Abstract:
Sri Lanka has 65,000 sq.km of land area with many areas prone to manmade
and natural disasters. The last few decades has witnessed the occurrence of
an increased number of natural disasters in Sri Lanka. The Ratnapura
District is highly prone to natural disasters such as landslides, floods and
strong winds. The main objectives of the Study are to identify the disaster
prone areas by their severity and to discover the real causes of flood
disasters in the study area, with a view to developing a disaster management
plan for the study area using Geographical Information Systems (GIS)
technology. The Ratnapura District is 3,275 square kilometers in land
extent. Thus this study has been restricted to two areas namely; the
Ratnapura Municipality and the Elapatha Divisional Secretariat Division
(DSD).
The Study is based on the data collected from both primary and secondary
sources. Data was collected from published information sources, particularly
on flood generation factors such as rainfall. The flood gauge levels required
for the Study were obtained from gauges used by the Survey Department,
Meteorological Department and the Irrigation Department of Sri Lanka.
Other secondary sources consist of relevant literature and digital maps
(1:10000) of the Surveyor General’s Department of Sri Lanka. Primary data
was collected through field surveys and interviews. Field observations were
carried out to identify the drainage pattern of the Kalu Ganga, flood prone
areas etc. Questionnaire survey was administered to ascertain the impact of
floods such as; loss of lives, damage to property and houses, number of days of inundation and water levels etc. ArcGIS 9.3, ILWIS technique and the
statistical analysis software (SPSS 13.0) were used for digitizing, modeling,
data analysis, mapping and interpretation. Hazard areas and risk areas were
identified through maps and classified in to high, medium and low hazard
zones. Areas with a high risk of flood hazard are located towards the center
of the Ratnapura Municipality. The Randola and Hangamuwa areas of the
Elapatha DSD also had to face similar impacts from the floods.
It is envisioned that the hazard maps produced through this research will
help planners and decision makers to take rational decisions on mitigation of
negative impacts of floods and in the Ratnapura Municipality and the
Elapatha DSD.
