GIS-based flash flood risk estimation in urban areas. Kaunas city case study

Abstract

The climate change is continually creating new challenges for researchers from various fields because it affects rainfall pattern and consequently the runoff and river flow over the world. The unpredictable flash floods of the last summer make it necessary to adjust the methods used in urban hydrology. On the other hand, intensifying urban development takes place without respecting the principles of sustainable development, which inevitably leads to unexpected problems, which cannot be solved without research. Flash floods causing inundation of relatively small urban areas localizing the damage to both the population’s assets and the city’s infrastructure. To reduce the damage, it is first necessary to identify it, assess the extent of its and distribution in the city’s territory and reveal the causes. The new achievements of remote sensing technologies in the last decade enables the rapid and timely acquisition of spatial information that can be used to identify potentially inundated areas and estimate their geometric parameters. The aim of this article is to determine potentially inundated areas by screening of local depressions using conventional GIS technologies and LIDAR data and develop a digital map for decision makers to maintain the sounder urban planning process. Total number of local depression with area > 1 ha is 256 (the smaller one were not accounted) and total area of them 981 ha, average depth of depresions - 1.2 m. Probably inundated streets length are 11 km and total number of buildings at risk – 4221. We cannot estimate whether all of 256 depressions determined here present the real danger, as this could be checked if street floods were registered and respective data was collected on such events. However, having compared several cases described in the press with provided images and dates, the determined locations of depressions are quite precise have been found.