Flomfrekvensanalyse og flomvannlinjeberegninger for byvassdrag

Abstract

“Flood frequency analysis and flood water level calculation for rivers in cities”. Urbanization and climate change are two driving factors that have increased risk of flooding and pollution and caused other adverse consequences in cities. In contrast to large river basins, intensive rainfall or storm events in cities may generate significant runoff discharges from local impervious areas to the small rivers and cause flooding in very short times. As a tool for compliance to EU’s flood Directive and NVE’s guideline of flood safety control for planning and development in dangerous areas along the rivers, flood risk analysis for rivers in cities has been a vital task for municipalities in Norway. The paper, taking a project in Sandnes as an example, introduces a stepwise approach of estimating flood frequency in urban catchment and calculating flood water levels in rivers. Data collection and data quality are highlighted to be important for increasing the reliability of analyses. It is concluded that implementation of local flood risk analysis and flood risk mapping is an important step to assist municipal flood risk management and planning for future development in cities. Furthermore the risk analysis results should be updated within a few years due to the changed climate and land uses.