Flooding at Karlshamnsverket - Analysis and Recommendations

Sammanfattning: Karlshamnsverket is a power plant located at the Baltic Sea in southern Sweden. Due to the coastal location this important infrastructure already experienced flooding in its basement in the past. The objective of this study is to conduct an initial analysis to determine the underlying reasons for the flooding and to provide suitable measures to increase the resilience of the power plant, also with regards to the future. For that reason, an initial analysis of sea water levels and rainfall data was performed and altered for a prospective climate scenario. Further information was gathered from measurements, original construction documents and literature to obtain a better understanding of the hydro(geo-)logical situation in the area. Based on this information suggestions were developed. Recommendations also include a maintenance plan for the drainage pipe system, developed after international standards. Flooding in the basement mostly stems from the stormwater pipe system, which is susceptible to high water levels in the surge basins and downpour events. Flooding is to be expected frequently and thus it is recommended to alter the current pipe system layout. Significant surface flooding of the power plant area, that constitutes a fill made of friction soil and blast rock, is unlikely. Most of the fill surface is located 265 cm above mean sea level, while the highest water level to be expected is 233 cm in the year 2100. Sea water is instead thought to enter the fill through a permeable seawall, which needs to be confirmed by constructing observation wells.