Flood Prevention Measures In Cities Undergoing Urban Expansion

The world’s urban population is growing and changing. If current trends are seen in the future also, it is estimated that in 2050, world population will reach 16 billion, almost double than that of 2010. Given this scenario, it appears that more than 50% of future urban areas are still undeveloped. According to Cohen, Montgomery, Reed and Stren [1], future urban population will be located mostly in medium and small cities, which will witness a rapid urban expansion, compared to the big cities, that will have a slower rate of growth. Urban development and occupation of the lands with constructions directly affect the characteristics of freshwater. Interventions that occur on land on which are built new constructions can have a major negative impact on the natural water cycle, on the mode of transport and its natural storage. The new developed residential and commercial areas generate impervious surfaces and compact soil infiltrating a small percentage of rainwater. Therefore, flow coefficient increases and decreases the volume of water that seeps directly into the ground. These phenomena and also the increasing of the rain intensity in short time periods have implications in increasing the frequency, intensity and severity of urban flooding. This is a major and a current problem for big cities. So, in order to prevent small and medium cities confrontation with this problems, it is necessary to pay specific attention to spatial planning and rainwater management. So, first it is essential to include “Green infrastructure” concept and its techniqual equipments in the expansion and development planning phase of small and medium cities and second to preserve the land where this equipments will be located. The concept of “Green infrastructure” is based on the use of the properties of green spaces to improve the urban environment as they (the green spaces of urban park or square type, green roofs, land plots in residential areas, etc.) contribute to climate change mitigation.