APPLICATION OF GIS TO
THE EFFECTIVE
MANAGEMENT OF GULLY
EROSION IN ANAMBRA
STATE
INTRODUCTION
What is Gully Erosion?
It is the removal of soil along drainage
lines by surface water run-off.
How do they Occur?
They occur when water is channeled
across unprotected land and washes away
the soil along drainage lines.
Gully Site in Obosi in Onitsha South L.G.A, Anambra State
Causes of Gully Erosion
The main cause are:
• Deforestation
• Excavation
• Soil Saturation
• Poor Drainage
Other causes include Groundwater
Sapping and Anthropogenic causes
Gully Erosion in Anambra
• There are over 100 gully sites in Anambra
distributed in various local governments
Objectives of the Project
• To create a digitized map of Anambra
State showing all gully erosion sites.
• To create a database of all necessary data
needed in the control of gully erosion.
• To use the graphical and textual data to
create a functional G.I.S
• To proffer solutions to the problems of
gully erosion in Anambra State
Methodology Applied
•
•
•
•
•
Acquisition of Data
Classification of Data
Database Design
Conversion of Data
Storage of Data
Result and Analysis
1. Digital Maps of Anambra State in G.I.S
format:
•
•
•
•
Map showing gully erosion sites in L.G.A
Map showing population density in L.G.A
Map showing soil texture of the state
Topo Map of Anambra
Analysis
• The results shows that topography, soil texture,
and population density contributed a lot to
erosion in Anambra.
• There are more gullies in the areas of higher
gradient (i.e. Aguata) than in the areas of lower
plane ( i.e. Onitsha).
• Also shows that gullies are more in the areas
that has loamy soil and this areas has the
sharpest gradient.
• Onitsha is sandy and mostly populated but has
the lowest number of gullies because its almost
on a level plane.
Map showing population density of Anambra
Map showing soil texture
Topographic Map of Anambra
• Map showing flood patterns
• Query showing proximity of gully sites to roads
3. Charts
Fig 15a: Graph Showing the Percentage of
Controlled to Uncontrolled Gully Sites in Anambra
State.
81%
Controlled
Uncontrolled
19%
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Graph Showing Number of Gully Sites in each L.G.A of
Anambra State.
16
14
12
10
8
6
4
2
0
No. Of Gully
Site
Conclusion
• The success of any gully control measure undoubtedly depends on
the stage of gully development, the local geological setting
(stratigraphy and groundwater conditions), the characteristics and
hydro-geotechnical properties of the eroded soils and their response
to varying meteorological and hydrological conditions
• G.I.S and its related technology will help greatly in the acquisition,
organization, management and analysis of these large volumes of
data, allowing for better understanding of natural disasters and the
importance of record for future use.
Recommendations
• This method of monitoring and controlling the gully
erosion can also be applied throughout the Nation.
• Data acquisition is rather stressful; hence the Federal
Government should support research financially in order
to ease acquisition procedures.
• The Federal Office of Statistics should increase the
scope of data which they acquire so that one may easily
acquire data from them.
• Students who engage in expensive projects such as this
should be supported in all ramifications especially due to
the costly nature of such projects.