3.1 Topography and land cover
Derived land cover classes (Figure 3a) were broadly spread across
cultivated plots (26%), open pastoral land (30%) including homestead
farm areas with sporadic tree and shrub cover and exposed soil surfaces
in and around village buildings. Areas with patchy grass and rough shrub
cover, often with intermittent soil loss and vegetation disturbance due
to erosion, were classed as scrub (10%). Areas of notable bare ground
were observed in the severely eroded mid to lower slope region (Figure
4) that receives much of the concentrated overland flow from the
hillslopes above.
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Figure 3: (a) land cover classification and (b) derived mean slope for
cultivated plots
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Figure 4: Severely degraded pastoral land in the mid to lower region of
the catchment (photos Carey Marks/University of Plymouth, taken March
2017)
The cultivated plots occupied the east and southeastern side of the
catchment upland zone and hence represent potential overland flow
contribution areas to the mid and lower slope gullied zones. The group
of cultivated plots to the east of the system are the most recently
converted (from open grazing to cultivation) land (ca 1-3 years prior to
survey) with boundaries set to shallow ditches and bunds akin to
‘slow-forming’ terrace approaches (Chapagain and Raizada, 2017; Dercon
et al., 2003). Vegetation along these boundaries was largely immature
grasses. The cultivated plots to the south were more established (over 7
years) with notable establishment of edge-of-plot bunds and mature
vegetation along boundaries. In both areas of cultivation, uppermost
plots showed steeper slopes (Figure 3b) graduating to more gentle slopes
toward and on the open pastoral land.
The cultivated land plots are interconnected with unmetalled trackways
commonly used to drive livestock and for pedestrian and motorbike
access. All tracks are incised to varying degrees with notable incision
on downslope reaches of tracks from upper cultivated plots. Severe
erosion of pastoral land originates from apparent overland flow spill
over and concentration from track in centre west of the study area
(Figure 3b). Severe gully erosion has resulted in upslope relocation of
the track on more than one occasion.