Abstract:
Urban flood hazard is a typical natural disaster that occurs due to the
reduction of permeable surfaces as a result of land use conversion and changes
in rainfall intensity. It ensures the need of different mitigation strategies such
as sufficient drainage system, and it is a simple mitigation measure that can be
applied in the ground. This paper is timely due to the lack of research studies
undertaken that are related to the study area. Natural disasters, flood hazard,
influence of urbanization for urban flood, and negative influence of urban
flood in the context of the world and Asian region have been discussed in the
available literature. Limited research has been undertaken on urban flood
mitigation based on hydrological analysis and run off volume calculation in
Kaduwela Municipal Council (KMC) area. With this limitation, this paper
focuses on analysing the runoff rainwater volume to mitigate urban flood in
2030 (predicted land use) by calculating the rainwater volume in natural and
artificial possible outfalls of each watersheds in KMC. The analysis consists
of three phases such as: land use prediction, hydrological analysis, and
calculation. A GIS-based land use prediction is simulated to analyse the land
use changes in relation to green, blue, and brown fills. The revealed land use
conversion is also processing day by day as a result of land use conversion and
rapid urbanization which will increase the runoff volume in 2030. A GISbased Hydrological analysis was carried out to identify the outfalls and
watersheds of the study area. The possible outfalls function as outlets of runoff
water which were collected in each watershed. Runoff volume was calculated
by using rational formula (Q = 0.0028CIA) and the parameters of the equation
used were the coefficient of land use in 2030, rainfall intensity, and 90 acres
portion of the watersheds. A sufficient drainage system was also designed to
make KMC a disaster resilient municipality. This research will be important
in the process of decision-making and policy implementation in the fields of
urban planning and flood mitigation.
