Abstract:
Landslide mitigation largely depends on the
understanding of the nature of the factors
that have direct bearing on the occurrence
oflandslides. Identification of these factors
is of paramount importance in setting out
appropriate and strategic landslides control
measures. The present study focused on the
identification of the major factors influencing
the occurrence oflandslides in the Northern
slopes of the Uluguru Mountains, Tanzania.
The main objective was to establish
relationship between spatial distribution of
landslides and their causative factors. Such
information would enable the planning of
appropriate and strategic control measures.
Aerial photographs, field survey and
Geographic Information System (GIS)
techniques were employed to identify the
landslides features which occurred during
EL NINO rains, spatial distribution and their
corresponding factors. The results show that
landslides dominate the geomorphic units
with slope gradient ranging from 25% to
over 80%. The most affected geomorphic
units are in the order: debris slopes>
incisions and V-shaped valleys >
amphitheatres. Factors which cause theoccurrence of landslides are both soil and
terrain related. The most important soil
characteristics are presence of shallow soil
solum with low bulk density and high macro
porosity overlying a relatively less porous
saprolite or hard bed rock. The terrain
related factors include: undercutting of
slopes by roads and pathways and presence
of very steep concave side slopes. Water
flow from roads and pathways and seepage
from irrigation channels are precursors for
the triggering oflandslides in the study area.
