SECOND SINO-AMERICAN WORKSHOP ON ADVANCED COMPUTATIONAL MODELLING IN HYDROSCIENCE &
ENGINEERING, November 25-26, 2006, Beijing, China
1
NUMERICAL PREDICTION OF LANDSLIDE GENERATED WAVES IN LAKE SAREZ
USING CCHE2D-FLOOD MODEL
Xinya Ying1, Mustafa S. Altinakar2, Patrice Droz3
Located in Tajikistan, at the very heart of Pamir Mountains at an altitude of over 3000m,
Lake Sarez was formed in February 1911, due to a massive landslide triggered by an earthquake.
The landslide formed on the right flank of the mountain, and carried approximately 2km3 of rock
and debris into the valley to create a 600m-high natural dam, which buried the village of Usoy,
and completely blocked the flow of Murgab River. The water level rose at the upstream and
formed a lake by drowning the village of Sarez. The lake became stable around 1940’s. The
natural dam, and the lake were named as Usoy Dam and Lake Sarez with reference to the names
of the two villages destroyed by the landslide and the flooding waters, respectively (see Fig. 1).
Usoy Dam measures 3.7km at the crown, and the length of its base along the thalweg of
Murgab river is approximately 5km. With a height of over 550m, it is the tallest dam, natural or
man-made, in the world. Lake Sarez is 61 km long and has a surface area of 15km 2. It has an
average width of 1.44km. The average surface elevation is about 3265 m.a.s.l., and the length of
the shoreline at this level is 170km. The lake contains over 2,220 million cubic meters of water.
The average depth of the lake is about 185m. Near the dam, however, the depth reaches 505m.
Engineers, scientists, and various governmental and international organizations have long
been expressing their concern about the potential risk of a dambreak by internal erosion due to
seepage or a massive overtopping and partial washout due to a huge wave generated by the
failure of an unstable zone on the right bank slope (see Fig. 2). Pessimistic scenarios estimate that
such a flood could affect some 5 million people living along the Bartang, Panj, and Amu-Darya
rivers.
The present paper investigates the numerical prediction of landslide generated waves in
Lake Sarez, and the resulting wave run up on upstream slope of Usoy Dam. The numerical
computations are carried out with CCHE2D_FLOOD model, which solves the conservative form
of the two-dimensional shallow water equations using a finite volume method. The inter-cell
fluxes are computed by the upwind method and the water-level-gradient is evaluated as a
weighted average of upwind and downwind gradients. The model uses a regular mesh, which can
be directly imported from GIS digital elevation model. Computations were done for various
landslide scenarios by using different initial conditions. In some cases the computations were
started with a perturbed initial water surface (see Fig. 3). In other cases the wave was generated
by gradually modifying the bottom topography according to a predefined landslide scenario. The
1
Research Scientist, National Center for Computational Hydroscience and Engineering, The University of
Mississippi, MS 38677, USA (ying @ ncche.olemiss.edu)
2
Research Professor, National Center for Computational Hydroscience and Engineering, The University of
Mississippi, MS 38677, USA (altinakar @ ncche.olemiss.edu)
3
Senior Engineer and Project Manager, Stucky Consulting Engineers Ltd, Rue du Lac 33, P.O. Box, Renens VD
1020, Switzerland (pdroz@stucky.ch)
2
SECOND SINO-AMERICAN WORKSHOP ON ADVANCED COMPUTATIONAL MODELLING IN HYDROSCIENCE &
ENGINEERING, November 25-26, 2006, Beijing, China
paper presents the results of computations for various landslide scenarios, and discusses the
possible consequences of resulting waves.
REFERENCES
Stucky Consulting Engineers (2003): Lake Sarez Mitigation Project (ID67610), Complementary
Site Investigations; Part I Geological Report, Part II Report on Tracer Experiments at Lake Sarez
2002. Report for State Secretariat for Economic Affairs, Switzerland, and Ministry for
Emergencies of Tajikistan.
Figure 1 Aerial views of Lake Sarez (on the
left) and Usoy Dam (above). In the image on
the left Usoy Dam is also visible in the upper
left corner. The arrow shows the location of
the potential slide on the right bank (taken from Lake Sarez Mitigation Project- ID67610).
Figure 2 Image showing the
main subdivisions of the
Right Bank Slope (taken
from Lake Sarez Mitigation
Project- ID67610).
t = 0s
t = 20s
t = 40s
Figure 3 Different stages of the propagation of a landslide induced wave in Lake Sarez as
calculated using CCHE2D-FLOOD Model. The height of the initial wave in the first image is
50m.