Environmental Engineering Reference
In-Depth Information
Fig. 11.50
Seriesof
E
1
,
E
2
and
E
3
Fig. 11.51
The Liujia Gully watershed and the locations of landslides and avalanches in the period from 1960
to 2009
Field investigations and measurements were conducted in the Liujia Gully in 2008-2009. Twenty three
landslides and 2 avalanches were found in the small watershed. These events occurred in the period from
1960 to 2009. The occurrence time of the events were determined by local records and talks with local
residents. The volume of the landslides and avalanches was measured with laser rangefinders. The largest
landslide had a volume of 9.9 million m
3
and the smallest landslide had a volume of 0.1 million m
3
. The
avalanches had volumes of 6800 and 900 m
3
. The total volume of landslides and avalanches was 34.7
million m
3
. Thus, the value of
E
1
is 60,218 m
3
/km
2
yr. Only 4% of the deposits of the landslides and
avalanches have been transported by flowing water, which means the value of
T
1
is 2400 m
3
/km
2
yr.
The value of
E
2
was determined by comparing the digital maps for 1984 and 2005. The eroded sediment
amount due to bank failure and gully erosion was determined as 0.97 million m
3
. Thus, the value of
E
2
is
3900 m
3
/km
2
yr, of which a major fraction deposited on the river bed (
D
2
).
The value of
E
3
was determined by using the fallout
137
Cs technique (Jia and Wang, 2010). More than
100 samples were taken from 10 sites and 20 hillslopes with a 10 cm diameter hand-operated core driller,
each sample was 60 cm long and about 10 kg in weight. The
137
Cs activity was analyzed by gamma
spectrometry using a BE5030 detector. The simplified mass balance model and the profile distribution
model were used in calculating the soil erosion and deposition rates. The local
137
Cs reference inventories
range from 1600 to 2402 Bqm
-2
, and the average reference inventory is 2022 Bqm
-2
. This indicates an
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