In the present paper topographical elevation map for the
study area was developed by Digital Elevation Model
(DEM) extracted from the Shuttle Radar Topography Mission
(SRTM) data. For this, the DEM was subjected to two directional
gradient filters (one in x-direction and another in ydirection).
The resultant maps were used to generate a slope
map of the study area using ARCGIS Spatial Analyst tools.
The highest topographic elevations (551 m and lowest 387
AMSL) exist in the western and northwestern portions of the
area which induces highest runoff and hence less possibility
of rainfall infiltration. The slope map of the study area has
grouped in five classes in degrees viz. 1–3 (Gentle) , 3–5
(Moderate) , 5–10 (Steep) , 10–35 (Very Steep) and >35
(Very Very Steep) (Fig. 4).
It is observed that the most of the area of Orr river basin
comes under gentle and moderate slope which indicates almost
flat topography of the area. Gentle slopes were designated in
the ‘‘excellent’’ category for groundwater management as the
nearly flat terrain is the most favorable for infiltration. Moderate
slopes also come under good zone due to slightly undulating
topography which gives maximum percolation or partial
runoff. The steep class and having a high surface runoff with
a negligible amount of infiltration are marked under good zone
for construction of stop dams etc. Slope is a critical parameter
which directly controls runoff and infiltration of any terrain.
Runoff in higher slope regions causes less infiltration. This factor
significantly controls the development of aquifers.