A Participatory GIS Approach to Identify Critical Land Degradation Areas and Prioritize Soil Conservation for Mountainous Olive Groves (Case Study)

Abstract

Climate change scenarios predict an
increase in the frequency of heavy rainfall events in
some areas. This will increase runoff and soil erosion,
and reduce agricultural productivity, particularly on
vulnerable mountainous agricultural lands that is
already exhibiting high rates of soil erosion.
Haphazard implementation of soil and water
conservation (SWC) interventions on scattered fields
is inefficient in reducing soil erosion. The objective of
this study was to identify areas at high risk of erosion
to aid the design and implementation of sustainable
SWC using GIS analysis and farmers’ participation
approach. A 25 m digital elevation model (DEM) was
used to derive layers of flow accumulation, slope
steepness and land curvature, which were used to
derive an erosion-risk (priority) map for the whole
watershed. Boundaries of farmers’ fields were
mapped and verified by the community and each field
was classified into high, moderate or low erosion risk.
Fields with low flow accumulation (top of hill) and/or
steep slope and/or convex slope were assigned high
erosion risk and therefore high implementation
priority. The study showed that more than 64% of the
fields were classified into high erosion risk areas.
Accordingly, a community-watershed plan was
established, revised and approved by the community Incentive loans to implement SWC measures were
distributed to 100 farmers based on the priorities of
their fields. Judged by local farmers and using 16
randomly selected fields, 90% of the targeted areas
were correctly identified using the erosion risk map.
After two years, the conservation measures had led to
marked improvement of soil conservation. The
approach is simple and easy to comprehend by the
community and provides scientific basis to prioritize
the implementation of SWC and to target the most
degraded areas, which amplify the impact of these in
reducing the vulnerability to land degradation