Abstract:
Flooding is one of the most destructive natural hazards which causes high-intensity rainfall events
and massive floods and the condition is common in some parts of Sri Lanka. This study has been
conducted on the Malwathu Oya flood which is Flowing through the Wessgiriya Grama Niladhari
Division in Anuradhapura District. Malwathu Oya basin is the second-largest catchment among the
river basins in Sri Lanka (3284 km2), and one of the most widely used sources of water for irrigation,
water supply, and other diversions in the North Central province. The river basin experiences water
scarcity during the dry periods and the downstream areas of the catchment are flooded during the wet
period. The main objective of the study was to assess the causes of the Flooding of the Malwathu
Oya River. Accordingly, the primary and secondary data were explored to achieve the study
objectives. Based on that, the Study is presented the flood characteristics identified through the
Massive Floods that Occurred from 2014 to 2015 and find out the causes of the Malwatthu Oya
Flood. Therefore, the primary data were obtained from Observation, Questionnaire, and Systematic
Interview, Focus Group Discussion (FGD), and Secondary Data were collected from the Divisional
Secretariat Division, Department of Irrigation, Department of Meteorology, Disaster Management
office. Based on the result of the study examined the causes of the Malwattu Oya flood are that surrounded
lowest land, the structure of the soil, weaknesses of water reservoir dams, some human activities that
trigger the flood, high level of runoff, the connection between the Malwattu Oya river basin and
Nachanthuva reservoir, unplanned drainage system, soil excavation, an excessive settlement near to
river basin, etc. Therefore this study is significant to reduce the future flood hazard in the study area.
