Spatial Distribution of Floods in Mathara District: with Special Focus on 2003 and 2017 Flood Events

Abstract

Floods are one of the most devastative disasters in the world, and it is most prominent in tropical regions of the world. Sri Lanka being located in between two tropics, witnesses flood every year due to the monsoon, convection rains and sometimes rain due to cyclones. Therefore, this study is mainly focused on Mathara district with the main objective of assessing the impact of floods along with its distribution. Both primary and secondary data were used for the study. Impact data was obtained from the Disaster Management Center and the flood inundation area, and rainfall data was obtained from the Department of Irrigation and Department of Meteorology of Sri Lanka respectively. A questionnaire survey was conducted on selected 100 households from the Peddapitiya Grama Niladhari Division (GND) of Akuressa Divisional Secretariat Division (DSD) which has the highest impact. Spatial analysis techniques were mainly used in this study, specially the weighted overlay method, to identify the affected regions. Statistical analysis methods of descriptive statistics were also used in order to identify the relationship between daily discharge and daily rainfall levels. According to the analysis Kirama ara, Digili oya, Kotapola oya and Urubokka oya tributaries of Nilwala river record the highest impact from floods. It is also clear that April, May and June are the most prominent time period due to the South West Monsoon (SWM) and September, and November due to Second Inter Monsoon (SIM) conventional rains. Comparison between 2003 floods with 2017established that the impact is more devastative in year 2017 flood.