International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
N
BEH -: 5: Slight
E] 8- 10: Moderate
ES 10-20: High
0 - 40: Very High
E] 40- 80: Severe
^ 80: Very Severe
Figure 2. Spatial distribution of soil loss in Indravati catchment
Soil | Erosion Area Area Soil Soil
loss | risk (Kn?) (96) loss loss
(t Classes (Million | (96)
ha”! tons)
y)
«5 | Slight 22400.88 | 54.26 | 5.79 7.81
5- | Moderate | 6584.12 | 15.95 | 4.59 6.20
10
10- | High 4161.32 | 10.08 | 5.89 7.95
20
20- | Very 343312 1833 5s 1324
40 | high
40— | Severe 2638.72 | 6.39 14.84 20.03
80
>80 | Very 2066.76 | 5.01 33.17 44.77
severe
Total 41284.84 | 100.00 | 74.11 100.00
Table 2. Soil loss and erosion risk classes
SDR, sediment yield at the out let of the basin is found to be
22.3 Million tons per year. The observed average annual
sediment yield at Pathagudem gauge site which is obtained
from Central Water Commission (CWC), Government of India,
at the out let of the basin support our results (Table 3). Almost
Station Duration Observed | Computed %
Name & Million tons error
No.
Pathagudem Annual 21.21 22 31 + 4.93
(AGGOOB5) average
(1992-2002)
Table 3. Computed and observed values (CWC, India) of
sediment yield
half of the Indravati catchment (54.26 %) falls under slight
erosion risk class where soil loss is lower than 5 t h'! y' (Table
2). Areas covered by moderate, high, very high, severe and very
severe erosion potential zones are 15.95, 10.08, 8.32, 6.39 and
5.01 percent respectively (Table 2). Overall 19.71 % of the
area is undergoing high erosion rates which are a major
contributor to the sediment yield (78.04 96) in the catchment.
This area represents high-priority area for management in order
to reduce soil losses, which are mostly found in upstream of the
catchment.
Indravathi basin is divided into 424 sub-watersheds as shown in
Figure 3. Soil loss for each sub-watershed is calculated.
foe
SESE
SE
Figure 3. Sub-watershed of Indravati basin
Average annual soil loss for sub-watersheds in Indravathi basin
varies from 1.93 t/ha/yr to 167.29 t/ha/yr. As per the model
prediction minimum soil loss occurs in sub-watershed number
407 and maximum soil loss occurs in sub-watershed number
41. Figure 4 shows distribution of the 424 sub-watersheds of
N
BE - 3: Slight (P6)
EJ 8- 10: Moderate (P5)
EE 10-20: High (P4)
20 - 40: Very High (P3
EC] 40-80: Severe (P2)
780: Very Severe (P1)
Figure 4. Prioritization Map of Different Sub-Watersheds in
the Indravathi Basin
Indravathi basin according to soil loss intensity. From the
analysis, it is observed that the number of watersheds falls in
first priority zone (i.e., very severe erosion class; P1) is 11. It is
evident from analysis that the number of watersheds falls in P2,
P3, P4, P5, P6 zones are 50, 85, 81, 82, and 115 respectively.
All sub-watersheds in first priority zone (Pl) are found in
upstream of the basin and the total soil loss from these sub-
watersheds is 7.45 million tons. Most of the sub-watersheds in
second priority zone (P2) are also found in upstream of the
basin and the total soil loss from these sub-watersheds is 18.87
million tons. Overall analysis indicates that though the
percentage of total area under these two zones is 9.88, but it
contributes 35.52% of total soil loss in the basin. Therefore, it is
essential to take conservation practices in these two zones. The
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