IMPACT OF URBANISATION IN THE FLOODPLAIN OF THE NEMUNAS RIVER ON THE FLOOD RISK (ON THE EXAMPLE OF THE SECTION FROM THE CONFLUENCE OF NEMUNAS AND NERIS RIVERS TO VIRBALIŪNAI)

Abstract

Floods are one of the most commonly occurring natural phenomena, causing significant adverse impacts on human health and life, the environment, cultural heritage, economic activity and infrastructure.  The study “Impact of urbanisation in the floodplain of the Nemunas River on the flood risk (on the example of the section from the confluence of Nemunas and Neris rivers to Virbaliūnai)” is carried out in order to assess the change of floods and floodplains of the Nemunas River, to analyse the main causes of maximum floods, to predict the change of the floods and the floodplains due to the impact of the climate change and the effects of the urbanization, and to assess the impact of urbanization on the selected section of the river by means of the hydrodynamic modelling.

In developing the initial model of the section of the Nemunas River under study, its bathymetric data provided by Vidaus vandens kelių direkcija were used – a digital elevation model of the bottom and a model of the coastal elevation of this section. Also, data from natural measurements taken under steady flow conditions were used. The analysis of information sources examines the flood situation both in Lithuania and other countries of the world, flood management measures, possibilities, the impact of climate and urbanisation on the flooding of the Nemunas River, and the development of urbanisation in the stretch of the Nemunas River examined in this study. The software used and its capabilities are analysed in detail, and the results obtained during the study are presented, together with conclusions and recommendation.

The performed hydrodynamic modelling showed that the change in the water level influenced by coastal development, namely urbanisation in the stretch of the River Nemunas under study, would not have a significant impact on the water level, which, even with a maximum flow of 3230 m3/s, in the case of intense coastal development, would only result in a flood of 0.46 m at the end of the stretch, upstream.