Also there are objectives in my research.• Monitoring past and current flood levels and flooded areas.• Mapping of flooded areas and height of floods for future flood scenarios.• Long term planning and organization of land use.• Technical design and construction of structures for flood control or resistance.
• Short-term monitoring, alert and response.MethodologyStudy area: Kelani river basin around Kaduwela area was selected as the study area for this research. Kaduwela is the one of most populated and industrial area in Gampaha district.Data collection: In HEC HMS modelling, it needs to find the number of catchments and area of each catchments in my study area. So Arc GIS software can use to find those parameters by using DEM (Digital Elevation Modelling) file which can collect from Survey Department of Sri Lanka. Also rainfall data can be collected from rain gauge stations which are situated in catchments of my study area and cross-section details of Kelani river can be collected from Irrigation Department of Sri Lanka.