computed 
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1servation 
IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India, 2002 
  
3.2 Sediment Yield Index (SYD) for watershed 
prioritization 
Watershed was prioritized following sediment yield index 
(SYI) approach of All India Soil and Land Use Survey (AIS 
LUS, 1991) described by Equation 7. 
SYI- » (EI*Aie*d/ Aw) * 100 (7) 
Where SYI = Sediment Yield Index 
El = Weight value of erosion 
Aie = Area of the erosion intensity / composite unit 
d = Delivary ratio in percentage 
Aw = Total area of watershed 
Physiography map, slope map derived from DEM and land use 
/ land cover map were combined to generate composite map 
with classes of various combination of physiography, land use 
and slope class. These units were assigned weightage values 
ranging 13 to 19 and were added to attribute table. The delivary 
ratio values were assigned to different sub-watershed varied 
from 0.60 to 0.85. The SYI was computed for each sub- 
watershed using equation 7. The SYI values were grouped into 
priority category codes following the standards adopted by AIS 
LUS. 
3.3 Land capability classification 
Treatment-oriented land capability classification (Sheng, 1972) 
was used to assess the capability of land for suggesting 
conservation measures. The land capability classification 
consider the terrain slope and soil depth to assess the capability 
class. 
4. RESULT AND DISCUSSION 
Umkhen watershed was divided into 29 sub-watershed for 
prioritization on the basis of average soil loss and silt yield 
index. Nine physiographic units were identified in the 
watershed to study soils. The soils are shallow to deep in depth 
and well to moderately well drained. Soils belongs to loamy 
skeletal, coarse loamy and fine loamy textural class. Slope map 
was generated from DEM reveals that 7.25 per cent land are 
nearly leveled whereas 29.60, 35.63 and 27.52 percent land are 
undulating/ rolling, moderately sloping and steep sloping, 
respectively. Land use / land cover map prepared from merged 
LISS III + PAN data on scale 1:25,000 show that 67.32 percent 
area of watershed is under pine forest with varying density 
classes viz., moderate forest (30.79 %), open forest (28.38 %) 
and dense forest (8.15%) whereas 26.26 percent area falls under 
agriculture comprising areal extent under fallow (upland), 
shifting fallow, bun agriculture and fallow (valley fills) are 
11.44, 8.32, 4.90 and 1.60 percent, respectively. 
  
Figure 1. Land use / land cover in Umkhen watershed 
Erosion hazard was assessed following USLE model and 
grouped into five classes ranging from very slight to very 
severe as presented in Table 1 and Figure 2. Erosion hazard 
analysis reveals that 33.83 percent area experience very severe 
erosion hazard followed by severe ( 22.95 %), moderate (19.91 
%) and slight (13.95 %) erosion hazard in the watershed. 
  
  
  
  
  
  
  
Soil loss Erosion Area in ha. Area in % 
t/ha/year hazard 
class 
<3 Very slight 1567 9.37 
3-10 Slight 2336 13.94 
10-25 Moderate 3337 19.91 
25-50 Severe 3847 22.95 
>50 Very 5670 33.83 
severe 
  
  
  
  
  
Table 1. Erosion hazard classes based on USLE model 
     
HEC 
* 
ii 
iru 
LL LLLA 
H] 
Figure 2. Soil erosion hazard in the Umkhen watershed 
Land use land cover map was intersected with erosion hazard 
(soil loss) map to predict average soil loss in various land use / 
land cover. Among agriculture land, valley fills area has slight 
erosion hazard (average 6.16  t/ha/yr) due to nearly level 
topography and well management practices. Fallow upland and 
shifting fallow land witness severe erosion hazard (average loss 
54.48 to 83.05 U/ha/yr) because of moderate to steep sloping 
topography with poor management practices, Highest average 
soil loss was noticed (average loss 124.55 t/ha/yr) in barren / 
scrub lands due to absence of adequate vegetal cover associated 
with moderate to steep sloping terrain. Area under dense pine 
forest has moderate erosion hazard ( average 23.33 t/ha/yr) 
whereas moderate pine forest and open pine forest area have 
severe erosion hazard (average loss 39.98 to 45.79 t/ha/yr). 
Erosion hazard map was intersected with sub-watershed map to 
compute weighted average soil loss in each sub-watershed to 
determine priority of sub-watershed as high, medium and low 
priority class. Analysis reveals that 6 sub-watershed belongs to 
high , 15 sub-watershed to medium and 8 sub-watershed to 
low priority category. 
Sediment Yield Index ( SYI) was computed to prioritize the 
sub-watershed for conservation planning. Composite map was 
generated by integrating physiography, land-use, soil texture 
and slope resulting 16 different Erosion Intensity Units (EIU). 
Weightage values and delivery ratio values for each EIU were 
assigned. Sediment Yield Index (SYI) of the sub-watersheds 
ranging from 849 to 1194 (Table 2). The study reveals that 11 
sub-watershed belong to high, 11 sub-watershed to medium 
and 5 sub-watershed to low priority class, respectively.