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August during 2005-2010 found 1235 l/s/km
2
whereas in the same month
during 1985-1990 it was quite low with the rate of 1076 l/s/km
2
(Table
11.5). The spatial distribution of fl ood runoff for year 1990 and 2010 has
been demonstrated in Fig. 11.5a.
Accelerated Soil Erosion:
Under natural circumstances the total sediment
load of streams varied from 66 tons/km
2
/year in the dense forest to
398 tons/km
2
/year in the barren land in the watershed (Table 11.5).
Anthropogenic activities have accelerated the rate of load generation by
four times (302 tons/km
2
/year) in agricultural land and six times (398 tons/
km
2
/year) in barren land. Presently the average rate of total load delivery
from Dabka watershed stands at 224.45 tons/km
2
/year whereas 20 years
back during 1985-1990 it was just 158.93 tons/km
2
/year (Table 11.5). The
average annual rate of soil erosion of the Dabka watershed stands at 0.68
mm/year at the present time, however it was just 0.42 mm/year 20 years
back during 1985-1990 (Table 11.5). The spatial distribution map of soil
erosion and denudation depicting fi ve zones and advocating that the soil
erosion and denudation rates has been increased (Fig. 11.5b and Table 11.5)
which accelerated several hydrological hazards such as river-line fl ood,
fl ash fl ood, landslides and slope failure, etc.
Increasing Landslide Hazard:
After delineating all the exiting landslides
during fi eld work a spatial distribution and density map of landslides
have been carried out by GIS mapping following grid and the isopleth's
technique (Fig. 11.5c). The map suggested that the maximum area of the
watershed had very high to high spatial density of landslide which stands
respectively 39% (26.93 km
2
) and 32% (22.10 km
2
) area of the watershed
whereas minimum area of the watershed about 7% (4.83 km
2
) occupied by
low spatial density of landslide. Moderate spatial distribution density of
landslide covers about 22% (km
2
) area of the watershed (Fig. 11.5c). Low
and moderate spatial landslide density zone have respectively less than 4
and 4-8 landslide/km
2
whereas high to very high landslide spatial density
zone have 8-12 and above 12 landslide/km
2
(Fig. 11.5c). Comparatively Fig.
11.5c also depicts that 20 year back the landslide density was quite low for
all landslide hazard zones.
Increasing Hydro-hazard Frequency:
The integrated monsoon hydro-
hazard frequency map generated after overlaying fl ood, erosion and
landslide hazard maps, shows four hydro-hazard frequency zones in the
watershed (Fig. 11.5d). On evaluating the area statistics of present hydro-
hazard frequency it was found that out of the total area of the watershed
34% is under very high hydro-hazard frequency (above 60 events/year/
km
2
) 21% under high hydro-hazard frequency (40-60 events/year/km
2
),
17% as moderate hydro-hazard frequency (20-40 events/year/km
2
) and
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