measure sediment and total flow in the
downstream end of the flume. The arrangement to
measure outflow hydrograph both sediment and total
discharge at the channel outlet can be achieved by
employing container to trap sediment and servo-type
water gauge in the downstream tank. The submerged
weight of the sediment trapped in the container was
measured with the help of load cell at fixed time inter-
val. Similarly, change in water level of container used
to collect discharge in the downstream was meas-
ured by servotype water level gauge. More details of
measurement apparatus can be found in a
wal
(2008).
Three video cameras were used to capture eroded
shape of the moraine dam and propagation of waves.
The summary of experiments is shown in Table 2.
Basically experiments can be divided into three catego-
ries: (i) waves overtopping over rigid dam, (ii) waves
overtopping and erosion from full channel width and
(iii) waves overtopping and erosion from partial chan-
nel width (central and side channel breach).
RESULTS AND DISCUSSIONS
A wave was initiated in the reservoir by dropping
different size blocks. The reservoir was filled with wa-
ter up to a depth according to desired freeboard. The
water was then left to seep through the dam. The block
was dropped from height close to water surface when
seepage flow reached downstream toe. Propagation
of waves generated by falling Block A and Block B
(FB=2 cm) are shown in Fig. 6 and Fig. 7 respectively.
The waves measured at two locations in the upstream
reservoir by using servo-type water level gauge and
video captured from side of the flume are shown in
Fig. 8 and Fig. 9. The amplitude of waves generated
by Block B was higher than Block A. Wave amplitude
decreased quickly when the water level was almost
full (FB=0) in the reservoir (Fig. 8), however it took
Fig. 6 - Propagation of waves generated by
falling block (Block A)
Fig. 7 - Propagation of waves generated by fall-
ing block (Block B)
Fig. 8 - waves measured at different locations in the up-
stream reservoir for FB = 0
Fig. 9 - waves measured at different locations in the up-
stream reservoir for FB = 2 cm
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R. AwAL, H. NAkAGAwA, k. kAwAIkE, Y. BABA & H. ZHANG
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5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
by both rigid blocks, Block A and B in both shape of the
dams were similar. However, peak discharge produced
after erosion of the dam in the triangular dam was higher
and occurred earlier compare with trapezoidal dam. The
small difference in freeboard (1.5mm) between two
shapes of the dam caused only minimal influence on
outflow hydrographs. Erosion of the dam was started
from outer face in both shapes as shown in Fig. 12 and
Fig. 13. However, it took some time to erode flat crest
of the trapezoidal dam, so peak discharge occurred ear-
lier in the case of triangular dam. Thus narrow dams are
more vulnerable to overtopping and erosion.
Effect of freeboard on outflow hydrographs
Volume of water drained from the lake and ampli-
tude of wave generated in the lake depends on depth
of water in the reservoir. When freeboard is low, the
overtopping water depth in the dam crest Initial WL
Freeboard Initial WL Freeboard due to waves is higher
and erode dam body very fast, so peak discharge occur
earlier and magnitude of peak discharge is also higher
as shown in Fig. 14. Therefore the lake with little free-
board is more vulnerable to overtopping and erosion
by displacement waves from ice/rock avalanches.
long time to stabilize the wave amplitude in the reser-
voir with freeboard of 2 cm (Fig. 9).
In all experiments wave was initiated by em-
ploying same method and measured using servo-
type water level gauge.
Overtopping waves may carry enough water over
stable moraine dam. Rigid dams of wood are used to
make stable dam. Most of the glacial lakes are narrow
in the width. If the volume of ice/rock avalanche is
very big, overtopping may occur from whole width of
end moraine. However, most of the wave overtopping
occurs from partial width of end moraine from exist-
ing channel. Therefore, in this study, we have consid-
ered following three cases:
OUTFLOw HYDROGRAPH DUE TO wAVES
OVERTOPPING OVER RIGID DAM
Figure 10 shows the outflow hydrographs due
to waves overtopping over rigid dams. The resulting
peak discharge in the trapezoidal and triangular rigid
dams were similar for different initial water depths in
the lake and blocks used to generate waves. The total
volume of water drained from the lakes with freeboard
of 0cm was almost equal in both shaped dams. How-
ever, in the case of freeboard of 2 cm the total volume
of water drained in the triangular dam was 8 to 15%
higher than trapezoidal dam.
OUTFLOw HYDROGRAPH DUE TO wAVES
OVERTOPPING AND EROSION OF MORAINE
DAM (FULL CHANNEL wIDTH)
Numbers of experiments were done to study the
effects of shape of the dam, freeboard, dam material
and upstream slope of the dam on outflow hydrograph.
Effect of shape of the dam on outflow hydrographs
Trapezoidal dam with freeboard of 2cm was sta-
ble for waves generated by Block A. Figure 11 shows
the outflow hydrographs due to waves overtopping and
erosion of the moraine dam for flow from full channel
width. The waves generated by dropping a block in the
lake overtopped moraine dam and produced initial peak
discharge in the downstream. Flow was reduced during
runback of waves. The reflected waves repeatedly over-
topped the dam and produced multiple peaks. Breaching
of moraine dam and rapid lowering of lake water level
occurred after erosion of crest and overtopping of reflec-
tion waves many times. The initial discharge produced
Fig. 10 - Outflow hydrographs due to waves overtopping
over rigid dam
Fig. 11 - Outflow hydrographs due to waves overtopping
and erosion of moraine dam (for dam with dif-
ferent shapes)
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STUDY ON MORAINE DAM FAILURE AND RESULTING FLOOD/DEBRIS FLOW
HYDROGRAPH DUE TO WAVES OVERTOPPING AND EROSION
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
9
suction is higher for sediment Mix: 1-7 com-
pared with bigger sized sediemnt Mix: 1-6. This
is the main reason for rapid erosion of the dam
prepared from Mix: 1-6 compared with dam pre-
pared from Mix: 1-7 even if the mean diameter
of sediment is bigger (see Fig. 16).
Effect of upstream slope of the dam on outflow
hydrographs
The longitudinal profiles (see Fig. 17) of
some of the potentially dangerous glacial lakes
in Nepal (Tsho Rolpa, Imja, Thulagi and Lower
Barun) derived from m
ool
et alii (2001) shows
that the upstream slope of end moraines are
flatter (9 to 17 degree). The result of experi-
ments 16, 17 and 18 showed the effect of slope
of inner face of the moraine dam in outflow
hydrographs. Multiple peak discharges due to
waves overtopping and erosion of the dam was
higher in the dam with steeper slope of inner
face (see Fig. 18). The total volume of water
drained from the lake was also higher in the
dam with steeper slope of inner face. The temporal
changes of dam shape for different upstream slopes
of the dam are shown in Fig. 19. The eroded slope
Effect of dam material on outflow hydrographs
Sediment mixes 1-6 and 1-7 were used to pre-
pare dam. The mean diameter of Mix: 1-6 was big-
ger than Mix: 1-7. However, shear strength due to
suction plays vital role in erosion of unsaturated fine
sediments. With reference to v
anaPalli
et alii (1996),
increase in shear strength due to suction (Δτ) can be
expressed by following equation:
where, u
a
- u
w
is the matric suction, f is the angle
of internal friction of soil, θ is the soil volumetric
water content, θ
s
is the saturated moisture content,
θ
r
is the residual moisture content and ψ is the soil
water pressure head.
The graphical representation of Eq. (1) is shown
in Fig. 15. Increase in resisting shear strength due to
Fig. 12 - Dam surface erosion (Expt: 11)
Fig. 13 - Dam surface erosion (Expt: 15)
Fig. 14 - Outflow hydrographs for dam with different freeboards
Fig. 15 - Relationship between Δτ and |ψ|
Fig. 16 - Outflow hydrographs for dam of different sedi-
ment mixes
Fig. 17 - Longitudinal profiles of potentially dangerous
glacial lakes in Nepal
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R. AwAL, H. NAkAGAwA, k. kAwAIkE, Y. BABA & H. ZHANG
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5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
of outer face of the dam continued to migrate back-
wards and the height of the eroded dam decreased
rapidly in the dam with steeper slope of inner face,
so the multiple peak discharges and total volume of
water drained from the lake were higher in the dam
with steeper slope of inner face.
The multiple peaks in all cases are due to
overtopping and erosion of the dam from reflected
waves. The magnitude of multiple peaks will be
also affected by size (length and breadth) of the res-
ervoir. However, in this study, the size of the reser-
voir used in all cases is the same.
OUTFLOw HYDROGRAPH DUE TO wAVES
OVERTOPPING AND EROSION OF THE MO-
RAINE DAM (PARTIAL CHANNEL wIDTH)
Notch of the width 10 cm and depth 0.8
cm was incised at the center (PCW-C) and side
(PCW-S) of the dam crest and downstream face
of the dam. At the beginning, overtopping oc-
curred from full channel width. The reflected
waves generated in the later stage caused channel
breaching. The trapezoidal dam of experiment 23
was stable for waves generated by block A even
if overtopping occurred in the beginning. The
breaching of channel in the triangular dam was
faster compare with trapezoidal dam as shown in
Fig. 20. Similarly, breaching of the dam prepared
from Mix: 1-6 was faster compare with Mix: 1-7
for both channel breach at center and side (see
Fig. 20 and Fig. 21). The temporal change of lon-
gitudinal profile of breached channel is shown in
Fig. 22, which shows rapid incision of dam pre-
pared by using sediment Mix: 1-6. The section
of breached channel at crest was almost vertical
(overhanging in some cases) in the dam prepared
by using sediment Mix: 1-7. Armouring effect
was also negligible compared with dam prepared
by using sediment Mix: 1-6. This is the main rea-
son for higher depth of breached channel in the
dam prepared by using Mix: 1-7. The shape of
breached channel (Front view and top view) for
dam prepared by using sediment Mix: 1-7 and
Mix 1-6 are shown in Fig. 23.
CONCLUSIONS
About 80% of GLOFs were initiated by dis-
placement waves from ice avalanches that col-
lapsed into the lakes from hanging or calving
glaciers and rock avalanches. However, an integrated
model to predict waves and outflow hydrograph for
such type of failure mode is still lacking. Therefore, an
integrate model is essential for the i) prediction of waves
generated by ice/rock avalanche, ii) prediction of out-
flow hydrograph due to waves overtopping and erosion
of moraine dam and iii) flow and sediment routing in the
erodible river and floodplain for flood risk assessment.
Extensive laboratory experiments were per-
formed to study moraine dam failure due to waves
overtopping and erosion. The outflow hydrographs
produced by waves overtopping and erosion consist
Fig. 18 - Outflow hydrographs for dam with different upstream
slopes
Fig. 19 - Dam surface erosion
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STUDY ON MORAINE DAM FAILURE AND RESULTING FLOOD/DEBRIS FLOW
HYDROGRAPH DUE TO WAVES OVERTOPPING AND EROSION
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
11
peak discharges due to waves overtopping and
erosion of the dam was higher in the dam with
steeper slope of inner face. Trapezoidal dam
with sufficient freeboard was stable for waves
generated by ice/rock avalanche of 1/8 of lake
volume. The outflow hydrograph depends on
many factors such as dam shape, freeboard,
dam material, size of ice/rock avalanche, size
of the lake etc, so further study should be di-
rected towards development of numerical
model to predict outflow hydrograph resulting
from waves overtopping and erosion of mo-
raine dam.
ACKNOWLEDGEMENTS
This work was supported by the Japan Society
for the Promotion of Science Postdoctoral Fel-
lowship Program (grant-in-aid P 09080).
multiple peaks. For the same falling block and lake
water level, the initial peaks produced by overtop-
ping were similar for both triangular and trapezoidal
dams. However, magnitude and timing of subse-
quent peaks were different according to dam shapes
and dam materials. The shape of outflow hydrograph
also depends on upstream slope of the dam. Multiple
Fig. 22 - Longitudinal profile of breached channel at the flume edge
Fig. 23 - Shape of breached channel
Fig. 20 - Outflow hydrographs due to waves overtopping and
erosion of moraine dam (Partial channel width - center)
Fig. 21 - Outflow hydrographs due to waves overtopping and
erosion of moraine dam (Partial channel width - side)
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5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
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