Abstract:
Basin morphometric analysis is a means of mathematically quantifying different aspects
of a drainage basin. In this thesis, morphometric analysis of Didessa and Jema sub basin
was done to assess the hydrological characteristics and soil erosion potentials based on
the morphological characteristics. The study was carried out using DEM data (30 m by
30m) in GIS environment. The extracted drainage network for both sub basins has 5th
order according to Strahler’s stream orders. The basic parameter (stream order, stream
number, stream length, basin area, basin perimeter and basin length) from GIS software
were used for analysis of Linear, areal and relief aspect of Morphometric parameter. The
linear parameter (bifurcation ratio, drainage density, stream frequency and drainage
texture ratio) and relief aspect parameter (basin relief, relief ratio and ruggedness
number) have direct correlation with soil erosion. But the areal parameter (form factor,
circularity ratio, elongation ratio and constant channel maintenance) have inverse
relationship with soil erosion. The Average of all these parameter for each sub
watersheds was calculated to determine the final priority classes and categorized as high
( 2.55), medium (2.55 to 3.55) and low ( 3.55). Moreover the final priority Map also
indicates that; high priority classes of Jema sub watersheds covers larger area of about
7292.57km2 (49.45% ) for both J-3 and J-1, whereas 5099.43km2 (29.85%) of D-6 from
Didessa sub watersheds were vulnerable to soil erosion. This indicates that
comparatively; Jema watersheds were more vulnerable to soil erosion than that of
Didessa watersheds where phase wise implementation of soil and water conservation
measure has to be taken 1st. The Sub-Watershed (J-2 & J-5 from Jema and D-3 & D-4
from Didessa) 2nd priority were needed for reclamation and conservation process. The
sub watershed (J-4 from Jema and D-1, D-2 and D-5 from Didessa) have a low risk of
land degradation hence it should be given lowest priority in sub-basin conservation
practices.
