Floodplain retention capacity assessment for Lužnice river

One of main topics of interdisciplinary project NIVA - Water Retention in Floodplains and Possibilities of Retention Capacity Increase is the assessment of flood wave transformation in the floodplain. The project focuses on broad field of floodplain ecosystem services and flood mitigation is a phenomenon which is researched by the team from Czech Technical University from different points of view and using different methods. Despite the fact that the main influence on flood wave transformation is flow retardation due to the flow velocity decrease, the retention in surface depressions within floodplain has been analyzed to get better overview of whole transformation process. Detailed digital relief model (DRM) has been used for given purposes to be able to analyze terrain depressions volumes. First, the methodology of analysis was prepared and tested on artificial surface. This surface was created using random raster generation, filtration and resampling with final resolution of 1,000 × 1,000 units and height of maximum 10 units above datum. The methodology itself is based on analysis of areas inundated by water at different elevation levels. Volume is then calculated for each depression using extraction of terrain elevations under corresponding water level. The method was then applied on the area of Lužnice River floodplain section to assess the retention capacity of real floodplain with natural character which usually means higher surface retention capacity in comparison to trained rivers. Results obtained from above mentioned analysis applied on Lužnice river are presented in this paper. The importance of floodplain retention capacity for flood transformation is low as results from obtained values.51