ABSTRACT
With the aid of Global Positioning System (GPS) and Satellite Aerial Photo, a comparative
characterization and mapping of soil gully erosion features on two geological formations
were carried out in Nsukka area of eastern Nigeria. The two geological formations were
Ajali and Mamu formations. The study involved the use of base map created using a
Geographic Information System (GIS) (GPS Track Marker) and Satellite Photo downloaded
from the internet using the same GIS (GPS Track Marker). This aided the field work for
erosion site study and data collection. A total of seventy (70) erosion sites with an average
length of about 1606.5 meters, average width of about 64.2 meters and average depth of 8.6
meters were visited in Ajali formation. On the other hand, only nine with an average length
of about 484.2 meters, average width of about 6.5 meters and an average depth of about 3.7
meters were visited in Mamu. In Ajali formation, forty three new erosion sites were
identified to add to the twenty seven old sites while in Manu formation only five new sites
were identified to add to the four old sites. Three profile pits were dug in each formation to
represent the soils. They are sites of Ada (Mpt1), Agu-Orba (Mpt2) and Agu-Ekwegbe
(Mpt3) on Mamu Formation while Iheaka (Apt1), Ede-Oballa (Apt2) and Aku (Apt3) were
sites on Ajali Formation.